4.0.0 Release 🚀

We will update the required Java version at some point, the only question is when.

.github/ISSUE_TEMPLATE/bug_report.yml

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+name: Bug Report
+description: Report a bug or console error
+
+body:
+  - type: markdown
+    attributes:
+      value: |
+        **Before reporting a bug, please see if using master/dev builds from https://ci.viaversion.com/ fixes your issue.**
+        Whenever you see fit, you can upload images or video to any of the textfields.
+
+  - type: input
+    attributes:
+      label: "`/viaversion dump` Output"
+      description: |
+        Run `/viaversion dump` in the console or in the chat, then copy and paste the given link here.
+      placeholder: |
+        https://dump.viaversion.com/...
+    validations:
+      required: true
+
+  - type: textarea
+    attributes:
+      label: Console Error
+      description: |
+        If you encounter warnings/errors in your console, **paste them with https://paste.gg/ and put the paste link here**.
+        If the error is small/less than 10 lines, you may put it directly into this field.
+      value: |
+        ```
+        Put the paste.gg link or text here.
+        ```
+      placeholder: Please do not remove the grave accents; simply replace the line of text in the middle.
+    validations:
+      required: false
+
+  - type: textarea
+    attributes:
+      label: Bug Description
+      description: |
+        Describe the unexpected behavior.
+        If you want to attach screenshots, use the comment field at the bottom of the page.
+      placeholder: |
+        Example: "Placing signs on 1.13.2 causes text to disappear."
+    validations:
+      required: true
+
+  - type: textarea
+    attributes:
+      label: Steps to Reproduce
+      description: |
+        List the steps on how we can reproduce the issue. Make sure we can easily understand what you mean with each step.
+      placeholder: |
+        Example:
+        1. Login with a 1.13.2 client
+        2. Place a sign
+        3. The sign text is displayed wrong
+    validations:
+      required: true
+
+  - type: textarea
+    attributes:
+      label: Expected Behavior
+      description: |
+        Describe what exactly you expected to happen.
+      placeholder: |
+        Example: "Placed sign text should not disappear."
+    validations:
+      required: true
+
+  - type: textarea
+    attributes:
+      label: Additional Server Info
+      description: |
+        Do you use a proxy (eg. BungeeCord)? What software do you use and what plugins?
+      placeholder: |
+        Example: "I also use BungeeCord with the following plugins: x, y, z"
+    validations:
+      required: false
+
+  - type: checkboxes
+    attributes:
+      label: Checklist
+      description: Make sure you have followed each of the steps outlined here.
+      options:
+        - label: Via plugins are only running on **EITHER** the backend servers (e.g. Paper) **OR** the proxy (e.g. BungeeCord), **not on both**.
+          required: true
+        - label: I have included a ViaVersion dump.
+          required: true
+        - label: If applicable, I have included a paste (**not a screenshot**) of the error.
+          required: true
+        - label: I have tried a build from https://ci.viaversion.com/ and the issue still persists.
+          required: true

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,8 @@
+blank_issues_enabled: false
+contact_links:
+  - name: Dev builds
+    url: https://ci.viaversion.com/
+    about: Before reporting a bug, please check if using master/dev builds from our ci fixes your issue.
+  - name: ViaVersion Discord
+    url: https://discord.gg/viaversion
+    about: For smaller issues or questions, you can also join our Discord server.

.github/ISSUE_TEMPLATE/feature_request.yml

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+name: Feature Request
+description: Suggest a feature to be added
+
+body:
+  - type: textarea
+    attributes:
+      label: Problem Description
+      description: |
+        Describe the issue you are facing or why you need the feature to be added.
+      placeholder: |
+        I am always frustrated with...
+    validations:
+      required: true
+
+  - type: textarea
+    attributes:
+      label: Solution Description
+      description: |
+        Describe the solution you would like to see.
+    validations:
+      required: true
+
+  - type: textarea
+    attributes:
+      label: Alternatives
+      description: |
+        Describe alternatives you have considered.
+    validations:
+      required: false
+
+  - type: textarea
+    attributes:
+      label: Additional Info
+      description: |
+        Does the feature apply to any specific version or environment?
+    validations:
+      required: false

.github/workflows/gradle.yml

@@ -0,0 +1,28 @@
+# This workflow will build a Java project with Gradle
+# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-gradle
+
+name: Java CI with Gradle
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    # Only run on PRs if the source branch is on a different repo. We do not need run everything twice.
+    if: ${{ github.event_name != 'pull_request' || github.repository != github.event.pull_request.head.repo.full_name }}
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - uses: gradle/wrapper-validation-action@v1
+    - name: Set up JDK 11
+      uses: actions/setup-java@v2
+      with:
+        distribution: 'adopt'
+        java-version: 11
+    - name: Build with Gradle
+      run: ./gradlew build
+    - uses: actions/upload-artifact@v2
+      with:
+        name: artifact
+        path: build/libs

.gitignore

@@ -1,3 +1,113 @@
-target/
-.idea/
+### Java files ###
+*.class
+
+# Package Files
+#*.jar
+*.war
+*.ear
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+
+
+### Intellij ###
+# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm
+# Ignore project files
 *.iml
+
+# Ignore IDEA directory
+.idea/*
+
+# Include the project's dictionary
+!.idea/dictionaries/
+!.idea/dictionaries/*
+
+# File-based project format:
+*.ipr
+*.iws
+
+### Plugin-specific files: ###
+# IntelliJ
+/out/
+
+# mpeltonen/sbt-idea plugin
+.idea_modules/
+
+# JIRA plugin
+atlassian-ide-plugin.xml
+
+# Crashlytics plugin (for Android Studio and IntelliJ)
+com_crashlytics_export_strings.xml
+crashlytics.properties
+crashlytics-build.properties
+
+
+
+### Eclipse ###
+*.pydevproject
+.metadata
+.gradle
+bin/
+tmp/
+*.tmp
+*.bak
+*.swp
+*~.nib
+local.properties
+.settings/
+.loadpath
+
+# Eclipse Core
+.project
+
+# External tool builders
+.externalToolBuilders/
+
+# Locally stored "Eclipse launch configurations"
+*.launch
+
+# CDT-specific
+.cproject
+
+# JDT-specific (Eclipse Java Development Tools)
+.classpath
+
+# PDT-specific
+.buildpath
+
+# sbteclipse plugin
+.target
+
+# TeXlipse plugin
+.texlipse
+
+
+
+### Maven ###
+target/
+pom.xml.tag
+pom.xml.releaseBackup
+pom.xml.versionsBackup
+pom.xml.next
+release.properties
+dependency-reduced-pom.xml
+buildNumber.properties
+
+
+
+### NetBeans ###
+nbproject/private/
+build/
+nbbuild/
+dist/
+nbdist/
+nbactions.xml
+nb-configuration.xml
+.nb-gradle/
+
+
+
+### Git ###
+# Don't exclude the .gitignore itself
+!.gitignore

LICENSE

@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
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+software and other kinds of works.
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+
+  Nothing in this License shall be construed as excluding or limiting
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+
+  12. No Surrender of Others' Freedom.
+
+  If conditions are imposed on you (whether by court order, agreement or
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+
+  13. Use with the GNU Affero General Public License.
+
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+
+  14. Revised Versions of this License.
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+  The Free Software Foundation may publish revised and/or new versions of
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+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
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+option of following the terms and conditions either of that numbered
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+
+  If the Program specifies that a proxy can decide which future
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+
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+
+  17. Interpretation of Sections 15 and 16.
+
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+above cannot be given local legal effect according to their terms,
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+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
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+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
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+
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+    Copyright (C) <year>  <name of author>
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+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
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+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<https://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<https://www.gnu.org/licenses/why-not-lgpl.html>.

README.md

@@ -0,0 +1,79 @@
+# ViaVersion - Spigot, Sponge, BungeeCord, Velocity
+
+[![Latest Release](https://img.shields.io/github/v/release/ViaVersion/ViaVersion)](https://viaversion.com)
+[![Build Status](https://github.com/ViaVersion/ViaVersion/actions/workflows/gradle.yml/badge.svg?branch=master)](https://github.com/ViaVersion/ViaVersion/actions)
+[![Discord](https://img.shields.io/badge/chat-on%20discord-blue.svg)](https://viaversion.com/discord)
+
+**Allows the connection of higher client versions to lower server versions**
+
+Supported Versions:
+
+![Table (https://i.imgur.com/uDM9HR8.png)](https://i.imgur.com/uDM9HR8.png)
+
+On Paper you may also use ProtocolSupport, but ensure you have the right build for your server version.
+
+**User Docs:** https://docs.viaversion.com/display/VIAVERSION/
+
+
+Sources:
+--------
+**[wiki.vg](https://wiki.vg)** (Used for information regarding packet structure, we also contribute back)
+
+**[Burger](https://github.com/Pokechu22/Burger)** (See [PAaaS](https://github.com/Matsv/Paaas))
+
+**[OpenNBT](https://github.com/ViaVersion/OpenNBT)**
+
+
+Releases / Dev Builds:
+--------
+You can find official releases here:
+
+https://www.spigotmc.org/resources/viaversion.19254/history
+
+----------
+
+You can find official dev builds here:
+
+**Jenkins:** https://ci.viaversion.com
+
+**JavaDocs:** https://jd.viaversion.com
+
+**Maven Repository:**
+```xml
+<repository>
+    <id>viaversion-repo</id>
+    <url>https://repo.viaversion.com</url>
+</repository>
+```
+
+**API-artifact:**
+```xml
+<dependency>
+    <groupId>com.viaversion</groupId>
+    <artifactId>viaversion-api</artifactId>
+    <version>LATEST</version>
+    <scope>provided</scope>
+</dependency>
+```
+
+Replace the version depending on your needs.
+
+If you need access to the existing protocol or platform implementations, use the parent artifact `viaversion`.
+Please note the [differences in licensing](#license).
+
+
+Building:
+--------
+After cloning this repository, build the project with Gradle by running `./gradlew build` and take the created jar out of
+the `build/libs` directory.
+
+
+License:
+--------
+The entirety of the [API directory](api) (including the legacy API directory) is licensed under the MIT License; see [licenses/MIT.md](licenses/MIT.md) for
+details.
+
+Everything else, unless explicitly stated otherwise, is licensed under the GNU General Public License, including the end
+product as a whole; see [licenses/GPL.md](licenses/GPL.md) for details.
+
+Special thanks to all our [Contributors](https://github.com/ViaVersion/ViaVersion/graphs/contributors).

adventure/build.gradle.kts

@@ -0,0 +1,25 @@
+plugins {
+    id("com.github.johnrengelman.shadow")
+}
+
+// Shade and relocate adventure in an extra module, so that common/the rest can directly depend on a
+// relocated adventure without breaking native platform's adventure usage with project wide relocation
+tasks {
+    shadowJar {
+        relocate("net.kyori", "com.viaversion.viaversion.libs.kyori")
+    }
+    build {
+        dependsOn(shadowJar)
+    }
+}
+
+dependencies {
+    api(libs.bundles.adventure) {
+        exclude("org.checkerframework")
+        exclude("net.kyori", "adventure-api")
+        exclude("net.kyori", "adventure-bom")
+        exclude("com.google.code.gson", "gson")
+    }
+}
+
+publishShadowJar()

api-legacy/build.gradle.kts

@@ -0,0 +1,3 @@
+dependencies {
+    compileOnly(projects.viaversionApi)
+}

api-legacy/src/main/java/us/myles/ViaVersion/api/Via.java

@@ -0,0 +1,102 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package us.myles.ViaVersion.api;
+
+import io.netty.buffer.ByteBuf;
+import us.myles.ViaVersion.api.boss.BossBar;
+import us.myles.ViaVersion.api.boss.BossColor;
+import us.myles.ViaVersion.api.boss.BossStyle;
+
+import java.util.SortedSet;
+import java.util.UUID;
+
+/**
+ * @deprecated may be removed at some point, use {@link com.viaversion.viaversion.api.Via}
+ */
+@Deprecated
+public class Via<T> implements ViaAPI<T> {
+
+    private static final ViaAPI INSTANCE = new Via();
+
+    private Via() {
+    }
+
+    @Deprecated
+    public static ViaAPI getAPI() {
+        return INSTANCE;
+    }
+
+    @Override
+    public int getPlayerVersion(T player) {
+        return com.viaversion.viaversion.api.Via.getAPI().getPlayerVersion(player);
+    }
+
+    @Override
+    public int getPlayerVersion(UUID uuid) {
+        return com.viaversion.viaversion.api.Via.getAPI().getPlayerVersion(uuid);
+    }
+
+    @Override
+    public boolean isInjected(UUID playerUUID) {
+        return com.viaversion.viaversion.api.Via.getAPI().isInjected(playerUUID);
+    }
+
+    @Override
+    public String getVersion() {
+        return com.viaversion.viaversion.api.Via.getAPI().getVersion();
+    }
+
+    @Override
+    public void sendRawPacket(T player, ByteBuf packet) {
+        com.viaversion.viaversion.api.Via.getAPI().sendRawPacket(player, packet);
+    }
+
+    @Override
+    public void sendRawPacket(UUID uuid, ByteBuf packet) {
+        com.viaversion.viaversion.api.Via.getAPI().sendRawPacket(uuid, packet);
+    }
+
+    @Override
+    public BossBar createBossBar(String title, BossColor color, BossStyle style) {
+        return new BossBar(com.viaversion.viaversion.api.Via.getAPI().legacyAPI().createLegacyBossBar(title,
+                com.viaversion.viaversion.api.legacy.bossbar.BossColor.values()[color.ordinal()],
+                com.viaversion.viaversion.api.legacy.bossbar.BossStyle.values()[style.ordinal()]));
+    }
+
+    @Override
+    public BossBar createBossBar(String title, float health, BossColor color, BossStyle style) {
+        return new BossBar(com.viaversion.viaversion.api.Via.getAPI().legacyAPI().createLegacyBossBar(title, health,
+                com.viaversion.viaversion.api.legacy.bossbar.BossColor.values()[color.ordinal()],
+                com.viaversion.viaversion.api.legacy.bossbar.BossStyle.values()[style.ordinal()]));
+    }
+
+    @Override
+    public SortedSet<Integer> getSupportedVersions() {
+        return com.viaversion.viaversion.api.Via.getAPI().getSupportedVersions();
+    }
+
+    @Override
+    public SortedSet<Integer> getFullSupportedVersions() {
+        return com.viaversion.viaversion.api.Via.getAPI().getFullSupportedVersions();
+    }
+}

api-legacy/src/main/java/us/myles/ViaVersion/api/ViaAPI.java

@@ -0,0 +1,63 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package us.myles.ViaVersion.api;
+
+import com.viaversion.viaversion.api.Via;
+import io.netty.buffer.ByteBuf;
+import us.myles.ViaVersion.api.boss.BossBar;
+import us.myles.ViaVersion.api.boss.BossColor;
+import us.myles.ViaVersion.api.boss.BossStyle;
+
+import java.util.SortedSet;
+import java.util.UUID;
+
+/**
+ * @deprecated may be removed at some point, use {@link Via#getAPI()}
+ */
+@Deprecated
+public interface ViaAPI<T> {
+
+    int getPlayerVersion(T player);
+
+    int getPlayerVersion(UUID uuid);
+
+    default boolean isPorted(UUID playerUUID) {
+        return isInjected(playerUUID);
+    }
+
+    boolean isInjected(UUID playerUUID);
+
+    String getVersion();
+
+    void sendRawPacket(T player, ByteBuf packet);
+
+    void sendRawPacket(UUID uuid, ByteBuf packet);
+
+    BossBar createBossBar(String title, BossColor color, BossStyle style);
+
+    BossBar createBossBar(String title, float health, BossColor color, BossStyle style);
+
+    SortedSet<Integer> getSupportedVersions();
+
+    SortedSet<Integer> getFullSupportedVersions();
+}

api-legacy/src/main/java/us/myles/ViaVersion/api/boss/BossBar.java

@@ -0,0 +1,133 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package us.myles.ViaVersion.api.boss;
+
+import java.util.Set;
+import java.util.UUID;
+
+@Deprecated
+public class BossBar<T> {
+
+    private final com.viaversion.viaversion.api.legacy.bossbar.BossBar bossBar;
+
+    public BossBar(com.viaversion.viaversion.api.legacy.bossbar.BossBar bossBar) {
+        this.bossBar = bossBar;
+    }
+
+    public String getTitle() {
+        return bossBar.getTitle();
+    }
+
+    public BossBar setTitle(String title) {
+        bossBar.setTitle(title);
+        return this;
+    }
+
+    public float getHealth() {
+        return bossBar.getHealth();
+    }
+
+    public BossBar setHealth(float health) {
+        bossBar.setHealth(health);
+        return this;
+    }
+
+    public BossColor getColor() {
+        return BossColor.values()[bossBar.getColor().ordinal()];
+    }
+
+    public BossBar setColor(BossColor color) {
+        bossBar.setColor(com.viaversion.viaversion.api.legacy.bossbar.BossColor.values()[color.ordinal()]);
+        return this;
+    }
+
+    public BossStyle getStyle() {
+        return BossStyle.values()[bossBar.getStyle().ordinal()];
+    }
+
+    public BossBar setStyle(BossStyle style) {
+        bossBar.setStyle(com.viaversion.viaversion.api.legacy.bossbar.BossStyle.values()[style.ordinal()]);
+        return this;
+    }
+
+    @Deprecated
+    public BossBar addPlayer(T player) {
+        return this;
+    }
+
+    public BossBar addPlayer(UUID player) {
+        bossBar.addPlayer(player);
+        return this;
+    }
+
+    @Deprecated
+    public BossBar addPlayers(T... players) {
+        return this;
+    }
+
+    @Deprecated
+    public BossBar removePlayer(T player) {
+        return this;
+    }
+
+    public BossBar removePlayer(UUID uuid) {
+        bossBar.removePlayer(uuid);
+        return this;
+    }
+
+    public BossBar addFlag(BossFlag flag) {
+        bossBar.addFlag(com.viaversion.viaversion.api.legacy.bossbar.BossFlag.values()[flag.ordinal()]);
+        return this;
+    }
+
+    public BossBar removeFlag(BossFlag flag) {
+        bossBar.removeFlag(com.viaversion.viaversion.api.legacy.bossbar.BossFlag.values()[flag.ordinal()]);
+        return this;
+    }
+
+    public boolean hasFlag(BossFlag flag) {
+        return bossBar.hasFlag(com.viaversion.viaversion.api.legacy.bossbar.BossFlag.values()[flag.ordinal()]);
+    }
+
+    public Set<UUID> getPlayers() {
+        return bossBar.getPlayers();
+    }
+
+    public BossBar show() {
+        bossBar.show();
+        return this;
+    }
+
+    public BossBar hide() {
+        bossBar.hide();
+        return this;
+    }
+
+    public boolean isVisible() {
+        return bossBar.isVisible();
+    }
+
+    public UUID getId() {
+        return bossBar.getId();
+    }
+}

api-legacy/src/main/java/us/myles/ViaVersion/api/boss/BossColor.java

@@ -0,0 +1,45 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package us.myles.ViaVersion.api.boss;
+
+@Deprecated
+public enum BossColor {
+
+    PINK(0),
+    BLUE(1),
+    RED(2),
+    GREEN(3),
+    YELLOW(4),
+    PURPLE(5),
+    WHITE(6);
+
+    private final int id;
+
+    BossColor(int id) {
+        this.id = id;
+    }
+
+    public int getId() {
+        return id;
+    }
+}

api-legacy/src/main/java/us/myles/ViaVersion/api/boss/BossFlag.java

@@ -0,0 +1,40 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package us.myles.ViaVersion.api.boss;
+
+@Deprecated
+public enum BossFlag {
+
+    DARKEN_SKY(1),
+    PLAY_BOSS_MUSIC(2);
+
+    private final int id;
+
+    BossFlag(int id) {
+        this.id = id;
+    }
+
+    public int getId() {
+        return id;
+    }
+}

api-legacy/src/main/java/us/myles/ViaVersion/api/boss/BossStyle.java

@@ -0,0 +1,43 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package us.myles.ViaVersion.api.boss;
+
+@Deprecated
+public enum BossStyle {
+
+    SOLID(0),
+    SEGMENTED_6(1),
+    SEGMENTED_10(2),
+    SEGMENTED_12(3),
+    SEGMENTED_20(4);
+
+    private final int id;
+
+    BossStyle(int id) {
+        this.id = id;
+    }
+
+    public int getId() {
+        return id;
+    }
+}

api-legacy/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolRegistry.java

@@ -0,0 +1,33 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package us.myles.ViaVersion.api.protocol;
+
+/**
+ * @deprecated may be removed at some point, use {@link com.viaversion.viaversion.api.protocol.ProtocolManager}
+ */
+@Deprecated
+public class ProtocolRegistry {
+
+    @Deprecated
+    public static int SERVER_PROTOCOL = -1;
+}

api-legacy/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolVersion.java

@@ -0,0 +1,244 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package us.myles.ViaVersion.api.protocol;
+
+import com.google.common.base.Preconditions;
+import com.viaversion.viaversion.api.protocol.version.VersionRange;
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * @deprecated will no longer be updated and may be removed at some point, use {@link com.viaversion.viaversion.api.protocol.version.ProtocolVersion}
+ */
+@Deprecated
+public class ProtocolVersion {
+    private static final Int2ObjectMap<ProtocolVersion> versions = new Int2ObjectOpenHashMap<>();
+    private static final List<ProtocolVersion> versionList = new ArrayList<>();
+
+    public static final ProtocolVersion v1_4_6 = register(51, "1.4.6/7", new VersionRange("1.4", 6, 7));
+    public static final ProtocolVersion v1_5_1 = register(60, "1.5.1");
+    public static final ProtocolVersion v1_5_2 = register(61, "1.5.2");
+    public static final ProtocolVersion v_1_6_1 = register(73, "1.6.1");
+    public static final ProtocolVersion v_1_6_2 = register(74, "1.6.2");
+    public static final ProtocolVersion v_1_6_3 = register(77, "1.6.3");
+    public static final ProtocolVersion v_1_6_4 = register(78, "1.6.4");
+    public static final ProtocolVersion v1_7_1 = register(4, "1.7-1.7.5", new VersionRange("1.7", 0, 5));
+    public static final ProtocolVersion v1_7_6 = register(5, "1.7.6-1.7.10", new VersionRange("1.7", 6, 10));
+    public static final ProtocolVersion v1_8 = register(47, "1.8.x");
+    public static final ProtocolVersion v1_9 = register(107, "1.9");
+    public static final ProtocolVersion v1_9_1 = register(108, "1.9.1");
+    public static final ProtocolVersion v1_9_2 = register(109, "1.9.2");
+    public static final ProtocolVersion v1_9_3 = register(110, "1.9.3/4", new VersionRange("1.9", 3, 4));
+    public static final ProtocolVersion v1_10 = register(210, "1.10.x");
+    public static final ProtocolVersion v1_11 = register(315, "1.11");
+    public static final ProtocolVersion v1_11_1 = register(316, "1.11.1/2", new VersionRange("1.11", 1, 2));
+    public static final ProtocolVersion v1_12 = register(335, "1.12");
+    public static final ProtocolVersion v1_12_1 = register(338, "1.12.1");
+    public static final ProtocolVersion v1_12_2 = register(340, "1.12.2");
+    public static final ProtocolVersion v1_13 = register(393, "1.13");
+    public static final ProtocolVersion v1_13_1 = register(401, "1.13.1");
+    public static final ProtocolVersion v1_13_2 = register(404, "1.13.2");
+    public static final ProtocolVersion v1_14 = register(477, "1.14");
+    public static final ProtocolVersion v1_14_1 = register(480, "1.14.1");
+    public static final ProtocolVersion v1_14_2 = register(485, "1.14.2");
+    public static final ProtocolVersion v1_14_3 = register(490, "1.14.3");
+    public static final ProtocolVersion v1_14_4 = register(498, "1.14.4");
+    public static final ProtocolVersion v1_15 = register(573, "1.15");
+    public static final ProtocolVersion v1_15_1 = register(575, "1.15.1");
+    public static final ProtocolVersion v1_15_2 = register(578, "1.15.2");
+    public static final ProtocolVersion v1_16 = register(735, "1.16");
+    public static final ProtocolVersion v1_16_1 = register(736, "1.16.1");
+    public static final ProtocolVersion v1_16_2 = register(751, "1.16.2");
+    public static final ProtocolVersion v1_16_3 = register(753, "1.16.3");
+    public static final ProtocolVersion v1_16_4 = register(754, "1.16.4/5", new VersionRange("1.16", 4, 5));
+    public static final ProtocolVersion unknown = register(-1, "UNKNOWN");
+
+    public static ProtocolVersion register(int version, String name) {
+        return register(version, -1, name);
+    }
+
+    public static ProtocolVersion register(int version, int snapshotVersion, String name) {
+        return register(version, snapshotVersion, name, null);
+    }
+
+    public static ProtocolVersion register(int version, String name, @Nullable VersionRange versionRange) {
+        return register(version, -1, name, versionRange);
+    }
+
+    public static ProtocolVersion register(int version, int snapshotVersion, String name, @Nullable VersionRange versionRange) {
+        ProtocolVersion protocol = new ProtocolVersion(version, snapshotVersion, name, versionRange);
+        versionList.add(protocol);
+        versions.put(protocol.getVersion(), protocol);
+        if (protocol.isSnapshot()) {
+            versions.put(protocol.getFullSnapshotVersion(), protocol);
+        }
+        return protocol;
+    }
+
+    public static boolean isRegistered(int id) {
+        return versions.containsKey(id);
+    }
+
+    public static @NonNull ProtocolVersion getProtocol(int id) {
+        ProtocolVersion protocolVersion = versions.get(id);
+        if (protocolVersion != null) {
+            return protocolVersion;
+        } else {
+            return new ProtocolVersion(id, "Unknown (" + id + ")");
+        }
+    }
+
+    public static int getIndex(ProtocolVersion version) {
+        return versionList.indexOf(version);
+    }
+
+    public static List<ProtocolVersion> getProtocols() {
+        return Collections.unmodifiableList(new ArrayList<>(versions.values()));
+    }
+
+    public static @Nullable ProtocolVersion getClosest(String protocol) {
+        for (ProtocolVersion version : versions.values()) {
+            String name = version.getName();
+            if (name.equals(protocol)) {
+                return version;
+            }
+
+            if (version.isVersionWildcard()) {
+                // Test against the major version with and without a minor version
+                String majorVersion = name.substring(0, name.length() - 2);
+                if (majorVersion.equals(protocol) || (protocol.startsWith(name.substring(0, name.length() - 1)))) {
+                    return version;
+                }
+            } else if (version.isRange()) {
+                if (version.getIncludedVersions().contains(protocol)) {
+                    return version;
+                }
+            }
+        }
+        return null;
+    }
+
+    private final int version;
+    private final int snapshotVersion;
+    private final String name;
+    private final boolean versionWildcard;
+    private final Set<String> includedVersions;
+
+    public ProtocolVersion(int version, String name) {
+        this(version, -1, name, null);
+    }
+
+    public ProtocolVersion(int version, int snapshotVersion, String name, @Nullable VersionRange versionRange) {
+        this.version = version;
+        this.snapshotVersion = snapshotVersion;
+        this.name = name;
+        this.versionWildcard = name.endsWith(".x");
+
+        Preconditions.checkArgument(!versionWildcard || versionRange == null, "A version cannot be a wildcard and a range at the same time!");
+        if (versionRange != null) {
+            includedVersions = new LinkedHashSet<>();
+            for (int i = versionRange.getRangeFrom(); i <= versionRange.getRangeTo(); i++) {
+                if (i == 0) {
+                    includedVersions.add(versionRange.getBaseVersion()); // Keep both the base version and with ".0" appended
+                }
+
+                includedVersions.add(versionRange.getBaseVersion() + "." + i);
+            }
+        } else {
+            includedVersions = Collections.singleton(name);
+        }
+    }
+
+    public int getVersion() {
+        return version;
+    }
+
+    public int getSnapshotVersion() {
+        Preconditions.checkArgument(isSnapshot());
+        return snapshotVersion;
+    }
+
+    public int getFullSnapshotVersion() {
+        Preconditions.checkArgument(isSnapshot());
+        return (1 << 30) | snapshotVersion; // Bit indicating snapshot versions
+    }
+
+    public int getOriginalVersion() {
+        return snapshotVersion == -1 ? version : ((1 << 30) | snapshotVersion);
+    }
+
+    public boolean isKnown() {
+        return version != -1;
+    }
+
+    public boolean isRange() {
+        return includedVersions.size() != 1;
+    }
+
+    public Set<String> getIncludedVersions() {
+        return Collections.unmodifiableSet(includedVersions);
+    }
+
+    public boolean isVersionWildcard() {
+        return versionWildcard;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public boolean isSnapshot() {
+        return snapshotVersion != -1;
+    }
+
+    public int getId() {
+        return version;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        ProtocolVersion that = (ProtocolVersion) o;
+        return version == that.version;
+    }
+
+    @Override
+    public int hashCode() {
+        return version;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("%s (%d)", this.name, this.version);
+    }
+}

api/build.gradle.kts

@@ -0,0 +1,27 @@
+plugins {
+    id("net.kyori.blossom")
+    id("via.shadow-conventions")
+}
+
+blossom {
+    replaceToken("\$VERSION", project.version)
+    replaceToken("\$IMPL_VERSION", "git-ViaVersion-${project.version}:${rootProject.latestCommitHash()}")
+}
+
+dependencies {
+    api(projects.adventure) {
+        targetConfiguration = "shadow"
+    }
+    api(libs.fastutil)
+    api(libs.openNBT)
+    api(libs.gson)
+
+    compileOnlyApi(libs.snakeYaml)
+    compileOnlyApi(libs.netty)
+    compileOnlyApi(libs.guava)
+    compileOnlyApi(libs.checkerQual)
+}
+
+java {
+    withJavadocJar()
+}

api/src/main/java/com/viaversion/viaversion/api/Via.java

@@ -0,0 +1,81 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api;
+
+import com.google.common.base.Preconditions;
+import com.viaversion.viaversion.api.configuration.ViaVersionConfig;
+import com.viaversion.viaversion.api.platform.ViaPlatform;
+
+public final class Via {
+    private static ViaManager manager;
+
+    /**
+     * Returns the API associated with the current platform.
+     *
+     * @return API instance
+     * @throws IllegalArgumentException if the platform has not loaded yet
+     */
+    public static ViaAPI getAPI() {
+        return manager().getPlatform().getApi();
+    }
+
+    /**
+     * Returns the ViaManager with methods beyond the simple API {@link ViaAPI} provides.
+     *
+     * @return manager to interact with various Via parts
+     * @throws IllegalArgumentException if the platform has not loaded yet
+     */
+    public static ViaManager getManager() {
+        return manager();
+    }
+
+    /**
+     * Returns the config associated with the current platform.
+     *
+     * @return config instance
+     * @throws IllegalArgumentException if the platform has not loaded yet
+     */
+    public static ViaVersionConfig getConfig() {
+        return manager().getPlatform().getConf();
+    }
+
+    public static ViaPlatform getPlatform() {
+        return manager().getPlatform();
+    }
+
+    /**
+     * Register the ViaManager associated with the platform.
+     *
+     * @param viaManager The ViaManager
+     * @throws IllegalArgumentException if the manager has already been set
+     */
+    public static void init(ViaManager viaManager) {
+        Preconditions.checkArgument(manager == null, "ViaManager is already set");
+        Via.manager = viaManager;
+    }
+
+    private static ViaManager manager() {
+        Preconditions.checkArgument(manager != null, "ViaVersion has not loaded the platform yet");
+        return manager;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/ViaAPI.java

@@ -0,0 +1,148 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api;
+
+import com.viaversion.viaversion.api.connection.ConnectionManager;
+import com.viaversion.viaversion.api.connection.UserConnection;
+import com.viaversion.viaversion.api.legacy.LegacyViaAPI;
+import com.viaversion.viaversion.api.platform.ViaPlatform;
+import com.viaversion.viaversion.api.protocol.ProtocolManager;
+import com.viaversion.viaversion.api.protocol.version.ServerProtocolVersion;
+import io.netty.buffer.ByteBuf;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.SortedSet;
+import java.util.UUID;
+
+/**
+ * General api point. For more specialized api methods, see {@link Via#getManager()}.
+ *
+ * @param <T> player type for the specific platform
+ * @see ViaManager
+ * @see ProtocolManager
+ * @see ConnectionManager
+ * @see ViaPlatform
+ */
+public interface ViaAPI<T> {
+
+    /**
+     * Returns the API version incremented with meaningful API changes.
+     * This includes breaking changes to existing API and larger additions.
+     *
+     * @return API version incremented with meaningful API changes
+     */
+    default int apiVersion() {
+        return 3;
+    }
+
+    /**
+     * Returns the server's protocol version info.
+     *
+     * @return the server's protocol version info
+     */
+    ServerProtocolVersion getServerVersion();
+
+    /**
+     * Returns the protocol version of a player.
+     * This will also retrieve the version from ProtocolSupport if it's being used.
+     *
+     * @param player the platform's player object, e.g. Bukkit this is Player
+     * @return protocol version, for example (47=1.8-1.8.8, 107=1.9, 108=1.9.1), or -1 if no longer connected
+     */
+    int getPlayerVersion(T player);
+
+    /**
+     * Returns the protocol version of a player.
+     *
+     * @param uuid UUID of a player
+     * @return protocol version, for example (47=1.8-1.8.8, 107=1.9, 108=1.9.1), or -1 if not connected
+     */
+    int getPlayerVersion(UUID uuid);
+
+    /**
+     * Returns whether Via injected into this player connection.
+     *
+     * @param uuid uuid of the player
+     * @return whether Via has a cached a UserConnection for this player
+     */
+    boolean isInjected(UUID uuid);
+
+    /**
+     * Returns the Via injected UserConnection if present.
+     *
+     * @param uuid uuid of the player
+     * @return user connection if present
+     */
+    @Nullable UserConnection getConnection(UUID uuid);
+
+    /**
+     * Returns the version of the plugin.
+     *
+     * @return plugin version
+     */
+    String getVersion();
+
+    /**
+     * Sends a raw packet to the player.
+     *
+     * @param player the platform's player object, e.g. for Bukkit this is Player
+     * @param packet the packet; you need a VarInt Id, then the packet contents
+     * @throws IllegalArgumentException if the player is not injected by Via
+     */
+    void sendRawPacket(T player, ByteBuf packet);
+
+    /**
+     * Sends a raw packet to the player.
+     *
+     * @param uuid   the uuid from the player to send packet
+     * @param packet the packet; you need a VarInt Id, then the packet contents
+     * @throws IllegalArgumentException if the player is not injected by Via
+     */
+    void sendRawPacket(UUID uuid, ByteBuf packet);
+
+    /**
+     * Returns the supported protocol versions.
+     * This method removes any blocked protocol versions.
+     *
+     * @return a list of protocol versions
+     * @see #getFullSupportedVersions() for a full list
+     */
+    SortedSet<Integer> getSupportedVersions();
+
+    /**
+     * Returns the supported protocol versions, including blocked protocols.
+     *
+     * @return a list of protocol versions
+     */
+    SortedSet<Integer> getFullSupportedVersions();
+
+    /**
+     * Returns legacy api only applicable on/to legacy versions.
+     * <p>
+     * These methods are safe to use and are unlikely to be removed,
+     * but it is important to be aware of their limited use.
+     *
+     * @return legacy api only applicable on/to legacy versions
+     */
+    LegacyViaAPI<T> legacyAPI();
+}

api/src/main/java/com/viaversion/viaversion/api/ViaManager.java

@@ -0,0 +1,114 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api;
+
+import com.viaversion.viaversion.api.command.ViaVersionCommand;
+import com.viaversion.viaversion.api.connection.ConnectionManager;
+import com.viaversion.viaversion.api.platform.ViaInjector;
+import com.viaversion.viaversion.api.platform.ViaPlatform;
+import com.viaversion.viaversion.api.platform.ViaPlatformLoader;
+import com.viaversion.viaversion.api.platform.providers.ViaProviders;
+import com.viaversion.viaversion.api.protocol.ProtocolManager;
+
+import java.util.Set;
+
+public interface ViaManager {
+
+    /**
+     * Returns the protocol manager for registering/getting protocols and their mapping data loading.
+     *
+     * @return protocol manager
+     */
+    ProtocolManager getProtocolManager();
+
+    /**
+     * Returns platform for handling platform specific configuration, tasks, and plugin data.
+     *
+     * @return platform
+     */
+    ViaPlatform<?> getPlatform();
+
+    /**
+     * Returns the userconnection manager for handling clients connected to the server.
+     *
+     * @return userconnection manager
+     */
+    ConnectionManager getConnectionManager();
+
+    /**
+     * Returns the manager for Via providers.
+     *
+     * @return provider manager
+     */
+    ViaProviders getProviders();
+
+    /**
+     * Returns the injector for injecting netty handlers and initially getting the server protocol version.
+     *
+     * @return injector
+     */
+    ViaInjector getInjector();
+
+    /**
+     * Returns the command handler for managing ViaVersion subcommands.
+     *
+     * @return command handler
+     */
+    ViaVersionCommand getCommandHandler();
+
+    /**
+     * Returns the platform loader responsible for registering listeners, providers and such.
+     *
+     * @return platform loader
+     */
+    ViaPlatformLoader getLoader();
+
+    /**
+     * If debug is enabled, packets and other otherwise suppressed warnings will be logged.
+     *
+     * @return true if enabled
+     */
+    boolean isDebug();
+
+    /**
+     * Sets the debug mode. If enabled, packets and other otherwise suppressed warnings will be logged.
+     *
+     * @param debug whether debug should be enabled
+     */
+    void setDebug(boolean debug);
+
+    /**
+     * Returns a mutable set of self-added subplatform version strings.
+     * This set is expanded by the subplatform itself (e.g. ViaBackwards), and may not contain all running ones.
+     *
+     * @return mutable set of subplatform versions
+     */
+    Set<String> getSubPlatforms();
+
+    /**
+     * Adds a runnable to be executed when ViaVersion has finished its init before the full server load.
+     *
+     * @param runnable runnable to be executed
+     */
+    void addEnableListener(Runnable runnable);
+}

api/src/main/java/com/viaversion/viaversion/api/command/ViaCommandSender.java

@@ -0,0 +1,56 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.command;
+
+import java.util.UUID;
+
+public interface ViaCommandSender {
+    /**
+     * Check if the sender has a permission.
+     *
+     * @param permission Permission string eg. viaversion.admin
+     * @return True if the sender has the permission
+     */
+    boolean hasPermission(String permission);
+
+    /**
+     * Send a message to the sender
+     *
+     * @param msg The message to send
+     */
+    void sendMessage(String msg);
+
+    /**
+     * Get the senders UUID.
+     *
+     * @return The senders UUID
+     */
+    UUID getUUID();
+
+    /**
+     * Get the senders name.
+     *
+     * @return The senders name
+     */
+    String getName();
+}

api/src/main/java/com/viaversion/viaversion/api/command/ViaSubCommand.java

@@ -0,0 +1,105 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.command;
+
+import com.viaversion.viaversion.util.ChatColorUtil;
+
+import java.util.Collections;
+import java.util.List;
+
+public abstract class ViaSubCommand {
+
+    /**
+     * Subcommand name
+     *
+     * @return The commands name
+     */
+    public abstract String name();
+
+    /**
+     * subcommand description, this'll show in /viaversion list
+     *
+     * @return The commands description
+     */
+    public abstract String description();
+
+    /**
+     * Usage example:
+     * "playerversion [name]"
+     *
+     * @return The commands usage
+     */
+    public String usage() {
+        return name();
+    }
+
+    /**
+     * Permission, null for everyone
+     *
+     * @return The permission required to use the commands
+     */
+    public String permission() {
+        return "viaversion.admin";
+    }
+
+    /**
+     * Gets triggered on execution
+     *
+     * @param sender Command sender
+     * @param args   Arguments
+     * @return commands executed succesfully if false, show usage
+     */
+    public abstract boolean execute(ViaCommandSender sender, String[] args);
+
+    /**
+     * Yay, possibility to implement tab-completion
+     *
+     * @param sender Command sender
+     * @param args   args
+     * @return tab complete possibilities
+     */
+    public List<String> onTabComplete(ViaCommandSender sender, String[] args) {
+        return Collections.emptyList();
+    }
+
+    /**
+     * Replaces color codes in a string.
+     *
+     * @param s string to replace
+     * @return output String
+     */
+    public static String color(String s) {
+        return ChatColorUtil.translateAlternateColorCodes(s);
+    }
+
+    /**
+     * Send a color coded string with replacements to a user.
+     *
+     * @param sender  target to send the message to
+     * @param message message
+     * @param args    objects to replace
+     */
+    public static void sendMessage(ViaCommandSender sender, String message, Object... args) {
+        sender.sendMessage(color(args == null ? message : String.format(message, args)));
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/command/ViaVersionCommand.java

@@ -0,0 +1,73 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.command;
+
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.List;
+
+public interface ViaVersionCommand {
+    /**
+     * Register your own subcommand inside ViaVersion
+     *
+     * @param command Your own SubCommand instance to handle it.
+     * @throws Exception throws an exception when the subcommand already exists or if it's not valid, example: spacee
+     */
+    void registerSubCommand(ViaSubCommand command) throws Exception;
+
+    /**
+     * Check if a subcommand is registered.
+     *
+     * @param name Subcommand name
+     * @return true if it exists
+     */
+    boolean hasSubCommand(String name);
+
+    /**
+     * Get subcommand instance by name
+     *
+     * @param name subcommand name
+     * @return ViaSubCommand instance
+     */
+    @Nullable ViaSubCommand getSubCommand(String name);
+
+    /**
+     * Executed when the Command sender executes the commands
+     *
+     * @param sender Sender object
+     * @param args   arguments provided
+     * @return was successful
+     */
+    boolean onCommand(ViaCommandSender sender, String[] args);
+
+    /**
+     * Executed when the Command sender tab-completes
+     *
+     * @param sender Sender object
+     * @param args   arguments provided
+     * @return was successful
+     */
+    List<String> onTabComplete(ViaCommandSender sender, String[] args);
+
+    void showHelp(ViaCommandSender sender);
+}

api/src/main/java/com/viaversion/viaversion/api/configuration/ConfigurationProvider.java

@@ -0,0 +1,53 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.configuration;
+
+import java.util.Map;
+
+public interface ConfigurationProvider {
+
+    /**
+     * Sets the specified path to the given value.
+     *
+     * @param path  Path of the object to set.
+     * @param value New value to set the path to
+     */
+    void set(String path, Object value);
+
+    /**
+     * Saves the config
+     */
+    void saveConfig();
+
+    /**
+     * Reloads the config
+     */
+    void reloadConfig();
+
+    /**
+     * Get all the configuration values
+     *
+     * @return Map with key-values
+     */
+    Map<String, Object> getValues();
+}

api/src/main/java/com/viaversion/viaversion/api/configuration/ViaVersionConfig.java

@@ -0,0 +1,417 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.configuration;
+
+import it.unimi.dsi.fastutil.ints.IntSet;
+
+public interface ViaVersionConfig {
+
+    /**
+     * Get if the plugin should check for updates
+     *
+     * @return true if update checking is enabled
+     */
+    boolean isCheckForUpdates();
+
+    /**
+     * Sets whether to check for updates. This updates the internally cached value
+     * as well as the config, but does not save the config to disk.
+     *
+     * @param checkForUpdates true to check for updates on server start and joins
+     */
+    void setCheckForUpdates(boolean checkForUpdates);
+
+    /**
+     * Get if collision preventing for players is enabled
+     *
+     * @return true if collision preventing is enabled
+     */
+    boolean isPreventCollision();
+
+    /**
+     * Get if 1.9 & 1.10 clients are shown the new effect indicator in the top-right corner
+     *
+     * @return true if the using of the new effect indicator is enabled
+     */
+    boolean isNewEffectIndicator();
+
+    /**
+     * Get if 1.9 & 1.10 clients are shown the new death message on the death screen
+     *
+     * @return true if enabled
+     */
+    boolean isShowNewDeathMessages();
+
+    /**
+     * Get if metadata errors will be suppressed
+     *
+     * @return true if metadata errors suppression is enabled
+     */
+    boolean isSuppressMetadataErrors();
+
+    /**
+     * Get if blocking in 1.9 & 1.10 appears as a player holding a shield
+     *
+     * @return true if shield blocking is enabled
+     */
+    boolean isShieldBlocking();
+
+    /**
+     * Whether the player can block with the shield without a delay.
+     * <p>
+     * This option requires {@link #isShowShieldWhenSwordInHand()} to be disabled
+     *
+     * @return {@code true} if non delayed shield blocking is enabled.
+     */
+    boolean isNoDelayShieldBlocking();
+
+    /**
+     * Puts the shield into the second hand when holding a sword.
+     * The shield will disappear when switching to another item.
+     * <p>
+     * This option requires {@link #isShieldBlocking()} to be enabled
+     *
+     * @return {@code true} if the shield should appear when holding a sword
+     */
+    boolean isShowShieldWhenSwordInHand();
+
+    /**
+     * Get if armor stand positions are fixed so holograms show up at the correct height in 1.9 &amp; 1.10
+     *
+     * @return true if hologram patching is enabled
+     */
+    boolean isHologramPatch();
+
+    /**
+     * Get if the 1.11 piston animation patch is enabled
+     *
+     * @return true if the piston patch is enabled.
+     */
+    boolean isPistonAnimationPatch();
+
+    /**
+     * Get if boss bars are fixed for 1.9 &amp; 1.10 clients
+     *
+     * @return true if boss bar patching is enabled
+     */
+    boolean isBossbarPatch();
+
+    /**
+     * Get if the boss bars for 1.9 &amp; 1.10 clients are being stopped from flickering
+     * This will keep all boss bars on 100% (not recommended)
+     *
+     * @return true if boss bar anti flickering is enabled
+     */
+    boolean isBossbarAntiflicker();
+
+    /**
+     * Get the vertical offset armor stands are being moved with when the hologram patch is enabled
+     *
+     * @return the vertical offset holograms will be moved with
+     */
+    double getHologramYOffset();
+
+    /**
+     * Get if players will be automatically put in the same team when collision preventing is enabled
+     *
+     * @return true if automatic teaming is enabled
+     */
+    boolean isAutoTeam();
+
+    /**
+     * Get the maximum number of packets a client can send per second.
+     *
+     * @return The number of packets a client can send per second.
+     */
+    int getMaxPPS();
+
+    /**
+     * Get the kick message sent if the user hits the max packets per second.
+     *
+     * @return Kick message, with colour codes using '&amp;amp;'
+     */
+    String getMaxPPSKickMessage();
+
+    /**
+     * The time in seconds that should be tracked for warnings
+     *
+     * @return Time in seconds that should be tracked for warnings
+     */
+    int getTrackingPeriod();
+
+    /**
+     * The number of packets per second to count as a warning
+     *
+     * @return The number of packets per second to count as a warning.
+     */
+    int getWarningPPS();
+
+    /**
+     * Get the maximum number of warnings the client can have in the interval
+     *
+     * @return The number of packets a client can send per second.
+     */
+    int getMaxWarnings();
+
+    /**
+     * Get the kick message sent if the user goes over the warnings in the interval
+     *
+     * @return Kick message, with colour codes using '&amp;amp;'
+     */
+    String getMaxWarningsKickMessage();
+
+    /**
+     * Is anti-xray enabled?
+     *
+     * @return A boolean
+     */
+    boolean isAntiXRay();
+
+    /**
+     * Send supported versions in the status response packet
+     *
+     * @return If true, enabled
+     */
+    boolean isSendSupportedVersions();
+
+    /**
+     * Stimulate the player tick
+     *
+     * @return if true, enabled
+     */
+    boolean isSimulatePlayerTick();
+
+    /**
+     * Use the item cache to prevent high resource usage
+     *
+     * @return if true, enabled
+     */
+    boolean isItemCache();
+
+    /**
+     * Use the NMS player ticking
+     *
+     * @return if true, enabled
+     */
+    boolean isNMSPlayerTicking();
+
+    /**
+     * Replace extended pistons on 1.10 chunk loading.
+     *
+     * @return true if to replace them
+     */
+    boolean isReplacePistons();
+
+    /**
+     * Get the id for replacing extended pistons.
+     *
+     * @return The integer id
+     */
+    int getPistonReplacementId();
+
+    /**
+     * Force json transform
+     *
+     * @return true if enabled
+     */
+    boolean isForceJsonTransform();
+
+    /**
+     * Should we fix nbt array's in json chat messages for 1.12 clients
+     *
+     * @return true if enabled
+     */
+    boolean is1_12NBTArrayFix();
+
+    /**
+     * Should we make team colours based on the last colour in team prefix
+     *
+     * @return true if enabled
+     */
+    boolean is1_13TeamColourFix();
+
+    /**
+     * Should we fix shift quick move action for 1.12 clients
+     *
+     * @return true if enabled
+     */
+    boolean is1_12QuickMoveActionFix();
+
+    /**
+     * Get the blocked protocols
+     *
+     * @return An Integer list
+     */
+    IntSet getBlockedProtocols();
+
+    /**
+     * Get the custom disconnect message
+     *
+     * @return Disconnect message
+     */
+    String getBlockedDisconnectMsg();
+
+    /**
+     * Get the message sent to players being kicked on reload.
+     * Players are kicked to stop the server crashing
+     *
+     * @return Disconnect message
+     */
+    String getReloadDisconnectMsg();
+
+    /**
+     * Should we hide errors that occur when trying to convert block and item data over versions?
+     *
+     * @return true if enabled
+     */
+    boolean isSuppressConversionWarnings();
+
+    /**
+     * Should we disable the 1.13 auto-complete feature to stop spam kicks? (for any server lower than 1.13)
+     *
+     * @return true if enabled
+     */
+    boolean isDisable1_13AutoComplete();
+
+    /**
+     * Tries to minimize cooldown animation.
+     *
+     * @return true if enabled
+     */
+    boolean isMinimizeCooldown();
+
+    /**
+     * Enable the serverside blockconnections for 1.13+ clients
+     *
+     * @return true if enabled
+     */
+    boolean isServersideBlockConnections();
+
+    /**
+     * Get the type of block-connection provider which should be used
+     *
+     * @return String world for world-level or packet for packet-level
+     */
+    String getBlockConnectionMethod();
+
+    /**
+     * When activated, only the most important blocks are saved in the BlockStorage.
+     *
+     * @return true if enabled
+     */
+    boolean isReduceBlockStorageMemory();
+
+    /**
+     * When activated with serverside-blockconnections, flower parts with blocks above will be sent as stems.
+     * Useful for lobbyservers where users can't build and those stems are used decoratively.
+     *
+     * @return true if enabled
+     */
+    boolean isStemWhenBlockAbove();
+
+    /**
+     * Vines not connected to any blocks will be mapped to air for 1.13+ clients to prevent them from climbing up.
+     *
+     * @return true if enabled
+     */
+    boolean isVineClimbFix();
+
+    /**
+     * When activated, the 1-layer snow will be sent as 2-layer snow to 1.13+ clients to have collision.
+     *
+     * @return true if enabled
+     */
+    boolean isSnowCollisionFix();
+
+    /**
+     * When activated, infested blocks will be mapped to their normal stone variants for 1.13+ clients.
+     *
+     * @return true if enabled
+     */
+    boolean isInfestedBlocksFix();
+
+    /**
+     * When greater than 0, enables tab complete request delaying by x ticks
+     *
+     * @return the delay in ticks
+     */
+    int get1_13TabCompleteDelay();
+
+    /**
+     * When activated, edited books with more than 50 pages will be shortened to 50.
+     *
+     * @return true if enabled
+     */
+    boolean isTruncate1_14Books();
+
+    /**
+     * Handles left handed info by using unused bit 7 on Client Settings packet
+     *
+     * @return true if enabled
+     */
+    boolean isLeftHandedHandling();
+
+    /**
+     * Fixes velocity bugs due to different hitbox for 1.9-1.13 clients on 1.8 servers.
+     *
+     * @return true if enabled
+     */
+    boolean is1_9HitboxFix();
+
+    /**
+     * Fixes velocity bugs due to different hitbox for 1.14+ clients on sub 1.14 servers.
+     *
+     * @return true if enabled
+     */
+    boolean is1_14HitboxFix();
+
+    /**
+     * Fixes non full blocks having 0 light for 1.14+ clients on sub 1.14 servers.
+     *
+     * @return true if enabled
+     */
+    boolean isNonFullBlockLightFix();
+
+    boolean is1_14HealthNaNFix();
+
+    /**
+     * Should 1.15 clients respawn instantly / without showing the death screen.
+     *
+     * @return true if enabled
+     */
+    boolean is1_15InstantRespawn();
+
+    /**
+     * Ignores incoming plugin channel messages of 1.16+ clients with channel names longer than 32 charatcers.
+     *
+     * @return true if enabled
+     */
+    boolean isIgnoreLong1_16ChannelNames();
+
+    /**
+     * Force 1.17+ client to accept the server resource pack.
+     *
+     * @return true if enabled
+     */
+    boolean isForcedUse1_17ResourcePack();
+}

api/src/main/java/com/viaversion/viaversion/api/connection/ConnectionManager.java

@@ -0,0 +1,104 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.connection;
+
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.Map;
+import java.util.Set;
+import java.util.UUID;
+
+/**
+ * Handles injected UserConnections
+ */
+public interface ConnectionManager {
+
+    /**
+     * Returns if Via injected into this player connection.
+     *
+     * @param playerId player uuid
+     * @return true if the player is handled by Via
+     */
+    boolean isClientConnected(UUID playerId);
+
+    /**
+     * Frontend connections will have the UUID stored. Override this if your platform isn't always frontend.
+     * UUIDs can't be duplicate between frontend connections.
+     *
+     * @return true if the user is a frontend connection
+     */
+    default boolean isFrontEnd(UserConnection connection) {
+        return !connection.isClientSide();
+    }
+
+    /**
+     * Returns the frontend UserConnection from the player connected to this proxy server
+     * Returns null when there isn't a server or connection was not found
+     * When ViaVersion is reloaded, this method may not return some players.
+     * May not return ProtocolSupport players.
+     * <p>
+     * Note that connections are removed as soon as their channel is closed,
+     * so avoid using this method during player quits for example.
+     *
+     * @return frontend UserConnection of the player connected to this proxy server
+     */
+    @Nullable UserConnection getConnectedClient(UUID clientIdentifier);
+
+    /**
+     * Returns the UUID from the frontend connection to this proxy server
+     * Returns null when there isn't a server or this connection isn't frontend or it doesn't have an id
+     * When ViaVersion is reloaded, this method may not return some players.
+     * May not return ProtocolSupport players.
+     * <p>
+     * Note that connections are removed as soon as their channel is closed,
+     * so avoid using this method during player quits for example.
+     *
+     * @return UUID of the frontend connection to this proxy server
+     */
+    @Nullable UUID getConnectedClientId(UserConnection connection);
+
+    /**
+     * Returns all UserConnections which are registered
+     * May contain duplicated UUIDs on multiple ProtocolInfo.
+     * May contain frontend, backend and/or client-sided connections.
+     * When ViaVersion is reloaded, this method may not return some players.
+     * May not contain ProtocolSupport players.
+     *
+     * @return connected UserConnections
+     */
+    Set<UserConnection> getConnections();
+
+    /**
+     * Returns a map containing the UUIDs and frontend UserConnections from players connected to this proxy server
+     * Returns empty list when there isn't a server
+     * When ViaVersion is reloaded, this method may not return some players.
+     * May not contain ProtocolSupport players.
+     *
+     * @return map containing the UUIDs and frontend UserConnections from players connected to this proxy server
+     */
+    Map<UUID, UserConnection> getConnectedClients();
+
+    void onLoginSuccess(UserConnection connection);
+
+    void onDisconnect(UserConnection connection);
+}

api/src/main/java/com/viaversion/viaversion/api/connection/ProtocolInfo.java

@@ -0,0 +1,97 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.connection;
+
+import com.viaversion.viaversion.api.protocol.ProtocolPipeline;
+import com.viaversion.viaversion.api.protocol.packet.State;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.UUID;
+
+public interface ProtocolInfo {
+
+    /**
+     * Returns the protocol state the user is currently in.
+     *
+     * @return protocol state
+     */
+    State getState();
+
+    void setState(State state);
+
+    /**
+     * Returns the user's protocol version, or -1 if not set.
+     * This is set during the {@link State#HANDSHAKE} state.
+     *
+     * @return protocol version, or -1 if not set
+     */
+    int getProtocolVersion();
+
+    void setProtocolVersion(int protocolVersion);
+
+    /**
+     * Returns the server protocol version the user is connected to, or -1 if not set.
+     * This is set during the {@link State#HANDSHAKE} state.
+     *
+     * @return server protocol version, or -1 if not set
+     */
+    int getServerProtocolVersion();
+
+    void setServerProtocolVersion(int serverProtocolVersion);
+
+    /**
+     * Returns the username associated with this connection.
+     * This is set once the connection enters the {@link State#PLAY} state.
+     *
+     * @return username, set when entering the {@link State#PLAY} state
+     */
+    @Nullable String getUsername();
+
+    void setUsername(String username);
+
+    /**
+     * Returns the uuid associated with this connection.
+     * This is set once the connection enters the {@link State#PLAY} state.
+     *
+     * @return uuid, set when entering the {@link State#PLAY} state
+     */
+    @Nullable UUID getUuid();
+
+    void setUuid(UUID uuid);
+
+    /**
+     * Returns the user's pipeline.
+     *
+     * @return protocol pipeline
+     */
+    ProtocolPipeline getPipeline();
+
+    void setPipeline(ProtocolPipeline pipeline);
+
+    /**
+     * Returns the user connection this info represents.
+     *
+     * @return user connection
+     */
+    UserConnection getUser();
+}

api/src/main/java/com/viaversion/viaversion/api/connection/StorableObject.java

@@ -0,0 +1,32 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.connection;
+
+/**
+ * Dummy interface used to explicitly identify objects storable in user connections.
+ *
+ * @see UserConnection#get(Class)
+ * @see UserConnection#put(StorableObject)
+ */
+public interface StorableObject {
+}

api/src/main/java/com/viaversion/viaversion/api/connection/StoredObject.java

@@ -0,0 +1,35 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.connection;
+
+public abstract class StoredObject implements StorableObject {
+    private final UserConnection user;
+
+    protected StoredObject(UserConnection user) {
+        this.user = user;
+    }
+
+    public UserConnection getUser() {
+        return user;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/connection/UserConnection.java

@@ -0,0 +1,307 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.connection;
+
+import com.viaversion.viaversion.api.configuration.ViaVersionConfig;
+import com.viaversion.viaversion.api.data.entity.EntityTracker;
+import com.viaversion.viaversion.api.protocol.Protocol;
+import com.viaversion.viaversion.api.protocol.packet.PacketTracker;
+import com.viaversion.viaversion.api.protocol.packet.PacketWrapper;
+import com.viaversion.viaversion.exception.CancelException;
+import com.viaversion.viaversion.exception.InformativeException;
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelFuture;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.Collection;
+import java.util.Map;
+import java.util.UUID;
+import java.util.function.Function;
+
+public interface UserConnection {
+
+    /**
+     * Get an object from the storage.
+     *
+     * @param objectClass The class of the object to get
+     * @param <T>         The type of the class you want to get.
+     * @return The requested object
+     */
+    @Nullable <T extends StorableObject> T get(Class<T> objectClass);
+
+    /**
+     * Check if the storage has an object.
+     *
+     * @param objectClass The object class to check
+     * @return True if the object is in the storage
+     */
+    boolean has(Class<? extends StorableObject> objectClass);
+
+    /**
+     * Put an object into the stored objects based on class.
+     *
+     * @param object The object to store.
+     */
+    void put(StorableObject object);
+
+    /**
+     * Returns a collection of entity trackers currently registered.
+     *
+     * @return collection of entity trackers currently registered
+     */
+    Collection<EntityTracker> getEntityTrackers();
+
+    /**
+     * Returns the entity tracker by the given protocol class if present.
+     *
+     * @param protocolClass protocol class
+     * @param <T>           entity tracker type
+     * @return entity tracker if present
+     */
+    @Nullable <T extends EntityTracker> T getEntityTracker(Class<? extends Protocol> protocolClass);
+
+    /**
+     * Adds an entity tracker to the user connection.
+     *
+     * @param protocolClass protocol class
+     * @param tracker       entity tracker
+     */
+    void addEntityTracker(Class<? extends Protocol> protocolClass, EntityTracker tracker);
+
+    /**
+     * Clear all the stored objects.
+     * Used for bungee when switching servers.
+     */
+    void clearStoredObjects();
+
+    /**
+     * Sends a raw packet to the connection on the current thread.
+     *
+     * @param packet raw packet to send
+     */
+    void sendRawPacket(ByteBuf packet);
+
+    /**
+     * Send a raw packet to the player, submitted to the netty event loop.
+     *
+     * @param packet raw packet to send
+     */
+    void scheduleSendRawPacket(ByteBuf packet);
+
+    /**
+     * Send a raw packet to the player with returning the future.
+     *
+     * @param packet The raw packet to send
+     * @return ChannelFuture of the packet being sent
+     */
+    ChannelFuture sendRawPacketFuture(ByteBuf packet);
+
+    /**
+     * Returns the user's packet tracker used for the inbuilt packet-limiter.
+     *
+     * @return packet tracker
+     */
+    PacketTracker getPacketTracker();
+
+    /**
+     * Disconnect a connection.
+     *
+     * @param reason The reason to use, not used if player is not active.
+     */
+    void disconnect(String reason);
+
+    /**
+     * Sends a raw packet to the server on the current thread.
+     *
+     * @param packet raw packet to be sent
+     */
+    void sendRawPacketToServer(ByteBuf packet);
+
+    /**
+     * Sends a raw packet to the server, submitted to the netty event loop.
+     *
+     * @param packet raw packet to be sent
+     */
+    void scheduleSendRawPacketToServer(ByteBuf packet);
+
+    /**
+     * Monitors serverbound packets and returns whether a packet can/should be processed.
+     *
+     * @return false if this packet should be cancelled
+     */
+    boolean checkServerboundPacket();
+
+    /**
+     * Monitors clientbound packets and returns whether a packet can/should be processed.
+     *
+     * @return false if this packet should be cancelled
+     */
+    boolean checkClientboundPacket();
+
+    /**
+     * @see #checkClientboundPacket()
+     * @see #checkServerboundPacket()
+     */
+    default boolean checkIncomingPacket() {
+        return isClientSide() ? checkClientboundPacket() : checkServerboundPacket();
+    }
+
+    /**
+     * @see #checkClientboundPacket()
+     * @see #checkServerboundPacket()
+     */
+    default boolean checkOutgoingPacket() {
+        return isClientSide() ? checkServerboundPacket() : checkClientboundPacket();
+    }
+
+    /**
+     * Checks if packets needs transforming.
+     *
+     * @return whether packets should be passed through
+     */
+    boolean shouldTransformPacket();
+
+    /**
+     * Transforms the clientbound packet contained in ByteBuf.
+     *
+     * @param buf            ByteBuf with packet id and packet contents
+     * @param cancelSupplier function called with original CancelException for generating the Exception when the packet is cancelled
+     * @throws CancelException      if the packet should be cancelled
+     * @throws InformativeException if packet transforming failed
+     * @throws Exception            if any other processing outside of transforming fails
+     */
+    void transformClientbound(ByteBuf buf, Function<Throwable, Exception> cancelSupplier) throws Exception;
+
+    /**
+     * Transforms the serverbound packet contained in ByteBuf.
+     *
+     * @param buf            ByteBuf with packet id and packet contents
+     * @param cancelSupplier Function called with original CancelException for generating the Exception used when
+     *                       packet is cancelled
+     * @throws CancelException      if the packet should be cancelled
+     * @throws InformativeException if packet transforming failed
+     * @throws Exception            if any other processing outside of transforming fails
+     */
+    void transformServerbound(ByteBuf buf, Function<Throwable, Exception> cancelSupplier) throws Exception;
+
+    /**
+     * Transforms the packet depending on whether the connection is clientside or not.
+     *
+     * @see #transformClientbound(ByteBuf, Function)
+     * @see #transformServerbound(ByteBuf, Function)
+     */
+    default void transformOutgoing(ByteBuf buf, Function<Throwable, Exception> cancelSupplier) throws Exception {
+        if (isClientSide()) {
+            transformServerbound(buf, cancelSupplier);
+        } else {
+            transformClientbound(buf, cancelSupplier);
+        }
+    }
+
+    /**
+     * Transforms the packet depending on whether the connection is clientside or not.
+     *
+     * @see #transformClientbound(ByteBuf, Function)
+     * @see #transformServerbound(ByteBuf, Function)
+     */
+    default void transformIncoming(ByteBuf buf, Function<Throwable, Exception> cancelSupplier) throws Exception {
+        if (isClientSide()) {
+            transformClientbound(buf, cancelSupplier);
+        } else {
+            transformServerbound(buf, cancelSupplier);
+        }
+    }
+
+    /**
+     * Returns the internal id incremented for each new connection.
+     *
+     * @return internal id
+     */
+    long getId();
+
+    /**
+     * Returns the netty channel if present.
+     *
+     * @return netty channel if present
+     */
+    @Nullable Channel getChannel();
+
+    /**
+     * Returns info containing the current protocol state and userdata.
+     *
+     * @return info containing the current protocol state and userdata
+     */
+    ProtocolInfo getProtocolInfo();
+
+    /**
+     * Returns a map of stored objects.
+     *
+     * @return map of stored objects
+     * @see #has(Class)
+     * @see #get(Class)
+     * @see #put(StorableObject)
+     */
+    Map<Class<?>, StorableObject> getStoredObjects();
+
+    /**
+     * Returns whether the connection has protocols other than the base protocol applied.
+     *
+     * @return whether the connection is active
+     */
+    boolean isActive();
+
+    void setActive(boolean active);
+
+    /**
+     * Returns whether the connection is pending a disconnect, initiated through {@link #disconnect(String)}.
+     *
+     * @return whether the connection is pending a disconnect
+     */
+    boolean isPendingDisconnect();
+
+    void setPendingDisconnect(boolean pendingDisconnect);
+
+    /**
+     * Returns whether this is a client-side connection.
+     * This is a mod integrated into the client itself, or for example a backend Velocity connection.
+     *
+     * @return whether this is a client-side connection
+     */
+    boolean isClientSide();
+
+    /**
+     * Returns whether {@link ViaVersionConfig#getBlockedProtocols()} should be checked for this connection.
+     *
+     * @return whether blocked protocols should be applied
+     */
+    boolean shouldApplyBlockProtocol();
+
+    /**
+     * Returns a newly generated uuid that will let a packet be passed through without
+     * transformig its contents if used together with {@link PacketWrapper#PASSTHROUGH_ID}.
+     *
+     * @return generated passthrough token
+     */
+    UUID generatePassthroughToken();
+}

api/src/main/java/com/viaversion/viaversion/api/data/IntArrayMappings.java

@@ -0,0 +1,122 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.data;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonObject;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.Arrays;
+
+public class IntArrayMappings implements Mappings {
+    protected final int[] oldToNew;
+
+    public IntArrayMappings(int[] oldToNew) {
+        this.oldToNew = oldToNew;
+    }
+
+    /**
+     * Maps old identifiers to the new ones.
+     * If an old value cannot be found in the new mappings, the diffmapping will be checked for the given entry.
+     *
+     * @param size        set size of the underlying short array
+     * @param oldMapping  mappings to map from
+     * @param newMapping  mappings to map to
+     * @param diffMapping extra mappings that will be used/scanned when an entry cannot be found
+     */
+    public IntArrayMappings(int size, JsonObject oldMapping, JsonObject newMapping, @Nullable JsonObject diffMapping) {
+        oldToNew = new int[size];
+        Arrays.fill(oldToNew, -1);
+        MappingDataLoader.mapIdentifiers(oldToNew, oldMapping, newMapping, diffMapping);
+    }
+
+    public IntArrayMappings(JsonObject oldMapping, JsonObject newMapping, @Nullable JsonObject diffMapping) {
+        this(oldMapping.entrySet().size(), oldMapping, newMapping, diffMapping);
+    }
+
+    /**
+     * Maps old identifiers to the new ones.
+     *
+     * @param size       set size of the underlying short array
+     * @param oldMapping mappings to map from
+     * @param newMapping mappings to map to
+     */
+    public IntArrayMappings(int size, JsonObject oldMapping, JsonObject newMapping) {
+        oldToNew = new int[size];
+        Arrays.fill(oldToNew, -1);
+        MappingDataLoader.mapIdentifiers(oldToNew, oldMapping, newMapping);
+    }
+
+    public IntArrayMappings(JsonObject oldMapping, JsonObject newMapping) {
+        this(oldMapping.entrySet().size(), oldMapping, newMapping);
+    }
+
+    /**
+     * Maps old identifiers to the new ones.
+     *
+     * @param size          set size of the underlying short array
+     * @param oldMapping    mappings to map from
+     * @param newMapping    mappings to map to
+     * @param diffMapping   extra mappings that will be used/scanned when an entry cannot be found
+     * @param warnOnMissing should "No key for x" be printed if there is no matching identifier
+     */
+    public IntArrayMappings(int size, JsonArray oldMapping, JsonArray newMapping, JsonObject diffMapping, boolean warnOnMissing) {
+        oldToNew = new int[size];
+        Arrays.fill(oldToNew, -1);
+        MappingDataLoader.mapIdentifiers(oldToNew, oldMapping, newMapping, diffMapping, warnOnMissing);
+    }
+
+    public IntArrayMappings(int size, JsonArray oldMapping, JsonArray newMapping, boolean warnOnMissing) {
+        this(size, oldMapping, newMapping, null, warnOnMissing);
+    }
+
+    public IntArrayMappings(JsonArray oldMapping, JsonArray newMapping, boolean warnOnMissing) {
+        this(oldMapping.size(), oldMapping, newMapping, warnOnMissing);
+    }
+
+    public IntArrayMappings(int size, JsonArray oldMapping, JsonArray newMapping) {
+        this(size, oldMapping, newMapping, true);
+    }
+
+    public IntArrayMappings(JsonArray oldMapping, JsonArray newMapping, JsonObject diffMapping) {
+        this(oldMapping.size(), oldMapping, newMapping, diffMapping, true);
+    }
+
+    public IntArrayMappings(JsonArray oldMapping, JsonArray newMapping) {
+        this(oldMapping.size(), oldMapping, newMapping, true);
+    }
+
+    @Override
+    public int getNewId(int id) {
+        return id >= 0 && id < oldToNew.length ? oldToNew[id] : -1;
+    }
+
+    @Override
+    public void setNewId(int id, int newId) {
+        oldToNew[id] = newId;
+    }
+
+    public int[] getOldToNew() {
+        return oldToNew;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/data/MappingData.java

@@ -0,0 +1,103 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.data;
+
+import com.viaversion.viaversion.api.minecraft.RegistryType;
+import com.viaversion.viaversion.api.minecraft.TagData;
+import com.viaversion.viaversion.util.Int2IntBiMap;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.List;
+
+public interface MappingData {
+
+    /**
+     * Loads the mapping data.
+     */
+    void load();
+
+    /**
+     * Returns the mapped block state id, or -1 if unmapped.
+     *
+     * @param id unmapped block state id
+     * @return mapped block state id, or -1 if unmapped
+     * @throws NullPointerException if this mappingdata does not hold block state mappings
+     */
+    int getNewBlockStateId(int id);
+
+    /**
+     * Returns the mapped block id, or -1 if unmapped.
+     *
+     * @param id unmapped block id
+     * @return mapped block id, or -1 if unmapped
+     * @throws NullPointerException if this mappingdata does not hold block mappings
+     */
+    int getNewBlockId(int id);
+
+    /**
+     * Returns the mapped item id, or -1 if unmapped.
+     *
+     * @param id unmapped item id
+     * @return mapped item id, or -1 if unmapped
+     * @throws NullPointerException if this mappingdata does not hold item mappings
+     */
+    int getNewItemId(int id);
+
+    /**
+     * Returns the backwards mapped item id, or -1 if unmapped.
+     *
+     * @param id mapped item id
+     * @return backwards mapped item id, or -1 if unmapped
+     * @throws NullPointerException if this mappingdata does not hold item mappings
+     */
+    int getOldItemId(int id);
+
+    /**
+     * Returns the mapped particle id, or -1 if unmapped.
+     *
+     * @param id unmapped particle id
+     * @return mapped particle id, or -1 if unmapped
+     * @throws NullPointerException if this mappingdata does not hold particle mappings
+     */
+    int getNewParticleId(int id);
+
+    /**
+     * Returns a list of tags to send if present.
+     *
+     * @param type registry tag type
+     * @return list of tags to send if present, else null
+     */
+    @Nullable List<TagData> getTags(RegistryType type);
+
+    @Nullable Int2IntBiMap getItemMappings();
+
+    @Nullable ParticleMappings getParticleMappings();
+
+    @Nullable Mappings getBlockMappings();
+
+    @Nullable Mappings getBlockStateMappings();
+
+    @Nullable Mappings getSoundMappings();
+
+    @Nullable Mappings getStatisticsMappings();
+}

api/src/main/java/com/viaversion/viaversion/api/data/MappingDataBase.java

@@ -0,0 +1,234 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.data;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.viaversion.viaversion.api.Via;
+import com.viaversion.viaversion.api.minecraft.RegistryType;
+import com.viaversion.viaversion.api.minecraft.TagData;
+import com.viaversion.viaversion.util.Int2IntBiHashMap;
+import com.viaversion.viaversion.util.Int2IntBiMap;
+import it.unimi.dsi.fastutil.objects.Object2IntMap;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.ArrayList;
+import java.util.EnumMap;
+import java.util.List;
+import java.util.Map;
+import java.util.logging.Logger;
+
+public class MappingDataBase implements MappingData {
+    protected final String oldVersion;
+    protected final String newVersion;
+    protected final boolean hasDiffFile;
+    protected Int2IntBiMap itemMappings;
+    protected ParticleMappings particleMappings;
+    protected Mappings blockMappings;
+    protected Mappings blockStateMappings;
+    protected Mappings soundMappings;
+    protected Mappings statisticsMappings;
+    protected Map<RegistryType, List<TagData>> tags;
+    protected boolean loadItems = true;
+
+    public MappingDataBase(String oldVersion, String newVersion) {
+        this(oldVersion, newVersion, false);
+    }
+
+    public MappingDataBase(String oldVersion, String newVersion, boolean hasDiffFile) {
+        this.oldVersion = oldVersion;
+        this.newVersion = newVersion;
+        this.hasDiffFile = hasDiffFile;
+    }
+
+    @Override
+    public void load() {
+        getLogger().info("Loading " + oldVersion + " -> " + newVersion + " mappings...");
+        JsonObject diffmapping = hasDiffFile ? loadDiffFile() : null;
+        JsonObject oldMappings = MappingDataLoader.loadData("mapping-" + oldVersion + ".json", true);
+        JsonObject newMappings = MappingDataLoader.loadData("mapping-" + newVersion + ".json", true);
+
+        blockMappings = loadFromObject(oldMappings, newMappings, diffmapping, "blocks");
+        blockStateMappings = loadFromObject(oldMappings, newMappings, diffmapping, "blockstates");
+        soundMappings = loadFromArray(oldMappings, newMappings, diffmapping, "sounds");
+        statisticsMappings = loadFromArray(oldMappings, newMappings, diffmapping, "statistics");
+
+        Mappings particles = loadFromArray(oldMappings, newMappings, diffmapping, "particles");
+        if (particles != null) {
+            particleMappings = new ParticleMappings(oldMappings.getAsJsonArray("particles"), particles);
+        }
+
+        if (loadItems && newMappings.has("items")) {
+            itemMappings = new Int2IntBiHashMap();
+            itemMappings.defaultReturnValue(-1);
+            MappingDataLoader.mapIdentifiers(itemMappings, oldMappings.getAsJsonObject("items"), newMappings.getAsJsonObject("items"),
+                    diffmapping != null ? diffmapping.getAsJsonObject("items") : null);
+        }
+
+        if (diffmapping != null && diffmapping.has("tags")) {
+            this.tags = new EnumMap<>(RegistryType.class);
+            JsonObject tags = diffmapping.getAsJsonObject("tags");
+            if (tags.has(RegistryType.ITEM.getResourceLocation())) {
+                loadTags(RegistryType.ITEM, tags, MappingDataLoader.indexedObjectToMap(newMappings.getAsJsonObject("items")));
+            }
+            if (tags.has(RegistryType.BLOCK.getResourceLocation())) {
+                loadTags(RegistryType.BLOCK, tags, MappingDataLoader.indexedObjectToMap(newMappings.getAsJsonObject("blocks")));
+            }
+        }
+
+        loadExtras(oldMappings, newMappings, diffmapping);
+    }
+
+    private void loadTags(RegistryType type, JsonObject object, Object2IntMap<String> typeMapping) {
+        JsonObject tags = object.getAsJsonObject(type.getResourceLocation());
+        List<TagData> tagsList = new ArrayList<>(tags.size());
+        for (Map.Entry<String, JsonElement> entry : tags.entrySet()) {
+            JsonArray array = entry.getValue().getAsJsonArray();
+            int[] entries = new int[array.size()];
+            int i = 0;
+            for (JsonElement element : array) {
+                String stringId = element.getAsString();
+                if (!typeMapping.containsKey(stringId) && !typeMapping.containsKey(stringId = stringId.replace("minecraft:", ""))) { // aaa
+                    getLogger().warning(type + " Tags contains invalid type identifier " + stringId + " in tag " + entry.getKey());
+                    continue;
+                }
+
+                entries[i++] = typeMapping.getInt(stringId);
+            }
+            tagsList.add(new TagData(entry.getKey(), entries));
+        }
+
+        this.tags.put(type, tagsList);
+    }
+
+    @Override
+    public int getNewBlockStateId(int id) {
+        return checkValidity(id, blockStateMappings.getNewId(id), "blockstate");
+    }
+
+    @Override
+    public int getNewBlockId(int id) {
+        return checkValidity(id, blockMappings.getNewId(id), "block");
+    }
+
+    @Override
+    public int getNewItemId(int id) {
+        return checkValidity(id, itemMappings.get(id), "item");
+    }
+
+    @Override
+    public int getOldItemId(int id) {
+        int oldId = itemMappings.inverse().get(id);
+        // Remap new items to stone
+        return oldId != -1 ? oldId : 1;
+    }
+
+    @Override
+    public int getNewParticleId(int id) {
+        return checkValidity(id, particleMappings.getMappings().getNewId(id), "particles");
+    }
+
+    @Override
+    public @Nullable List<TagData> getTags(RegistryType type) {
+        return tags != null ? tags.get(type) : null;
+    }
+
+    @Override
+    public @Nullable Int2IntBiMap getItemMappings() {
+        return itemMappings;
+    }
+
+    @Override
+    public @Nullable ParticleMappings getParticleMappings() {
+        return particleMappings;
+    }
+
+    @Override
+    public @Nullable Mappings getBlockMappings() {
+        return blockMappings;
+    }
+
+    @Override
+    public @Nullable Mappings getBlockStateMappings() {
+        return blockStateMappings;
+    }
+
+    @Override
+    public @Nullable Mappings getSoundMappings() {
+        return soundMappings;
+    }
+
+    @Override
+    public @Nullable Mappings getStatisticsMappings() {
+        return statisticsMappings;
+    }
+
+    protected @Nullable Mappings loadFromArray(JsonObject oldMappings, JsonObject newMappings, @Nullable JsonObject diffMappings, String key) {
+        if (!oldMappings.has(key) || !newMappings.has(key)) return null;
+
+        JsonObject diff = diffMappings != null ? diffMappings.getAsJsonObject(key) : null;
+        return new IntArrayMappings(oldMappings.getAsJsonArray(key), newMappings.getAsJsonArray(key), diff);
+    }
+
+    protected @Nullable Mappings loadFromObject(JsonObject oldMappings, JsonObject newMappings, @Nullable JsonObject diffMappings, String key) {
+        if (!oldMappings.has(key) || !newMappings.has(key)) return null;
+
+        JsonObject diff = diffMappings != null ? diffMappings.getAsJsonObject(key) : null;
+        return new IntArrayMappings(oldMappings.getAsJsonObject(key), newMappings.getAsJsonObject(key), diff);
+    }
+
+    protected @Nullable JsonObject loadDiffFile() {
+        return MappingDataLoader.loadData("mappingdiff-" + oldVersion + "to" + newVersion + ".json");
+    }
+
+    protected Logger getLogger() {
+        return Via.getPlatform().getLogger();
+    }
+
+    /**
+     * Returns the given mapped id if valid, else 0 with a warning logged to the console.
+     *
+     * @param id       unmapped id
+     * @param mappedId mapped id
+     * @param type     mapping type (e.g. "item")
+     * @return the given mapped id if valid, else 0
+     */
+    protected int checkValidity(int id, int mappedId, String type) {
+        if (mappedId == -1) {
+            getLogger().warning(String.format("Missing %s %s for %s %s %d", newVersion, type, oldVersion, type, id));
+            return 0;
+        }
+        return mappedId;
+    }
+
+    /**
+     * To be overridden.
+     *
+     * @param oldMappings  old mappings
+     * @param newMappings  new mappings
+     * @param diffMappings diff mappings if present
+     */
+    protected void loadExtras(JsonObject oldMappings, JsonObject newMappings, @Nullable JsonObject diffMappings) {
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/data/MappingDataLoader.java

@@ -0,0 +1,246 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.data;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonIOException;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonSyntaxException;
+import com.viaversion.viaversion.api.Via;
+import com.viaversion.viaversion.util.GsonUtil;
+import com.viaversion.viaversion.util.Int2IntBiMap;
+import it.unimi.dsi.fastutil.objects.Object2IntMap;
+import it.unimi.dsi.fastutil.objects.Object2IntOpenHashMap;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.io.File;
+import java.io.FileReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+public class MappingDataLoader {
+
+    private static final Map<String, JsonObject> MAPPINGS_CACHE = new ConcurrentHashMap<>();
+    private static boolean cacheJsonMappings;
+
+    /**
+     * Returns true if a selected number of mappings should be cached.
+     * If enabled, cleanup should be done after the cache is no longer needed.
+     *
+     * @return true if mappings should be cached
+     */
+    public static boolean isCacheJsonMappings() {
+        return cacheJsonMappings;
+    }
+
+    public static void enableMappingsCache() {
+        cacheJsonMappings = true;
+    }
+
+    /**
+     * Returns the cached mappings. Cleared after ViaVersion has been fully loaded.
+     *
+     * @return cached mapping file json objects
+     * @see #isCacheJsonMappings()
+     */
+    public static Map<String, JsonObject> getMappingsCache() {
+        return MAPPINGS_CACHE;
+    }
+
+    /**
+     * Loads the file from the plugin folder if present, else from the bundled resources.
+     *
+     * @return loaded json object, or null if not found or invalid
+     */
+    public static @Nullable JsonObject loadFromDataDir(String name) {
+        File file = new File(Via.getPlatform().getDataFolder(), name);
+        if (!file.exists()) return loadData(name);
+
+        // Load the file from the platform's directory if present
+        try (FileReader reader = new FileReader(file)) {
+            return GsonUtil.getGson().fromJson(reader, JsonObject.class);
+        } catch (JsonSyntaxException e) {
+            // Users might mess up the format, so let's catch the syntax error
+            Via.getPlatform().getLogger().warning(name + " is badly formatted!");
+            e.printStackTrace();
+        } catch (IOException | JsonIOException e) {
+            e.printStackTrace();
+        }
+        return null;
+    }
+
+    /**
+     * Loads the file from the bundled resources. Uses the cache if enabled.
+     *
+     * @return loaded json object from bundled resources if present
+     */
+    public static @Nullable JsonObject loadData(String name) {
+        return loadData(name, false);
+    }
+
+    /**
+     * Loads the file from the bundled resources. Uses the cache if enabled.
+     *
+     * @param cacheIfEnabled whether loaded files should be cached
+     * @return loaded json object from bundled resources if present
+     */
+    public static @Nullable JsonObject loadData(String name, boolean cacheIfEnabled) {
+        if (cacheJsonMappings) {
+            JsonObject cached = MAPPINGS_CACHE.get(name);
+            if (cached != null) {
+                return cached;
+            }
+        }
+
+        InputStream stream = getResource(name);
+        if (stream == null) return null;
+
+        InputStreamReader reader = new InputStreamReader(stream);
+        try {
+            JsonObject object = GsonUtil.getGson().fromJson(reader, JsonObject.class);
+            if (cacheIfEnabled && cacheJsonMappings) {
+                MAPPINGS_CACHE.put(name, object);
+            }
+            return object;
+        } finally {
+            try {
+                reader.close();
+            } catch (IOException ignored) {
+                // Ignored
+            }
+        }
+    }
+
+    public static void mapIdentifiers(Int2IntBiMap output, JsonObject oldIdentifiers, JsonObject newIdentifiers, @Nullable JsonObject diffIdentifiers) {
+        Object2IntMap<String> newIdentifierMap = MappingDataLoader.indexedObjectToMap(newIdentifiers);
+        for (Map.Entry<String, JsonElement> entry : oldIdentifiers.entrySet()) {
+            int value = mapIdentifierEntry(entry, newIdentifierMap, diffIdentifiers);
+            if (value != -1) {
+                output.put(Integer.parseInt(entry.getKey()), value);
+            }
+        }
+    }
+
+    public static void mapIdentifiers(int[] output, JsonObject oldIdentifiers, JsonObject newIdentifiers) {
+        MappingDataLoader.mapIdentifiers(output, oldIdentifiers, newIdentifiers, null);
+    }
+
+    public static void mapIdentifiers(int[] output, JsonObject oldIdentifiers, JsonObject newIdentifiers, @Nullable JsonObject diffIdentifiers) {
+        Object2IntMap<String> newIdentifierMap = MappingDataLoader.indexedObjectToMap(newIdentifiers);
+        for (Map.Entry<String, JsonElement> entry : oldIdentifiers.entrySet()) {
+            int value = mapIdentifierEntry(entry, newIdentifierMap, diffIdentifiers);
+            if (value != -1) {
+                output[Integer.parseInt(entry.getKey())] = value;
+            }
+        }
+    }
+
+    private static int mapIdentifierEntry(Map.Entry<String, JsonElement> entry, Object2IntMap newIdentifierMap, @Nullable JsonObject diffIdentifiers) {
+        int value = newIdentifierMap.getInt(entry.getValue().getAsString());
+        if (value == -1) {
+            // Search in diff mappings
+            if (diffIdentifiers != null) {
+                JsonElement diffElement = diffIdentifiers.get(entry.getKey());
+                if (diffElement != null) {
+                    value = newIdentifierMap.getInt(diffElement.getAsString());
+                }
+            }
+            if (value == -1) {
+                if (!Via.getConfig().isSuppressConversionWarnings() || Via.getManager().isDebug()) {
+                    Via.getPlatform().getLogger().warning("No key for " + entry.getValue() + " :( ");
+                }
+                return -1;
+            }
+        }
+        return value;
+    }
+
+    public static void mapIdentifiers(int[] output, JsonArray oldIdentifiers, JsonArray newIdentifiers, boolean warnOnMissing) {
+        mapIdentifiers(output, oldIdentifiers, newIdentifiers, null, warnOnMissing);
+    }
+
+    public static void mapIdentifiers(int[] output, JsonArray oldIdentifiers, JsonArray newIdentifiers, @Nullable JsonObject diffIdentifiers, boolean warnOnMissing) {
+        Object2IntMap<String> newIdentifierMap = MappingDataLoader.arrayToMap(newIdentifiers);
+        for (int i = 0; i < oldIdentifiers.size(); i++) {
+            JsonElement oldIdentifier = oldIdentifiers.get(i);
+            int mappedId = newIdentifierMap.getInt(oldIdentifier.getAsString());
+            if (mappedId == -1) {
+                // Search in diff mappings
+                if (diffIdentifiers != null) {
+                    JsonElement diffElement = diffIdentifiers.get(oldIdentifier.getAsString());
+                    if (diffElement != null) {
+                        String mappedName = diffElement.getAsString();
+                        if (mappedName.isEmpty()) continue; // "empty" remaps
+
+                        mappedId = newIdentifierMap.getInt(mappedName);
+                    }
+                }
+                if (mappedId == -1) {
+                    if (warnOnMissing && !Via.getConfig().isSuppressConversionWarnings() || Via.getManager().isDebug()) {
+                        Via.getPlatform().getLogger().warning("No key for " + oldIdentifier + " :( ");
+                    }
+                    continue;
+                }
+            }
+            output[i] = mappedId;
+        }
+    }
+
+    /**
+     * Returns a map of the object entries hashed by their id value.
+     *
+     * @param object json object
+     * @return map with indexes hashed by their id value
+     */
+    public static Object2IntMap<String> indexedObjectToMap(JsonObject object) {
+        Object2IntMap<String> map = new Object2IntOpenHashMap<>(object.size(), 1F);
+        map.defaultReturnValue(-1);
+        for (Map.Entry<String, JsonElement> entry : object.entrySet()) {
+            map.put(entry.getValue().getAsString(), Integer.parseInt(entry.getKey()));
+        }
+        return map;
+    }
+
+    /**
+     * Returns a map of the array entries hashed by their id value.
+     *
+     * @param array json array
+     * @return map with indexes hashed by their id value
+     */
+    public static Object2IntMap<String> arrayToMap(JsonArray array) {
+        Object2IntMap<String> map = new Object2IntOpenHashMap<>(array.size(), 1F);
+        map.defaultReturnValue(-1);
+        for (int i = 0; i < array.size(); i++) {
+            map.put(array.get(i).getAsString(), i);
+        }
+        return map;
+    }
+
+    public static @Nullable InputStream getResource(String name) {
+        return MappingDataLoader.class.getClassLoader().getResourceAsStream("assets/viaversion/data/" + name);
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/data/Mappings.java

@@ -0,0 +1,43 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.data;
+
+public interface Mappings {
+
+    /**
+     * Returns the mapped id from the given id, or -1 if invalid/out of bounds.
+     *
+     * @param id unmapped id
+     * @return mapped id, or -1 if invalid/out of bounds
+     */
+    int getNewId(int id);
+
+    /**
+     * Manually maps a specific id.
+     *
+     * @param id    unmapped id
+     * @param newId mapped id
+     * @throws IndexOutOfBoundsException if the unmapped id is invalid
+     */
+    void setNewId(int id, int newId);
+}

api/src/main/java/com/viaversion/viaversion/api/data/ParticleMappings.java

@@ -0,0 +1,58 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.data;
+
+import com.google.gson.JsonArray;
+import it.unimi.dsi.fastutil.objects.Object2IntMap;
+
+public class ParticleMappings {
+    private final Mappings mappings;
+    private final int blockId;
+    private final int fallingDustId;
+    private final int itemId;
+
+    public ParticleMappings(JsonArray oldMappings, Mappings mappings) {
+        this.mappings = mappings;
+
+        Object2IntMap<String> map = MappingDataLoader.arrayToMap(oldMappings);
+        blockId = map.getInt("block");
+        fallingDustId = map.getInt("falling_dust");
+        itemId = map.getInt("item");
+    }
+
+    public Mappings getMappings() {
+        return mappings;
+    }
+
+    public int getBlockId() {
+        return blockId;
+    }
+
+    public int getFallingDustId() {
+        return fallingDustId;
+    }
+
+    public int getItemId() {
+        return itemId;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/data/entity/ClientEntityIdChangeListener.java

@@ -0,0 +1,28 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.data.entity;
+
+public interface ClientEntityIdChangeListener {
+
+    void setClientEntityId(int entityId);
+}

api/src/main/java/com/viaversion/viaversion/api/data/entity/EntityTracker.java

@@ -0,0 +1,129 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.data.entity;
+
+import com.viaversion.viaversion.api.connection.UserConnection;
+import com.viaversion.viaversion.api.minecraft.entities.EntityType;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public interface EntityTracker {
+
+    /**
+     * User connection the tracker belongs to.
+     *
+     * @return user connection
+     */
+    UserConnection user();
+
+    /**
+     * Tracks an entity.
+     *
+     * @param id   entity id
+     * @param type entity type
+     */
+    void addEntity(int id, EntityType type);
+
+    /**
+     * Returns whether the entity is currently tracked.
+     *
+     * @param id entity id
+     * @return whether the entity is tracked
+     */
+    boolean hasEntity(int id);
+
+    /**
+     * Entity type of the entity if tracked.
+     * This returning null does not necessarily mean no entity by the id exists.
+     *
+     * @param id entity id
+     * @return entity type of the entity if tracked
+     */
+    @Nullable EntityType entityType(int id);
+
+    /**
+     * Untracks an entity.
+     *
+     * @param id entity id
+     */
+    void removeEntity(int id);
+
+    /**
+     * Returns the stored entity data if an entity with the id is tracked, else null.
+     * If no data has been initialized yet, it will be done and returned by this method.
+     *
+     * @param id entity id
+     * @return stored entity data if an entity with the id is tracked, else null
+     */
+    @Nullable StoredEntityData entityData(int id);
+
+    /**
+     * Returns stored entity data if it has previously been initialized by {@link #entityData(int)}, else null.
+     *
+     * @param id entity id
+     * @return stored entity data if it has previously been initialized by {@link #entityData(int)}
+     */
+    @Nullable StoredEntityData entityDataIfPresent(int id);
+
+    /**
+     * Returns the client entity id or -1 if unset.
+     *
+     * @return client entity id or -1 if unset
+     */
+    int clientEntityId();
+
+    /**
+     * Sets the client entity id.
+     *
+     * @param clientEntityId client entity id
+     */
+    void setClientEntityId(int clientEntityId);
+
+    /**
+     * Returns the current world section height.
+     * Always 16 for sub 1.17 worlds.
+     *
+     * @return current world section height
+     */
+    int currentWorldSectionHeight();
+
+    /**
+     * Sets the current world section height.
+     *
+     * @param currentWorldSectionHeight world section height
+     */
+    void setCurrentWorldSectionHeight(int currentWorldSectionHeight);
+
+    /**
+     * Returns the minimum y of the current player world.
+     *
+     * @return minimum y of the current world
+     */
+    int currentMinY();
+
+    /**
+     * Sets the minimum y of the current player world.
+     *
+     * @param currentMinY minimum y of the current world
+     */
+    void setCurrentMinY(int currentMinY);
+}

api/src/main/java/com/viaversion/viaversion/api/data/entity/StoredEntityData.java

@@ -0,0 +1,60 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.data.entity;
+
+import com.viaversion.viaversion.api.minecraft.entities.EntityType;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public interface StoredEntityData {
+
+    /**
+     * Returns the entity type of the stored entity.
+     *
+     * @return entity type
+     */
+    EntityType type();
+
+    /**
+     * Checks if the storage contains an object of the given type.
+     *
+     * @param objectClass object class to check
+     * @return whether an object of the given type is in the storage
+     */
+    boolean has(Class<?> objectClass);
+
+    /**
+     * Returns an object from the storage if present.
+     *
+     * @param objectClass class of the object to get
+     * @param <T>         object type
+     * @return object if present
+     */
+    @Nullable <T> T get(Class<T> objectClass);
+
+    /**
+     * Stores an object based on its class.
+     *
+     * @param object object to store
+     */
+    void put(Object object);
+}

api/src/main/java/com/viaversion/viaversion/api/legacy/LegacyViaAPI.java

@@ -0,0 +1,58 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.legacy;
+
+import com.viaversion.viaversion.api.legacy.bossbar.BossBar;
+import com.viaversion.viaversion.api.legacy.bossbar.BossColor;
+import com.viaversion.viaversion.api.legacy.bossbar.BossStyle;
+
+/**
+ * API only applicable on or to legacy versions of Minecraft.
+ *
+ * @param <T> player type
+ */
+public interface LegacyViaAPI<T> {
+
+    /**
+     * Creates a new bossbar instance. This only works on pre 1.9 servers for 1.9+ clients.
+     *
+     * @param title  title
+     * @param health health, between 0 and 1 (inclusive)
+     * @param color  color
+     * @param style  style
+     * @return new bossbar instance
+     */
+    BossBar createLegacyBossBar(String title, float health, BossColor color, BossStyle style);
+
+    /**
+     * Creates a new bossbar instance with full health. This only works on pre 1.9 servers for 1.9+ clients.
+     *
+     * @param title title
+     * @param color color
+     * @param style style
+     * @return new bossbar instance
+     */
+    default BossBar createLegacyBossBar(String title, BossColor color, BossStyle style) {
+        return createLegacyBossBar(title, 1F, color, style);
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/legacy/bossbar/BossBar.java

@@ -0,0 +1,187 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.legacy.bossbar;
+
+import com.viaversion.viaversion.api.connection.UserConnection;
+
+import java.util.Set;
+import java.util.UUID;
+
+public interface BossBar {
+
+    /**
+     * Get the current title
+     *
+     * @return the title
+     */
+    String getTitle();
+
+    /**
+     * Change the title
+     *
+     * @param title Title can be in either JSON or just text
+     * @return The BossBar object
+     */
+    BossBar setTitle(String title);
+
+    /**
+     * Get the health
+     *
+     * @return float between 0F - 1F
+     */
+    float getHealth();
+
+    /**
+     * Change the health
+     *
+     * @param health this float has to be between 0F - 1F
+     * @return The BossBar object
+     */
+    BossBar setHealth(float health);
+
+    /**
+     * Get the bossbar color
+     *
+     * @return The colour
+     */
+    BossColor getColor();
+
+    /**
+     * Yay colors!
+     *
+     * @param color Whatever color you want!
+     * @return The BossBar object
+     */
+    BossBar setColor(BossColor color);
+
+    /**
+     * Get the bosbar style
+     *
+     * @return BossStyle
+     */
+    BossStyle getStyle();
+
+    /**
+     * Change the bosbar style
+     *
+     * @param style BossStyle
+     * @return The BossBar object
+     */
+    BossBar setStyle(BossStyle style);
+
+    /**
+     * Show the bossbar to a player (uuid). This only works for frontend connections. Use #addConnection(UserConnection) for other types.
+     *
+     * @param player uuid of the player
+     * @return The BossBar object
+     */
+    BossBar addPlayer(UUID player);
+
+    /**
+     * Show the bossbar to a player connection.
+     *
+     * @param conn UserConnection of the connection
+     * @return The BossBar object
+     */
+    BossBar addConnection(UserConnection conn);
+
+    /**
+     * Removes the bossbar from a player. This only works for frontend connections. For others types, use #removeConnection(UserConnection)
+     *
+     * @param uuid The players UUID
+     * @return The BossBar object
+     */
+    BossBar removePlayer(UUID uuid);
+
+    /**
+     * Removes the bossbar from a player connection.
+     *
+     * @param conn The UserConnection
+     * @return The BossBar object
+     */
+    BossBar removeConnection(UserConnection conn);
+
+    /**
+     * Add flags
+     *
+     * @param flag The flag to add
+     * @return The BossBar object
+     */
+    BossBar addFlag(BossFlag flag);
+
+    /**
+     * Remove flags.
+     *
+     * @param flag The flag to remove
+     * @return The BossBar object
+     */
+    BossBar removeFlag(BossFlag flag);
+
+    /**
+     * @param flag The flag to check against
+     * @return True if it has the flag
+     */
+    boolean hasFlag(BossFlag flag);
+
+    /**
+     * Get players. Only returns UUIDs which are front-end. For all connections, use #getConnections()
+     *
+     * @return UUIDS from players (sorry I lied)
+     */
+    Set<UUID> getPlayers();
+
+    /**
+     * Get UserConnections.
+     *
+     * @return UserConnection from players
+     */
+    Set<UserConnection> getConnections();
+
+    /**
+     * Show the bossbar to everyone (In the getPlayer set)
+     *
+     * @return The BossBar object
+     */
+    BossBar show();
+
+    /**
+     * Hide the bossbar from everyone (In the getPlayer set)
+     *
+     * @return The BossBar object
+     */
+    BossBar hide();
+
+    /**
+     * Is it visible?
+     *
+     * @return visibility changable with show() and hide()
+     */
+    boolean isVisible();
+
+    /**
+     * Get the UUID of this bossbar
+     *
+     * @return Unique Id for this bossbar
+     */
+    UUID getId();
+}

api/src/main/java/com/viaversion/viaversion/api/legacy/bossbar/BossColor.java

@@ -0,0 +1,44 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.legacy.bossbar;
+
+public enum BossColor {
+
+    PINK(0),
+    BLUE(1),
+    RED(2),
+    GREEN(3),
+    YELLOW(4),
+    PURPLE(5),
+    WHITE(6);
+
+    private final int id;
+
+    BossColor(int id) {
+        this.id = id;
+    }
+
+    public int getId() {
+        return id;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/legacy/bossbar/BossFlag.java

@@ -0,0 +1,39 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.legacy.bossbar;
+
+public enum BossFlag {
+
+    DARKEN_SKY(1),
+    PLAY_BOSS_MUSIC(2);
+
+    private final int id;
+
+    BossFlag(int id) {
+        this.id = id;
+    }
+
+    public int getId() {
+        return id;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/legacy/bossbar/BossStyle.java

@@ -0,0 +1,42 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.legacy.bossbar;
+
+public enum BossStyle {
+
+    SOLID(0),
+    SEGMENTED_6(1),
+    SEGMENTED_10(2),
+    SEGMENTED_12(3),
+    SEGMENTED_20(4);
+
+    private final int id;
+
+    BossStyle(int id) {
+        this.id = id;
+    }
+
+    public int getId() {
+        return id;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/BlockChangeRecord.java

@@ -0,0 +1,68 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft;
+
+public interface BlockChangeRecord {
+
+    /**
+     * Returns the relative x coordinate within the chunk section.
+     *
+     * @return relative x coordinate within the chunk section
+     */
+    byte getSectionX();
+
+    /**
+     * Returns the relative y coordinate within the chunk section.
+     *
+     * @return relative y coordinate within the chunk section
+     */
+    byte getSectionY();
+
+    /**
+     * Returns the relative z coordinate within the chunk section.
+     *
+     * @return relative z coordinate within the chunk section
+     */
+    byte getSectionZ();
+
+    /**
+     * Returns the absolute y coordinate based on the given chunk section y.
+     *
+     * @param chunkSectionY chunk section
+     * @return absolute y coordinate
+     */
+    short getY(int chunkSectionY);
+
+    /**
+     * @return absolute y coordinate
+     * @deprecated 1.16+ stores the relative y coordinate
+     */
+    @Deprecated
+    default short getY() {
+        return getY(-1);
+    }
+
+    int getBlockId();
+
+    void setBlockId(int blockId);
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/BlockChangeRecord1_16_2.java

@@ -0,0 +1,72 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft;
+
+import com.google.common.base.Preconditions;
+
+public class BlockChangeRecord1_16_2 implements BlockChangeRecord {
+    private final byte sectionX;
+    private final byte sectionY;
+    private final byte sectionZ;
+    private int blockId;
+
+    public BlockChangeRecord1_16_2(byte sectionX, byte sectionY, byte sectionZ, int blockId) {
+        this.sectionX = sectionX;
+        this.sectionY = sectionY;
+        this.sectionZ = sectionZ;
+        this.blockId = blockId;
+    }
+
+    public BlockChangeRecord1_16_2(int sectionX, int sectionY, int sectionZ, int blockId) {
+        this((byte) sectionX, (byte) sectionY, (byte) sectionZ, blockId);
+    }
+
+    @Override
+    public byte getSectionX() {
+        return sectionX;
+    }
+
+    @Override
+    public byte getSectionY() {
+        return sectionY;
+    }
+
+    @Override
+    public byte getSectionZ() {
+        return sectionZ;
+    }
+
+    @Override
+    public short getY(int chunkSectionY) {
+        Preconditions.checkArgument(chunkSectionY >= 0 && chunkSectionY < 16, "Invalid chunkSectionY: " + chunkSectionY);
+        return (short) ((chunkSectionY << 4) + sectionY);
+    }
+
+    public int getBlockId() {
+        return blockId;
+    }
+
+    public void setBlockId(int blockId) {
+        this.blockId = blockId;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/BlockChangeRecord1_8.java

@@ -0,0 +1,76 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft;
+
+public class BlockChangeRecord1_8 implements BlockChangeRecord {
+    private final byte sectionX;
+    private final short y;
+    private final byte sectionZ;
+    private int blockId;
+
+    public BlockChangeRecord1_8(byte sectionX, short y, byte sectionZ, int blockId) {
+        this.sectionX = sectionX;
+        this.y = y;
+        this.sectionZ = sectionZ;
+        this.blockId = blockId;
+    }
+
+    public BlockChangeRecord1_8(int sectionX, int y, int sectionZ, int blockId) {
+        this((byte) sectionX, (short) y, (byte) sectionZ, blockId);
+    }
+
+    /**
+     * @return x coordinate within the chunk section
+     */
+    public byte getSectionX() {
+        return sectionX;
+    }
+
+    @Override
+    public byte getSectionY() {
+        return (byte) (y & 0xF);
+    }
+
+    /**
+     * @return y coordinate
+     */
+    @Override
+    public short getY(int chunkSectionY) {
+        return y;
+    }
+
+    /**
+     * @return z coordinate within the chunk section
+     */
+    public byte getSectionZ() {
+        return sectionZ;
+    }
+
+    public int getBlockId() {
+        return blockId;
+    }
+
+    public void setBlockId(int blockId) {
+        this.blockId = blockId;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/BlockFace.java

@@ -0,0 +1,82 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public enum BlockFace {
+    NORTH((byte) 0, (byte) 0, (byte) -1, EnumAxis.Z),
+    SOUTH((byte) 0, (byte) 0, (byte) 1, EnumAxis.Z),
+    EAST((byte) 1, (byte) 0, (byte) 0, EnumAxis.X),
+    WEST((byte) -1, (byte) 0, (byte) 0, EnumAxis.X),
+    TOP((byte) 0, (byte) 1, (byte) 0, EnumAxis.Y),
+    BOTTOM((byte) 0, (byte) -1, (byte) 0, EnumAxis.Y);
+
+    private static final Map<BlockFace, BlockFace> opposites = new HashMap<>();
+
+    static {
+        opposites.put(BlockFace.NORTH, BlockFace.SOUTH);
+        opposites.put(BlockFace.SOUTH, BlockFace.NORTH);
+        opposites.put(BlockFace.EAST, BlockFace.WEST);
+        opposites.put(BlockFace.WEST, BlockFace.EAST);
+        opposites.put(BlockFace.TOP, BlockFace.BOTTOM);
+        opposites.put(BlockFace.BOTTOM, BlockFace.TOP);
+    }
+
+    private final byte modX;
+    private final byte modY;
+    private final byte modZ;
+    private final EnumAxis axis;
+
+    BlockFace(byte modX, byte modY, byte modZ, EnumAxis axis) {
+        this.modX = modX;
+        this.modY = modY;
+        this.modZ = modZ;
+        this.axis = axis;
+    }
+
+    public BlockFace opposite() {
+        return opposites.get(this);
+    }
+
+    public byte getModX() {
+        return modX;
+    }
+
+    public byte getModY() {
+        return modY;
+    }
+
+    public byte getModZ() {
+        return modZ;
+    }
+
+    public EnumAxis getAxis() {
+        return axis;
+    }
+
+    public enum EnumAxis {
+        X, Y, Z
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/Environment.java

@@ -0,0 +1,52 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft;
+
+public enum Environment {
+
+    NORMAL(0),
+    NETHER(-1),
+    END(1);
+
+    private final int id;
+
+    Environment(int id) {
+        this.id = id;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public static Environment getEnvironmentById(int id) {
+        switch (id) {
+            default:
+            case -1:
+                return NETHER;
+            case 0:
+                return NORMAL;
+            case 1:
+                return END;
+        }
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/EulerAngle.java

@@ -0,0 +1,47 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft;
+
+public class EulerAngle {
+    private final float x;
+    private final float y;
+    private final float z;
+
+    public EulerAngle(final float x, final float y, final float z) {
+        this.x = x;
+        this.y = y;
+        this.z = z;
+    }
+
+    public float getX() {
+        return x;
+    }
+
+    public float getY() {
+        return y;
+    }
+
+    public float getZ() {
+        return z;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/Position.java

@@ -0,0 +1,88 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft;
+
+public class Position {
+    private final int x;
+    private final int y;
+    private final int z;
+
+    public Position(int x, int y, int z) {
+        this.x = x;
+        this.y = y;
+        this.z = z;
+    }
+
+    public Position(int x, short y, int z) {
+        this.x = x;
+        this.y = y;
+        this.z = z;
+    }
+
+    public Position(Position toCopy) {
+        this(toCopy.getX(), toCopy.getY(), toCopy.getZ());
+    }
+
+    public Position getRelative(BlockFace face) {
+        return new Position(x + face.getModX(), (short) (y + face.getModY()), z + face.getModZ());
+    }
+
+    public int getX() {
+        return x;
+    }
+
+    public int getY() {
+        return y;
+    }
+
+    public int getZ() {
+        return z;
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Position position = (Position) o;
+        if (x != position.x) return false;
+        if (y != position.y) return false;
+        return z == position.z;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = x;
+        result = 31 * result + y;
+        result = 31 * result + z;
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "Position{" +
+                "x=" + x +
+                ", y=" + y +
+                ", z=" + z +
+                '}';
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/RegistryType.java

@@ -0,0 +1,64 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft;
+
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public enum RegistryType {
+
+    BLOCK("block"),
+    ITEM("item"),
+    FLUID("fluid"),
+    ENTITY("entity_type"),
+    GAME_EVENT("game_event");
+
+    private static final Map<String, RegistryType> MAP = new HashMap<>();
+    private static final RegistryType[] VALUES = values();
+
+    static {
+        for (RegistryType type : getValues()) {
+            MAP.put(type.resourceLocation, type);
+        }
+    }
+
+    public static RegistryType[] getValues() {
+        return VALUES;
+    }
+
+    public static @Nullable RegistryType getByKey(String resourceKey) {
+        return MAP.get(resourceKey);
+    }
+
+    private final String resourceLocation;
+
+    RegistryType(final String resourceLocation) {
+        this.resourceLocation = resourceLocation;
+    }
+
+    public String getResourceLocation() {
+        return resourceLocation;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/TagData.java

@@ -0,0 +1,41 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft;
+
+public final class TagData {
+    private final String identifier;
+    private final int[] entries;
+
+    public TagData(String identifier, int[] entries) {
+        this.identifier = identifier;
+        this.entries = entries;
+    }
+
+    public String identifier() {
+        return identifier;
+    }
+
+    public int[] entries() {
+        return entries;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/Vector.java

@@ -0,0 +1,59 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft;
+
+public class Vector {
+    private int blockX;
+    private int blockY;
+    private int blockZ;
+
+    public Vector(int blockX, int blockY, int blockZ) {
+        this.blockX = blockX;
+        this.blockY = blockY;
+        this.blockZ = blockZ;
+    }
+
+    public int getBlockX() {
+        return blockX;
+    }
+
+    public void setBlockX(int blockX) {
+        this.blockX = blockX;
+    }
+
+    public int getBlockY() {
+        return blockY;
+    }
+
+    public void setBlockY(int blockY) {
+        this.blockY = blockY;
+    }
+
+    public int getBlockZ() {
+        return blockZ;
+    }
+
+    public void setBlockZ(int blockZ) {
+        this.blockZ = blockZ;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/VillagerData.java

@@ -0,0 +1,47 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft;
+
+public class VillagerData {
+    private final int type;
+    private final int profession;
+    private final int level;
+
+    public VillagerData(final int type, final int profession, final int level) {
+        this.type = type;
+        this.profession = profession;
+        this.level = level;
+    }
+
+    public int getType() {
+        return type;
+    }
+
+    public int getProfession() {
+        return profession;
+    }
+
+    public int getLevel() {
+        return level;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/chunks/BaseChunk.java

@@ -0,0 +1,150 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.chunks;
+
+import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.BitSet;
+import java.util.List;
+
+//TODO Move methods from distinctly different versions to different objects/interfaces
+public class BaseChunk implements Chunk {
+    protected final int x;
+    protected final int z;
+    protected final boolean fullChunk;
+    protected boolean ignoreOldLightData;
+    protected BitSet chunkSectionBitSet;
+    protected int bitmask;
+    protected ChunkSection[] sections;
+    protected int[] biomeData;
+    protected CompoundTag heightMap;
+    protected final List<CompoundTag> blockEntities;
+
+    public BaseChunk(int x, int z, boolean fullChunk, boolean ignoreOldLightData, @Nullable BitSet chunkSectionBitSet,
+                     ChunkSection[] sections, int @Nullable [] biomeData, @Nullable CompoundTag heightMap, List<CompoundTag> blockEntities) {
+        this.x = x;
+        this.z = z;
+        this.fullChunk = fullChunk;
+        this.ignoreOldLightData = ignoreOldLightData;
+        this.chunkSectionBitSet = chunkSectionBitSet;
+        this.sections = sections;
+        this.biomeData = biomeData;
+        this.heightMap = heightMap;
+        this.blockEntities = blockEntities;
+    }
+
+    public BaseChunk(int x, int z, boolean fullChunk, boolean ignoreOldLightData, int bitmask, ChunkSection[] sections, int[] biomeData, CompoundTag heightMap, List<CompoundTag> blockEntities) {
+        this(x, z, fullChunk, ignoreOldLightData, null, sections, biomeData, heightMap, blockEntities);
+        this.bitmask = bitmask;
+    }
+
+    public BaseChunk(int x, int z, boolean fullChunk, boolean ignoreOldLightData, int bitmask, ChunkSection[] sections, int[] biomeData, List<CompoundTag> blockEntities) {
+        this(x, z, fullChunk, ignoreOldLightData, bitmask, sections, biomeData, null, blockEntities);
+    }
+
+    @Override
+    public boolean isBiomeData() {
+        return biomeData != null;
+    }
+
+    @Override
+    public int getX() {
+        return x;
+    }
+
+    @Override
+    public int getZ() {
+        return z;
+    }
+
+    @Override
+    public boolean isFullChunk() {
+        return fullChunk;
+    }
+
+    @Override
+    public boolean isIgnoreOldLightData() {
+        return ignoreOldLightData;
+    }
+
+    @Override
+    public void setIgnoreOldLightData(boolean ignoreOldLightData) {
+        this.ignoreOldLightData = ignoreOldLightData;
+    }
+
+    @Override
+    public int getBitmask() {
+        return bitmask;
+    }
+
+    @Override
+    public void setBitmask(int bitmask) {
+        this.bitmask = bitmask;
+    }
+
+    @Override
+    public @Nullable BitSet getChunkMask() {
+        return chunkSectionBitSet;
+    }
+
+    @Override
+    public void setChunkMask(BitSet chunkSectionMask) {
+        this.chunkSectionBitSet = chunkSectionMask;
+    }
+
+    @Override
+    public ChunkSection[] getSections() {
+        return sections;
+    }
+
+    @Override
+    public void setSections(ChunkSection[] sections) {
+        this.sections = sections;
+    }
+
+    @Override
+    public int @Nullable [] getBiomeData() {
+        return biomeData;
+    }
+
+    @Override
+    public void setBiomeData(int @Nullable [] biomeData) {
+        this.biomeData = biomeData;
+    }
+
+    @Override
+    public @Nullable CompoundTag getHeightMap() {
+        return heightMap;
+    }
+
+    @Override
+    public void setHeightMap(final CompoundTag heightMap) {
+        this.heightMap = heightMap;
+    }
+
+    @Override
+    public List<CompoundTag> getBlockEntities() {
+        return blockEntities;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/chunks/Chunk.java

@@ -0,0 +1,118 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.chunks;
+
+import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.BitSet;
+import java.util.List;
+
+public interface Chunk {
+
+    /**
+     * Returns the chunk x coordinate.
+     *
+     * @return chunk x coordinate
+     */
+    int getX();
+
+    /**
+     * Returns the chunk z coordinate.
+     *
+     * @return chunk z coordinate
+     */
+    int getZ();
+
+    /**
+     * Returns whether this chunk holds biome data, always true for 1.17+ chunks.
+     *
+     * @return true if this chunk holds biome data
+     */
+    boolean isBiomeData();
+
+    /**
+     * Returns whether this is a full chunk, always true for 1.17+ chunks.
+     *
+     * @return true if this is a full chunk
+     */
+    boolean isFullChunk();
+
+    boolean isIgnoreOldLightData();
+
+    void setIgnoreOldLightData(boolean ignoreOldLightData);
+
+    /**
+     * Returns the chunk section bit mask for chunks < 1.17.
+     *
+     * @return chunk section bit mask for chunks < 1.17
+     * @see #getChunkMask()
+     */
+    int getBitmask();
+
+    void setBitmask(int bitmask);
+
+    /**
+     * Returns the chunk section bit mask, only non-null for 1.17+ chunks.
+     *
+     * @return chunk section bit mask, only non-null for 1.17+ chunks
+     * @see #getBitmask()
+     */
+    @Nullable BitSet getChunkMask();
+
+    void setChunkMask(BitSet chunkSectionMask);
+
+    /**
+     * Returns an array of nullable chunk section entries.
+     *
+     * @return array of nullable chunk sections
+     */
+    @Nullable ChunkSection[] getSections();
+
+    void setSections(ChunkSection[] sections);
+
+    /**
+     * Returns the chunk's raw biome data. The format the biomes are stored may vary.
+     *
+     * @return raw biome data
+     */
+    int @Nullable [] getBiomeData();
+
+    void setBiomeData(int @Nullable [] biomeData);
+
+    /**
+     * Returns a compoundtag containing the chunk's heightmaps if present.
+     *
+     * @return compoundtag containing heightmaps if present
+     */
+    @Nullable CompoundTag getHeightMap();
+
+    void setHeightMap(@Nullable CompoundTag heightMap);
+
+    /**
+     * Returns a list of block entities.
+     *
+     * @return list of block entities
+     */
+    List<CompoundTag> getBlockEntities();
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/chunks/Chunk1_8.java

@@ -0,0 +1,60 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.chunks;
+
+import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Chunk1_8 extends BaseChunk {
+    private boolean unloadPacket;
+
+    public Chunk1_8(int x, int z, boolean groundUp, int bitmask, ChunkSection[] sections, int[] biomeData, List<CompoundTag> blockEntities) {
+        super(x, z, groundUp, false, bitmask, sections, biomeData, blockEntities);
+    }
+
+    /**
+     * Chunk unload.
+     *
+     * @param x coord
+     * @param z coord
+     */
+    public Chunk1_8(int x, int z) {
+        this(x, z, true, 0, new ChunkSection[16], null, new ArrayList<>());
+        this.unloadPacket = true;
+    }
+
+    /**
+     * Does this chunks have biome data
+     *
+     * @return True if the chunks has biome data
+     */
+    public boolean hasBiomeData() {
+        return biomeData != null && fullChunk;
+    }
+
+    public boolean isUnloadPacket() {
+        return unloadPacket;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/chunks/ChunkSection.java

@@ -0,0 +1,201 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.chunks;
+
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public interface ChunkSection {
+
+    /**
+     * Size (dimensions) of blocks in a chunks section.
+     */
+    int SIZE = 16 * 16 * 16; // width * depth * height
+
+    /**
+     * Returns the block index of the given coordinates within a section.
+     *
+     * @param x section x
+     * @param y section y
+     * @param z section z
+     * @return section block index
+     */
+    static int index(int x, int y, int z) {
+        return y << 8 | z << 4 | x;
+    }
+
+    /**
+     * Returns the block state of the given index.
+     *
+     * @param idx block index within the section
+     * @return block state of the given index
+     */
+    int getFlatBlock(int idx);
+
+    /**
+     * Returns the block state of the section coordinate.
+     *
+     * @param x section x
+     * @param y section y
+     * @param z section z
+     * @return block state of the given section coordinate
+     */
+    default int getFlatBlock(int x, int y, int z) {
+        return getFlatBlock(index(x, y, z));
+    }
+
+    /**
+     * Set a block state in the chunk section.
+     * This method will not update non-air blocks count.
+     *
+     * @param idx block index within the section
+     * @param id  raw or flat id of the block state
+     */
+    void setFlatBlock(int idx, int id);
+
+    /**
+     * Set a block state in the chunk section.
+     * This method will not update non-air blocks count.
+     *
+     * @param x  section x
+     * @param y  section y
+     * @param z  section z
+     * @param id raw or flat id of the block state
+     */
+    default void setFlatBlock(int x, int y, int z, int id) {
+        setFlatBlock(index(x, y, z), id);
+    }
+
+    default int getBlockWithoutData(int x, int y, int z) {
+        return getFlatBlock(x, y, z) >> 4;
+    }
+
+    default int getBlockData(int x, int y, int z) {
+        return getFlatBlock(x, y, z) & 0xF;
+    }
+
+    /**
+     * Set a block in the chunks.
+     * This method will not update non-air blocks count.
+     *
+     * @param x    Block X
+     * @param y    Block Y
+     * @param z    Block Z
+     * @param type The type of the block
+     * @param data The data value of the block
+     */
+    default void setBlockWithData(int x, int y, int z, int type, int data) {
+        setFlatBlock(index(x, y, z), type << 4 | (data & 0xF));
+    }
+
+    default void setBlockWithData(int idx, int type, int data) {
+        setFlatBlock(idx, type << 4 | (data & 0xF));
+    }
+
+    /**
+     * Sets a block to the given palette index.
+     *
+     * @param idx   block index
+     * @param index palette index
+     */
+    void setPaletteIndex(int idx, int index);
+
+    /**
+     * Returns the palette index of the given block index.
+     *
+     * @param idx block index
+     * @return palette index of the given block index
+     */
+    int getPaletteIndex(int idx);
+
+    /**
+     * Returns the size of the palette.
+     *
+     * @return palette size
+     */
+    int getPaletteSize();
+
+    /**
+     * Returns the block state assigned to the given palette index.
+     *
+     * @param index palette index
+     * @return block state assigned to the given palette index
+     */
+    int getPaletteEntry(int index);
+
+    /**
+     * Assigns a block state assigned to the given palette index.
+     *
+     * @param index palette index
+     * @param id    block state
+     */
+    void setPaletteEntry(int index, int id);
+
+    /**
+     * Replaces a block state in the palette.
+     *
+     * @param oldId old block state
+     * @param newId new block state
+     */
+    void replacePaletteEntry(int oldId, int newId);
+
+    /**
+     * Adds a new block state to the palette.
+     *
+     * @param id block state
+     */
+    void addPaletteEntry(int id);
+
+    /**
+     * Clears the palette.
+     */
+    void clearPalette();
+
+    /**
+     * Returns the number of non-air blocks in this section.
+     *
+     * @return non-air blocks in this section
+     */
+    int getNonAirBlocksCount();
+
+    void setNonAirBlocksCount(int nonAirBlocksCount);
+
+    /**
+     * Returns whether this section holds light data.
+     * Only true for &lt; 1.14 chunks.
+     *
+     * @return whether this section holds light data
+     */
+    default boolean hasLight() {
+        return getLight() != null;
+    }
+
+    /**
+     * Returns the light of the chunk section.
+     * Only present for &lt; 1.14 chunks, otherwise sent separately.
+     *
+     * @return chunk section light if present
+     */
+    @Nullable ChunkSectionLight getLight();
+
+    void setLight(@Nullable ChunkSectionLight light);
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/chunks/ChunkSectionImpl.java

@@ -0,0 +1,160 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.chunks;
+
+import it.unimi.dsi.fastutil.ints.Int2IntMap;
+import it.unimi.dsi.fastutil.ints.Int2IntOpenHashMap;
+import it.unimi.dsi.fastutil.ints.IntArrayList;
+import it.unimi.dsi.fastutil.ints.IntList;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public class ChunkSectionImpl implements ChunkSection {
+
+    private final IntList palette;
+    private final Int2IntMap inversePalette;
+    private final int[] blocks;
+    private ChunkSectionLight light;
+    private int nonAirBlocksCount;
+
+    public ChunkSectionImpl(boolean holdsLight) {
+        this.blocks = new int[SIZE];
+        palette = new IntArrayList();
+        inversePalette = new Int2IntOpenHashMap();
+        inversePalette.defaultReturnValue(-1);
+        if (holdsLight) {
+            this.light = new ChunkSectionLightImpl();
+        }
+    }
+
+    public ChunkSectionImpl(boolean holdsLight, int expectedPaletteLength) {
+        this.blocks = new int[SIZE];
+        if (holdsLight) {
+            this.light = new ChunkSectionLightImpl();
+        }
+
+        // Pre-size the palette array/map
+        palette = new IntArrayList(expectedPaletteLength);
+        inversePalette = new Int2IntOpenHashMap(expectedPaletteLength);
+        inversePalette.defaultReturnValue(-1);
+    }
+
+    @Override
+    public int getFlatBlock(int idx) {
+        int index = blocks[idx];
+        return palette.getInt(index);
+    }
+
+    @Override
+    public void setFlatBlock(int idx, int id) {
+        int index = inversePalette.get(id);
+        if (index == -1) {
+            index = palette.size();
+            palette.add(id);
+            inversePalette.put(id, index);
+        }
+
+        blocks[idx] = index;
+    }
+
+    @Override
+    public int getPaletteIndex(int idx) {
+        return blocks[idx];
+    }
+
+    @Override
+    public void setPaletteIndex(int idx, int index) {
+        blocks[idx] = index;
+    }
+
+    @Override
+    public int getPaletteSize() {
+        return palette.size();
+    }
+
+    @Override
+    public int getPaletteEntry(int index) {
+        return palette.getInt(index);
+    }
+
+    @Override
+    public void setPaletteEntry(int index, int id) {
+        int oldId = palette.set(index, id);
+        if (oldId == id) return;
+
+        inversePalette.put(id, index);
+        if (inversePalette.get(oldId) == index) {
+            inversePalette.remove(oldId);
+            for (int i = 0; i < palette.size(); i++) {
+                if (palette.getInt(i) == oldId) {
+                    inversePalette.put(oldId, i);
+                    break;
+                }
+            }
+        }
+    }
+
+    @Override
+    public void replacePaletteEntry(int oldId, int newId) {
+        int index = inversePalette.remove(oldId);
+        if (index == -1) return;
+
+        inversePalette.put(newId, index);
+        for (int i = 0; i < palette.size(); i++) {
+            if (palette.getInt(i) == oldId) {
+                palette.set(i, newId);
+            }
+        }
+    }
+
+    @Override
+    public void addPaletteEntry(int id) {
+        inversePalette.put(id, palette.size());
+        palette.add(id);
+    }
+
+    @Override
+    public void clearPalette() {
+        palette.clear();
+        inversePalette.clear();
+    }
+
+    @Override
+    public int getNonAirBlocksCount() {
+        return nonAirBlocksCount;
+    }
+
+    @Override
+    public void setNonAirBlocksCount(int nonAirBlocksCount) {
+        this.nonAirBlocksCount = nonAirBlocksCount;
+    }
+
+    @Override
+    public @Nullable ChunkSectionLight getLight() {
+        return light;
+    }
+
+    @Override
+    public void setLight(@Nullable ChunkSectionLight light) {
+        this.light = light;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/chunks/ChunkSectionLight.java

@@ -0,0 +1,113 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.chunks;
+
+import io.netty.buffer.ByteBuf;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public interface ChunkSectionLight {
+
+    /**
+     * Length of the sky and block light nibble arrays.
+     */
+    int LIGHT_LENGTH = 16 * 16 * 16 / 2; // Dimensions / 2 (nibble bit count)
+
+    /**
+     * Returns whether the section has sky light.
+     *
+     * @return true if skylight is present
+     */
+    boolean hasSkyLight();
+
+    /**
+     * Returns whether the section has block light.
+     * This returns true unless specifically set to null.
+     *
+     * @return true if skylight is present
+     */
+    boolean hasBlockLight();
+
+    /**
+     * Returns the nibblearray's raw sky light byte array if present.
+     *
+     * @return the nibblearray's raw sky light byte array if present
+     * @see #hasSkyLight()
+     */
+    byte @Nullable [] getSkyLight();
+
+    /**
+     * Returns the nibblearray's raw block light byte array if present.
+     *
+     * @return the nibblearray's raw block light byte array if present
+     * @see #hasBlockLight()
+     */
+    byte @Nullable [] getBlockLight();
+
+    /**
+     * Set the sky light array.
+     *
+     * @param data raw sky light data
+     */
+    void setSkyLight(byte[] data);
+
+    /**
+     * Set the block light array.
+     *
+     * @param data raw block light data
+     */
+    void setBlockLight(byte[] data);
+
+    /**
+     * Returns the sky light nibblearray.
+     *
+     * @return sky light nibblearray
+     * @see #hasSkyLight()
+     */
+    @Nullable NibbleArray getSkyLightNibbleArray();
+
+    /**
+     * Returns the block light nibblearray.
+     *
+     * @return block light nibblearray
+     * @see #hasBlockLight()
+     */
+    @Nullable NibbleArray getBlockLightNibbleArray();
+
+    void readSkyLight(ByteBuf input);
+
+    void readBlockLight(ByteBuf input);
+
+    /**
+     * Write the sky light to a buffer.
+     *
+     * @param output buffer to write to
+     */
+    void writeSkyLight(ByteBuf output);
+
+    /**
+     * Write the block light to a buffer.
+     *
+     * @param output buffer to write to
+     */
+    void writeBlockLight(ByteBuf output);
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/chunks/ChunkSectionLightImpl.java

@@ -0,0 +1,113 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.chunks;
+
+import io.netty.buffer.ByteBuf;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public class ChunkSectionLightImpl implements ChunkSectionLight {
+
+    private NibbleArray blockLight;
+    private NibbleArray skyLight;
+
+    public ChunkSectionLightImpl() {
+        // Block light is always written
+        this.blockLight = new NibbleArray(ChunkSection.SIZE);
+    }
+
+    @Override
+    public void setBlockLight(byte[] data) {
+        if (data.length != LIGHT_LENGTH) throw new IllegalArgumentException("Data length != " + LIGHT_LENGTH);
+        if (this.blockLight == null) {
+            this.blockLight = new NibbleArray(data);
+        } else {
+            this.blockLight.setHandle(data);
+        }
+    }
+
+    @Override
+    public void setSkyLight(byte[] data) {
+        if (data.length != LIGHT_LENGTH) throw new IllegalArgumentException("Data length != " + LIGHT_LENGTH);
+        if (this.skyLight == null) {
+            this.skyLight = new NibbleArray(data);
+        } else {
+            this.skyLight.setHandle(data);
+        }
+    }
+
+    @Override
+    public byte @Nullable [] getBlockLight() {
+        return blockLight == null ? null : blockLight.getHandle();
+    }
+
+    @Override
+    public @Nullable NibbleArray getBlockLightNibbleArray() {
+        return blockLight;
+    }
+
+    @Override
+    public byte @Nullable [] getSkyLight() {
+        return skyLight == null ? null : skyLight.getHandle();
+    }
+
+    @Override
+    public @Nullable NibbleArray getSkyLightNibbleArray() {
+        return skyLight;
+    }
+
+    @Override
+    public void readBlockLight(ByteBuf input) {
+        if (this.blockLight == null) {
+            this.blockLight = new NibbleArray(LIGHT_LENGTH * 2);
+        }
+        input.readBytes(this.blockLight.getHandle());
+    }
+
+    @Override
+    public void readSkyLight(ByteBuf input) {
+        if (this.skyLight == null) {
+            this.skyLight = new NibbleArray(LIGHT_LENGTH * 2);
+        }
+        input.readBytes(this.skyLight.getHandle());
+    }
+
+    @Override
+    public void writeBlockLight(ByteBuf output) {
+        output.writeBytes(blockLight.getHandle());
+    }
+
+    @Override
+    public void writeSkyLight(ByteBuf output) {
+        output.writeBytes(skyLight.getHandle());
+    }
+
+    @Override
+    public boolean hasSkyLight() {
+        return skyLight != null;
+    }
+
+    @Override
+    public boolean hasBlockLight() {
+        return blockLight != null;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/chunks/NibbleArray.java

@@ -0,0 +1,150 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.chunks;
+
+import java.util.Arrays;
+
+public class NibbleArray {
+    private final byte[] handle;
+
+    public NibbleArray(int length) {
+        if (length == 0 || length % 2 != 0) {
+            throw new IllegalArgumentException("Length of nibble array must be a positive number dividable by 2!");
+        }
+
+        this.handle = new byte[length / 2];
+    }
+
+    public NibbleArray(byte[] handle) {
+        if (handle.length == 0 || handle.length % 2 != 0) {
+            throw new IllegalArgumentException("Length of nibble array must be a positive number dividable by 2!");
+        }
+
+        this.handle = handle;
+    }
+
+    /**
+     * Get the value at a desired X, Y, Z
+     *
+     * @param x Block X
+     * @param y Block Y
+     * @param z Block Z
+     * @return The value at the given XYZ
+     */
+    public byte get(int x, int y, int z) {
+        return get(ChunkSection.index(x, y, z));
+    }
+
+    /**
+     * Get the value at an index
+     *
+     * @param index The index to lookup
+     * @return The value at that index.
+     */
+    public byte get(int index) {
+        byte value = handle[index / 2];
+        if (index % 2 == 0) {
+            return (byte) (value & 0xF);
+        } else {
+            return (byte) ((value >> 4) & 0xF);
+        }
+    }
+
+    /**
+     * Set the value based on an x, y, z
+     *
+     * @param x     Block X
+     * @param y     Block Y
+     * @param z     Block Z
+     * @param value Desired Value
+     */
+    public void set(int x, int y, int z, int value) {
+        set(ChunkSection.index(x, y, z), value);
+    }
+
+    /**
+     * Set a value at an index
+     *
+     * @param index The index to set the value at.
+     * @param value The desired value
+     */
+    public void set(int index, int value) {
+        if (index % 2 == 0) {
+            index /= 2;
+            handle[index] = (byte) ((handle[index] & 0xF0) | (value & 0xF));
+        } else {
+            index /= 2;
+            handle[index] = (byte) ((handle[index] & 0xF) | ((value & 0xF) << 4));
+        }
+    }
+
+    /**
+     * The size of this nibble
+     *
+     * @return The size as an int of the nibble
+     */
+    public int size() {
+        return handle.length * 2;
+    }
+
+    /**
+     * Get the actual number of bytes
+     *
+     * @return The number of bytes based on the handle.
+     */
+    public int actualSize() {
+        return handle.length;
+    }
+
+    /**
+     * Fill the array with a value
+     *
+     * @param value Value to fill with
+     */
+    public void fill(byte value) {
+        value &= 0xF; // Max nibble size (= 16)
+        Arrays.fill(handle, (byte) ((value << 4) | value));
+    }
+
+    /**
+     * Get the byte array behind this nibble
+     *
+     * @return The byte array
+     */
+    public byte[] getHandle() {
+        return handle;
+    }
+
+    /**
+     * Copy a byte array into this nibble
+     *
+     * @param handle The byte array to copy in.
+     */
+    public void setHandle(byte[] handle) {
+        if (handle.length != this.handle.length) {
+            throw new IllegalArgumentException("Length of handle must equal to size of nibble array!");
+        }
+
+        System.arraycopy(handle, 0, this.handle, 0, handle.length);
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/entities/Entity1_10Types.java

@@ -0,0 +1,242 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.entities;
+
+import com.viaversion.viaversion.api.Via;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+
+// 1.10 Entity / Object ids
+public class Entity1_10Types {
+
+    public static EntityType getTypeFromId(int typeID, boolean isObject) {
+        Optional<EntityType> type;
+
+        if (isObject)
+            type = ObjectType.getPCEntity(typeID);
+        else
+            type = EntityType.findById(typeID);
+
+        if (!type.isPresent()) {
+            Via.getPlatform().getLogger().severe("Could not find 1.10 type id " + typeID + " isObject=" + isObject);
+            return EntityType.ENTITY; // Fall back to the basic ENTITY
+        }
+
+        return type.get();
+    }
+
+    public enum EntityType implements com.viaversion.viaversion.api.minecraft.entities.EntityType {
+        ENTITY(-1),
+        DROPPED_ITEM(1, ENTITY),
+        EXPERIENCE_ORB(2, ENTITY),
+        LEASH_HITCH(8, ENTITY), // Actually entity hanging but it doesn't make a lot of difference for metadata
+        PAINTING(9, ENTITY), // Actually entity hanging but it doesn't make a lot of difference for metadata
+        ARROW(10, ENTITY),
+        SNOWBALL(11, ENTITY), // Actually EntityProjectile
+        FIREBALL(12, ENTITY),
+        SMALL_FIREBALL(13, ENTITY),
+        ENDER_PEARL(14, ENTITY), // Actually EntityProjectile
+        ENDER_SIGNAL(15, ENTITY),
+        THROWN_EXP_BOTTLE(17, ENTITY),
+        ITEM_FRAME(18, ENTITY), // Actually EntityHanging
+        WITHER_SKULL(19, ENTITY),
+        PRIMED_TNT(20, ENTITY),
+        FALLING_BLOCK(21, ENTITY),
+        FIREWORK(22, ENTITY),
+        TIPPED_ARROW(23, ARROW),
+        SPECTRAL_ARROW(24, ARROW),
+        SHULKER_BULLET(25, ENTITY),
+        DRAGON_FIREBALL(26, FIREBALL),
+
+        ENTITY_LIVING(-1, ENTITY),
+        ENTITY_INSENTIENT(-1, ENTITY_LIVING),
+        ENTITY_AGEABLE(-1, ENTITY_INSENTIENT),
+        ENTITY_TAMEABLE_ANIMAL(-1, ENTITY_AGEABLE),
+        ENTITY_HUMAN(-1, ENTITY_LIVING),
+
+        ARMOR_STAND(30, ENTITY_LIVING),
+
+        // Vehicles
+        MINECART_ABSTRACT(-1, ENTITY),
+        MINECART_COMMAND(40, MINECART_ABSTRACT),
+        BOAT(41, ENTITY),
+        MINECART_RIDEABLE(42, MINECART_ABSTRACT),
+        MINECART_CHEST(43, MINECART_ABSTRACT),
+        MINECART_FURNACE(44, MINECART_ABSTRACT),
+        MINECART_TNT(45, MINECART_ABSTRACT),
+        MINECART_HOPPER(46, MINECART_ABSTRACT),
+        MINECART_MOB_SPAWNER(47, MINECART_ABSTRACT),
+
+        CREEPER(50, ENTITY_INSENTIENT),
+        SKELETON(51, ENTITY_INSENTIENT),
+        SPIDER(52, ENTITY_INSENTIENT),
+        GIANT(53, ENTITY_INSENTIENT),
+        ZOMBIE(54, ENTITY_INSENTIENT),
+        SLIME(55, ENTITY_INSENTIENT),
+        GHAST(56, ENTITY_INSENTIENT),
+        PIG_ZOMBIE(57, ZOMBIE),
+        ENDERMAN(58, ENTITY_INSENTIENT),
+        CAVE_SPIDER(59, SPIDER),
+        SILVERFISH(60, ENTITY_INSENTIENT),
+        BLAZE(61, ENTITY_INSENTIENT),
+        MAGMA_CUBE(62, SLIME),
+        ENDER_DRAGON(63, ENTITY_INSENTIENT),
+        WITHER(64, ENTITY_INSENTIENT),
+        BAT(65, ENTITY_INSENTIENT),
+        WITCH(66, ENTITY_INSENTIENT),
+        ENDERMITE(67, ENTITY_INSENTIENT),
+        GUARDIAN(68, ENTITY_INSENTIENT),
+        IRON_GOLEM(99, ENTITY_INSENTIENT), // moved up to avoid illegal forward references
+        SHULKER(69, IRON_GOLEM),
+        PIG(90, ENTITY_AGEABLE),
+        SHEEP(91, ENTITY_AGEABLE),
+        COW(92, ENTITY_AGEABLE),
+        CHICKEN(93, ENTITY_AGEABLE),
+        SQUID(94, ENTITY_INSENTIENT),
+        WOLF(95, ENTITY_TAMEABLE_ANIMAL),
+        MUSHROOM_COW(96, COW),
+        SNOWMAN(97, IRON_GOLEM),
+        OCELOT(98, ENTITY_TAMEABLE_ANIMAL),
+        HORSE(100, ENTITY_AGEABLE),
+        RABBIT(101, ENTITY_AGEABLE),
+        POLAR_BEAR(102, ENTITY_AGEABLE),
+        VILLAGER(120, ENTITY_AGEABLE),
+        ENDER_CRYSTAL(200, ENTITY),
+        SPLASH_POTION(-1, ENTITY),
+        LINGERING_POTION(-1, SPLASH_POTION),
+        AREA_EFFECT_CLOUD(-1, ENTITY),
+        EGG(-1, ENTITY),
+        FISHING_HOOK(-1, ENTITY),
+        LIGHTNING(-1, ENTITY),
+        WEATHER(-1, ENTITY),
+        PLAYER(-1, ENTITY_HUMAN),
+        COMPLEX_PART(-1, ENTITY);
+
+        private static final Map<Integer, EntityType> TYPES = new HashMap<>();
+
+        private final int id;
+        private final EntityType parent;
+
+        EntityType(int id) {
+            this.id = id;
+            this.parent = null;
+        }
+
+        EntityType(int id, EntityType parent) {
+            this.id = id;
+            this.parent = parent;
+        }
+
+        static {
+            for (EntityType type : EntityType.values()) {
+                TYPES.put(type.id, type);
+            }
+        }
+
+        public static Optional<EntityType> findById(int id) {
+            if (id == -1)  // Check if this is called
+                return Optional.empty();
+            return Optional.ofNullable(TYPES.get(id));
+        }
+
+        @Override
+        public int getId() {
+            return id;
+        }
+
+        @Override
+        public EntityType getParent() {
+            return parent;
+        }
+    }
+
+    public enum ObjectType implements com.viaversion.viaversion.api.minecraft.entities.ObjectType {
+        BOAT(1, EntityType.BOAT),
+        ITEM(2, EntityType.DROPPED_ITEM),
+        AREA_EFFECT_CLOUD(3, EntityType.AREA_EFFECT_CLOUD),
+        MINECART(10, EntityType.MINECART_RIDEABLE),
+        TNT_PRIMED(50, EntityType.PRIMED_TNT),
+        ENDER_CRYSTAL(51, EntityType.ENDER_CRYSTAL),
+        TIPPED_ARROW(60, EntityType.TIPPED_ARROW),
+        SNOWBALL(61, EntityType.SNOWBALL),
+        EGG(62, EntityType.EGG),
+        FIREBALL(63, EntityType.FIREBALL),
+        SMALL_FIREBALL(64, EntityType.SMALL_FIREBALL),
+        ENDER_PEARL(65, EntityType.ENDER_PEARL),
+        WITHER_SKULL(66, EntityType.WITHER_SKULL),
+        SHULKER_BULLET(67, EntityType.SHULKER_BULLET),
+        FALLING_BLOCK(70, EntityType.FALLING_BLOCK),
+        ITEM_FRAME(71, EntityType.ITEM_FRAME),
+        ENDER_SIGNAL(72, EntityType.ENDER_SIGNAL),
+        POTION(73, EntityType.SPLASH_POTION),
+        THROWN_EXP_BOTTLE(75, EntityType.THROWN_EXP_BOTTLE),
+        FIREWORK(76, EntityType.FIREWORK),
+        LEASH(77, EntityType.LEASH_HITCH),
+        ARMOR_STAND(78, EntityType.ARMOR_STAND),
+        FISHIHNG_HOOK(90, EntityType.FISHING_HOOK),
+        SPECTRAL_ARROW(91, EntityType.SPECTRAL_ARROW),
+        DRAGON_FIREBALL(93, EntityType.DRAGON_FIREBALL);
+
+        private static final Map<Integer, ObjectType> TYPES = new HashMap<>();
+
+        private final int id;
+        private final EntityType type;
+
+        static {
+            for (ObjectType type : ObjectType.values()) {
+                TYPES.put(type.id, type);
+            }
+        }
+
+        ObjectType(int id, EntityType type) {
+            this.id = id;
+            this.type = type;
+        }
+
+        @Override
+        public int getId() {
+            return id;
+        }
+
+        @Override
+        public EntityType getType() {
+            return type;
+        }
+
+        public static Optional<ObjectType> findById(int id) {
+            if (id == -1)
+                return Optional.empty();
+            return Optional.ofNullable(TYPES.get(id));
+        }
+
+        public static Optional<EntityType> getPCEntity(int id) {
+            Optional<ObjectType> output = findById(id);
+
+            if (!output.isPresent())
+                return Optional.empty();
+            return Optional.of(output.get().type);
+        }
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/entities/Entity1_11Types.java

@@ -0,0 +1,272 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.entities;
+
+import com.viaversion.viaversion.api.Via;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+
+// 1.11 Entity / Object ids TODO maybe in the future instead of copying it, some api.
+public class Entity1_11Types {
+
+    public static EntityType getTypeFromId(int typeID, boolean isObject) {
+        Optional<EntityType> type;
+
+        if (isObject)
+            type = ObjectType.getPCEntity(typeID);
+        else
+            type = EntityType.findById(typeID);
+
+        if (!type.isPresent()) {
+            Via.getPlatform().getLogger().severe("Could not find 1.11 type id " + typeID + " isObject=" + isObject);
+            return EntityType.ENTITY; // Fall back to the basic ENTITY
+        }
+
+        return type.get();
+    }
+
+    public enum EntityType implements com.viaversion.viaversion.api.minecraft.entities.EntityType {
+        ENTITY(-1),
+        DROPPED_ITEM(1, ENTITY),
+        EXPERIENCE_ORB(2, ENTITY),
+        LEASH_HITCH(8, ENTITY), // Actually entity hanging but it doesn't make a lot of difference for metadata
+        PAINTING(9, ENTITY), // Actually entity hanging but it doesn't make a lot of difference for metadata
+        ARROW(10, ENTITY),
+        SNOWBALL(11, ENTITY), // Actually EntityProjectile
+        FIREBALL(12, ENTITY),
+        SMALL_FIREBALL(13, ENTITY),
+        ENDER_PEARL(14, ENTITY), // Actually EntityProjectile
+        ENDER_SIGNAL(15, ENTITY),
+        THROWN_EXP_BOTTLE(17, ENTITY),
+        ITEM_FRAME(18, ENTITY), // Actually EntityHanging
+        WITHER_SKULL(19, ENTITY),
+        PRIMED_TNT(20, ENTITY),
+        FALLING_BLOCK(21, ENTITY),
+        FIREWORK(22, ENTITY),
+        SPECTRAL_ARROW(24, ARROW),
+        SHULKER_BULLET(25, ENTITY),
+        DRAGON_FIREBALL(26, FIREBALL),
+        EVOCATION_FANGS(33, ENTITY),
+
+
+        ENTITY_LIVING(-1, ENTITY),
+        ENTITY_INSENTIENT(-1, ENTITY_LIVING),
+        ENTITY_AGEABLE(-1, ENTITY_INSENTIENT),
+        ENTITY_TAMEABLE_ANIMAL(-1, ENTITY_AGEABLE),
+        ENTITY_HUMAN(-1, ENTITY_LIVING),
+
+        ARMOR_STAND(30, ENTITY_LIVING),
+        EVOCATION_ILLAGER(34, ENTITY_INSENTIENT),
+        VEX(35, ENTITY_INSENTIENT),
+        VINDICATION_ILLAGER(36, ENTITY_INSENTIENT),
+
+        // Vehicles
+        MINECART_ABSTRACT(-1, ENTITY),
+        MINECART_COMMAND(40, MINECART_ABSTRACT),
+        BOAT(41, ENTITY),
+        MINECART_RIDEABLE(42, MINECART_ABSTRACT),
+        MINECART_CHEST(43, MINECART_ABSTRACT),
+        MINECART_FURNACE(44, MINECART_ABSTRACT),
+        MINECART_TNT(45, MINECART_ABSTRACT),
+        MINECART_HOPPER(46, MINECART_ABSTRACT),
+        MINECART_MOB_SPAWNER(47, MINECART_ABSTRACT),
+
+        CREEPER(50, ENTITY_INSENTIENT),
+
+        ABSTRACT_SKELETON(-1, ENTITY_INSENTIENT),
+        SKELETON(51, ABSTRACT_SKELETON),
+        WITHER_SKELETON(5, ABSTRACT_SKELETON),
+        STRAY(6, ABSTRACT_SKELETON),
+
+        SPIDER(52, ENTITY_INSENTIENT),
+        GIANT(53, ENTITY_INSENTIENT),
+
+        ZOMBIE(54, ENTITY_INSENTIENT),
+        HUSK(23, ZOMBIE),
+        ZOMBIE_VILLAGER(27, ZOMBIE),
+
+        SLIME(55, ENTITY_INSENTIENT),
+        GHAST(56, ENTITY_INSENTIENT),
+        PIG_ZOMBIE(57, ZOMBIE),
+        ENDERMAN(58, ENTITY_INSENTIENT),
+        CAVE_SPIDER(59, SPIDER),
+        SILVERFISH(60, ENTITY_INSENTIENT),
+        BLAZE(61, ENTITY_INSENTIENT),
+        MAGMA_CUBE(62, SLIME),
+        ENDER_DRAGON(63, ENTITY_INSENTIENT),
+        WITHER(64, ENTITY_INSENTIENT),
+        BAT(65, ENTITY_INSENTIENT),
+        WITCH(66, ENTITY_INSENTIENT),
+        ENDERMITE(67, ENTITY_INSENTIENT),
+
+        GUARDIAN(68, ENTITY_INSENTIENT),
+        ELDER_GUARDIAN(4, GUARDIAN), // Moved down to avoid illegal forward reference
+
+        IRON_GOLEM(99, ENTITY_INSENTIENT), // moved up to avoid illegal forward references
+        SHULKER(69, IRON_GOLEM),
+        PIG(90, ENTITY_AGEABLE),
+        SHEEP(91, ENTITY_AGEABLE),
+        COW(92, ENTITY_AGEABLE),
+        CHICKEN(93, ENTITY_AGEABLE),
+        SQUID(94, ENTITY_INSENTIENT),
+        WOLF(95, ENTITY_TAMEABLE_ANIMAL),
+        MUSHROOM_COW(96, COW),
+        SNOWMAN(97, IRON_GOLEM),
+        OCELOT(98, ENTITY_TAMEABLE_ANIMAL),
+
+        ABSTRACT_HORSE(-1, ENTITY_AGEABLE),
+        HORSE(100, ABSTRACT_HORSE),
+        SKELETON_HORSE(28, ABSTRACT_HORSE),
+        ZOMBIE_HORSE(29, ABSTRACT_HORSE),
+
+        CHESTED_HORSE(-1, ABSTRACT_HORSE),
+        DONKEY(31, CHESTED_HORSE),
+        MULE(32, CHESTED_HORSE),
+        LIAMA(103, CHESTED_HORSE),
+
+
+        RABBIT(101, ENTITY_AGEABLE),
+        POLAR_BEAR(102, ENTITY_AGEABLE),
+        VILLAGER(120, ENTITY_AGEABLE),
+        ENDER_CRYSTAL(200, ENTITY),
+        SPLASH_POTION(-1, ENTITY),
+        LINGERING_POTION(-1, SPLASH_POTION),
+        AREA_EFFECT_CLOUD(-1, ENTITY),
+        EGG(-1, ENTITY),
+        FISHING_HOOK(-1, ENTITY),
+        LIGHTNING(-1, ENTITY),
+        WEATHER(-1, ENTITY),
+        PLAYER(-1, ENTITY_HUMAN),
+        COMPLEX_PART(-1, ENTITY),
+        LIAMA_SPIT(-1, ENTITY);
+
+        private static final Map<Integer, EntityType> TYPES = new HashMap<>();
+
+        private final int id;
+        private final EntityType parent;
+
+        EntityType(int id) {
+            this.id = id;
+            this.parent = null;
+        }
+
+        EntityType(int id, EntityType parent) {
+            this.id = id;
+            this.parent = parent;
+        }
+
+        @Override
+        public int getId() {
+            return id;
+        }
+
+        @Override
+        public EntityType getParent() {
+            return parent;
+        }
+
+        static {
+            for (EntityType type : EntityType.values()) {
+                TYPES.put(type.id, type);
+            }
+        }
+
+        public static Optional<EntityType> findById(int id) {
+            if (id == -1)  // Check if this is called
+                return Optional.empty();
+            return Optional.ofNullable(TYPES.get(id));
+        }
+    }
+
+    public enum ObjectType implements com.viaversion.viaversion.api.minecraft.entities.ObjectType {
+        BOAT(1, EntityType.BOAT),
+        ITEM(2, EntityType.DROPPED_ITEM),
+        AREA_EFFECT_CLOUD(3, EntityType.AREA_EFFECT_CLOUD),
+        MINECART(10, EntityType.MINECART_RIDEABLE),
+        TNT_PRIMED(50, EntityType.PRIMED_TNT),
+        ENDER_CRYSTAL(51, EntityType.ENDER_CRYSTAL),
+        TIPPED_ARROW(60, EntityType.ARROW),
+        SNOWBALL(61, EntityType.SNOWBALL),
+        EGG(62, EntityType.EGG),
+        FIREBALL(63, EntityType.FIREBALL),
+        SMALL_FIREBALL(64, EntityType.SMALL_FIREBALL),
+        ENDER_PEARL(65, EntityType.ENDER_PEARL),
+        WITHER_SKULL(66, EntityType.WITHER_SKULL),
+        SHULKER_BULLET(67, EntityType.SHULKER_BULLET),
+        LIAMA_SPIT(68, EntityType.LIAMA_SPIT),
+        FALLING_BLOCK(70, EntityType.FALLING_BLOCK),
+        ITEM_FRAME(71, EntityType.ITEM_FRAME),
+        ENDER_SIGNAL(72, EntityType.ENDER_SIGNAL),
+        POTION(73, EntityType.SPLASH_POTION),
+        THROWN_EXP_BOTTLE(75, EntityType.THROWN_EXP_BOTTLE),
+        FIREWORK(76, EntityType.FIREWORK),
+        LEASH(77, EntityType.LEASH_HITCH),
+        ARMOR_STAND(78, EntityType.ARMOR_STAND),
+        EVOCATION_FANGS(79, EntityType.EVOCATION_FANGS),
+        FISHIHNG_HOOK(90, EntityType.FISHING_HOOK),
+        SPECTRAL_ARROW(91, EntityType.SPECTRAL_ARROW),
+        DRAGON_FIREBALL(93, EntityType.DRAGON_FIREBALL);
+
+        private static final Map<Integer, ObjectType> TYPES = new HashMap<>();
+
+        private final int id;
+        private final EntityType type;
+
+        static {
+            for (ObjectType type : ObjectType.values()) {
+                TYPES.put(type.id, type);
+            }
+        }
+
+        ObjectType(int id, EntityType type) {
+            this.id = id;
+            this.type = type;
+        }
+
+        @Override
+        public int getId() {
+            return id;
+        }
+
+        @Override
+        public EntityType getType() {
+            return type;
+        }
+
+        public static Optional<ObjectType> findById(int id) {
+            if (id == -1)
+                return Optional.empty();
+            return Optional.ofNullable(TYPES.get(id));
+        }
+
+        public static Optional<EntityType> getPCEntity(int id) {
+            Optional<ObjectType> output = findById(id);
+
+            if (!output.isPresent())
+                return Optional.empty();
+            return Optional.of(output.get().type);
+        }
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/entities/Entity1_12Types.java

@@ -0,0 +1,276 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package com.viaversion.viaversion.api.minecraft.entities;
+
+import com.viaversion.viaversion.api.Via;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+
+// 1.12 Entity / Object taken from https://github.com/Matsv/ViaBackwards/blob/master/core/src/main/java/nl/matsv/viabackwards/api/entities/types/EntityType1_12.java
+public class Entity1_12Types {
+
+    public static EntityType getTypeFromId(int typeID, boolean isObject) {
+        Optional<EntityType> type;
+
+        if (isObject)
+            type = ObjectType.getPCEntity(typeID);
+        else
+            type = EntityType.findById(typeID);
+
+        if (!type.isPresent()) {
+            Via.getPlatform().getLogger().severe("Could not find 1.12 type id " + typeID + " isObject=" + isObject);
+            return EntityType.ENTITY; // Fall back to the basic ENTITY
+        }
+
+        return type.get();
+    }
+
+    public enum EntityType implements com.viaversion.viaversion.api.minecraft.entities.EntityType {
+        ENTITY(-1),
+        DROPPED_ITEM(1, ENTITY),
+        EXPERIENCE_ORB(2, ENTITY),
+        LEASH_HITCH(8, ENTITY), // Actually entity hanging but it doesn't make a lot of difference for metadata
+        PAINTING(9, ENTITY), // Actually entity hanging but it doesn't make a lot of difference for metadata
+        ARROW(10, ENTITY),
+        SNOWBALL(11, ENTITY), // Actually EntityProjectile
+        FIREBALL(12, ENTITY),
+        SMALL_FIREBALL(13, ENTITY),
+        ENDER_PEARL(14, ENTITY), // Actually EntityProjectile
+        ENDER_SIGNAL(15, ENTITY),
+        THROWN_EXP_BOTTLE(17, ENTITY),
+        ITEM_FRAME(18, ENTITY), // Actually EntityHanging
+        WITHER_SKULL(19, ENTITY),
+        PRIMED_TNT(20, ENTITY),
+        FALLING_BLOCK(21, ENTITY),
+        FIREWORK(22, ENTITY),
+        SPECTRAL_ARROW(24, ARROW),
+        SHULKER_BULLET(25, ENTITY),
+        DRAGON_FIREBALL(26, FIREBALL),
+        EVOCATION_FANGS(33, ENTITY),
+
+
+        ENTITY_LIVING(-1, ENTITY),
+        ENTITY_INSENTIENT(-1, ENTITY_LIVING),
+        ENTITY_AGEABLE(-1, ENTITY_INSENTIENT),
+        ENTITY_TAMEABLE_ANIMAL(-1, ENTITY_AGEABLE),
+        ENTITY_HUMAN(-1, ENTITY_LIVING),
+
+        ARMOR_STAND(30, ENTITY_LIVING),
+        ENTITY_ILLAGER_ABSTRACT(-1, ENTITY_INSENTIENT),
+        EVOCATION_ILLAGER(34, ENTITY_ILLAGER_ABSTRACT),
+        VEX(35, ENTITY_INSENTIENT),
+        VINDICATION_ILLAGER(36, ENTITY_ILLAGER_ABSTRACT),
+        ILLUSION_ILLAGER(37, EVOCATION_ILLAGER),
+
+        // Vehicles
+        MINECART_ABSTRACT(-1, ENTITY),
+        MINECART_COMMAND(40, MINECART_ABSTRACT),
+        BOAT(41, ENTITY),
+        MINECART_RIDEABLE(42, MINECART_ABSTRACT),
+        MINECART_CHEST(43, MINECART_ABSTRACT),
+        MINECART_FURNACE(44, MINECART_ABSTRACT),
+        MINECART_TNT(45, MINECART_ABSTRACT),
+        MINECART_HOPPER(46, MINECART_ABSTRACT),
+        MINECART_MOB_SPAWNER(47, MINECART_ABSTRACT),
+
+        CREEPER(50, ENTITY_INSENTIENT),
+
+        ABSTRACT_SKELETON(-1, ENTITY_INSENTIENT),
+        SKELETON(51, ABSTRACT_SKELETON),
+        WITHER_SKELETON(5, ABSTRACT_SKELETON),
+        STRAY(6, ABSTRACT_SKELETON),
+
+        SPIDER(52, ENTITY_INSENTIENT),
+        GIANT(53, ENTITY_INSENTIENT),
+
+        ZOMBIE(54, ENTITY_INSENTIENT),
+        HUSK(23, ZOMBIE),
+        ZOMBIE_VILLAGER(27, ZOMBIE),
+
+        SLIME(55, ENTITY_INSENTIENT),
+        GHAST(56, ENTITY_INSENTIENT),
+        PIG_ZOMBIE(57, ZOMBIE),
+        ENDERMAN(58, ENTITY_INSENTIENT),
+        CAVE_SPIDER(59, SPIDER),
+        SILVERFISH(60, ENTITY_INSENTIENT),
+        BLAZE(61, ENTITY_INSENTIENT),
+        MAGMA_CUBE(62, SLIME),
+        ENDER_DRAGON(63, ENTITY_INSENTIENT),
+        WITHER(64, ENTITY_INSENTIENT),
+        BAT(65, ENTITY_INSENTIENT),
+        WITCH(66, ENTITY_INSENTIENT),
+        ENDERMITE(67, ENTITY_INSENTIENT),
+
+        GUARDIAN(68, ENTITY_INSENTIENT),
+        ELDER_GUARDIAN(4, GUARDIAN), // Moved down to avoid illegal forward reference
+
+        IRON_GOLEM(99, ENTITY_INSENTIENT), // moved up to avoid illegal forward references
+        SHULKER(69, IRON_GOLEM),
+        PIG(90, ENTITY_AGEABLE),
+        SHEEP(91, ENTITY_AGEABLE),
+        COW(92, ENTITY_AGEABLE),
+        CHICKEN(93, ENTITY_AGEABLE),
+        SQUID(94, ENTITY_INSENTIENT),
+        WOLF(95, ENTITY_TAMEABLE_ANIMAL),
+        MUSHROOM_COW(96, COW),
+        SNOWMAN(97, IRON_GOLEM),
+        OCELOT(98, ENTITY_TAMEABLE_ANIMAL),
+        PARROT(105, ENTITY_TAMEABLE_ANIMAL),
+
+        ABSTRACT_HORSE(-1, ENTITY_AGEABLE),
+        HORSE(100, ABSTRACT_HORSE),
+        SKELETON_HORSE(28, ABSTRACT_HORSE),
+        ZOMBIE_HORSE(29, ABSTRACT_HORSE),
+
+        CHESTED_HORSE(-1, ABSTRACT_HORSE),
+        DONKEY(31, CHESTED_HORSE),
+        MULE(32, CHESTED_HORSE),
+        LIAMA(103, CHESTED_HORSE),
+
+
+        RABBIT(101, ENTITY_AGEABLE),
+        POLAR_BEAR(102, ENTITY_AGEABLE),
+        VILLAGER(120, ENTITY_AGEABLE),
+        ENDER_CRYSTAL(200, ENTITY),
+        SPLASH_POTION(-1, ENTITY),
+        LINGERING_POTION(-1, SPLASH_POTION),
+        AREA_EFFECT_CLOUD(-1, ENTITY),
+        EGG(-1, ENTITY),
+        FISHING_HOOK(-1, ENTITY),
+        LIGHTNING(-1, ENTITY),
+        WEATHER(-1, ENTITY),
+        PLAYER(-1, ENTITY_HUMAN),
+        COMPLEX_PART(-1, ENTITY),
+        LIAMA_SPIT(-1, ENTITY);
+
+        private static final Map<Integer, EntityType> TYPES = new HashMap<>();
+
+        private final int id;
+        private final EntityType parent;
+
+        EntityType(int id) {
+            this.id = id;
+            this.parent = null;
+        }
+
+        EntityType(int id, EntityType parent) {
+            this.id = id;
+            this.parent = parent;
+        }
+
+        @Override
+        public int getId() {
+            return id;
+        }
+
+        @Override
+        public EntityType getParent() {
+            return parent;
+        }
+
+        static {
+            for (EntityType type : EntityType.values()) {
+                TYPES.put(type.id, type);
+            }
+        }
+
+        public static Optional<EntityType> findById(int id) {
+            if (id == -1)  // Check if this is called
+                return Optional.empty();
+            return Optional.ofNullable(TYPES.get(id));
+        }
+    }
+
+    public enum ObjectType implements com.viaversion.viaversion.api.minecraft.entities.ObjectType {
+        BOAT(1, EntityType.BOAT),
+        ITEM(2, EntityType.DROPPED_ITEM),
+        AREA_EFFECT_CLOUD(3, EntityType.AREA_EFFECT_CLOUD),
+        MINECART(10, EntityType.MINECART_RIDEABLE),
+        TNT_PRIMED(50, EntityType.PRIMED_TNT),
+        ENDER_CRYSTAL(51, EntityType.ENDER_CRYSTAL),
+        TIPPED_ARROW(60, EntityType.ARROW),
+        SNOWBALL(61, EntityType.SNOWBALL),
+        EGG(62, EntityType.EGG),
+        FIREBALL(63, EntityType.FIREBALL),
+        SMALL_FIREBALL(64, EntityType.SMALL_FIREBALL),
+        ENDER_PEARL(65, EntityType.ENDER_PEARL),
+        WITHER_SKULL(66, EntityType.WITHER_SKULL),
+        SHULKER_BULLET(67, EntityType.SHULKER_BULLET),
+        LIAMA_SPIT(68, EntityType.LIAMA_SPIT),
+        FALLING_BLOCK(70, EntityType.FALLING_BLOCK),
+        ITEM_FRAME(71, EntityType.ITEM_FRAME),
+        ENDER_SIGNAL(72, EntityType.ENDER_SIGNAL),
+        POTION(73, EntityType.SPLASH_POTION),
+        THROWN_EXP_BOTTLE(75, EntityType.THROWN_EXP_BOTTLE),
+        FIREWORK(76, EntityType.FIREWORK),
+        LEASH(77, EntityType.LEASH_HITCH),
+        ARMOR_STAND(78, EntityType.ARMOR_STAND),
+        EVOCATION_FANGS(79, EntityType.EVOCATION_FANGS),
+        FISHIHNG_HOOK(90, EntityType.FISHING_HOOK),
+        SPECTRAL_ARROW(91, EntityType.SPECTRAL_ARROW),
+        DRAGON_FIREBALL(93, EntityType.DRAGON_FIREBALL);
+
+        private static final Map<Integer, ObjectType> TYPES = new HashMap<>();
+
+        private final int id;
+        private final EntityType type;
+
+        static {
+            for (ObjectType type : ObjectType.values()) {
+                TYPES.put(type.id, type);
+            }
+        }
+
+        ObjectType(int id, EntityType type) {
+            this.id = id;
+            this.type = type;
+        }
+
+        @Override
+        public int getId() {
+            return id;
+        }
+
+        @Override
+        public EntityType getType() {
+            return type;
+        }
+
+        public static Optional<ObjectType> findById(int id) {
+            if (id == -1)
+                return Optional.empty();
+            return Optional.ofNullable(TYPES.get(id));
+        }
+
+        public static Optional<EntityType> getPCEntity(int id) {
+            Optional<ObjectType> output = findById(id);
+
+            if (!output.isPresent())
+                return Optional.empty();
+            return Optional.of(output.get().type);
+        }
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/entities/Entity1_13Types.java

@@ -0,0 +1,332 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.entities;
+
+import com.viaversion.viaversion.api.Via;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+
+public class Entity1_13Types {
+
+    public static EntityType getTypeFromId(int typeID, boolean isObject) {
+        Optional<EntityType> type;
+
+        if (isObject)
+            type = ObjectType.getPCEntity(typeID);
+        else
+            type = EntityType.findById(typeID);
+
+        if (!type.isPresent()) {
+            Via.getPlatform().getLogger().severe("Could not find 1.13 type id " + typeID + " isObject=" + isObject);
+            return EntityType.ENTITY; // Fall back to the basic ENTITY
+        }
+
+        return type.get();
+    }
+
+    public enum EntityType implements com.viaversion.viaversion.api.minecraft.entities.EntityType {
+        // Auto generated
+
+        ENTITY(-1), // abm
+
+        AREA_EFFECT_CLOUD(0, ENTITY), // abk
+        END_CRYSTAL(16, ENTITY), // aho
+        EVOKER_FANGS(20, ENTITY), // ala
+        EXPERIENCE_ORB(22, ENTITY), // abs
+        EYE_OF_ENDER(23, ENTITY), // alb
+        FALLING_BLOCK(24, ENTITY), // aix
+        FIREWORK_ROCKET(25, ENTITY), // alc
+        ITEM(32, ENTITY), // aiy
+        LLAMA_SPIT(37, ENTITY), // ale
+        TNT(55, ENTITY), // aiz
+        SHULKER_BULLET(60, ENTITY), // alh
+        FISHING_BOBBER(93, ENTITY), // ais
+
+        LIVINGENTITY(-1, ENTITY), // abv
+        ARMOR_STAND(1, LIVINGENTITY), // ail
+        PLAYER(92, LIVINGENTITY), // aks
+
+        ABSTRACT_INSENTIENT(-1, LIVINGENTITY), // abw
+        ENDER_DRAGON(17, ABSTRACT_INSENTIENT), // ahp
+
+        ABSTRACT_CREATURE(-1, ABSTRACT_INSENTIENT), // acd
+
+        ABSTRACT_AGEABLE(-1, ABSTRACT_CREATURE), // abj
+        VILLAGER(79, ABSTRACT_AGEABLE), // akn
+
+        // Animals
+        ABSTRACT_ANIMAL(-1, ABSTRACT_AGEABLE), // agd
+        CHICKEN(7, ABSTRACT_ANIMAL), // age
+        COW(9, ABSTRACT_ANIMAL), // agg
+        MOOSHROOM(47, COW), // agi
+        PIG(51, ABSTRACT_ANIMAL), // agl
+        POLAR_BEAR(54, ABSTRACT_ANIMAL), // agm
+        RABBIT(56, ABSTRACT_ANIMAL), // ago
+        SHEEP(58, ABSTRACT_ANIMAL), // agq
+        TURTLE(73, ABSTRACT_ANIMAL), // agv
+
+        ABSTRACT_TAMEABLE_ANIMAL(-1, ABSTRACT_ANIMAL), // acg
+        OCELOT(48, ABSTRACT_TAMEABLE_ANIMAL), // agj
+        WOLF(86, ABSTRACT_TAMEABLE_ANIMAL), // agy
+
+        ABSTRACT_PARROT(-1, ABSTRACT_TAMEABLE_ANIMAL), // agr
+        PARROT(50, ABSTRACT_PARROT), // agk
+
+        // Horses
+        ABSTRACT_HORSE(-1, ABSTRACT_ANIMAL), // aha
+        CHESTED_HORSE(-1, ABSTRACT_HORSE), // agz
+        DONKEY(11, CHESTED_HORSE), // ahb
+        MULE(46, CHESTED_HORSE), // ahf
+        LLAMA(36, CHESTED_HORSE), // ahe
+        HORSE(29, ABSTRACT_HORSE), // ahc
+        SKELETON_HORSE(63, ABSTRACT_HORSE), // ahg
+        ZOMBIE_HORSE(88, ABSTRACT_HORSE), // ahi
+
+        // Golem
+        ABSTRACT_GOLEM(-1, ABSTRACT_CREATURE), // agc
+        SNOW_GOLEM(66, ABSTRACT_GOLEM), // ags
+        IRON_GOLEM(80, ABSTRACT_GOLEM), // agw
+        SHULKER(59, ABSTRACT_GOLEM), // ajx
+
+        // Fish
+        ABSTRACT_FISHES(-1, ABSTRACT_CREATURE), // agb
+        COD(8, ABSTRACT_FISHES), // agf
+        PUFFERFISH(52, ABSTRACT_FISHES), // agn
+        SALMON(57, ABSTRACT_FISHES), // agp
+        TROPICAL_FISH(72, ABSTRACT_FISHES), // agu
+
+        // Monsters
+        ABSTRACT_MONSTER(-1, ABSTRACT_CREATURE), // ajs
+        BLAZE(4, ABSTRACT_MONSTER), // ajd
+        CREEPER(10, ABSTRACT_MONSTER), // ajf
+        ENDERMITE(19, ABSTRACT_MONSTER), // ajj
+        ENDERMAN(18, ABSTRACT_MONSTER), // aji
+        GIANT(27, ABSTRACT_MONSTER), // ajn
+        SILVERFISH(61, ABSTRACT_MONSTER), // ajy
+        VEX(78, ABSTRACT_MONSTER), // ake
+        WITCH(82, ABSTRACT_MONSTER), // akg
+        WITHER(83, ABSTRACT_MONSTER), // aij
+
+        // Illagers
+        ABSTRACT_ILLAGER_BASE(-1, ABSTRACT_MONSTER), // ajb
+        ABSTRACT_EVO_ILLU_ILLAGER(-1, ABSTRACT_ILLAGER_BASE), // akb
+        EVOKER(21, ABSTRACT_EVO_ILLU_ILLAGER), // ajl
+        ILLUSIONER(31, ABSTRACT_EVO_ILLU_ILLAGER), // ajq
+        VINDICATOR(81, ABSTRACT_ILLAGER_BASE), // akf
+
+        // Skeletons
+        ABSTRACT_SKELETON(-1, ABSTRACT_MONSTER), // ajc
+        SKELETON(62, ABSTRACT_SKELETON), // ajz
+        STRAY(71, ABSTRACT_SKELETON), // akd
+        WITHER_SKELETON(84, ABSTRACT_SKELETON), // akh
+
+        // Guardians
+        GUARDIAN(28, ABSTRACT_MONSTER), // ajo
+        ELDER_GUARDIAN(15, GUARDIAN), // ajh
+
+        // Spiders
+        SPIDER(69, ABSTRACT_MONSTER), // akc
+        CAVE_SPIDER(6, SPIDER), // aje
+
+        // Zombies - META CHECKED
+        ZOMBIE(87, ABSTRACT_MONSTER), // aki
+        DROWNED(14, ZOMBIE), // ajg
+        HUSK(30, ZOMBIE), // ajp
+        ZOMBIE_PIGMAN(53, ZOMBIE), // aju
+        ZOMBIE_VILLAGER(89, ZOMBIE), // akj
+
+        // Flying entities
+        ABSTRACT_FLYING(-1, ABSTRACT_INSENTIENT), // abt
+        GHAST(26, ABSTRACT_FLYING), // ajm
+        PHANTOM(90, ABSTRACT_FLYING), // ajt
+
+        ABSTRACT_AMBIENT(-1, ABSTRACT_INSENTIENT), // afy
+        BAT(3, ABSTRACT_AMBIENT), // afz
+
+        ABSTRACT_WATERMOB(-1, ABSTRACT_INSENTIENT), // agx
+        SQUID(70, ABSTRACT_WATERMOB), // agt
+        DOLPHIN(12, ABSTRACT_WATERMOB),
+
+        // Slimes
+        SLIME(64, ABSTRACT_INSENTIENT), // aka
+        MAGMA_CUBE(38, SLIME), // ajr
+
+        // Hangable objects
+        ABSTRACT_HANGING(-1, ENTITY), // aim
+        LEASH_KNOT(35, ABSTRACT_HANGING), // aio
+        ITEM_FRAME(33, ABSTRACT_HANGING), // ain
+        PAINTING(49, ABSTRACT_HANGING), // aiq
+
+        ABSTRACT_LIGHTNING(-1, ENTITY), // aiu
+        LIGHTNING_BOLT(91, ABSTRACT_LIGHTNING), // aiv
+
+        // Arrows
+        ABSTRACT_ARROW(-1, ENTITY), // akw
+        ARROW(2, ABSTRACT_ARROW), // aky
+        SPECTRAL_ARROW(68, ABSTRACT_ARROW), // alk
+        TRIDENT(94, ABSTRACT_ARROW), // alq
+
+        // Fireballs
+        ABSTRACT_FIREBALL(-1, ENTITY), // akx
+        DRAGON_FIREBALL(13, ABSTRACT_FIREBALL), // akz
+        FIREBALL(34, ABSTRACT_FIREBALL), // ald
+        SMALL_FIREBALL(65, ABSTRACT_FIREBALL), // ali
+        WITHER_SKULL(85, ABSTRACT_FIREBALL), // alr
+
+        // Projectiles
+        PROJECTILE_ABSTRACT(-1, ENTITY), // all
+        SNOWBALL(67, PROJECTILE_ABSTRACT), // alj
+        ENDER_PEARL(75, PROJECTILE_ABSTRACT), // aln
+        EGG(74, PROJECTILE_ABSTRACT), // alm
+        POTION(77, PROJECTILE_ABSTRACT), // alp
+        EXPERIENCE_BOTTLE(76, PROJECTILE_ABSTRACT), // alo
+
+        // Vehicles
+        MINECART_ABSTRACT(-1, ENTITY), // alt
+        CHESTED_MINECART_ABSTRACT(-1, MINECART_ABSTRACT), // alu
+        CHEST_MINECART(40, CHESTED_MINECART_ABSTRACT), // alx
+        HOPPER_MINECART(43, CHESTED_MINECART_ABSTRACT), // ama
+        MINECART(39, MINECART_ABSTRACT), // alw
+        FURNACE_MINECART(42, MINECART_ABSTRACT), // alz
+        COMMAND_BLOCK_MINECART(41, MINECART_ABSTRACT), // aly
+        TNT_MINECART(45, MINECART_ABSTRACT), // amc
+        SPAWNER_MINECART(44, MINECART_ABSTRACT), // amb
+        BOAT(5, ENTITY); // alv
+
+        private static final Map<Integer, EntityType> TYPES = new HashMap<>();
+
+        private final int id;
+        private final EntityType parent;
+
+        EntityType(int id) {
+            this.id = id;
+            this.parent = null;
+        }
+
+        EntityType(int id, EntityType parent) {
+            this.id = id;
+            this.parent = parent;
+        }
+
+        @Override
+        public int getId() {
+            return id;
+        }
+
+        @Override
+        public EntityType getParent() {
+            return parent;
+        }
+
+        static {
+            for (EntityType type : EntityType.values()) {
+                TYPES.put(type.id, type);
+            }
+        }
+
+        public static Optional<EntityType> findById(int id) {
+            if (id == -1)  // Check if this is called
+                return Optional.empty();
+            return Optional.ofNullable(TYPES.get(id));
+        }
+    }
+
+    public enum ObjectType implements com.viaversion.viaversion.api.minecraft.entities.ObjectType {
+        BOAT(1, EntityType.BOAT),
+        ITEM(2, EntityType.ITEM),
+        AREA_EFFECT_CLOUD(3, EntityType.AREA_EFFECT_CLOUD),
+        MINECART(10, EntityType.MINECART),
+        TNT_PRIMED(50, EntityType.TNT),
+        ENDER_CRYSTAL(51, EntityType.END_CRYSTAL),
+        TIPPED_ARROW(60, EntityType.ARROW),
+        SNOWBALL(61, EntityType.SNOWBALL),
+        EGG(62, EntityType.EGG),
+        FIREBALL(63, EntityType.FIREBALL),
+        SMALL_FIREBALL(64, EntityType.SMALL_FIREBALL),
+        ENDER_PEARL(65, EntityType.ENDER_PEARL),
+        WITHER_SKULL(66, EntityType.WITHER_SKULL),
+        SHULKER_BULLET(67, EntityType.SHULKER_BULLET),
+        LLAMA_SPIT(68, EntityType.LLAMA_SPIT),
+        FALLING_BLOCK(70, EntityType.FALLING_BLOCK),
+        ITEM_FRAME(71, EntityType.ITEM_FRAME),
+        EYE_OF_ENDER(72, EntityType.EYE_OF_ENDER),
+        POTION(73, EntityType.POTION),
+        EXPERIENCE_BOTTLE(75, EntityType.EXPERIENCE_BOTTLE),
+        FIREWORK_ROCKET(76, EntityType.FIREWORK_ROCKET),
+        LEASH(77, EntityType.LEASH_KNOT),
+        ARMOR_STAND(78, EntityType.ARMOR_STAND),
+        EVOKER_FANGS(79, EntityType.EVOKER_FANGS),
+        FISHIHNG_HOOK(90, EntityType.FISHING_BOBBER),
+        SPECTRAL_ARROW(91, EntityType.SPECTRAL_ARROW),
+        DRAGON_FIREBALL(93, EntityType.DRAGON_FIREBALL),
+        TRIDENT(94, EntityType.TRIDENT);
+
+        private static final Map<Integer, ObjectType> TYPES = new HashMap<>();
+
+        private final int id;
+        private final EntityType type;
+
+        static {
+            for (ObjectType type : ObjectType.values()) {
+                TYPES.put(type.id, type);
+            }
+        }
+
+        ObjectType(int id, EntityType type) {
+            this.id = id;
+            this.type = type;
+        }
+
+        @Override
+        public int getId() {
+            return id;
+        }
+
+        @Override
+        public EntityType getType() {
+            return type;
+        }
+
+        public static Optional<ObjectType> findById(int id) {
+            if (id == -1)
+                return Optional.empty();
+            return Optional.ofNullable(TYPES.get(id));
+        }
+
+        public static Optional<EntityType> getPCEntity(int id) {
+            Optional<ObjectType> output = findById(id);
+            if (!output.isPresent())
+                return Optional.empty();
+            return Optional.of(output.get().type);
+        }
+
+        public static Optional<ObjectType> fromEntityType(EntityType type) {
+            for (ObjectType ent : ObjectType.values())
+                if (ent.type == type)
+                    return Optional.of(ent);
+            return Optional.empty();
+        }
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/entities/Entity1_14Types.java

@@ -0,0 +1,234 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.entities;
+
+import com.viaversion.viaversion.util.EntityTypeUtil;
+
+public enum Entity1_14Types implements EntityType {
+
+    ENTITY(-1),
+
+    AREA_EFFECT_CLOUD(0, ENTITY),
+    END_CRYSTAL(17, ENTITY),
+    EVOKER_FANGS(21, ENTITY),
+    EXPERIENCE_ORB(23, ENTITY),
+    EYE_OF_ENDER(24, ENTITY),
+    FALLING_BLOCK(25, ENTITY),
+    FIREWORK_ROCKET(26, ENTITY),
+    ITEM(34, ENTITY),
+    LLAMA_SPIT(39, ENTITY),
+    TNT(58, ENTITY),
+    SHULKER_BULLET(63, ENTITY),
+    FISHING_BOBBER(101, ENTITY),
+
+    LIVINGENTITY(-1, ENTITY),
+    ARMOR_STAND(1, LIVINGENTITY),
+    PLAYER(100, LIVINGENTITY),
+
+    ABSTRACT_INSENTIENT(-1, LIVINGENTITY),
+    ENDER_DRAGON(18, ABSTRACT_INSENTIENT),
+
+    ABSTRACT_CREATURE(-1, ABSTRACT_INSENTIENT),
+
+    ABSTRACT_AGEABLE(-1, ABSTRACT_CREATURE),
+    VILLAGER(84, ABSTRACT_AGEABLE),
+    WANDERING_TRADER(88, ABSTRACT_AGEABLE),
+
+    // Animals
+    ABSTRACT_ANIMAL(-1, ABSTRACT_AGEABLE),
+    DOLPHIN(13, ABSTRACT_INSENTIENT),
+    CHICKEN(8, ABSTRACT_ANIMAL),
+    COW(10, ABSTRACT_ANIMAL),
+    MOOSHROOM(49, COW),
+    PANDA(52, ABSTRACT_INSENTIENT),
+    PIG(54, ABSTRACT_ANIMAL),
+    POLAR_BEAR(57, ABSTRACT_ANIMAL),
+    RABBIT(59, ABSTRACT_ANIMAL),
+    SHEEP(61, ABSTRACT_ANIMAL),
+    TURTLE(77, ABSTRACT_ANIMAL),
+    FOX(27, ABSTRACT_ANIMAL),
+
+    ABSTRACT_TAMEABLE_ANIMAL(-1, ABSTRACT_ANIMAL),
+    CAT(6, ABSTRACT_TAMEABLE_ANIMAL),
+    OCELOT(50, ABSTRACT_TAMEABLE_ANIMAL),
+    WOLF(93, ABSTRACT_TAMEABLE_ANIMAL),
+
+    ABSTRACT_PARROT(-1, ABSTRACT_TAMEABLE_ANIMAL),
+    PARROT(53, ABSTRACT_PARROT),
+
+    // Horses
+    ABSTRACT_HORSE(-1, ABSTRACT_ANIMAL),
+    CHESTED_HORSE(-1, ABSTRACT_HORSE),
+    DONKEY(12, CHESTED_HORSE),
+    MULE(48, CHESTED_HORSE),
+    LLAMA(38, CHESTED_HORSE),
+    TRADER_LLAMA(75, CHESTED_HORSE),
+    HORSE(31, ABSTRACT_HORSE),
+    SKELETON_HORSE(66, ABSTRACT_HORSE),
+    ZOMBIE_HORSE(95, ABSTRACT_HORSE),
+
+    // Golem
+    ABSTRACT_GOLEM(-1, ABSTRACT_CREATURE),
+    SNOW_GOLEM(69, ABSTRACT_GOLEM),
+    IRON_GOLEM(85, ABSTRACT_GOLEM),
+    SHULKER(62, ABSTRACT_GOLEM),
+
+    // Fish
+    ABSTRACT_FISHES(-1, ABSTRACT_CREATURE),
+    COD(9, ABSTRACT_FISHES),
+    PUFFERFISH(55, ABSTRACT_FISHES),
+    SALMON(60, ABSTRACT_FISHES),
+    TROPICAL_FISH(76, ABSTRACT_FISHES),
+
+    // Monsters
+    ABSTRACT_MONSTER(-1, ABSTRACT_CREATURE),
+    BLAZE(4, ABSTRACT_MONSTER),
+    CREEPER(11, ABSTRACT_MONSTER),
+    ENDERMITE(20, ABSTRACT_MONSTER),
+    ENDERMAN(19, ABSTRACT_MONSTER),
+    GIANT(29, ABSTRACT_MONSTER),
+    SILVERFISH(64, ABSTRACT_MONSTER),
+    VEX(83, ABSTRACT_MONSTER),
+    WITCH(89, ABSTRACT_MONSTER),
+    WITHER(90, ABSTRACT_MONSTER),
+    RAVAGER(98, ABSTRACT_MONSTER),
+
+    // Illagers
+    ABSTRACT_ILLAGER_BASE(-1, ABSTRACT_MONSTER),
+    ABSTRACT_EVO_ILLU_ILLAGER(-1, ABSTRACT_ILLAGER_BASE),
+    EVOKER(22, ABSTRACT_EVO_ILLU_ILLAGER),
+    ILLUSIONER(33, ABSTRACT_EVO_ILLU_ILLAGER),
+    VINDICATOR(86, ABSTRACT_ILLAGER_BASE),
+    PILLAGER(87, ABSTRACT_ILLAGER_BASE),
+
+    // Skeletons
+    ABSTRACT_SKELETON(-1, ABSTRACT_MONSTER),
+    SKELETON(65, ABSTRACT_SKELETON),
+    STRAY(74, ABSTRACT_SKELETON),
+    WITHER_SKELETON(91, ABSTRACT_SKELETON),
+
+    // Guardians
+    GUARDIAN(30, ABSTRACT_MONSTER),
+    ELDER_GUARDIAN(16, GUARDIAN),
+
+    // Spiders
+    SPIDER(72, ABSTRACT_MONSTER),
+    CAVE_SPIDER(7, SPIDER),
+
+    // Zombies - META CHECKED
+    ZOMBIE(94, ABSTRACT_MONSTER),
+    DROWNED(15, ZOMBIE),
+    HUSK(32, ZOMBIE),
+    ZOMBIE_PIGMAN(56, ZOMBIE),
+    ZOMBIE_VILLAGER(96, ZOMBIE),
+
+    // Flying entities
+    ABSTRACT_FLYING(-1, ABSTRACT_INSENTIENT),
+    GHAST(28, ABSTRACT_FLYING),
+    PHANTOM(97, ABSTRACT_FLYING),
+
+    ABSTRACT_AMBIENT(-1, ABSTRACT_INSENTIENT),
+    BAT(3, ABSTRACT_AMBIENT),
+
+    ABSTRACT_WATERMOB(-1, ABSTRACT_INSENTIENT),
+    SQUID(73, ABSTRACT_WATERMOB),
+
+    // Slimes
+    SLIME(67, ABSTRACT_INSENTIENT),
+    MAGMA_CUBE(40, SLIME),
+
+    // Hangable objects
+    ABSTRACT_HANGING(-1, ENTITY),
+    LEASH_KNOT(37, ABSTRACT_HANGING),
+    ITEM_FRAME(35, ABSTRACT_HANGING),
+    PAINTING(51, ABSTRACT_HANGING),
+
+    ABSTRACT_LIGHTNING(-1, ENTITY),
+    LIGHTNING_BOLT(99, ABSTRACT_LIGHTNING),
+
+    // Arrows
+    ABSTRACT_ARROW(-1, ENTITY),
+    ARROW(2, ABSTRACT_ARROW),
+    SPECTRAL_ARROW(71, ABSTRACT_ARROW),
+    TRIDENT(82, ABSTRACT_ARROW),
+
+    // Fireballs
+    ABSTRACT_FIREBALL(-1, ENTITY),
+    DRAGON_FIREBALL(14, ABSTRACT_FIREBALL),
+    FIREBALL(36, ABSTRACT_FIREBALL),
+    SMALL_FIREBALL(68, ABSTRACT_FIREBALL),
+    WITHER_SKULL(92, ABSTRACT_FIREBALL),
+
+    // Projectiles
+    PROJECTILE_ABSTRACT(-1, ENTITY),
+    SNOWBALL(70, PROJECTILE_ABSTRACT),
+    ENDER_PEARL(79, PROJECTILE_ABSTRACT),
+    EGG(78, PROJECTILE_ABSTRACT),
+    POTION(81, PROJECTILE_ABSTRACT),
+    EXPERIENCE_BOTTLE(80, PROJECTILE_ABSTRACT),
+
+    // Vehicles
+    MINECART_ABSTRACT(-1, ENTITY),
+    CHESTED_MINECART_ABSTRACT(-1, MINECART_ABSTRACT),
+    CHEST_MINECART(42, CHESTED_MINECART_ABSTRACT),
+    HOPPER_MINECART(45, CHESTED_MINECART_ABSTRACT),
+    MINECART(41, MINECART_ABSTRACT),
+    FURNACE_MINECART(44, MINECART_ABSTRACT),
+    COMMAND_BLOCK_MINECART(43, MINECART_ABSTRACT),
+    TNT_MINECART(47, MINECART_ABSTRACT),
+    SPAWNER_MINECART(46, MINECART_ABSTRACT),
+    BOAT(5, ENTITY);
+
+    private static final EntityType[] TYPES;
+
+    private final int id;
+    private final EntityType parent;
+
+    Entity1_14Types(int id) {
+        this.id = id;
+        this.parent = null;
+    }
+
+    Entity1_14Types(int id, EntityType parent) {
+        this.id = id;
+        this.parent = parent;
+    }
+
+    @Override
+    public int getId() {
+        return id;
+    }
+
+    @Override
+    public EntityType getParent() {
+        return parent;
+    }
+
+    static {
+        TYPES = EntityTypeUtil.toOrderedArray(values());
+    }
+
+    public static EntityType getTypeFromId(int typeId) {
+        return EntityTypeUtil.getTypeFromId(TYPES, typeId, ENTITY);
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/entities/Entity1_15Types.java

@@ -0,0 +1,236 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.entities;
+
+import com.viaversion.viaversion.util.EntityTypeUtil;
+
+public enum Entity1_15Types implements EntityType {
+
+    ENTITY(-1),
+
+    AREA_EFFECT_CLOUD(0, ENTITY),
+    END_CRYSTAL(18, ENTITY),
+    EVOKER_FANGS(22, ENTITY),
+    EXPERIENCE_ORB(24, ENTITY),
+    EYE_OF_ENDER(25, ENTITY),
+    FALLING_BLOCK(26, ENTITY),
+    FIREWORK_ROCKET(27, ENTITY),
+    ITEM(35, ENTITY),
+    LLAMA_SPIT(40, ENTITY),
+    TNT(59, ENTITY),
+    SHULKER_BULLET(64, ENTITY),
+    FISHING_BOBBER(102, ENTITY),
+
+    LIVINGENTITY(-1, ENTITY),
+    ARMOR_STAND(1, LIVINGENTITY),
+    PLAYER(101, LIVINGENTITY),
+
+    ABSTRACT_INSENTIENT(-1, LIVINGENTITY),
+    ENDER_DRAGON(19, ABSTRACT_INSENTIENT),
+
+    BEE(4, ABSTRACT_INSENTIENT),
+
+    ABSTRACT_CREATURE(-1, ABSTRACT_INSENTIENT),
+
+    ABSTRACT_AGEABLE(-1, ABSTRACT_CREATURE),
+    VILLAGER(85, ABSTRACT_AGEABLE),
+    WANDERING_TRADER(89, ABSTRACT_AGEABLE),
+
+    // Animals
+    ABSTRACT_ANIMAL(-1, ABSTRACT_AGEABLE),
+    DOLPHIN(14, ABSTRACT_INSENTIENT),
+    CHICKEN(9, ABSTRACT_ANIMAL),
+    COW(11, ABSTRACT_ANIMAL),
+    MOOSHROOM(50, COW),
+    PANDA(53, ABSTRACT_INSENTIENT),
+    PIG(55, ABSTRACT_ANIMAL),
+    POLAR_BEAR(58, ABSTRACT_ANIMAL),
+    RABBIT(60, ABSTRACT_ANIMAL),
+    SHEEP(62, ABSTRACT_ANIMAL),
+    TURTLE(78, ABSTRACT_ANIMAL),
+    FOX(28, ABSTRACT_ANIMAL),
+
+    ABSTRACT_TAMEABLE_ANIMAL(-1, ABSTRACT_ANIMAL),
+    CAT(7, ABSTRACT_TAMEABLE_ANIMAL),
+    OCELOT(51, ABSTRACT_TAMEABLE_ANIMAL),
+    WOLF(94, ABSTRACT_TAMEABLE_ANIMAL),
+
+    ABSTRACT_PARROT(-1, ABSTRACT_TAMEABLE_ANIMAL),
+    PARROT(54, ABSTRACT_PARROT),
+
+    // Horses
+    ABSTRACT_HORSE(-1, ABSTRACT_ANIMAL),
+    CHESTED_HORSE(-1, ABSTRACT_HORSE),
+    DONKEY(13, CHESTED_HORSE),
+    MULE(49, CHESTED_HORSE),
+    LLAMA(39, CHESTED_HORSE),
+    TRADER_LLAMA(76, CHESTED_HORSE),
+    HORSE(32, ABSTRACT_HORSE),
+    SKELETON_HORSE(67, ABSTRACT_HORSE),
+    ZOMBIE_HORSE(96, ABSTRACT_HORSE),
+
+    // Golem
+    ABSTRACT_GOLEM(-1, ABSTRACT_CREATURE),
+    SNOW_GOLEM(70, ABSTRACT_GOLEM),
+    IRON_GOLEM(86, ABSTRACT_GOLEM),
+    SHULKER(63, ABSTRACT_GOLEM),
+
+    // Fish
+    ABSTRACT_FISHES(-1, ABSTRACT_CREATURE),
+    COD(10, ABSTRACT_FISHES),
+    PUFFERFISH(56, ABSTRACT_FISHES),
+    SALMON(61, ABSTRACT_FISHES),
+    TROPICAL_FISH(77, ABSTRACT_FISHES),
+
+    // Monsters
+    ABSTRACT_MONSTER(-1, ABSTRACT_CREATURE),
+    BLAZE(5, ABSTRACT_MONSTER),
+    CREEPER(12, ABSTRACT_MONSTER),
+    ENDERMITE(21, ABSTRACT_MONSTER),
+    ENDERMAN(20, ABSTRACT_MONSTER),
+    GIANT(30, ABSTRACT_MONSTER),
+    SILVERFISH(65, ABSTRACT_MONSTER),
+    VEX(84, ABSTRACT_MONSTER),
+    WITCH(90, ABSTRACT_MONSTER),
+    WITHER(91, ABSTRACT_MONSTER),
+    RAVAGER(99, ABSTRACT_MONSTER),
+
+    // Illagers
+    ABSTRACT_ILLAGER_BASE(-1, ABSTRACT_MONSTER),
+    ABSTRACT_EVO_ILLU_ILLAGER(-1, ABSTRACT_ILLAGER_BASE),
+    EVOKER(23, ABSTRACT_EVO_ILLU_ILLAGER),
+    ILLUSIONER(34, ABSTRACT_EVO_ILLU_ILLAGER),
+    VINDICATOR(87, ABSTRACT_ILLAGER_BASE),
+    PILLAGER(88, ABSTRACT_ILLAGER_BASE),
+
+    // Skeletons
+    ABSTRACT_SKELETON(-1, ABSTRACT_MONSTER),
+    SKELETON(66, ABSTRACT_SKELETON),
+    STRAY(75, ABSTRACT_SKELETON),
+    WITHER_SKELETON(92, ABSTRACT_SKELETON),
+
+    // Guardians
+    GUARDIAN(31, ABSTRACT_MONSTER),
+    ELDER_GUARDIAN(17, GUARDIAN),
+
+    // Spiders
+    SPIDER(73, ABSTRACT_MONSTER),
+    CAVE_SPIDER(8, SPIDER),
+
+    // Zombies
+    ZOMBIE(95, ABSTRACT_MONSTER),
+    DROWNED(16, ZOMBIE),
+    HUSK(33, ZOMBIE),
+    ZOMBIE_PIGMAN(57, ZOMBIE),
+    ZOMBIE_VILLAGER(97, ZOMBIE),
+
+    // Flying entities
+    ABSTRACT_FLYING(-1, ABSTRACT_INSENTIENT),
+    GHAST(29, ABSTRACT_FLYING),
+    PHANTOM(98, ABSTRACT_FLYING),
+
+    ABSTRACT_AMBIENT(-1, ABSTRACT_INSENTIENT),
+    BAT(3, ABSTRACT_AMBIENT),
+
+    ABSTRACT_WATERMOB(-1, ABSTRACT_INSENTIENT),
+    SQUID(74, ABSTRACT_WATERMOB),
+
+    // Slimes
+    SLIME(68, ABSTRACT_INSENTIENT),
+    MAGMA_CUBE(41, SLIME),
+
+    // Hangable objects
+    ABSTRACT_HANGING(-1, ENTITY),
+    LEASH_KNOT(38, ABSTRACT_HANGING),
+    ITEM_FRAME(36, ABSTRACT_HANGING),
+    PAINTING(52, ABSTRACT_HANGING),
+
+    ABSTRACT_LIGHTNING(-1, ENTITY),
+    LIGHTNING_BOLT(100, ABSTRACT_LIGHTNING),
+
+    // Arrows
+    ABSTRACT_ARROW(-1, ENTITY),
+    ARROW(2, ABSTRACT_ARROW),
+    SPECTRAL_ARROW(72, ABSTRACT_ARROW),
+    TRIDENT(83, ABSTRACT_ARROW),
+
+    // Fireballs
+    ABSTRACT_FIREBALL(-1, ENTITY),
+    DRAGON_FIREBALL(15, ABSTRACT_FIREBALL),
+    FIREBALL(37, ABSTRACT_FIREBALL),
+    SMALL_FIREBALL(69, ABSTRACT_FIREBALL),
+    WITHER_SKULL(93, ABSTRACT_FIREBALL),
+
+    // Projectiles
+    PROJECTILE_ABSTRACT(-1, ENTITY),
+    SNOWBALL(71, PROJECTILE_ABSTRACT),
+    ENDER_PEARL(80, PROJECTILE_ABSTRACT),
+    EGG(79, PROJECTILE_ABSTRACT),
+    POTION(82, PROJECTILE_ABSTRACT),
+    EXPERIENCE_BOTTLE(81, PROJECTILE_ABSTRACT),
+
+    // Vehicles
+    MINECART_ABSTRACT(-1, ENTITY),
+    CHESTED_MINECART_ABSTRACT(-1, MINECART_ABSTRACT),
+    CHEST_MINECART(43, CHESTED_MINECART_ABSTRACT),
+    HOPPER_MINECART(46, CHESTED_MINECART_ABSTRACT),
+    MINECART(42, MINECART_ABSTRACT),
+    FURNACE_MINECART(45, MINECART_ABSTRACT),
+    COMMAND_BLOCK_MINECART(44, MINECART_ABSTRACT),
+    TNT_MINECART(48, MINECART_ABSTRACT),
+    SPAWNER_MINECART(47, MINECART_ABSTRACT),
+    BOAT(6, ENTITY);
+
+    private static final EntityType[] TYPES;
+
+    private final int id;
+    private final EntityType parent;
+
+    Entity1_15Types(int id) {
+        this.id = id;
+        this.parent = null;
+    }
+
+    Entity1_15Types(int id, EntityType parent) {
+        this.id = id;
+        this.parent = parent;
+    }
+
+    @Override
+    public int getId() {
+        return id;
+    }
+
+    @Override
+    public EntityType getParent() {
+        return parent;
+    }
+
+    static {
+        TYPES = EntityTypeUtil.toOrderedArray(values());
+    }
+
+    public static EntityType getTypeFromId(int typeId) {
+        return EntityTypeUtil.getTypeFromId(TYPES, typeId, ENTITY);
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/entities/Entity1_16Types.java

@@ -0,0 +1,241 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.entities;
+
+import com.viaversion.viaversion.util.EntityTypeUtil;
+
+public enum Entity1_16Types implements EntityType {
+
+    ENTITY(-1),
+
+    AREA_EFFECT_CLOUD(0, ENTITY),
+    END_CRYSTAL(18, ENTITY),
+    EVOKER_FANGS(23, ENTITY),
+    EXPERIENCE_ORB(24, ENTITY),
+    EYE_OF_ENDER(25, ENTITY),
+    FALLING_BLOCK(26, ENTITY),
+    FIREWORK_ROCKET(27, ENTITY),
+    ITEM(37, ENTITY),
+    LLAMA_SPIT(43, ENTITY),
+    TNT(63, ENTITY),
+    SHULKER_BULLET(70, ENTITY),
+    FISHING_BOBBER(106, ENTITY),
+
+    LIVINGENTITY(-1, ENTITY),
+    ARMOR_STAND(1, LIVINGENTITY),
+    PLAYER(105, LIVINGENTITY),
+
+    ABSTRACT_INSENTIENT(-1, LIVINGENTITY),
+    ENDER_DRAGON(19, ABSTRACT_INSENTIENT),
+
+    BEE(4, ABSTRACT_INSENTIENT),
+
+    ABSTRACT_CREATURE(-1, ABSTRACT_INSENTIENT),
+
+    ABSTRACT_AGEABLE(-1, ABSTRACT_CREATURE),
+    VILLAGER(92, ABSTRACT_AGEABLE),
+    WANDERING_TRADER(94, ABSTRACT_AGEABLE),
+
+    // Animals
+    ABSTRACT_ANIMAL(-1, ABSTRACT_AGEABLE),
+    DOLPHIN(13, ABSTRACT_INSENTIENT),
+    CHICKEN(9, ABSTRACT_ANIMAL),
+    COW(11, ABSTRACT_ANIMAL),
+    MOOSHROOM(53, COW),
+    PANDA(56, ABSTRACT_INSENTIENT),
+    PIG(59, ABSTRACT_ANIMAL),
+    POLAR_BEAR(62, ABSTRACT_ANIMAL),
+    RABBIT(65, ABSTRACT_ANIMAL),
+    SHEEP(68, ABSTRACT_ANIMAL),
+    TURTLE(90, ABSTRACT_ANIMAL),
+    FOX(28, ABSTRACT_ANIMAL),
+
+    ABSTRACT_TAMEABLE_ANIMAL(-1, ABSTRACT_ANIMAL),
+    CAT(7, ABSTRACT_TAMEABLE_ANIMAL),
+    OCELOT(54, ABSTRACT_TAMEABLE_ANIMAL),
+    WOLF(99, ABSTRACT_TAMEABLE_ANIMAL),
+
+    ABSTRACT_PARROT(-1, ABSTRACT_TAMEABLE_ANIMAL),
+    PARROT(57, ABSTRACT_PARROT),
+
+    // Horses
+    ABSTRACT_HORSE(-1, ABSTRACT_ANIMAL),
+    CHESTED_HORSE(-1, ABSTRACT_HORSE),
+    DONKEY(14, CHESTED_HORSE),
+    MULE(52, CHESTED_HORSE),
+    LLAMA(42, CHESTED_HORSE),
+    TRADER_LLAMA(88, CHESTED_HORSE),
+    HORSE(33, ABSTRACT_HORSE),
+    SKELETON_HORSE(73, ABSTRACT_HORSE),
+    ZOMBIE_HORSE(102, ABSTRACT_HORSE),
+
+    // Golem
+    ABSTRACT_GOLEM(-1, ABSTRACT_CREATURE),
+    SNOW_GOLEM(76, ABSTRACT_GOLEM),
+    IRON_GOLEM(36, ABSTRACT_GOLEM),
+    SHULKER(69, ABSTRACT_GOLEM),
+
+    // Fish
+    ABSTRACT_FISHES(-1, ABSTRACT_CREATURE),
+    COD(10, ABSTRACT_FISHES),
+    PUFFERFISH(64, ABSTRACT_FISHES),
+    SALMON(67, ABSTRACT_FISHES),
+    TROPICAL_FISH(89, ABSTRACT_FISHES),
+
+    // Monsters
+    ABSTRACT_MONSTER(-1, ABSTRACT_CREATURE),
+    BLAZE(5, ABSTRACT_MONSTER),
+    CREEPER(12, ABSTRACT_MONSTER),
+    ENDERMITE(21, ABSTRACT_MONSTER),
+    ENDERMAN(20, ABSTRACT_MONSTER),
+    GIANT(30, ABSTRACT_MONSTER),
+    SILVERFISH(71, ABSTRACT_MONSTER),
+    VEX(91, ABSTRACT_MONSTER),
+    WITCH(95, ABSTRACT_MONSTER),
+    WITHER(96, ABSTRACT_MONSTER),
+    RAVAGER(66, ABSTRACT_MONSTER),
+    PIGLIN(60, ABSTRACT_MONSTER),
+
+    HOGLIN(32, ABSTRACT_ANIMAL),
+    STRIDER(82, ABSTRACT_ANIMAL),
+    ZOGLIN(100, ABSTRACT_MONSTER),
+
+    // Illagers
+    ABSTRACT_ILLAGER_BASE(-1, ABSTRACT_MONSTER),
+    ABSTRACT_EVO_ILLU_ILLAGER(-1, ABSTRACT_ILLAGER_BASE),
+    EVOKER(22, ABSTRACT_EVO_ILLU_ILLAGER),
+    ILLUSIONER(35, ABSTRACT_EVO_ILLU_ILLAGER),
+    VINDICATOR(93, ABSTRACT_ILLAGER_BASE),
+    PILLAGER(61, ABSTRACT_ILLAGER_BASE),
+
+    // Skeletons
+    ABSTRACT_SKELETON(-1, ABSTRACT_MONSTER),
+    SKELETON(72, ABSTRACT_SKELETON),
+    STRAY(81, ABSTRACT_SKELETON),
+    WITHER_SKELETON(97, ABSTRACT_SKELETON),
+
+    // Guardians
+    GUARDIAN(31, ABSTRACT_MONSTER),
+    ELDER_GUARDIAN(17, GUARDIAN),
+
+    // Spiders
+    SPIDER(79, ABSTRACT_MONSTER),
+    CAVE_SPIDER(8, SPIDER),
+
+    // Zombies
+    ZOMBIE(101, ABSTRACT_MONSTER),
+    DROWNED(16, ZOMBIE),
+    HUSK(34, ZOMBIE),
+    ZOMBIFIED_PIGLIN(104, ZOMBIE),
+    ZOMBIE_VILLAGER(103, ZOMBIE),
+
+    // Flying entities
+    ABSTRACT_FLYING(-1, ABSTRACT_INSENTIENT),
+    GHAST(29, ABSTRACT_FLYING),
+    PHANTOM(58, ABSTRACT_FLYING),
+
+    ABSTRACT_AMBIENT(-1, ABSTRACT_INSENTIENT),
+    BAT(3, ABSTRACT_AMBIENT),
+
+    ABSTRACT_WATERMOB(-1, ABSTRACT_INSENTIENT),
+    SQUID(80, ABSTRACT_WATERMOB),
+
+    // Slimes
+    SLIME(74, ABSTRACT_INSENTIENT),
+    MAGMA_CUBE(44, SLIME),
+
+    // Hangable objects
+    ABSTRACT_HANGING(-1, ENTITY),
+    LEASH_KNOT(40, ABSTRACT_HANGING),
+    ITEM_FRAME(38, ABSTRACT_HANGING),
+    PAINTING(55, ABSTRACT_HANGING),
+
+    ABSTRACT_LIGHTNING(-1, ENTITY),
+    LIGHTNING_BOLT(41, ABSTRACT_LIGHTNING),
+
+    // Arrows
+    ABSTRACT_ARROW(-1, ENTITY),
+    ARROW(2, ABSTRACT_ARROW),
+    SPECTRAL_ARROW(78, ABSTRACT_ARROW),
+    TRIDENT(87, ABSTRACT_ARROW),
+
+    // Fireballs
+    ABSTRACT_FIREBALL(-1, ENTITY),
+    DRAGON_FIREBALL(15, ABSTRACT_FIREBALL),
+    FIREBALL(39, ABSTRACT_FIREBALL),
+    SMALL_FIREBALL(75, ABSTRACT_FIREBALL),
+    WITHER_SKULL(98, ABSTRACT_FIREBALL),
+
+    // Projectiles
+    PROJECTILE_ABSTRACT(-1, ENTITY),
+    SNOWBALL(77, PROJECTILE_ABSTRACT),
+    ENDER_PEARL(84, PROJECTILE_ABSTRACT),
+    EGG(83, PROJECTILE_ABSTRACT),
+    POTION(86, PROJECTILE_ABSTRACT),
+    EXPERIENCE_BOTTLE(85, PROJECTILE_ABSTRACT),
+
+    // Vehicles
+    MINECART_ABSTRACT(-1, ENTITY),
+    CHESTED_MINECART_ABSTRACT(-1, MINECART_ABSTRACT),
+    CHEST_MINECART(46, CHESTED_MINECART_ABSTRACT),
+    HOPPER_MINECART(49, CHESTED_MINECART_ABSTRACT),
+    MINECART(45, MINECART_ABSTRACT),
+    FURNACE_MINECART(48, MINECART_ABSTRACT),
+    COMMAND_BLOCK_MINECART(47, MINECART_ABSTRACT),
+    TNT_MINECART(51, MINECART_ABSTRACT),
+    SPAWNER_MINECART(50, MINECART_ABSTRACT),
+    BOAT(6, ENTITY);
+
+    private static final EntityType[] TYPES;
+
+    private final int id;
+    private final EntityType parent;
+
+    Entity1_16Types(int id) {
+        this.id = id;
+        this.parent = null;
+    }
+
+    Entity1_16Types(int id, EntityType parent) {
+        this.id = id;
+        this.parent = parent;
+    }
+
+    @Override
+    public int getId() {
+        return id;
+    }
+
+    @Override
+    public EntityType getParent() {
+        return parent;
+    }
+
+    static {
+        TYPES = EntityTypeUtil.toOrderedArray(values());
+    }
+
+    public static EntityType getTypeFromId(int typeId) {
+        return EntityTypeUtil.getTypeFromId(TYPES, typeId, ENTITY);
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/entities/Entity1_16_2Types.java

@@ -0,0 +1,245 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.entities;
+
+import com.viaversion.viaversion.util.EntityTypeUtil;
+
+public enum Entity1_16_2Types implements EntityType {
+
+    ENTITY(-1),
+
+    AREA_EFFECT_CLOUD(0, ENTITY),
+    END_CRYSTAL(18, ENTITY),
+    EVOKER_FANGS(23, ENTITY),
+    EXPERIENCE_ORB(24, ENTITY),
+    EYE_OF_ENDER(25, ENTITY),
+    FALLING_BLOCK(26, ENTITY),
+    FIREWORK_ROCKET(27, ENTITY),
+    ITEM(37, ENTITY),
+    LLAMA_SPIT(43, ENTITY),
+    TNT(64, ENTITY),
+    SHULKER_BULLET(71, ENTITY),
+    FISHING_BOBBER(107, ENTITY),
+
+    LIVINGENTITY(-1, ENTITY),
+    ARMOR_STAND(1, LIVINGENTITY),
+    PLAYER(106, LIVINGENTITY),
+
+    ABSTRACT_INSENTIENT(-1, LIVINGENTITY),
+    ENDER_DRAGON(19, ABSTRACT_INSENTIENT),
+
+    BEE(4, ABSTRACT_INSENTIENT),
+
+    ABSTRACT_CREATURE(-1, ABSTRACT_INSENTIENT),
+
+    ABSTRACT_AGEABLE(-1, ABSTRACT_CREATURE),
+    VILLAGER(93, ABSTRACT_AGEABLE),
+    WANDERING_TRADER(95, ABSTRACT_AGEABLE),
+
+    // Animals
+    ABSTRACT_ANIMAL(-1, ABSTRACT_AGEABLE),
+    DOLPHIN(13, ABSTRACT_INSENTIENT),
+    CHICKEN(9, ABSTRACT_ANIMAL),
+    COW(11, ABSTRACT_ANIMAL),
+    MOOSHROOM(53, COW),
+    PANDA(56, ABSTRACT_INSENTIENT),
+    PIG(59, ABSTRACT_ANIMAL),
+    POLAR_BEAR(63, ABSTRACT_ANIMAL),
+    RABBIT(66, ABSTRACT_ANIMAL),
+    SHEEP(69, ABSTRACT_ANIMAL),
+    TURTLE(91, ABSTRACT_ANIMAL),
+    FOX(28, ABSTRACT_ANIMAL),
+
+    ABSTRACT_TAMEABLE_ANIMAL(-1, ABSTRACT_ANIMAL),
+    CAT(7, ABSTRACT_TAMEABLE_ANIMAL),
+    OCELOT(54, ABSTRACT_TAMEABLE_ANIMAL),
+    WOLF(100, ABSTRACT_TAMEABLE_ANIMAL),
+
+    ABSTRACT_PARROT(-1, ABSTRACT_TAMEABLE_ANIMAL),
+    PARROT(57, ABSTRACT_PARROT),
+
+    // Horses
+    ABSTRACT_HORSE(-1, ABSTRACT_ANIMAL),
+    CHESTED_HORSE(-1, ABSTRACT_HORSE),
+    DONKEY(14, CHESTED_HORSE),
+    MULE(52, CHESTED_HORSE),
+    LLAMA(42, CHESTED_HORSE),
+    TRADER_LLAMA(89, CHESTED_HORSE),
+    HORSE(33, ABSTRACT_HORSE),
+    SKELETON_HORSE(74, ABSTRACT_HORSE),
+    ZOMBIE_HORSE(103, ABSTRACT_HORSE),
+
+    // Golem
+    ABSTRACT_GOLEM(-1, ABSTRACT_CREATURE),
+    SNOW_GOLEM(77, ABSTRACT_GOLEM),
+    IRON_GOLEM(36, ABSTRACT_GOLEM),
+    SHULKER(70, ABSTRACT_GOLEM),
+
+    // Fish
+    ABSTRACT_FISHES(-1, ABSTRACT_CREATURE),
+    COD(10, ABSTRACT_FISHES),
+    PUFFERFISH(65, ABSTRACT_FISHES),
+    SALMON(68, ABSTRACT_FISHES),
+    TROPICAL_FISH(90, ABSTRACT_FISHES),
+
+    // Monsters
+    ABSTRACT_MONSTER(-1, ABSTRACT_CREATURE),
+    BLAZE(5, ABSTRACT_MONSTER),
+    CREEPER(12, ABSTRACT_MONSTER),
+    ENDERMITE(21, ABSTRACT_MONSTER),
+    ENDERMAN(20, ABSTRACT_MONSTER),
+    GIANT(30, ABSTRACT_MONSTER),
+    SILVERFISH(72, ABSTRACT_MONSTER),
+    VEX(92, ABSTRACT_MONSTER),
+    WITCH(96, ABSTRACT_MONSTER),
+    WITHER(97, ABSTRACT_MONSTER),
+    RAVAGER(67, ABSTRACT_MONSTER),
+
+    ABSTRACT_PIGLIN(-1, ABSTRACT_MONSTER),
+
+    PIGLIN(60, ABSTRACT_PIGLIN),
+    PIGLIN_BRUTE(61, ABSTRACT_PIGLIN),
+
+    HOGLIN(32, ABSTRACT_ANIMAL),
+    STRIDER(83, ABSTRACT_ANIMAL),
+    ZOGLIN(101, ABSTRACT_MONSTER),
+
+    // Illagers
+    ABSTRACT_ILLAGER_BASE(-1, ABSTRACT_MONSTER),
+    ABSTRACT_EVO_ILLU_ILLAGER(-1, ABSTRACT_ILLAGER_BASE),
+    EVOKER(22, ABSTRACT_EVO_ILLU_ILLAGER),
+    ILLUSIONER(35, ABSTRACT_EVO_ILLU_ILLAGER),
+    VINDICATOR(94, ABSTRACT_ILLAGER_BASE),
+    PILLAGER(62, ABSTRACT_ILLAGER_BASE),
+
+    // Skeletons
+    ABSTRACT_SKELETON(-1, ABSTRACT_MONSTER),
+    SKELETON(73, ABSTRACT_SKELETON),
+    STRAY(82, ABSTRACT_SKELETON),
+    WITHER_SKELETON(98, ABSTRACT_SKELETON),
+
+    // Guardians
+    GUARDIAN(31, ABSTRACT_MONSTER),
+    ELDER_GUARDIAN(17, GUARDIAN),
+
+    // Spiders
+    SPIDER(80, ABSTRACT_MONSTER),
+    CAVE_SPIDER(8, SPIDER),
+
+    // Zombies
+    ZOMBIE(102, ABSTRACT_MONSTER),
+    DROWNED(16, ZOMBIE),
+    HUSK(34, ZOMBIE),
+    ZOMBIFIED_PIGLIN(105, ZOMBIE),
+    ZOMBIE_VILLAGER(104, ZOMBIE),
+
+    // Flying entities
+    ABSTRACT_FLYING(-1, ABSTRACT_INSENTIENT),
+    GHAST(29, ABSTRACT_FLYING),
+    PHANTOM(58, ABSTRACT_FLYING),
+
+    ABSTRACT_AMBIENT(-1, ABSTRACT_INSENTIENT),
+    BAT(3, ABSTRACT_AMBIENT),
+
+    ABSTRACT_WATERMOB(-1, ABSTRACT_INSENTIENT),
+    SQUID(81, ABSTRACT_WATERMOB),
+
+    // Slimes
+    SLIME(75, ABSTRACT_INSENTIENT),
+    MAGMA_CUBE(44, SLIME),
+
+    // Hangable objects
+    ABSTRACT_HANGING(-1, ENTITY),
+    LEASH_KNOT(40, ABSTRACT_HANGING),
+    ITEM_FRAME(38, ABSTRACT_HANGING),
+    PAINTING(55, ABSTRACT_HANGING),
+
+    ABSTRACT_LIGHTNING(-1, ENTITY),
+    LIGHTNING_BOLT(41, ABSTRACT_LIGHTNING),
+
+    // Arrows
+    ABSTRACT_ARROW(-1, ENTITY),
+    ARROW(2, ABSTRACT_ARROW),
+    SPECTRAL_ARROW(79, ABSTRACT_ARROW),
+    TRIDENT(88, ABSTRACT_ARROW),
+
+    // Fireballs
+    ABSTRACT_FIREBALL(-1, ENTITY),
+    DRAGON_FIREBALL(15, ABSTRACT_FIREBALL),
+    FIREBALL(39, ABSTRACT_FIREBALL),
+    SMALL_FIREBALL(76, ABSTRACT_FIREBALL),
+    WITHER_SKULL(99, ABSTRACT_FIREBALL),
+
+    // Projectiles
+    PROJECTILE_ABSTRACT(-1, ENTITY),
+    SNOWBALL(78, PROJECTILE_ABSTRACT),
+    ENDER_PEARL(85, PROJECTILE_ABSTRACT),
+    EGG(84, PROJECTILE_ABSTRACT),
+    POTION(87, PROJECTILE_ABSTRACT),
+    EXPERIENCE_BOTTLE(86, PROJECTILE_ABSTRACT),
+
+    // Vehicles
+    MINECART_ABSTRACT(-1, ENTITY),
+    CHESTED_MINECART_ABSTRACT(-1, MINECART_ABSTRACT),
+    CHEST_MINECART(46, CHESTED_MINECART_ABSTRACT),
+    HOPPER_MINECART(49, CHESTED_MINECART_ABSTRACT),
+    MINECART(45, MINECART_ABSTRACT),
+    FURNACE_MINECART(48, MINECART_ABSTRACT),
+    COMMAND_BLOCK_MINECART(47, MINECART_ABSTRACT),
+    TNT_MINECART(51, MINECART_ABSTRACT),
+    SPAWNER_MINECART(50, MINECART_ABSTRACT),
+    BOAT(6, ENTITY);
+
+    private static final EntityType[] TYPES;
+
+    private final int id;
+    private final EntityType parent;
+
+    Entity1_16_2Types(int id) {
+        this.id = id;
+        this.parent = null;
+    }
+
+    Entity1_16_2Types(int id, EntityType parent) {
+        this.id = id;
+        this.parent = parent;
+    }
+
+    @Override
+    public int getId() {
+        return id;
+    }
+
+    @Override
+    public EntityType getParent() {
+        return parent;
+    }
+
+    static {
+        TYPES = EntityTypeUtil.toOrderedArray(values());
+    }
+
+    public static EntityType getTypeFromId(int typeId) {
+        return EntityTypeUtil.getTypeFromId(TYPES, typeId, ENTITY);
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/entities/Entity1_17Types.java

@@ -0,0 +1,250 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.entities;
+
+import com.viaversion.viaversion.util.EntityTypeUtil;
+
+public enum Entity1_17Types implements EntityType {
+
+    ENTITY(-1),
+
+    AREA_EFFECT_CLOUD(0, ENTITY),
+    END_CRYSTAL(19, ENTITY),
+    EVOKER_FANGS(24, ENTITY),
+    EXPERIENCE_ORB(25, ENTITY),
+    EYE_OF_ENDER(26, ENTITY),
+    FALLING_BLOCK(27, ENTITY),
+    FIREWORK_ROCKET(28, ENTITY),
+    ITEM(41, ENTITY),
+    LLAMA_SPIT(47, ENTITY),
+    TNT(69, ENTITY),
+    SHULKER_BULLET(76, ENTITY),
+    FISHING_BOBBER(112, ENTITY),
+
+    LIVINGENTITY(-1, ENTITY),
+    ARMOR_STAND(1, LIVINGENTITY),
+    MARKER(49, ENTITY),
+    PLAYER(111, LIVINGENTITY),
+
+    ABSTRACT_INSENTIENT(-1, LIVINGENTITY),
+    ENDER_DRAGON(20, ABSTRACT_INSENTIENT),
+
+    BEE(5, ABSTRACT_INSENTIENT),
+
+    ABSTRACT_CREATURE(-1, ABSTRACT_INSENTIENT),
+
+    ABSTRACT_AGEABLE(-1, ABSTRACT_CREATURE),
+    VILLAGER(98, ABSTRACT_AGEABLE),
+    WANDERING_TRADER(100, ABSTRACT_AGEABLE),
+
+    // Animals
+    ABSTRACT_ANIMAL(-1, ABSTRACT_AGEABLE),
+    AXOLOTL(3, ABSTRACT_ANIMAL),
+    DOLPHIN(14, ABSTRACT_INSENTIENT),
+    CHICKEN(10, ABSTRACT_ANIMAL),
+    COW(12, ABSTRACT_ANIMAL),
+    MOOSHROOM(58, COW),
+    PANDA(61, ABSTRACT_INSENTIENT),
+    PIG(64, ABSTRACT_ANIMAL),
+    POLAR_BEAR(68, ABSTRACT_ANIMAL),
+    RABBIT(71, ABSTRACT_ANIMAL),
+    SHEEP(74, ABSTRACT_ANIMAL),
+    TURTLE(96, ABSTRACT_ANIMAL),
+    FOX(29, ABSTRACT_ANIMAL),
+    GOAT(34, ABSTRACT_ANIMAL),
+
+    ABSTRACT_TAMEABLE_ANIMAL(-1, ABSTRACT_ANIMAL),
+    CAT(8, ABSTRACT_TAMEABLE_ANIMAL),
+    OCELOT(59, ABSTRACT_TAMEABLE_ANIMAL),
+    WOLF(105, ABSTRACT_TAMEABLE_ANIMAL),
+
+    ABSTRACT_PARROT(-1, ABSTRACT_TAMEABLE_ANIMAL),
+    PARROT(62, ABSTRACT_PARROT),
+
+    // Horses
+    ABSTRACT_HORSE(-1, ABSTRACT_ANIMAL),
+    CHESTED_HORSE(-1, ABSTRACT_HORSE),
+    DONKEY(15, CHESTED_HORSE),
+    MULE(57, CHESTED_HORSE),
+    LLAMA(46, CHESTED_HORSE),
+    TRADER_LLAMA(94, CHESTED_HORSE),
+    HORSE(37, ABSTRACT_HORSE),
+    SKELETON_HORSE(79, ABSTRACT_HORSE),
+    ZOMBIE_HORSE(108, ABSTRACT_HORSE),
+
+    // Golem
+    ABSTRACT_GOLEM(-1, ABSTRACT_CREATURE),
+    SNOW_GOLEM(82, ABSTRACT_GOLEM),
+    IRON_GOLEM(40, ABSTRACT_GOLEM),
+    SHULKER(75, ABSTRACT_GOLEM),
+
+    // Fish
+    ABSTRACT_FISHES(-1, ABSTRACT_CREATURE),
+    COD(11, ABSTRACT_FISHES),
+    PUFFERFISH(70, ABSTRACT_FISHES),
+    SALMON(73, ABSTRACT_FISHES),
+    TROPICAL_FISH(95, ABSTRACT_FISHES),
+
+    // Monsters
+    ABSTRACT_MONSTER(-1, ABSTRACT_CREATURE),
+    BLAZE(6, ABSTRACT_MONSTER),
+    CREEPER(13, ABSTRACT_MONSTER),
+    ENDERMITE(22, ABSTRACT_MONSTER),
+    ENDERMAN(21, ABSTRACT_MONSTER),
+    GIANT(31, ABSTRACT_MONSTER),
+    SILVERFISH(77, ABSTRACT_MONSTER),
+    VEX(97, ABSTRACT_MONSTER),
+    WITCH(101, ABSTRACT_MONSTER),
+    WITHER(102, ABSTRACT_MONSTER),
+    RAVAGER(72, ABSTRACT_MONSTER),
+
+    ABSTRACT_PIGLIN(-1, ABSTRACT_MONSTER),
+
+    PIGLIN(65, ABSTRACT_PIGLIN),
+    PIGLIN_BRUTE(66, ABSTRACT_PIGLIN),
+
+    HOGLIN(36, ABSTRACT_ANIMAL),
+    STRIDER(88, ABSTRACT_ANIMAL),
+    ZOGLIN(106, ABSTRACT_MONSTER),
+
+    // Illagers
+    ABSTRACT_ILLAGER_BASE(-1, ABSTRACT_MONSTER),
+    ABSTRACT_EVO_ILLU_ILLAGER(-1, ABSTRACT_ILLAGER_BASE),
+    EVOKER(23, ABSTRACT_EVO_ILLU_ILLAGER),
+    ILLUSIONER(39, ABSTRACT_EVO_ILLU_ILLAGER),
+    VINDICATOR(99, ABSTRACT_ILLAGER_BASE),
+    PILLAGER(67, ABSTRACT_ILLAGER_BASE),
+
+    // Skeletons
+    ABSTRACT_SKELETON(-1, ABSTRACT_MONSTER),
+    SKELETON(78, ABSTRACT_SKELETON),
+    STRAY(87, ABSTRACT_SKELETON),
+    WITHER_SKELETON(103, ABSTRACT_SKELETON),
+
+    // Guardians
+    GUARDIAN(35, ABSTRACT_MONSTER),
+    ELDER_GUARDIAN(18, GUARDIAN),
+
+    // Spiders
+    SPIDER(85, ABSTRACT_MONSTER),
+    CAVE_SPIDER(9, SPIDER),
+
+    // Zombies
+    ZOMBIE(107, ABSTRACT_MONSTER),
+    DROWNED(17, ZOMBIE),
+    HUSK(38, ZOMBIE),
+    ZOMBIFIED_PIGLIN(110, ZOMBIE),
+    ZOMBIE_VILLAGER(109, ZOMBIE),
+
+    // Flying entities
+    ABSTRACT_FLYING(-1, ABSTRACT_INSENTIENT),
+    GHAST(30, ABSTRACT_FLYING),
+    PHANTOM(63, ABSTRACT_FLYING),
+
+    ABSTRACT_AMBIENT(-1, ABSTRACT_INSENTIENT),
+    BAT(4, ABSTRACT_AMBIENT),
+
+    ABSTRACT_WATERMOB(-1, ABSTRACT_INSENTIENT),
+    SQUID(86, ABSTRACT_WATERMOB),
+    GLOW_SQUID(33, SQUID),
+
+    // Slimes
+    SLIME(80, ABSTRACT_INSENTIENT),
+    MAGMA_CUBE(48, SLIME),
+
+    // Hangable objects
+    ABSTRACT_HANGING(-1, ENTITY),
+    LEASH_KNOT(44, ABSTRACT_HANGING),
+    ITEM_FRAME(42, ABSTRACT_HANGING),
+    GLOW_ITEM_FRAME(32, ITEM_FRAME),
+    PAINTING(60, ABSTRACT_HANGING),
+
+    ABSTRACT_LIGHTNING(-1, ENTITY),
+    LIGHTNING_BOLT(45, ABSTRACT_LIGHTNING),
+
+    // Arrows
+    ABSTRACT_ARROW(-1, ENTITY),
+    ARROW(2, ABSTRACT_ARROW),
+    SPECTRAL_ARROW(84, ABSTRACT_ARROW),
+    TRIDENT(93, ABSTRACT_ARROW),
+
+    // Fireballs
+    ABSTRACT_FIREBALL(-1, ENTITY),
+    DRAGON_FIREBALL(16, ABSTRACT_FIREBALL),
+    FIREBALL(43, ABSTRACT_FIREBALL),
+    SMALL_FIREBALL(81, ABSTRACT_FIREBALL),
+    WITHER_SKULL(104, ABSTRACT_FIREBALL),
+
+    // Projectiles
+    PROJECTILE_ABSTRACT(-1, ENTITY),
+    SNOWBALL(83, PROJECTILE_ABSTRACT),
+    ENDER_PEARL(90, PROJECTILE_ABSTRACT),
+    EGG(89, PROJECTILE_ABSTRACT),
+    POTION(92, PROJECTILE_ABSTRACT),
+    EXPERIENCE_BOTTLE(91, PROJECTILE_ABSTRACT),
+
+    // Vehicles
+    MINECART_ABSTRACT(-1, ENTITY),
+    CHESTED_MINECART_ABSTRACT(-1, MINECART_ABSTRACT),
+    CHEST_MINECART(51, CHESTED_MINECART_ABSTRACT),
+    HOPPER_MINECART(54, CHESTED_MINECART_ABSTRACT),
+    MINECART(50, MINECART_ABSTRACT),
+    FURNACE_MINECART(53, MINECART_ABSTRACT),
+    COMMAND_BLOCK_MINECART(52, MINECART_ABSTRACT),
+    TNT_MINECART(56, MINECART_ABSTRACT),
+    SPAWNER_MINECART(55, MINECART_ABSTRACT),
+    BOAT(7, ENTITY);
+
+    private static final EntityType[] TYPES;
+
+    private final int id;
+    private final EntityType parent;
+
+    Entity1_17Types(int id) {
+        this.id = id;
+        this.parent = null;
+    }
+
+    Entity1_17Types(int id, EntityType parent) {
+        this.id = id;
+        this.parent = parent;
+    }
+
+    @Override
+    public int getId() {
+        return id;
+    }
+
+    @Override
+    public EntityType getParent() {
+        return parent;
+    }
+
+    static {
+        TYPES = EntityTypeUtil.toOrderedArray(values());
+    }
+
+    public static EntityType getTypeFromId(int typeId) {
+        return EntityTypeUtil.getTypeFromId(TYPES, typeId, ENTITY);
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/entities/EntityType.java

@@ -0,0 +1,82 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.entities;
+
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public interface EntityType {
+
+    /**
+     * Returns the entity id.
+     *
+     * @return entity id
+     */
+    int getId();
+
+    /**
+     * Returns the parent entity type if present.
+     *
+     * @return parent entity type if present
+     */
+    @Nullable EntityType getParent();
+
+    /**
+     * Returns the entity type name, not necessarily matching the Vanilla type name.
+     *
+     * @return entity type name
+     */
+    String name();
+
+    default boolean is(EntityType... types) {
+        for (EntityType type : types) {
+            if (this == type) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    default boolean is(EntityType type) {
+        return this == type;
+    }
+
+    /**
+     * Returns whether the current type is equal to the given type, or has it as a parent type.
+     *
+     * @param type entity type to check against
+     * @return true if the current type is equal to the given type, or has it as a parent type
+     */
+    default boolean isOrHasParent(EntityType type) {
+        EntityType parent = this;
+
+        do {
+            if (parent == type) {
+                return true;
+            }
+
+            parent = parent.getParent();
+        } while (parent != null);
+
+        return false;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/entities/ObjectType.java

@@ -0,0 +1,33 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.entities;
+
+/**
+ * Represents a legacy object entity type.
+ */
+public interface ObjectType {
+
+    int getId();
+
+    EntityType getType();
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/item/DataItem.java

@@ -0,0 +1,124 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.item;
+
+import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
+import com.google.gson.annotations.SerializedName;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.Objects;
+
+public class DataItem implements Item {
+    @SerializedName(value = "identifier", alternate = "id")
+    private int identifier;
+    private byte amount;
+    private short data;
+    private CompoundTag tag;
+
+    public DataItem() {
+    }
+
+    public DataItem(int identifier, byte amount, short data, @Nullable CompoundTag tag) {
+        this.identifier = identifier;
+        this.amount = amount;
+        this.data = data;
+        this.tag = tag;
+    }
+
+    public DataItem(Item toCopy) {
+        this(toCopy.identifier(), (byte) toCopy.amount(), toCopy.data(), toCopy.tag());
+    }
+
+    @Override
+    public int identifier() {
+        return identifier;
+    }
+
+    @Override
+    public void setIdentifier(int identifier) {
+        this.identifier = identifier;
+    }
+
+    @Override
+    public int amount() {
+        return amount;
+    }
+
+    @Override
+    public void setAmount(int amount) {
+        if (amount > Byte.MAX_VALUE || amount < Byte.MIN_VALUE) {
+            throw new IllegalArgumentException("Invalid item amount: " + amount);
+        }
+        this.amount = (byte) amount;
+    }
+
+    @Override
+    public short data() {
+        return data;
+    }
+
+    @Override
+    public void setData(short data) {
+        this.data = data;
+    }
+
+    @Override
+    public @Nullable CompoundTag tag() {
+        return tag;
+    }
+
+    @Override
+    public void setTag(@Nullable CompoundTag tag) {
+        this.tag = tag;
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        DataItem item = (DataItem) o;
+        if (identifier != item.identifier) return false;
+        if (amount != item.amount) return false;
+        if (data != item.data) return false;
+        return Objects.equals(tag, item.tag);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = identifier;
+        result = 31 * result + (int) amount;
+        result = 31 * result + (int) data;
+        result = 31 * result + (tag != null ? tag.hashCode() : 0);
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "Item{" +
+                "identifier=" + identifier +
+                ", amount=" + amount +
+                ", data=" + data +
+                ", tag=" + tag +
+                '}';
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/item/Item.java

@@ -0,0 +1,90 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.item;
+
+import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public interface Item {
+
+    /**
+     * Returns the item identifier.
+     *
+     * @return item identifier
+     */
+    int identifier();
+
+    /**
+     * Sets the item identifier.
+     *
+     * @param identifier item identifier
+     */
+    void setIdentifier(int identifier);
+
+    /**
+     * Returns the item amount.
+     *
+     * @return item amount
+     */
+    int amount();
+
+    /**
+     * Returns the item amount.
+     *
+     * @param amount item amount
+     */
+    void setAmount(int amount);
+
+    /**
+     * Returns the item data. Always 0 for 1.13+ items.
+     *
+     * @return item data
+     */
+    default short data() {
+        return 0;
+    }
+
+    /**
+     * Sets the item data used in versions before 1.13.
+     *
+     * @param data item data
+     * @throws UnsupportedOperationException if the item implementation does not store data
+     */
+    default void setData(short data) {
+        throw new UnsupportedOperationException();
+    }
+
+    /**
+     * Returns the item compound tag if present.
+     *
+     * @return item tag
+     */
+    @Nullable CompoundTag tag();
+
+    /**
+     * Sets the item compound tag.
+     *
+     * @param tag item tag
+     */
+    void setTag(@Nullable CompoundTag tag);
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/MetaType.java

@@ -0,0 +1,42 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.metadata;
+
+import com.viaversion.viaversion.api.type.Type;
+
+public interface MetaType {
+
+    /**
+     * Get the write/read type
+     *
+     * @return Type instance
+     */
+    Type type();
+
+    /**
+     * Get type id from the specific MetaDataType
+     *
+     * @return Type id as an integer
+     */
+    int typeId();
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/Metadata.java

@@ -0,0 +1,144 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.metadata;
+
+import com.google.common.base.Preconditions;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.Objects;
+
+public final class Metadata {
+    private int id;
+    private MetaType metaType;
+    private Object value;
+
+    /**
+     * Creates a new metadata instance.
+     *
+     * @param id       metadata index
+     * @param metaType metadata type
+     * @param value    value if present
+     * @throws IllegalArgumentException if the value and metaType are incompatible
+     */
+    public Metadata(int id, MetaType metaType, @Nullable Object value) {
+        this.id = id;
+        this.metaType = metaType;
+        this.value = checkValue(metaType, value);
+    }
+
+    public int id() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public MetaType metaType() {
+        return metaType;
+    }
+
+    /**
+     * Sets the metadata type if compatible with the current value.
+     *
+     * @param metaType metadata type
+     * @throws IllegalArgumentException if the metadata type and current value are incompatible
+     * @see #setTypeAndValue(MetaType, Object)
+     */
+    public void setMetaType(MetaType metaType) {
+        checkValue(metaType, this.value);
+        this.metaType = metaType;
+    }
+
+    public @Nullable <T> T value() {
+        return (T) value;
+    }
+
+    public @Nullable Object getValue() {
+        return value;
+    }
+
+    /**
+     * Sets the metadata value if compatible with the current meta type.
+     *
+     * @param value value
+     * @throws IllegalArgumentException if the value and current metaType are incompatible
+     * @see #setTypeAndValue(MetaType, Object)
+     */
+    public void setValue(@Nullable Object value) {
+        this.value = checkValue(this.metaType, value);
+    }
+
+    /**
+     * Sets metadata type and value.
+     *
+     * @param metaType metadata type
+     * @param value    value
+     * @throws IllegalArgumentException if the value and metaType are incompatible
+     */
+    public void setTypeAndValue(MetaType metaType, @Nullable Object value) {
+        this.value = checkValue(metaType, value);
+        this.metaType = metaType;
+    }
+
+    private Object checkValue(MetaType metaType, @Nullable Object value) {
+        Preconditions.checkNotNull(metaType);
+        if (value != null && !metaType.type().getOutputClass().isAssignableFrom(value.getClass())) {
+            throw new IllegalArgumentException("Metadata value and metaType are incompatible. Type=" + metaType
+                    + ", value=" + (value != null ? value + " (" + value.getClass().getSimpleName() + ")" : "null"));
+        }
+        return value;
+    }
+
+    @Deprecated
+    public void setMetaTypeUnsafe(MetaType type) {
+        this.metaType = type;
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Metadata metadata = (Metadata) o;
+        if (id != metadata.id) return false;
+        if (metaType != metaType) return false;
+        return Objects.equals(value, metadata.value);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = id;
+        result = 31 * result + metaType.hashCode();
+        result = 31 * result + (value != null ? value.hashCode() : 0);
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "Metadata{" +
+                "id=" + id +
+                ", metaType=" + metaType +
+                ", value=" + value +
+                '}';
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_12.java

@@ -0,0 +1,65 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.metadata.types;
+
+import com.viaversion.viaversion.api.minecraft.metadata.MetaType;
+import com.viaversion.viaversion.api.type.Type;
+
+public enum MetaType1_12 implements MetaType {
+    Byte(0, Type.BYTE),
+    VarInt(1, Type.VAR_INT),
+    Float(2, Type.FLOAT),
+    String(3, Type.STRING),
+    Chat(4, Type.COMPONENT),
+    Slot(5, Type.ITEM),
+    Boolean(6, Type.BOOLEAN),
+    Vector3F(7, Type.ROTATION),
+    Position(8, Type.POSITION),
+    OptPosition(9, Type.OPTIONAL_POSITION),
+    Direction(10, Type.VAR_INT),
+    OptUUID(11, Type.OPTIONAL_UUID),
+    BlockID(12, Type.VAR_INT),
+    NBTTag(13, Type.NBT);
+
+    private final int typeID;
+    private final Type type;
+
+    MetaType1_12(int typeID, Type type) {
+        this.typeID = typeID;
+        this.type = type;
+    }
+
+    public static MetaType1_12 byId(int id) {
+        return values()[id];
+    }
+
+    @Override
+    public int typeId() {
+        return typeID;
+    }
+
+    @Override
+    public Type type() {
+        return type;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_13.java

@@ -0,0 +1,68 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.metadata.types;
+
+import com.viaversion.viaversion.api.minecraft.metadata.MetaType;
+import com.viaversion.viaversion.api.type.Type;
+import com.viaversion.viaversion.api.type.types.version.Types1_13;
+
+public enum MetaType1_13 implements MetaType {
+    Byte(0, Type.BYTE),
+    VarInt(1, Type.VAR_INT),
+    Float(2, Type.FLOAT),
+    String(3, Type.STRING),
+    Chat(4, Type.COMPONENT),
+    OptChat(5, Type.OPTIONAL_COMPONENT),
+    Slot(6, Type.FLAT_ITEM),
+    Boolean(7, Type.BOOLEAN),
+    Vector3F(8, Type.ROTATION),
+    Position(9, Type.POSITION),
+    OptPosition(10, Type.OPTIONAL_POSITION),
+    Direction(11, Type.VAR_INT),
+    OptUUID(12, Type.OPTIONAL_UUID),
+    BlockID(13, Type.VAR_INT),
+    NBTTag(14, Type.NBT),
+    PARTICLE(15, Types1_13.PARTICLE);
+
+    private final int typeID;
+    private final Type type;
+
+    MetaType1_13(int typeID, Type type) {
+        this.typeID = typeID;
+        this.type = type;
+    }
+
+    public static MetaType1_13 byId(int id) {
+        return values()[id];
+    }
+
+    @Override
+    public int typeId() {
+        return typeID;
+    }
+
+    @Override
+    public Type type() {
+        return type;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_13_2.java

@@ -0,0 +1,68 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.metadata.types;
+
+import com.viaversion.viaversion.api.minecraft.metadata.MetaType;
+import com.viaversion.viaversion.api.type.Type;
+import com.viaversion.viaversion.api.type.types.version.Types1_13_2;
+
+public enum MetaType1_13_2 implements MetaType {
+    Byte(0, Type.BYTE),
+    VarInt(1, Type.VAR_INT),
+    Float(2, Type.FLOAT),
+    String(3, Type.STRING),
+    Chat(4, Type.COMPONENT),
+    OptChat(5, Type.OPTIONAL_COMPONENT),
+    Slot(6, Type.FLAT_VAR_INT_ITEM),
+    Boolean(7, Type.BOOLEAN),
+    Vector3F(8, Type.ROTATION),
+    Position(9, Type.POSITION),
+    OptPosition(10, Type.OPTIONAL_POSITION),
+    Direction(11, Type.VAR_INT),
+    OptUUID(12, Type.OPTIONAL_UUID),
+    BlockID(13, Type.VAR_INT),
+    NBTTag(14, Type.NBT),
+    PARTICLE(15, Types1_13_2.PARTICLE);
+
+    private final int typeID;
+    private final Type type;
+
+    MetaType1_13_2(int typeID, Type type) {
+        this.typeID = typeID;
+        this.type = type;
+    }
+
+    public static MetaType1_13_2 byId(int id) {
+        return values()[id];
+    }
+
+    @Override
+    public int typeId() {
+        return typeID;
+    }
+
+    @Override
+    public Type type() {
+        return type;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_14.java

@@ -0,0 +1,71 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.metadata.types;
+
+import com.viaversion.viaversion.api.minecraft.metadata.MetaType;
+import com.viaversion.viaversion.api.type.Type;
+import com.viaversion.viaversion.api.type.types.version.Types1_14;
+
+public enum MetaType1_14 implements MetaType {
+    Byte(0, Type.BYTE),
+    VarInt(1, Type.VAR_INT),
+    Float(2, Type.FLOAT),
+    String(3, Type.STRING),
+    Chat(4, Type.COMPONENT),
+    OptChat(5, Type.OPTIONAL_COMPONENT),
+    Slot(6, Type.FLAT_VAR_INT_ITEM),
+    Boolean(7, Type.BOOLEAN),
+    Vector3F(8, Type.ROTATION),
+    Position(9, Type.POSITION1_14),
+    OptPosition(10, Type.OPTIONAL_POSITION_1_14),
+    Direction(11, Type.VAR_INT),
+    OptUUID(12, Type.OPTIONAL_UUID),
+    BlockID(13, Type.VAR_INT),
+    NBTTag(14, Type.NBT),
+    PARTICLE(15, Types1_14.PARTICLE),
+    VillagerData(16, Type.VILLAGER_DATA),
+    OptVarInt(17, Type.OPTIONAL_VAR_INT),
+    Pose(18, Type.VAR_INT);
+
+    private final int typeID;
+    private final Type type;
+
+    MetaType1_14(int typeID, Type type) {
+        this.typeID = typeID;
+        this.type = type;
+    }
+
+    public static MetaType1_14 byId(int id) {
+        return values()[id];
+    }
+
+    @Override
+    public int typeId() {
+        return typeID;
+    }
+
+    @Override
+    public Type type() {
+        return type;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_17.java

@@ -0,0 +1,72 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.metadata.types;
+
+import com.viaversion.viaversion.api.minecraft.metadata.MetaType;
+import com.viaversion.viaversion.api.type.Type;
+import com.viaversion.viaversion.api.type.types.version.Types1_17;
+
+public enum MetaType1_17 implements MetaType {
+    BYTE(0, Type.BYTE),
+    VAR_INT(1, Type.VAR_INT),
+    FLOAT(2, Type.FLOAT),
+    STRING(3, Type.STRING),
+    COMPONENT(4, Type.COMPONENT),
+    OPT_COMPONENT(5, Type.OPTIONAL_COMPONENT),
+    ITEM(6, Type.FLAT_VAR_INT_ITEM),
+    BOOLEAN(7, Type.BOOLEAN),
+    ROTATION(8, Type.ROTATION),
+    POSITION(9, Type.POSITION1_14),
+    OPT_POSITION(10, Type.OPTIONAL_POSITION_1_14),
+    DIRECTION(11, Type.VAR_INT),
+    OPT_UUID(12, Type.OPTIONAL_UUID),
+    BLOCK_STATE(13, Type.VAR_INT),
+    NBT(14, Type.NBT),
+    PARTICLE(15, Types1_17.PARTICLE),
+    VILLAGER_DATA(16, Type.VILLAGER_DATA),
+    OPT_VAR_INT(17, Type.OPTIONAL_VAR_INT),
+    POSE(18, Type.VAR_INT);
+
+    private static final MetaType1_17[] VALUES = values();
+    private final int typeId;
+    private final Type type;
+
+    MetaType1_17(int typeId, Type type) {
+        this.typeId = typeId;
+        this.type = type;
+    }
+
+    public static MetaType1_17 byId(int id) {
+        return VALUES[id];
+    }
+
+    @Override
+    public int typeId() {
+        return typeId;
+    }
+
+    @Override
+    public Type type() {
+        return type;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_8.java

@@ -0,0 +1,61 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.metadata.types;
+
+import com.viaversion.viaversion.api.minecraft.metadata.MetaType;
+import com.viaversion.viaversion.api.type.Type;
+
+public enum MetaType1_8 implements MetaType {
+    Byte(0, Type.BYTE),
+    Short(1, Type.SHORT),
+    Int(2, Type.INT),
+    Float(3, Type.FLOAT),
+    String(4, Type.STRING),
+    Slot(5, Type.ITEM),
+    Position(6, Type.VECTOR),
+    Rotation(7, Type.ROTATION),
+    @Deprecated
+    NonExistent(-1, Type.NOTHING);
+
+    private final int typeID;
+    private final Type type;
+
+    MetaType1_8(int typeID, Type type) {
+        this.typeID = typeID;
+        this.type = type;
+    }
+
+    public static MetaType1_8 byId(int id) {
+        return values()[id];
+    }
+
+    @Override
+    public int typeId() {
+        return typeID;
+    }
+
+    @Override
+    public Type type() {
+        return type;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/metadata/types/MetaType1_9.java

@@ -0,0 +1,64 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.metadata.types;
+
+import com.viaversion.viaversion.api.minecraft.metadata.MetaType;
+import com.viaversion.viaversion.api.type.Type;
+
+public enum MetaType1_9 implements MetaType {
+    Byte(0, Type.BYTE),
+    VarInt(1, Type.VAR_INT),
+    Float(2, Type.FLOAT),
+    String(3, Type.STRING),
+    Chat(4, Type.COMPONENT),
+    Slot(5, Type.ITEM),
+    Boolean(6, Type.BOOLEAN),
+    Vector3F(7, Type.ROTATION),
+    Position(8, Type.POSITION),
+    OptPosition(9, Type.OPTIONAL_POSITION),
+    Direction(10, Type.VAR_INT),
+    OptUUID(11, Type.OPTIONAL_UUID),
+    BlockID(12, Type.VAR_INT);
+
+    private final int typeID;
+    private final Type type;
+
+    MetaType1_9(int typeID, Type type) {
+        this.typeID = typeID;
+        this.type = type;
+    }
+
+    public static MetaType1_9 byId(int id) {
+        return values()[id];
+    }
+
+    @Override
+    public int typeId() {
+        return typeID;
+    }
+
+    @Override
+    public Type type() {
+        return type;
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/nbt/BinaryTagIO.java

@@ -0,0 +1,212 @@
+/*
+ * This file is part of adventure, licensed under the MIT License.
+ *
+ * Copyright (c) 2017-2020 KyoriPowered
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.nbt;
+
+import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
+import org.checkerframework.checker.nullness.qual.NonNull;
+
+import java.io.BufferedInputStream;
+import java.io.DataInput;
+import java.io.DataInputStream;
+import java.io.DataOutput;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.zip.GZIPInputStream;
+import java.util.zip.GZIPOutputStream;
+
+/**
+ * See https://github.com/KyoriPowered/adventure.
+ */
+public final class BinaryTagIO {
+    private BinaryTagIO() {
+    }
+
+    /**
+     * Reads a compound tag from {@code path}.
+     *
+     * @param path the path
+     * @return the compound tag
+     * @throws IOException if an exception was encountered while reading a compound tag
+     */
+    public static @NonNull CompoundTag readPath(final @NonNull Path path) throws IOException {
+        return readInputStream(Files.newInputStream(path));
+    }
+
+    /**
+     * Reads a compound tag from an input stream.
+     *
+     * @param input the input stream
+     * @return the compound tag
+     * @throws IOException if an exception was encountered while reading a compound tag
+     */
+    public static @NonNull CompoundTag readInputStream(final @NonNull InputStream input) throws IOException {
+        try (final DataInputStream dis = new DataInputStream(input)) {
+            return readDataInput(dis);
+        }
+    }
+
+    /**
+     * Reads a compound tag from {@code path} using GZIP decompression.
+     *
+     * @param path the path
+     * @return the compound tag
+     * @throws IOException if an exception was encountered while reading a compound tag
+     */
+    public static @NonNull CompoundTag readCompressedPath(final @NonNull Path path) throws IOException {
+        return readCompressedInputStream(Files.newInputStream(path));
+    }
+
+    /**
+     * Reads a compound tag from an input stream using GZIP decompression.
+     *
+     * @param input the input stream
+     * @return the compound tag
+     * @throws IOException if an exception was encountered while reading a compound tag
+     */
+    public static @NonNull CompoundTag readCompressedInputStream(final @NonNull InputStream input) throws IOException {
+        try (final DataInputStream dis = new DataInputStream(new BufferedInputStream(new GZIPInputStream(input)))) {
+            return readDataInput(dis);
+        }
+    }
+
+    /**
+     * Reads a compound tag from {@code input}.
+     *
+     * @param input the input
+     * @return the compound tag
+     * @throws IOException if an exception was encountered while reading a compound tag
+     */
+    public static @NonNull CompoundTag readDataInput(final @NonNull DataInput input) throws IOException {
+        byte type = input.readByte();
+        if (type != CompoundTag.ID) {
+            throw new IOException(String.format("Expected root tag to be a CompoundTag, was %s", type));
+        }
+        input.skipBytes(input.readUnsignedShort()); // read empty name
+
+        final CompoundTag compoundTag = new CompoundTag();
+        compoundTag.read(input);
+        return compoundTag;
+    }
+
+    /**
+     * Writes a compound tag to {@code path}.
+     *
+     * @param tag  the compound tag
+     * @param path the path
+     * @throws IOException if an exception was encountered while writing the compound tag
+     */
+    public static void writePath(final @NonNull CompoundTag tag, final @NonNull Path path) throws IOException {
+        writeOutputStream(tag, Files.newOutputStream(path));
+    }
+
+    /**
+     * Writes a compound tag to an output stream.
+     *
+     * @param tag    the compound tag
+     * @param output the output stream
+     * @throws IOException if an exception was encountered while writing the compound tag
+     */
+    public static void writeOutputStream(final @NonNull CompoundTag tag, final @NonNull OutputStream output) throws IOException {
+        try (final DataOutputStream dos = new DataOutputStream(output)) {
+            writeDataOutput(tag, dos);
+        }
+    }
+
+    /**
+     * Writes a compound tag to {@code path} using GZIP compression.
+     *
+     * @param tag  the compound tag
+     * @param path the path
+     * @throws IOException if an exception was encountered while writing the compound tag
+     */
+    public static void writeCompressedPath(final @NonNull CompoundTag tag, final @NonNull Path path) throws IOException {
+        writeCompressedOutputStream(tag, Files.newOutputStream(path));
+    }
+
+    /**
+     * Writes a compound tag to an output stream using GZIP compression.
+     *
+     * @param tag    the compound tag
+     * @param output the output stream
+     * @throws IOException if an exception was encountered while writing the compound tag
+     */
+    public static void writeCompressedOutputStream(final @NonNull CompoundTag tag, final @NonNull OutputStream output) throws IOException {
+        try (final DataOutputStream dos = new DataOutputStream(new GZIPOutputStream(output))) {
+            writeDataOutput(tag, dos);
+        }
+    }
+
+    /**
+     * Writes a compound tag to {@code output}.
+     *
+     * @param tag    the compound tag
+     * @param output the output
+     * @throws IOException if an exception was encountered while writing the compound tag
+     */
+    public static void writeDataOutput(final @NonNull CompoundTag tag, final @NonNull DataOutput output) throws IOException {
+        output.writeByte(CompoundTag.ID);
+        output.writeUTF(""); // write empty name
+        tag.write(output);
+    }
+
+    /**
+     * Reads a compound tag from a {@link String}.
+     *
+     * @param input the string
+     * @return the compound tag
+     * @throws IOException if an exception was encountered while reading a compound tag
+     */
+    public static @NonNull CompoundTag readString(final @NonNull String input) throws IOException {
+        try {
+            final CharBuffer buffer = new CharBuffer(input);
+            final TagStringReader parser = new TagStringReader(buffer);
+            final CompoundTag tag = parser.compound();
+            if (buffer.skipWhitespace().hasMore()) {
+                throw new IOException("Document had trailing content after first CompoundTag");
+            }
+            return tag;
+        } catch (final StringTagParseException ex) {
+            throw new IOException(ex);
+        }
+    }
+
+    /**
+     * Writes a compound tag to a {@link String}.
+     *
+     * @param tag the compound tag
+     * @return the string
+     * @throws IOException if an exception was encountered while writing the compound tag
+     */
+    public static @NonNull String writeString(final @NonNull CompoundTag tag) throws IOException {
+        final StringBuilder sb = new StringBuilder();
+        try (final TagStringWriter emit = new TagStringWriter(sb)) {
+            emit.writeTag(tag);
+        }
+        return sb.toString();
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/nbt/CharBuffer.java

@@ -0,0 +1,120 @@
+/*
+ * This file is part of adventure, licensed under the MIT License.
+ *
+ * Copyright (c) 2017-2020 KyoriPowered
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.nbt;
+
+/* package */ final class CharBuffer {
+    private final CharSequence sequence;
+    private int index;
+
+    CharBuffer(final CharSequence sequence) {
+        this.sequence = sequence;
+    }
+
+    /**
+     * Get the character at the current position
+     *
+     * @return The current character
+     */
+    public char peek() {
+        return this.sequence.charAt(this.index);
+    }
+
+    public char peek(final int offset) {
+        return this.sequence.charAt(this.index + offset);
+    }
+
+    /**
+     * Get the current character and advance
+     *
+     * @return current character
+     */
+    public char take() {
+        return this.sequence.charAt(this.index++);
+    }
+
+    public boolean advance() {
+        this.index++;
+        return this.hasMore();
+    }
+
+    public boolean hasMore() {
+        return this.index < this.sequence.length();
+    }
+
+    /**
+     * Search for the provided token, and advance the reader index past the {@code until} character.
+     *
+     * @param until Case-insensitive token
+     * @return the string starting at the current position (inclusive) and going until the location of {@code until}, exclusive
+     */
+    public CharSequence takeUntil(char until) throws StringTagParseException {
+        until = Character.toLowerCase(until);
+        int endIdx = -1;
+        for (int idx = this.index; idx < this.sequence.length(); ++idx) {
+            if (this.sequence.charAt(idx) == Tokens.ESCAPE_MARKER) {
+                idx++;
+            } else if (Character.toLowerCase(this.sequence.charAt(idx)) == until) {
+                endIdx = idx;
+                break;
+            }
+        }
+        if (endIdx == -1) {
+            throw this.makeError("No occurrence of " + until + " was found");
+        }
+
+        final CharSequence result = this.sequence.subSequence(this.index, endIdx);
+        this.index = endIdx + 1;
+        return result;
+    }
+
+    /**
+     * Assert that the next non-whitespace character is the provided parameter.
+     *
+     * <p>If the assertion is successful, the token will be consumed.</p>
+     *
+     * @param expectedChar expected character
+     * @return this
+     * @throws StringTagParseException if EOF or non-matching value is found
+     */
+    public CharBuffer expect(final char expectedChar) throws StringTagParseException {
+        this.skipWhitespace();
+        if (!this.hasMore()) {
+            throw this.makeError("Expected character '" + expectedChar + "' but got EOF");
+        }
+        if (this.peek() != expectedChar) {
+            throw this.makeError("Expected character '" + expectedChar + "' but got '" + this.peek() + "'");
+        }
+        this.take();
+        return this;
+    }
+
+    public CharBuffer skipWhitespace() {
+        while (this.hasMore() && Character.isWhitespace(this.peek())) this.advance();
+        return this;
+    }
+
+    public StringTagParseException makeError(final String message) {
+        return new StringTagParseException(message, this.sequence, this.index);
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/nbt/StringTagParseException.java

@@ -0,0 +1,48 @@
+/*
+ * This file is part of adventure, licensed under the MIT License.
+ *
+ * Copyright (c) 2017-2020 KyoriPowered
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.nbt;
+
+import java.io.IOException;
+
+/**
+ * An exception thrown when parsing a string tag
+ */
+/* package */ class StringTagParseException extends IOException {
+    private static final long serialVersionUID = -3001637554903912905L;
+    private final CharSequence buffer;
+    private final int position;
+
+    public StringTagParseException(final String message, final CharSequence buffer, final int position) {
+        super(message);
+        this.buffer = buffer;
+        this.position = position;
+    }
+
+    // TODO: Provide more specific position information
+
+    @Override
+    public String getMessage() {
+        return super.getMessage() + "(at position " + this.position + ")";
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/nbt/TagStringReader.java

@@ -0,0 +1,314 @@
+/*
+ * This file is part of adventure, licensed under the MIT License.
+ *
+ * Copyright (c) 2017-2020 KyoriPowered
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.nbt;
+
+import com.github.steveice10.opennbt.tag.builtin.ByteArrayTag;
+import com.github.steveice10.opennbt.tag.builtin.ByteTag;
+import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
+import com.github.steveice10.opennbt.tag.builtin.DoubleTag;
+import com.github.steveice10.opennbt.tag.builtin.FloatTag;
+import com.github.steveice10.opennbt.tag.builtin.IntArrayTag;
+import com.github.steveice10.opennbt.tag.builtin.IntTag;
+import com.github.steveice10.opennbt.tag.builtin.ListTag;
+import com.github.steveice10.opennbt.tag.builtin.LongArrayTag;
+import com.github.steveice10.opennbt.tag.builtin.LongTag;
+import com.github.steveice10.opennbt.tag.builtin.NumberTag;
+import com.github.steveice10.opennbt.tag.builtin.ShortTag;
+import com.github.steveice10.opennbt.tag.builtin.StringTag;
+import com.github.steveice10.opennbt.tag.builtin.Tag;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.IntStream;
+
+/**
+ * See https://github.com/KyoriPowered/adventure.
+ */
+/* package */ final class TagStringReader {
+    private final CharBuffer buffer;
+
+    public TagStringReader(final CharBuffer buffer) {
+        this.buffer = buffer;
+    }
+
+    public CompoundTag compound() throws StringTagParseException {
+        this.buffer.expect(Tokens.COMPOUND_BEGIN);
+        final CompoundTag compoundTag = new CompoundTag();
+        if (this.buffer.peek() == Tokens.COMPOUND_END) {
+            this.buffer.take();
+            return compoundTag;
+        }
+
+        while (this.buffer.hasMore()) {
+            final String key = this.key();
+            final Tag tag = this.tag();
+            compoundTag.put(key, tag);
+            if (this.separatorOrCompleteWith(Tokens.COMPOUND_END)) {
+                return compoundTag;
+            }
+        }
+        throw this.buffer.makeError("Unterminated compound tag!");
+    }
+
+    public ListTag list() throws StringTagParseException {
+        final ListTag listTag = new ListTag();
+        this.buffer.expect(Tokens.ARRAY_BEGIN);
+        final boolean prefixedIndex = this.buffer.peek() == '0' && this.buffer.peek(1) == ':';
+        while (this.buffer.hasMore()) {
+            if (this.buffer.peek() == Tokens.ARRAY_END) {
+                this.buffer.advance();
+                return listTag;
+            }
+
+            if (prefixedIndex) {
+                this.buffer.takeUntil(':');
+            }
+
+            final Tag next = this.tag();
+            // TODO: validate type
+            listTag.add(next);
+            if (this.separatorOrCompleteWith(Tokens.ARRAY_END)) {
+                return listTag;
+            }
+        }
+        throw this.buffer.makeError("Reached end of file without end of list tag!");
+    }
+
+    /**
+     * Similar to a list tag in syntax, but returning a single array tag rather than a list of tags.
+     *
+     * @return array-typed tag
+     */
+    public Tag array(final char elementType) throws StringTagParseException {
+        this.buffer.expect(Tokens.ARRAY_BEGIN)
+                .expect(elementType)
+                .expect(Tokens.ARRAY_SIGNATURE_SEPARATOR);
+
+        if (elementType == Tokens.TYPE_BYTE) {
+            return new ByteArrayTag(this.byteArray());
+        } else if (elementType == Tokens.TYPE_INT) {
+            return new IntArrayTag(this.intArray());
+        } else if (elementType == Tokens.TYPE_LONG) {
+            return new LongArrayTag(this.longArray());
+        } else {
+            throw this.buffer.makeError("Type " + elementType + " is not a valid element type in an array!");
+        }
+    }
+
+    private byte[] byteArray() throws StringTagParseException {
+        final List<Byte> bytes = new ArrayList<>();
+        while (this.buffer.hasMore()) {
+            final CharSequence value = this.buffer.skipWhitespace().takeUntil(Tokens.TYPE_BYTE);
+            try {
+                bytes.add(Byte.valueOf(value.toString()));
+            } catch (final NumberFormatException ex) {
+                throw this.buffer.makeError("All elements of a byte array must be bytes!");
+            }
+
+            if (this.separatorOrCompleteWith(Tokens.ARRAY_END)) {
+                final byte[] result = new byte[bytes.size()];
+                for (int i = 0; i < bytes.size(); ++i) { // todo yikes, let's do less boxing
+                    result[i] = bytes.get(i);
+                }
+                return result;
+            }
+        }
+        throw this.buffer.makeError("Reached end of document without array close");
+    }
+
+    private int[] intArray() throws StringTagParseException {
+        final IntStream.Builder builder = IntStream.builder();
+        while (this.buffer.hasMore()) {
+            final Tag value = this.tag();
+            if (!(value instanceof IntTag)) {
+                throw this.buffer.makeError("All elements of an int array must be ints!");
+            }
+            builder.add(((NumberTag) value).asInt());
+            if (this.separatorOrCompleteWith(Tokens.ARRAY_END)) {
+                return builder.build().toArray();
+            }
+        }
+        throw this.buffer.makeError("Reached end of document without array close");
+    }
+
+    private long[] longArray() throws StringTagParseException {
+        final List<Long> longs = new ArrayList<>();
+        while (this.buffer.hasMore()) {
+            final CharSequence value = this.buffer.skipWhitespace().takeUntil(Tokens.TYPE_LONG);
+            try {
+                longs.add(Long.valueOf(value.toString()));
+            } catch (final NumberFormatException ex) {
+                throw this.buffer.makeError("All elements of a long array must be longs!");
+            }
+
+            if (this.separatorOrCompleteWith(Tokens.ARRAY_END)) {
+                final long[] result = new long[longs.size()];
+                for (int i = 0; i < longs.size(); ++i) { // todo yikes
+                    result[i] = longs.get(i);
+                }
+                return result;
+            }
+        }
+        throw this.buffer.makeError("Reached end of document without array close");
+    }
+
+    public String key() throws StringTagParseException {
+        this.buffer.skipWhitespace();
+        final char starChar = this.buffer.peek();
+        try {
+            if (starChar == Tokens.SINGLE_QUOTE || starChar == Tokens.DOUBLE_QUOTE) {
+                return unescape(this.buffer.takeUntil(this.buffer.take()).toString());
+            }
+
+            final StringBuilder builder = new StringBuilder();
+            while (this.buffer.peek() != ':') { // DO NOT CHECK FOR CHARACTER VALIDITY; LEGACY NBT ALLOWS ANY CHARACTER, EVEN WHEN UNQUOTED
+                builder.append(this.buffer.take());
+            }
+            return builder.toString();
+        } finally {
+            this.buffer.expect(Tokens.COMPOUND_KEY_TERMINATOR);
+        }
+    }
+
+    public Tag tag() throws StringTagParseException {
+        final char startToken = this.buffer.skipWhitespace().peek();
+        switch (startToken) {
+            case Tokens.COMPOUND_BEGIN:
+                return this.compound();
+            case Tokens.ARRAY_BEGIN:
+                if (this.buffer.peek(2) == ';') { // we know we're an array tag
+                    return this.array(this.buffer.peek(1));
+                } else {
+                    return this.list();
+                }
+            case Tokens.SINGLE_QUOTE:
+            case Tokens.DOUBLE_QUOTE:
+                // definitely a string tag
+                this.buffer.advance();
+                return new StringTag(unescape(this.buffer.takeUntil(startToken).toString()));
+            default: // scalar
+                return this.scalar();
+        }
+    }
+
+    /**
+     * A tag that is definitely some sort of scalar
+     *
+     * <p>Does not detect quoted strings, so </p>
+     *
+     * @return a parsed tag
+     */
+    private Tag scalar() {
+        final StringBuilder builder = new StringBuilder();
+        boolean possiblyNumeric = true;
+        while (this.buffer.hasMore()) {
+            final char current = this.buffer.peek();
+            if (possiblyNumeric && !Tokens.numeric(current)) {
+                if (builder.length() != 0) {
+                    Tag result = null;
+                    try {
+                        switch (Character.toUpperCase(current)) { // try to read and return as a number
+                            // case Tokens.TYPE_INTEGER: // handled below, ints are ~special~
+                            case Tokens.TYPE_BYTE:
+                                result = new ByteTag(Byte.parseByte(builder.toString()));
+                                break;
+                            case Tokens.TYPE_SHORT:
+                                result = new ShortTag(Short.parseShort(builder.toString()));
+                                break;
+                            case Tokens.TYPE_LONG:
+                                result = new LongTag(Long.parseLong(builder.toString()));
+                                break;
+                            case Tokens.TYPE_FLOAT:
+                                result = new FloatTag(Float.parseFloat(builder.toString()));
+                                break;
+                            case Tokens.TYPE_DOUBLE:
+                                result = new DoubleTag(Double.parseDouble(builder.toString()));
+                                break;
+                        }
+                    } catch (final NumberFormatException ex) {
+                        possiblyNumeric = false; // fallback to treating as a String
+                    }
+                    if (result != null) {
+                        this.buffer.take();
+                        return result;
+                    }
+                }
+            }
+            if (current == '\\') { // escape -- we are significantly more lenient than original format at the moment
+                this.buffer.advance();
+                builder.append(this.buffer.take());
+            } else if (Tokens.id(current)) {
+                builder.append(this.buffer.take());
+            } else { // end of value
+                break;
+            }
+        }
+        // if we run out of content without an explicit value separator, then we're either an integer or string tag -- all others have a character at the end
+        final String built = builder.toString();
+        if (possiblyNumeric) {
+            try {
+                return new IntTag(Integer.parseInt(built));
+            } catch (final NumberFormatException ex) {
+                // ignore
+            }
+        }
+        return new StringTag(built);
+
+    }
+
+    private boolean separatorOrCompleteWith(final char endCharacter) throws StringTagParseException {
+        if (this.buffer.skipWhitespace().peek() == endCharacter) {
+            this.buffer.take();
+            return true;
+        }
+        this.buffer.expect(Tokens.VALUE_SEPARATOR);
+        if (this.buffer.skipWhitespace().peek() == endCharacter) {
+            this.buffer.take();
+            return true;
+        }
+        return false;
+    }
+
+
+    /**
+     * Remove simple escape sequences from a string
+     *
+     * @param withEscapes input string with escapes
+     * @return string with escapes processed
+     */
+    private static String unescape(final String withEscapes) {
+        int escapeIdx = withEscapes.indexOf(Tokens.ESCAPE_MARKER);
+        if (escapeIdx == -1) { // nothing to unescape
+            return withEscapes;
+        }
+        int lastEscape = 0;
+        final StringBuilder output = new StringBuilder(withEscapes.length());
+        do {
+            output.append(withEscapes, lastEscape, escapeIdx);
+            lastEscape = escapeIdx + 1;
+        } while ((escapeIdx = withEscapes.indexOf(Tokens.ESCAPE_MARKER, lastEscape + 1)) != -1); // add one extra character to make sure we don't include escaped backslashes
+        output.append(withEscapes.substring(lastEscape));
+        return output.toString();
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/nbt/TagStringWriter.java

@@ -0,0 +1,257 @@
+/*
+ * This file is part of adventure, licensed under the MIT License.
+ *
+ * Copyright (c) 2017-2020 KyoriPowered
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.nbt;
+
+import com.github.steveice10.opennbt.tag.builtin.ByteArrayTag;
+import com.github.steveice10.opennbt.tag.builtin.ByteTag;
+import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
+import com.github.steveice10.opennbt.tag.builtin.DoubleTag;
+import com.github.steveice10.opennbt.tag.builtin.FloatTag;
+import com.github.steveice10.opennbt.tag.builtin.IntArrayTag;
+import com.github.steveice10.opennbt.tag.builtin.IntTag;
+import com.github.steveice10.opennbt.tag.builtin.ListTag;
+import com.github.steveice10.opennbt.tag.builtin.LongArrayTag;
+import com.github.steveice10.opennbt.tag.builtin.LongTag;
+import com.github.steveice10.opennbt.tag.builtin.ShortTag;
+import com.github.steveice10.opennbt.tag.builtin.StringTag;
+import com.github.steveice10.opennbt.tag.builtin.Tag;
+
+import java.io.IOException;
+import java.io.Writer;
+import java.util.Map;
+
+/**
+ * See https://github.com/KyoriPowered/adventure.
+ */
+/* package */ final class TagStringWriter implements AutoCloseable {
+    private final Appendable out;
+    private final String indent = "  "; // TODO: pretty-printing
+    private int level;
+    /**
+     * Whether a {@link Tokens#VALUE_SEPARATOR} needs to be printed before the beginning of the next object.
+     */
+    private boolean needsSeparator;
+
+    public TagStringWriter(final Appendable out) {
+        this.out = out;
+    }
+
+    // NBT-specific
+
+    public TagStringWriter writeTag(final Tag tag) throws IOException {
+        if (tag instanceof CompoundTag) {
+            return this.writeCompound((CompoundTag) tag);
+        } else if (tag instanceof ListTag) {
+            return this.writeList((ListTag) tag);
+        } else if (tag instanceof ByteArrayTag) {
+            return this.writeByteArray((ByteArrayTag) tag);
+        } else if (tag instanceof IntArrayTag) {
+            return this.writeIntArray((IntArrayTag) tag);
+        } else if (tag instanceof LongArrayTag) {
+            return this.writeLongArray((LongArrayTag) tag);
+        } else if (tag instanceof StringTag) {
+            return this.value(((StringTag) tag).getValue(), Tokens.EOF);
+        } else if (tag instanceof ByteTag) {
+            return this.value(Byte.toString(((ByteTag) tag).asByte()), Tokens.TYPE_BYTE);
+        } else if (tag instanceof ShortTag) {
+            return this.value(Short.toString(((ShortTag) tag).asShort()), Tokens.TYPE_SHORT);
+        } else if (tag instanceof IntTag) {
+            return this.value(Integer.toString(((IntTag) tag).asInt()), Tokens.TYPE_INT);
+        } else if (tag instanceof LongTag) {
+            return this.value(Long.toString(((LongTag) tag).asLong()), Tokens.TYPE_LONG);
+        } else if (tag instanceof FloatTag) {
+            return this.value(Float.toString(((FloatTag) tag).asFloat()), Tokens.TYPE_FLOAT);
+        } else if (tag instanceof DoubleTag) {
+            return this.value(Double.toString(((DoubleTag) tag).asDouble()), Tokens.TYPE_DOUBLE);
+        } else {
+            throw new IOException("Unknown tag type: " + tag.getClass().getSimpleName());
+            // unknown!
+        }
+    }
+
+    private TagStringWriter writeCompound(final CompoundTag tag) throws IOException {
+        this.beginCompound();
+        for (Map.Entry<String, Tag> entry : tag.entrySet()) {
+            this.key(entry.getKey());
+            this.writeTag(entry.getValue());
+        }
+        this.endCompound();
+        return this;
+    }
+
+    private TagStringWriter writeList(final ListTag tag) throws IOException {
+        this.beginList();
+        for (final Tag el : tag) {
+            this.printAndResetSeparator();
+            this.writeTag(el);
+        }
+        this.endList();
+        return this;
+    }
+
+    private TagStringWriter writeByteArray(final ByteArrayTag tag) throws IOException {
+        this.beginArray(Tokens.TYPE_BYTE);
+
+        final byte[] value = tag.getValue();
+        for (int i = 0, length = value.length; i < length; i++) {
+            this.printAndResetSeparator();
+            this.value(Byte.toString(value[i]), Tokens.TYPE_BYTE);
+        }
+        this.endArray();
+        return this;
+    }
+
+    private TagStringWriter writeIntArray(final IntArrayTag tag) throws IOException {
+        this.beginArray(Tokens.TYPE_INT);
+
+        final int[] value = tag.getValue();
+        for (int i = 0, length = value.length; i < length; i++) {
+            this.printAndResetSeparator();
+            this.value(Integer.toString(value[i]), Tokens.TYPE_INT);
+        }
+        this.endArray();
+        return this;
+    }
+
+    private TagStringWriter writeLongArray(final LongArrayTag tag) throws IOException {
+        this.beginArray(Tokens.TYPE_LONG);
+
+        final long[] value = tag.getValue();
+        for (int i = 0, length = value.length; i < length; i++) {
+            this.printAndResetSeparator();
+            this.value(Long.toString(value[i]), Tokens.TYPE_LONG);
+        }
+        this.endArray();
+        return this;
+    }
+
+    // Value types
+
+    public TagStringWriter beginCompound() throws IOException {
+        this.printAndResetSeparator();
+        this.level++;
+        this.out.append(Tokens.COMPOUND_BEGIN);
+        return this;
+    }
+
+    public TagStringWriter endCompound() throws IOException {
+        this.out.append(Tokens.COMPOUND_END);
+        this.level--;
+        this.needsSeparator = true;
+        return this;
+    }
+
+    public TagStringWriter key(final String key) throws IOException {
+        this.printAndResetSeparator();
+        this.writeMaybeQuoted(key, false);
+        this.out.append(Tokens.COMPOUND_KEY_TERMINATOR); // TODO: spacing/pretty-printing
+        return this;
+    }
+
+    public TagStringWriter value(final String value, final char valueType) throws IOException {
+        if (valueType == Tokens.EOF) { // string doesn't have its type
+            this.writeMaybeQuoted(value, true);
+        } else {
+            this.out.append(value);
+            if (valueType != Tokens.TYPE_INT) {
+                this.out.append(valueType);
+            }
+        }
+        this.needsSeparator = true;
+        return this;
+    }
+
+    public TagStringWriter beginList() throws IOException {
+        this.printAndResetSeparator();
+        this.level++;
+        this.out.append(Tokens.ARRAY_BEGIN);
+        return this;
+    }
+
+    public TagStringWriter endList() throws IOException {
+        this.out.append(Tokens.ARRAY_END);
+        this.level--;
+        this.needsSeparator = true;
+        return this;
+    }
+
+    private TagStringWriter beginArray(final char type) throws IOException {
+        this.beginList()
+                .out.append(type)
+                .append(Tokens.ARRAY_SIGNATURE_SEPARATOR);
+        return this;
+    }
+
+    private TagStringWriter endArray() throws IOException {
+        return this.endList();
+    }
+
+    private void writeMaybeQuoted(final String content, boolean requireQuotes) throws IOException {
+        if (!requireQuotes) {
+            for (int i = 0; i < content.length(); ++i) {
+                if (!Tokens.id(content.charAt(i))) {
+                    requireQuotes = true;
+                    break;
+                }
+            }
+        }
+        if (requireQuotes) { // TODO: single quotes
+            this.out.append(Tokens.DOUBLE_QUOTE);
+            this.out.append(escape(content, Tokens.DOUBLE_QUOTE));
+            this.out.append(Tokens.DOUBLE_QUOTE);
+        } else {
+            this.out.append(content);
+        }
+    }
+
+    private static String escape(final String content, final char quoteChar) {
+        final StringBuilder output = new StringBuilder(content.length());
+        for (int i = 0; i < content.length(); ++i) {
+            final char c = content.charAt(i);
+            if (c == quoteChar || c == '\\') {
+                output.append(Tokens.ESCAPE_MARKER);
+            }
+            output.append(c);
+        }
+        return output.toString();
+    }
+
+    private void printAndResetSeparator() throws IOException {
+        if (this.needsSeparator) {
+            this.out.append(Tokens.VALUE_SEPARATOR);
+            this.needsSeparator = false;
+        }
+    }
+
+
+    @Override
+    public void close() throws IOException {
+        if (this.level != 0) {
+            throw new IllegalStateException("Document finished with unbalanced start and end objects");
+        }
+        if (this.out instanceof Writer) {
+            ((Writer) this.out).flush();
+        }
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/minecraft/nbt/Tokens.java

@@ -0,0 +1,88 @@
+/*
+ * This file is part of adventure, licensed under the MIT License.
+ *
+ * Copyright (c) 2017-2020 KyoriPowered
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.minecraft.nbt;
+
+/**
+ * See https://github.com/KyoriPowered/adventure.
+ */
+/* package */ final class Tokens {
+    // Compounds
+    static final char COMPOUND_BEGIN = '{';
+    static final char COMPOUND_END = '}';
+    static final char COMPOUND_KEY_TERMINATOR = ':';
+
+    // Arrays
+    static final char ARRAY_BEGIN = '[';
+    static final char ARRAY_END = ']';
+    static final char ARRAY_SIGNATURE_SEPARATOR = ';';
+
+    static final char VALUE_SEPARATOR = ',';
+
+    static final char SINGLE_QUOTE = '\'';
+    static final char DOUBLE_QUOTE = '"';
+    static final char ESCAPE_MARKER = '\\';
+
+    static final char TYPE_BYTE = 'B';
+    static final char TYPE_SHORT = 'S';
+    static final char TYPE_INT = 'I'; // array only
+    static final char TYPE_LONG = 'L';
+    static final char TYPE_FLOAT = 'F';
+    static final char TYPE_DOUBLE = 'D';
+
+    static final char EOF = '\0';
+
+    private Tokens() {
+    }
+
+    /**
+     * Return if a character is a valid component in an identifier
+     *
+     * <p>An identifier character must match the expression {@code [a-zA-Z0-9_+.-]}</p>
+     *
+     * @param c the character
+     * @return identifier
+     */
+    static boolean id(final char c) {
+        return (c >= 'a' && c <= 'z')
+                || (c >= 'A' && c <= 'Z')
+                || (c >= '0' && c <= '9')
+                || c == '-' || c == '_'
+                || c == '.' || c == '+';
+    }
+
+    /**
+     * Return whether a character could be at some position in a number.
+     * <p>
+     * A string passing this check does not necessarily mean it is syntactically valid
+     *
+     * @param c character to check
+     * @return if possibly part of a number
+     */
+    static boolean numeric(final char c) {
+        return (c >= '0' && c <= '9') // digit
+                || c == '+' || c == '-' // positive or negative
+                || c == 'e' || c == 'E' // exponent
+                || c == '.'; // decimal
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/platform/PlatformTask.java

@@ -0,0 +1,46 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.platform;
+
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+/**
+ * @param <T> task type
+ */
+public interface PlatformTask<T> {
+
+    /**
+     * Returns the actual object represented by this task/task id.
+     * Null if task cannot be instantly tracked.
+     *
+     * @return platform based object, or null if not tracked/cancellable
+     */
+    @Nullable T getObject();
+
+    /**
+     * Cancels the task.
+     *
+     * @throws IllegalArgumentException if the task is not cancellable
+     */
+    void cancel();
+}

api/src/main/java/com/viaversion/viaversion/api/platform/UnsupportedSoftware.java

@@ -0,0 +1,47 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.platform;
+
+public interface UnsupportedSoftware {
+
+    /**
+     * Returns the software name.
+     *
+     * @return software name
+     */
+    String getName();
+
+    /**
+     * Returns the reason for being unsupported by Via.
+     *
+     * @return reason for being unsupported
+     */
+    String getReason();
+
+    /**
+     * Returns whether the unsupported software is present.
+     *
+     * @return true if the unsupported software is found
+     */
+    boolean findMatch();
+}

api/src/main/java/com/viaversion/viaversion/api/platform/ViaInjector.java

@@ -0,0 +1,96 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.platform;
+
+import com.google.gson.JsonObject;
+import it.unimi.dsi.fastutil.ints.IntSortedSet;
+import it.unimi.dsi.fastutil.ints.IntSortedSets;
+
+public interface ViaInjector {
+
+    /**
+     * Inject into the current Platform
+     *
+     * @throws Exception If there is an error with injecting
+     */
+    void inject() throws Exception;
+
+    /**
+     * Uninject into the current Platform
+     *
+     * @throws Exception If there is an error with uninjecting
+     */
+    void uninject() throws Exception;
+
+    /**
+     * Returns true if the protocol version cannot be used in the early init.
+     * Namely, this returns true for forks of Vanilla without extra API to get the protocol version.
+     *
+     * @return true if the protocol version cannot be used in the early init
+     */
+    default boolean lateProtocolVersionSetting() {
+        return false;
+    }
+
+    /**
+     * Returns the server protocol version.
+     * For proxies, this returns the lowest supported protocol version.
+     *
+     * @return server protocol version
+     * @throws Exception if there is an error with getting this info, eg. not binded
+     * @see ViaPlatform#isProxy()
+     */
+    int getServerProtocolVersion() throws Exception;
+
+    /**
+     * Returns the supported server protocol versions.
+     *
+     * @return server protocol versions
+     * @throws Exception if there is an error with getting this info, eg. not binded
+     * @see ViaPlatform#isProxy()
+     */
+    default IntSortedSet getServerProtocolVersions() throws Exception {
+        return IntSortedSets.singleton(getServerProtocolVersion());
+    }
+
+    /**
+     * Get the name of the encoder for then netty pipeline for this platform.
+     *
+     * @return The name
+     */
+    String getEncoderName();
+
+    /**
+     * Get the name of the decoder for then netty pipeline for this platform.
+     *
+     * @return The name
+     */
+    String getDecoderName();
+
+    /**
+     * Get any relevant data for debugging injection issues.
+     *
+     * @return JSONObject containing the data
+     */
+    JsonObject getDump();
+}

api/src/main/java/com/viaversion/viaversion/api/platform/ViaPlatform.java

@@ -0,0 +1,221 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.platform;
+
+import com.google.gson.JsonObject;
+import com.viaversion.viaversion.api.ViaAPI;
+import com.viaversion.viaversion.api.command.ViaCommandSender;
+import com.viaversion.viaversion.api.configuration.ConfigurationProvider;
+import com.viaversion.viaversion.api.configuration.ViaVersionConfig;
+import com.viaversion.viaversion.api.connection.UserConnection;
+
+import java.io.File;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.UUID;
+import java.util.logging.Logger;
+
+/**
+ * ViaPlatform represents a platform ViaVersion runs on
+ *
+ * @param <T> - The player type for the platform, used for API related methods
+ */
+public interface ViaPlatform<T> {
+
+    /**
+     * Get the logger for this platform
+     *
+     * @return Java Logger (may be a wrapper)
+     */
+    Logger getLogger();
+
+    /**
+     * Get the platform name
+     *
+     * @return Platform Name (simply its name)
+     */
+    String getPlatformName();
+
+    /**
+     * Get the platform version
+     *
+     * @return Platform version
+     */
+    String getPlatformVersion();
+
+    /**
+     * Returns true if the server Via is running on is a proxy server.
+     *
+     * @return true if the platform is a proxy
+     */
+    default boolean isProxy() {
+        return false;
+    }
+
+    /**
+     * Get the plugin version
+     *
+     * @return Plugin version as a semver string
+     */
+    String getPluginVersion();
+
+    /**
+     * Run a task Async
+     *
+     * @param runnable The task to run
+     * @return The Task ID
+     */
+    PlatformTask runAsync(Runnable runnable);
+
+    /**
+     * Run a task Sync
+     *
+     * @param runnable The task to run
+     * @return The Task ID
+     */
+    PlatformTask runSync(Runnable runnable);
+
+    /**
+     * Run a task Sync after a interval
+     * This must be only used after plugin enable.
+     *
+     * @param runnable The task to run
+     * @param ticks    The interval to run it after
+     * @return The Task ID
+     */
+    PlatformTask runSync(Runnable runnable, long ticks);
+
+    /**
+     * Run a task at a repeating interval.
+     * Initial interval is the same as repeat.
+     *
+     * @param runnable The task to run
+     * @param ticks    The interval to run it at
+     * @return The Task ID
+     */
+    PlatformTask runRepeatingSync(Runnable runnable, long ticks);
+
+    /**
+     * Get the online players
+     *
+     * @return Array of ViaCommandSender
+     */
+    ViaCommandSender[] getOnlinePlayers();
+
+    /**
+     * Send a message to a player
+     *
+     * @param uuid    The player's UUID
+     * @param message The message to send
+     */
+    void sendMessage(UUID uuid, String message);
+
+    /**
+     * Kick a player for a reason
+     *
+     * @param uuid    The player's UUID
+     * @param message The message to kick them with
+     * @return True if it was successful
+     */
+    boolean kickPlayer(UUID uuid, String message);
+
+    /**
+     * Disconnects an UserConnection for a reason
+     *
+     * @param connection The UserConnection
+     * @param message    The message to kick them with
+     * @return True if it was successful
+     */
+    default boolean disconnect(UserConnection connection, String message) {
+        if (connection.isClientSide()) return false;
+        UUID uuid = connection.getProtocolInfo().getUuid();
+        if (uuid == null) return false;
+        return kickPlayer(uuid, message);
+    }
+
+    /**
+     * Check if the plugin is enabled.
+     *
+     * @return True if it is enabled
+     */
+    boolean isPluginEnabled();
+
+    /**
+     * Get the API for this platform
+     *
+     * @return The API for the platform
+     */
+    ViaAPI<T> getApi();
+
+    /**
+     * Get the config API for this platform
+     *
+     * @return The config API
+     */
+    ViaVersionConfig getConf();
+
+    /**
+     * Get the backend configuration provider for this platform.
+     * (On some platforms this returns the same as getConf())
+     *
+     * @return The configuration provider
+     */
+    ConfigurationProvider getConfigurationProvider();
+
+    /**
+     * Get ViaVersions's data folder.
+     *
+     * @return data folder
+     */
+    File getDataFolder();
+
+    /**
+     * Called when a reload happens
+     */
+    void onReload();
+
+    /**
+     * Get the JSON data required for /viaversion dump
+     *
+     * @return The json data
+     */
+    JsonObject getDump();
+
+    /**
+     * Get if older clients are allowed to be used using ViaVersion.
+     * (Only 1.9 on 1.9.2 server is supported by ViaVersion alone)
+     *
+     * @return True if allowed
+     */
+    boolean isOldClientsAllowed();
+
+    /**
+     * Returns an immutable collection of classes to be checked as unsupported software with their software name.
+     * If any of the classes exist at runtime, a warning about their potential instability will be given to the console.
+     *
+     * @return immutable collection of unsupported software to be checked
+     */
+    default Collection<UnsupportedSoftware> getUnsupportedSoftwareClasses() {
+        return Collections.emptyList();
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/platform/ViaPlatformLoader.java

@@ -0,0 +1,33 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.platform;
+
+public interface ViaPlatformLoader {
+
+    /**
+     * Initialise the loading for a platform, eg. registering listeners / providers / events etc.
+     */
+    void load();
+
+    void unload();
+}

api/src/main/java/com/viaversion/viaversion/api/platform/providers/Provider.java

@@ -0,0 +1,26 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.platform.providers;
+
+public interface Provider {
+}

api/src/main/java/com/viaversion/viaversion/api/platform/providers/ViaProviders.java

@@ -0,0 +1,60 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.platform.providers;
+
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class ViaProviders {
+    private final Map<Class<? extends Provider>, Provider> providers = new HashMap<>();
+    private final List<Class<? extends Provider>> lonelyProviders = new ArrayList<>();
+
+    public void require(Class<? extends Provider> provider) {
+        lonelyProviders.add(provider);
+    }
+
+    public <T extends Provider> void register(Class<T> provider, T value) {
+        providers.put(provider, value);
+    }
+
+    public <T extends Provider> void use(Class<T> provider, T value) {
+        lonelyProviders.remove(provider);
+        providers.put(provider, value);
+    }
+
+    public @Nullable <T extends Provider> T get(Class<T> provider) {
+        Provider rawProvider = providers.get(provider);
+        if (rawProvider != null) {
+            return (T) rawProvider;
+        } else {
+            if (lonelyProviders.contains(provider)) {
+                throw new IllegalStateException("There was no provider for " + provider + ", one is required!");
+            }
+            return null;
+        }
+    }
+}

api/src/main/java/com/viaversion/viaversion/api/protocol/AbstractProtocol.java

@@ -0,0 +1,421 @@
+/*
+ * This file is part of ViaVersion - https://github.com/ViaVersion/ViaVersion
+ * Copyright (C) 2016-2021 ViaVersion and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.viaversion.viaversion.api.protocol;
+
+import com.google.common.base.Preconditions;
+import com.viaversion.viaversion.api.Via;
+import com.viaversion.viaversion.api.connection.UserConnection;
+import com.viaversion.viaversion.api.data.entity.EntityTracker;
+import com.viaversion.viaversion.api.protocol.packet.ClientboundPacketType;
+import com.viaversion.viaversion.api.protocol.packet.Direction;
+import com.viaversion.viaversion.api.protocol.packet.PacketType;
+import com.viaversion.viaversion.api.protocol.packet.PacketWrapper;
+import com.viaversion.viaversion.api.protocol.packet.ServerboundPacketType;
+import com.viaversion.viaversion.api.protocol.packet.State;
+import com.viaversion.viaversion.api.protocol.remapper.PacketRemapper;
+import com.viaversion.viaversion.exception.CancelException;
+import com.viaversion.viaversion.exception.InformativeException;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.logging.Level;
+
+public abstract class AbstractProtocol<C1 extends ClientboundPacketType, C2 extends ClientboundPacketType, S1 extends ServerboundPacketType, S2 extends ServerboundPacketType>
+        implements Protocol<C1, C2, S1, S2> {
+    private final Map<Packet, ProtocolPacket> serverbound = new HashMap<>();
+    private final Map<Packet, ProtocolPacket> clientbound = new HashMap<>();
+    private final Map<Class<?>, Object> storedObjects = new HashMap<>(); // currently only used for MetadataRewriters
+    protected final Class<C1> oldClientboundPacketEnum;
+    protected final Class<C2> newClientboundPacketEnum;
+    protected final Class<S1> oldServerboundPacketEnum;
+    protected final Class<S2> newServerboundPacketEnum;
+    private boolean initialized;
+
+    protected AbstractProtocol() {
+        this(null, null, null, null);
+    }
+
+    /**
+     * Creates a protocol with automated id mapping if the respective enums are not null.
+     */
+    protected AbstractProtocol(@Nullable Class<C1> oldClientboundPacketEnum, @Nullable Class<C2> clientboundPacketEnum,
+                               @Nullable Class<S1> oldServerboundPacketEnum, @Nullable Class<S2> serverboundPacketEnum) {
+        this.oldClientboundPacketEnum = oldClientboundPacketEnum;
+        this.newClientboundPacketEnum = clientboundPacketEnum;
+        this.oldServerboundPacketEnum = oldServerboundPacketEnum;
+        this.newServerboundPacketEnum = serverboundPacketEnum;
+    }
+
+    @Override
+    public final void initialize() {
+        Preconditions.checkArgument(!initialized);
+        initialized = true;
+
+        registerPackets();
+
+        // Register the rest of the ids with no handlers if necessary
+        if (oldClientboundPacketEnum != null && newClientboundPacketEnum != null
+                && oldClientboundPacketEnum != newClientboundPacketEnum) {
+            registerClientboundChannelIdChanges();
+        }
+        if (oldServerboundPacketEnum != null && newServerboundPacketEnum != null
+                && oldServerboundPacketEnum != newServerboundPacketEnum) {
+            registerServerboundChannelIdChanges();
+        }
+    }
+
+    protected void registerClientboundChannelIdChanges() {
+        ClientboundPacketType[] newConstants = newClientboundPacketEnum.getEnumConstants();
+        Map<String, ClientboundPacketType> newClientboundPackets = new HashMap<>(newConstants.length);
+        for (ClientboundPacketType newConstant : newConstants) {
+            newClientboundPackets.put(newConstant.getName(), newConstant);
+        }
+
+        for (ClientboundPacketType packet : oldClientboundPacketEnum.getEnumConstants()) {
+            ClientboundPacketType mappedPacket = newClientboundPackets.get(packet.getName());
+            int oldId = packet.getId();
+            if (mappedPacket == null) {
+                // Packet doesn't exist on new client
+                Preconditions.checkArgument(hasRegisteredClientbound(State.PLAY, oldId),
+                        "Packet " + packet + " in " + getClass().getSimpleName() + " has no mapping - it needs to be manually cancelled or remapped!");
+                continue;
+            }
+
+            int newId = mappedPacket.getId();
+            if (!hasRegisteredClientbound(State.PLAY, oldId)) {
+                registerClientbound(State.PLAY, oldId, newId);
+            }
+        }
+    }
+
+    protected void registerServerboundChannelIdChanges() {
+        ServerboundPacketType[] oldConstants = oldServerboundPacketEnum.getEnumConstants();
+        Map<String, ServerboundPacketType> oldServerboundConstants = new HashMap<>(oldConstants.length);
+        for (ServerboundPacketType oldConstant : oldConstants) {
+            oldServerboundConstants.put(oldConstant.getName(), oldConstant);
+        }
+
+        for (ServerboundPacketType packet : newServerboundPacketEnum.getEnumConstants()) {
+            ServerboundPacketType mappedPacket = oldServerboundConstants.get(packet.getName());
+            int newId = packet.getId();
+            if (mappedPacket == null) {
+                // Packet doesn't exist on old server
+                Preconditions.checkArgument(hasRegisteredServerbound(State.PLAY, newId),
+                        "Packet " + packet + " in " + getClass().getSimpleName() + " has no mapping - it needs to be manually cancelled or remapped!");
+                continue;
+            }
+
+            int oldId = mappedPacket.getId();
+            if (!hasRegisteredServerbound(State.PLAY, newId)) {
+                registerServerbound(State.PLAY, oldId, newId);
+            }
+        }
+    }
+
+    /**
+     * Register the packets for this protocol. To be overriden.
+     */
+    protected void registerPackets() {
+    }
+
+    @Override
+    public final void loadMappingData() {
+        getMappingData().load();
+        onMappingDataLoaded();
+    }
+
+    /**
+     * Called after {@link #loadMappingData()} is called; load extra mapping data for the protocol.
+     * <p>
+     * To be overridden if needed.
+     */
+    protected void onMappingDataLoaded() {
+    }
+
+    protected void addEntityTracker(UserConnection connection, EntityTracker tracker) {
+        connection.addEntityTracker(this.getClass(), tracker);
+    }
+
+    @Override
+    public void registerServerbound(State state, int oldPacketID, int newPacketID, PacketRemapper packetRemapper, boolean override) {
+        ProtocolPacket protocolPacket = new ProtocolPacket(state, oldPacketID, newPacketID, packetRemapper);
+        Packet packet = new Packet(state, newPacketID);
+        if (!override && serverbound.containsKey(packet)) {
+            Via.getPlatform().getLogger().log(Level.WARNING, packet + " already registered!" +
+                    " If this override is intentional, set override to true. Stacktrace: ", new Exception());
+        }
+        serverbound.put(packet, protocolPacket);
+    }
+
+    @Override
+    public void cancelServerbound(State state, int oldPacketID, int newPacketID) {
+        registerServerbound(state, oldPacketID, newPacketID, new PacketRemapper() {
+            @Override
+            public void registerMap() {
+                handler(PacketWrapper::cancel);
+            }
+        });
+    }
+
+    @Override
+    public void cancelClientbound(State state, int oldPacketID, int newPacketID) {
+        registerClientbound(state, oldPacketID, newPacketID, new PacketRemapper() {
+            @Override
+            public void registerMap() {
+                handler(PacketWrapper::cancel);
+            }
+        });
+    }
+
+    @Override
+    public void registerClientbound(State state, int oldPacketID, int newPacketID, PacketRemapper packetRemapper, boolean override) {
+        ProtocolPacket protocolPacket = new ProtocolPacket(state, oldPacketID, newPacketID, packetRemapper);
+        Packet packet = new Packet(state, oldPacketID);
+        if (!override && clientbound.containsKey(packet)) {
+            Via.getPlatform().getLogger().log(Level.WARNING, packet + " already registered!" +
+                    " If override is intentional, set override to true. Stacktrace: ", new Exception());
+        }
+        clientbound.put(packet, protocolPacket);
+    }
+
+
+    @Override
+    public void registerClientbound(C1 packetType, @Nullable PacketRemapper packetRemapper) {
+        checkPacketType(packetType, packetType.getClass() == oldClientboundPacketEnum);
+
+        ClientboundPacketType mappedPacket = oldClientboundPacketEnum == newClientboundPacketEnum ? packetType
+                : Arrays.stream(newClientboundPacketEnum.getEnumConstants()).filter(en -> en.getName().equals(packetType.getName())).findAny().orElse(null);
+        Preconditions.checkNotNull(mappedPacket, "Packet type " + packetType + " in " + packetType.getClass().getSimpleName() + " could not be automatically mapped!");
+
+        int oldId = packetType.getId();
+        int newId = mappedPacket.getId();
+        registerClientbound(State.PLAY, oldId, newId, packetRemapper);
+    }
+
+    @Override
+    public void registerClientbound(C1 packetType, @Nullable C2 mappedPacketType, @Nullable PacketRemapper packetRemapper) {
+        checkPacketType(packetType, packetType.getClass() == oldClientboundPacketEnum);
+        checkPacketType(mappedPacketType, mappedPacketType == null || mappedPacketType.getClass() == newClientboundPacketEnum);
+
+        registerClientbound(State.PLAY, packetType.getId(), mappedPacketType != null ? mappedPacketType.getId() : -1, packetRemapper);
+    }
+
+    @Override
+    public void cancelClientbound(C1 packetType) {
+        cancelClientbound(State.PLAY, packetType.getId(), packetType.getId());
+    }
+
+    @Override
+    public void registerServerbound(S2 packetType, @Nullable PacketRemapper packetRemapper) {
+        checkPacketType(packetType, packetType.getClass() == newServerboundPacketEnum);
+
+        ServerboundPacketType mappedPacket = oldServerboundPacketEnum == newServerboundPacketEnum ? packetType
+                : Arrays.stream(oldServerboundPacketEnum.getEnumConstants()).filter(en -> en.getName().equals(packetType.getName())).findAny().orElse(null);
+        Preconditions.checkNotNull(mappedPacket, "Packet type " + packetType + " in " + packetType.getClass().getSimpleName() + " could not be automatically mapped!");
+
+        int oldId = mappedPacket.getId();
+        int newId = packetType.getId();
+        registerServerbound(State.PLAY, oldId, newId, packetRemapper);
+    }
+
+    @Override
+    public void registerServerbound(S2 packetType, @Nullable S1 mappedPacketType, @Nullable PacketRemapper packetRemapper) {
+        checkPacketType(packetType, packetType.getClass() == newServerboundPacketEnum);
+        checkPacketType(mappedPacketType, mappedPacketType == null || mappedPacketType.getClass() == oldServerboundPacketEnum);
+
+        registerServerbound(State.PLAY, mappedPacketType != null ? mappedPacketType.getId() : -1, packetType.getId(), packetRemapper);
+    }
+
+    @Override
+    public void cancelServerbound(S2 packetType) {
+        Preconditions.checkArgument(packetType.getClass() == newServerboundPacketEnum);
+        cancelServerbound(State.PLAY, -1, packetType.getId());
+    }
+
+
+    @Override
+    public boolean hasRegisteredClientbound(State state, int oldPacketID) {
+        Packet packet = new Packet(state, oldPacketID);
+        return clientbound.containsKey(packet);
+    }
+
+    @Override
+    public boolean hasRegisteredServerbound(State state, int newPacketId) {
+        Packet packet = new Packet(state, newPacketId);
+        return serverbound.containsKey(packet);
+    }
+
+    @Override
+    public void transform(Direction direction, State state, PacketWrapper packetWrapper) throws Exception {
+        Packet statePacket = new Packet(state, packetWrapper.getId());
+        Map<Packet, ProtocolPacket> packetMap = (direction == Direction.CLIENTBOUND ? clientbound : serverbound);
+        ProtocolPacket protocolPacket = packetMap.get(statePacket);
+        if (protocolPacket == null) {
+            return;
+        }
+
+        // Write packet id
+        int oldId = packetWrapper.getId();
+        int newId = direction == Direction.CLIENTBOUND ? protocolPacket.getNewID() : protocolPacket.getOldID();
+        packetWrapper.setId(newId);
+
+        PacketRemapper remapper = protocolPacket.getRemapper();
+        if (remapper != null) {
+            try {
+                remapper.remap(packetWrapper);
+            } catch (InformativeException e) { // Catch InformativeExceptions, pass through CancelExceptions
+                throwRemapError(direction, state, oldId, newId, e);
+                return;
+            }
+
+            if (packetWrapper.isCancelled()) {
+                throw CancelException.generate();
+            }
+        }
+    }
+
+    private void throwRemapError(Direction direction, State state, int oldId, int newId, InformativeException e) throws InformativeException {
+        // Don't print errors during handshake
+        if (state == State.HANDSHAKE) {
+            throw e;
+        }
+
+        Class<? extends PacketType> packetTypeClass = state == State.PLAY ? (direction == Direction.CLIENTBOUND ? oldClientboundPacketEnum : newServerboundPacketEnum) : null;
+        if (packetTypeClass != null) {
+            PacketType[] enumConstants = packetTypeClass.getEnumConstants();
+            PacketType packetType = oldId < enumConstants.length && oldId >= 0 ? enumConstants[oldId] : null;
+            Via.getPlatform().getLogger().warning("ERROR IN " + getClass().getSimpleName() + " IN REMAP OF " + packetType + " (" + toNiceHex(oldId) + ")");
+        } else {
+            Via.getPlatform().getLogger().warning("ERROR IN " + getClass().getSimpleName()
+                    + " IN REMAP OF " + toNiceHex(oldId) + "->" + toNiceHex(newId));
+        }
+        throw e;
+    }
+
+    private String toNiceHex(int id) {
+        String hex = Integer.toHexString(id).toUpperCase();
+        return (hex.length() == 1 ? "0x0" : "0x") + hex;
+    }
+
+    /**
+     * @param packetType packet type
+     * @param isValid    expression to check the packet's validity
+     * @throws IllegalArgumentException if the given expression is not met
+     */
+    private void checkPacketType(PacketType packetType, boolean isValid) {
+        if (!isValid) {
+            throw new IllegalArgumentException("Packet type " + packetType + " in " + packetType.getClass().getSimpleName() + " is taken from the wrong enum");
+        }
+    }
+
+    @Override
+    public @Nullable <T> T get(Class<T> objectClass) {
+        return (T) storedObjects.get(objectClass);
+    }
+
+    @Override
+    public void put(Object object) {
+        storedObjects.put(object.getClass(), object);
+    }
+
+    @Override
+    public boolean hasMappingDataToLoad() {
+        return getMappingData() != null;
+    }
+
+    @Override
+    public String toString() {
+        return "Protocol:" + getClass().getSimpleName();
+    }
+
+    public static final class Packet {
+        private final State state;
+        private final int packetId;
+
+        public Packet(State state, int packetId) {
+            this.state = state;
+            this.packetId = packetId;
+        }
+
+        public State getState() {
+            return state;
+        }
+
+        public int getPacketId() {
+            return packetId;
+        }
+
+        @Override
+        public String toString() {
+            return "Packet{" + "state=" + state + ", packetId=" + packetId + '}';
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) return true;
+            if (o == null || getClass() != o.getClass()) return false;
+            Packet that = (Packet) o;
+            return packetId == that.packetId && state == that.state;
+        }
+
+        @Override
+        public int hashCode() {
+            int result = state != null ? state.hashCode() : 0;
+            result = 31 * result + packetId;
+            return result;
+        }
+    }
+
+    public static final class ProtocolPacket {
+        private final State state;
+        private final int oldID;
+        private final int newID;
+        private final PacketRemapper remapper;
+
+        public ProtocolPacket(State state, int oldID, int newID, @Nullable PacketRemapper remapper) {
+            this.state = state;
+            this.oldID = oldID;
+            this.newID = newID;
+            this.remapper = remapper;
+        }
+
+        public State getState() {
+            return state;
+        }
+
+        public int getOldID() {
+            return oldID;
+        }
+
+        public int getNewID() {
+            return newID;
+        }
+
+        @Nullable
+        public PacketRemapper getRemapper() {
+            return remapper;
+        }
+    }
+}