Implement new GeneratorManager system.

Add ReflectHelper class to better facilitate various reflection actions.

src/main/java/com/onarandombox/MultiverseCore/MultiverseCore.java

@@ -77,6 +77,8 @@ import com.onarandombox.MultiverseCore.destination.PlayerDestination;
 import com.onarandombox.MultiverseCore.destination.WorldDestination;
 import com.onarandombox.MultiverseCore.event.MVDebugModeEvent;
 import com.onarandombox.MultiverseCore.event.MVVersionEvent;
+import com.onarandombox.MultiverseCore.generators.GeneratorManager;
+import com.onarandombox.MultiverseCore.api.MVGeneratorManager;
 import com.onarandombox.MultiverseCore.listeners.MVAsyncPlayerChatListener;
 import com.onarandombox.MultiverseCore.listeners.MVChatListener;
 import com.onarandombox.MultiverseCore.listeners.MVEntityListener;
@@ -213,6 +215,7 @@ public class MultiverseCore extends JavaPlugin implements MVPlugin, Core {
     // Configurations
     private FileConfiguration multiverseConfig = null;
 
+    private MVGeneratorManager generatorManager;
     private final MVWorldManager worldManager = new WorldManager(this);
 
     // Setup the block/player/entity listener.
@@ -280,7 +283,7 @@ public class MultiverseCore extends JavaPlugin implements MVPlugin, Core {
         this.messaging = new MVMessaging();
         this.economist = new MVEconomist(this);
         // Load the defaultWorldGenerators
-        this.worldManager.getDefaultWorldGenerators();
+        this.generatorManager = new GeneratorManager(this);
 
         this.registerEvents();
         // Setup Permissions, we'll do an initial check for the Permissions plugin then fall back on isOP().
@@ -1014,6 +1017,14 @@ public class MultiverseCore extends JavaPlugin implements MVPlugin, Core {
         this.serverFolder = newServerFolder;
     }
 
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public MVGeneratorManager getMVGeneratorManager() {
+        return generatorManager;
+    }
+
     /**
      * {@inheritDoc}
      */

src/main/java/com/onarandombox/MultiverseCore/api/Core.java

@@ -94,6 +94,13 @@ public interface Core {
      */
     DestinationFactory getDestFactory();
 
+    /**
+     * Gets the class responsible for managing world generators plugins installed on the server.
+     *
+     * @return A valid {@link MVGeneratorManager}.
+     */
+    MVGeneratorManager getMVGeneratorManager();
+
     /**
      * Gets the primary class responsible for managing Multiverse Worlds.
      *

src/main/java/com/onarandombox/MultiverseCore/api/GeneratorPlugin.java

@@ -0,0 +1,101 @@
+package com.onarandombox.MultiverseCore.api;
+
+import org.bukkit.generator.ChunkGenerator;
+import org.bukkit.plugin.Plugin;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.Collection;
+
+/**
+ * <p>A generator API for Multiverse.</p>
+ *
+ * <p>Any generator plugin can register themselves to Multiverse. This will provide Multiverse with addition
+ * information about your generator plugin such as generator id suggestions, example usages and link to more
+ * info on your generator plugin.</p>
+ *
+ * <p>To register your plugin, implement this class and see {@link MVGeneratorManager#register(GeneratorPlugin)}.</p>
+ */
+public interface GeneratorPlugin {
+
+    /**
+     * <p>Suggest possible generator ids. To be used in command tab-completion.</p>
+     *
+     * <p>These suggestions can be static without relying on currentIdInput, or dynamically changed based
+     * on the currentIdInput.</p>
+     *
+     * @param currentIdInput    The current state user input. This may be null or empty if user has not started
+     *                          any input for generator id.
+     * @return Collection of suggested generator ids.
+     */
+    @NotNull
+    Collection<String> suggestIds(@Nullable String currentIdInput);
+
+    /**
+     * <p>Gets a default or any valid {@link ChunkGenerator}.</p>
+     *
+     * <p>This is used on {@link MVGeneratorManager#register(GeneratorPlugin)} to prove to Multiverse that
+     * you are a valid generator plugin. If this returns null or throw an exception, your generator plugin
+     * will not be registered.</p>
+     *
+     * @return A {@link ChunkGenerator} if possible, else null.
+     * @throws Exception When an error occurs in getting {@link ChunkGenerator}.
+     */
+    @Nullable
+    ChunkGenerator getDefaultChunkGenerator() throws Exception;
+
+    /**
+     * <p>Gets a chunk generator based on a world name and id specified.</p>
+     *
+     * <p>If this returns null or throw an exception, it will indicate to Multiverse that there is either an issue
+     * with your plugin, or the generator id given is invalid.</p>
+     *
+     * @param id        Target generator id.
+     * @param worldName Target world name to use generator on.
+     * @return A {@link ChunkGenerator} if possible, else null.
+     * @throws Exception When an error occurs in getting a {@link ChunkGenerator}.
+     */
+    @Nullable
+    ChunkGenerator getChunkGenerator(String id, String worldName) throws Exception;
+
+    /**
+     * <p>Gets command usages that users can try to generate a world with your generator plugin. Returning null means
+     * you do not wish to show any usage examples for your generator plugin.</p>
+     *
+     * <p>An example command: '/mv create myworld normal -g CoolGen:FunWorld'</p>
+     *
+     * <p>Notes on usage of this method:</p>
+     * <ul>
+     *     <li>Feel free to have colors in your command usage, but not Multiverse won't parse color codes for you.</li>
+     *     <li>Please include the starting slash '/' in your usage examples.</li>
+     *     <li>We suggest keeping the usage to at most 5 examples.</li>
+     *     <li>This should not be a full explanation on all your generator plugin, just basics usages to get people
+     *     started. For full guide, you can use {@link #getInfoLink()} to direct users.</li>
+     * </ul>
+     *
+     * @return A collection of command usage examples.
+     */
+    @Nullable
+    Collection<String> getExampleUsages();
+
+    /**
+     * <p>Gets a link with more information on your generator plugin. Returning null means you do not wish to link
+     * users to any website related to your generator plugin.</p>
+     *
+     * <p>An example info: 'Click on https://www.amazinggenerator.io ;)'</p>
+     *
+     * <p>Some suggested places you can link to are: spigot resource page, github repo or your own plugin site.</p>
+     *
+     * @return Link to more info on your generator plugin.
+     */
+    @Nullable
+    String getInfoLink();
+
+    /**
+     * Gets the java plugin for this generator. In short, return your own generator plugin instance.
+     *
+     * @return The associated plugin for this generator.
+     */
+    @NotNull
+    Plugin getPlugin();
+}

src/main/java/com/onarandombox/MultiverseCore/api/MVGeneratorManager.java

@@ -0,0 +1,134 @@
+package com.onarandombox.MultiverseCore.api;
+
+import org.bukkit.generator.ChunkGenerator;
+import org.bukkit.plugin.Plugin;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.Collection;
+import java.util.Map;
+
+/**
+ * API for handling generator plugins installed on the user's server.
+ */
+public interface MVGeneratorManager {
+
+    /**
+     * Register a generator plugin.
+     *
+     * @param generatorPlugin   The {@link GeneratorPlugin} to register.
+     * @return True if successfully registered, else false.
+     */
+    boolean register(@NotNull GeneratorPlugin generatorPlugin);
+
+    /**
+     * Check if a given generator string is valid.
+     *
+     * @param genString The generator string to check on.
+     * @param worldName The target world name to generate on.
+     * @return True if valid, else false.
+     */
+    boolean isValidGenerator(@NotNull String genString, @NotNull String worldName);
+
+    /**
+     * Check if a given generator string is valid with reason of failure with {@link TestResult}.
+     *
+     * @param genString The generator string to check on.
+     * @param worldName The target world name to generate on.
+     * @return Result of the validation.
+     */
+    @NotNull
+    TestResult validateGenerator(@NotNull String genString, @NotNull String worldName);
+
+    /**
+     * Checks if a plugin is a registered generator plugin.
+     *
+     * @param genPlugin The plugin to check on.
+     * @return True if is valid, else false.
+     */
+    boolean isGeneratorPlugin(@NotNull Plugin genPlugin);
+
+    /**
+     * Checks if a plugin is a registered generator plugin.
+     *
+     * @param pluginName The plugin name to check on.
+     * @return True if is valid, else false.
+     */
+    boolean isGeneratorPlugin(@NotNull String pluginName);
+
+    /**
+     * Gets the {@link GeneratorPlugin} for a given plugin if present.
+     *
+     * @param genPlugin The plugin that is associated to a {@link GeneratorPlugin}.
+     * @return The {@link GeneratorPlugin} if present, else null.
+     */
+    @Nullable
+    GeneratorPlugin getGeneratorPlugin(@NotNull Plugin genPlugin);
+
+    /**
+     * Gets the {@link GeneratorPlugin} for a given plugin if present.
+     *
+     * @param pluginName The plugin name that is associated to a {@link GeneratorPlugin}.
+     * @return The {@link GeneratorPlugin} if present, else null.
+     */
+    @Nullable
+    GeneratorPlugin getGeneratorPlugin(@NotNull String pluginName);
+
+    /**
+     * Gets all registered {@link GeneratorPlugin}.
+     *
+     * @return A collection of registered generator plugins.
+     */
+    @NotNull
+    Collection<GeneratorPlugin> getGeneratorPlugins();
+
+    /**
+     * Gets all registered plugin names associate with {@link GeneratorPlugin}.
+     *
+     * @return A collection of registered generator plugin names.
+     */
+    @NotNull
+    Collection<String> getGeneratorPluginNames();
+
+    /**
+     * Gets the default world generator string defined in 'bukkit.yml' for a given world.
+     *
+     * @param worldName The world to get default generator of.
+     * @return The generator string if present, else null.
+     */
+    @Nullable
+    String getDefaultWorldGen(String worldName);
+
+    /**
+     * Gets all the world generator strings defined in 'bukkit.yml'.
+     *
+     * @return Map if world names and its respective default world generator strings.
+     */
+    @NotNull
+    Map<String, String> getDefaultWorldGens();
+
+    /**
+     * Results from validating a generator.
+     */
+     enum TestResult {
+        /**
+         * Successfully got {@link ChunkGenerator} from the world generator plugin.
+         */
+        VALID,
+
+        /**
+         * Exceptions thrown while trying to get {@link ChunkGenerator} from the world generator plugin.
+         */
+        ERRORS,
+
+        /**
+         * Plugin is present on the server, but doesnt look like a world generator.
+         */
+        INVALID_GENERATOR,
+
+        /**
+         * Plugin not installed on the server.
+         */
+        PLUGIN_DOES_NOT_EXIST
+    }
+}

src/main/java/com/onarandombox/MultiverseCore/api/MVWorldManager.java

@@ -7,6 +7,7 @@
 
 package com.onarandombox.MultiverseCore.api;
 
+import com.onarandombox.MultiverseCore.generators.GeneratorManager;
 import com.onarandombox.MultiverseCore.utils.PurgeWorlds;
 import com.onarandombox.MultiverseCore.utils.SimpleWorldPurger;
 import org.bukkit.World;
@@ -154,7 +155,9 @@ public interface MVWorldManager {
      * @param generatorID The generator id.
      * @param worldName   The worldName to use as the default.
      * @return A {@link ChunkGenerator} or null
+     * @deprecated Use {@link MVGeneratorManager#validateGenerator(String, String)}
      */
+    @Deprecated
     ChunkGenerator getChunkGenerator(String generator, String generatorID, String worldName);
 
     /**
@@ -249,7 +252,9 @@ public interface MVWorldManager {
 
     /**
      * This method populates an internal list and needs to be called after multiverse initialization.
+     * @deprecated This is now done by {@link GeneratorManager}.
      */
+    @Deprecated
     void getDefaultWorldGenerators();
 
     /**

src/main/java/com/onarandombox/MultiverseCore/commands/CheckCommand.java

@@ -11,6 +11,7 @@ import com.onarandombox.MultiverseCore.MultiverseCore;
 import com.onarandombox.MultiverseCore.api.MVDestination;
 import com.onarandombox.MultiverseCore.destination.InvalidDestination;
 import com.onarandombox.MultiverseCore.utils.MVPermissions;
+import com.onarandombox.MultiverseCore.utils.PlayerFinder;
 import org.bukkit.ChatColor;
 import org.bukkit.command.CommandSender;
 import org.bukkit.entity.Player;
@@ -37,7 +38,7 @@ public class CheckCommand extends MultiverseCommand {
 
     @Override
     public void runCommand(CommandSender sender, List<String> args) {
-        Player p = this.plugin.getServer().getPlayerExact(args.get(0));
+        Player p = PlayerFinder.get(args.get(0), sender);
         if (p == null) {
             sender.sendMessage("Could not find player " + ChatColor.GREEN + args.get(0));
             sender.sendMessage("Are they online?");

src/main/java/com/onarandombox/MultiverseCore/commands/CreateCommand.java

@@ -9,6 +9,7 @@ package com.onarandombox.MultiverseCore.commands;
 
 import com.onarandombox.MultiverseCore.MultiverseCore;
 import com.onarandombox.MultiverseCore.api.MVWorldManager;
+import com.onarandombox.MultiverseCore.api.MVGeneratorManager;
 import com.pneumaticraft.commandhandler.CommandHandler;
 import org.bukkit.ChatColor;
 import org.bukkit.World.Environment;
@@ -18,8 +19,6 @@ import org.bukkit.command.CommandSender;
 import org.bukkit.permissions.PermissionDefault;
 
 import java.io.File;
-import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.List;
 
 /**
@@ -98,14 +97,26 @@ public class CreateCommand extends MultiverseCommand {
         }
         // Determine if the generator is valid. #918
         if (generator != null) {
-            List<String> genarray = new ArrayList<String>(Arrays.asList(generator.split(":")));
-            if (genarray.size() < 2) {
-                // If there was only one arg specified, pad with another empty one.
-                genarray.add("");
-            }
-            if (this.worldManager.getChunkGenerator(genarray.get(0), genarray.get(1), "test") == null) {
+            MVGeneratorManager.TestResult result = this.plugin.getMVGeneratorManager().validateGenerator(generator, worldName);
+            if (result != MVGeneratorManager.TestResult.VALID) {
                 // We have an invalid generator.
-                sender.sendMessage("Invalid generator! '" + generator + "'. " + ChatColor.RED + "Aborting world creation.");
+                switch (result) {
+                    case ERRORS:
+                        sender.sendMessage("An issue occurred while validating generator string '" + generator +
+                                "'! This may indicate an issue with your generator plugin or an invalid generator id. Check console for errors!");
+                        break;
+                    case INVALID_GENERATOR:
+                        sender.sendMessage("Invalid generator string '" + generator +
+                                "'! The generator id you use is probably not supported by your generator plugin.");
+                        break;
+                    case PLUGIN_DOES_NOT_EXIST:
+                        sender.sendMessage("That generator plugin is not installed on your server!");
+                        break;
+                    default:
+                        sender.sendMessage("Invalid generator string '" + generator + "'!");
+                        break;
+                }
+                sender.sendMessage(ChatColor.RED + "Aborting world creation...");
                 return;
             }
         }

src/main/java/com/onarandombox/MultiverseCore/commands/GamerulesCommand.java

@@ -8,9 +8,6 @@
 package com.onarandombox.MultiverseCore.commands;
 
 import com.onarandombox.MultiverseCore.MultiverseCore;
-import com.onarandombox.MultiverseCore.display.ColorAlternator;
-import com.onarandombox.MultiverseCore.display.ContentDisplay;
-import com.onarandombox.MultiverseCore.display.settings.MapDisplaySettings;
 import org.bukkit.Bukkit;
 import org.bukkit.ChatColor;
 import org.bukkit.GameRule;
@@ -19,9 +16,7 @@ import org.bukkit.command.CommandSender;
 import org.bukkit.entity.Player;
 import org.bukkit.permissions.PermissionDefault;
 
-import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
 
 /**
  * Allows management of Anchor Destinations.
@@ -73,23 +68,15 @@ public class GamerulesCommand extends MultiverseCommand {
             }
         }
 
-        ContentDisplay.forContent(getGameRuleMap(world))
-                .header("=== Gamerules for %s%s%s ===", ChatColor.AQUA, world.getName(), ChatColor.WHITE)
-                .colorTool(ColorAlternator.with(ChatColor.GREEN, ChatColor.GOLD))
-                .setting(MapDisplaySettings.OPERATOR, ": ")
-                .show(sender);
-    }
-
-    private Map<String, Object> getGameRuleMap(World world) {
-        Map<String, Object> gameRuleMap = new HashMap<>();
-        for (GameRule<?> rule : GameRule.values()) {
-            Object value = world.getGameRuleValue(rule);
-            if (value == null) {
-                gameRuleMap.put(rule.getName(), "null");
-                continue;
+        final StringBuilder gameRules = new StringBuilder();
+        for (final String gameRule : world.getGameRules()) {
+            if (gameRules.length() != 0) {
+                gameRules.append(ChatColor.WHITE).append(", ");
             }
-            gameRuleMap.put(rule.getName(), value);
+            gameRules.append(ChatColor.AQUA).append(gameRule).append(ChatColor.WHITE).append(": ");
+            gameRules.append(ChatColor.GREEN).append(world.getGameRuleValue(GameRule.getByName(gameRule)));
         }
-        return gameRuleMap;
+        sender.sendMessage("=== Gamerules for " + ChatColor.AQUA + world.getName() + ChatColor.WHITE + " ===");
+        sender.sendMessage(gameRules.toString());
     }
 }

src/main/java/com/onarandombox/MultiverseCore/commands/GeneratorCommand.java

@@ -9,12 +9,19 @@ package com.onarandombox.MultiverseCore.commands;
 
 import com.dumptruckman.minecraft.util.Logging;
 import com.onarandombox.MultiverseCore.MultiverseCore;
+import com.onarandombox.MultiverseCore.api.GeneratorPlugin;
+import com.onarandombox.MultiverseCore.generators.SimpleGeneratorPlugin;
+import net.milkbowl.vault.chat.Chat;
+import org.bukkit.Bukkit;
 import org.bukkit.ChatColor;
+import org.bukkit.command.Command;
 import org.bukkit.command.CommandSender;
+import org.bukkit.generator.ChunkGenerator;
 import org.bukkit.permissions.PermissionDefault;
 import org.bukkit.plugin.Plugin;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
 
 /**
@@ -25,36 +32,70 @@ public class GeneratorCommand extends MultiverseCommand {
     public GeneratorCommand(MultiverseCore plugin) {
         super(plugin);
         this.setName("World Information");
-        this.setCommandUsage("/mv generators");
-        this.setArgRange(0, 0);
+        this.setCommandUsage("/mv generators [plugin]");
+        this.setArgRange(0, 1);
         this.addKey("mv generators");
         this.addKey("mvgenerators");
         this.addKey("mv gens");
         this.addKey("mvgens");
         this.addCommandExample("/mv generators");
-        this.setPermission("multiverse.core.generator", "Returns a list of Loaded Generator Plugins.", PermissionDefault.OP);
+        this.addCommandExample("/mv generators VoidGenerator");
+        this.setPermission("multiverse.core.generator", "Returns info of Loaded Generator Plugins.", PermissionDefault.OP);
     }
 
     @Override
     public void runCommand(CommandSender sender, List<String> args) {
-        Logging.info("PLEASE IGNORE the 'Plugin X does not contain any generators' message below!");
-        Plugin[] plugins = this.plugin.getServer().getPluginManager().getPlugins();
-        List<String> generators = new ArrayList<String>();
-        for (Plugin p : plugins) {
-            if (p.isEnabled() && p.getDefaultWorldGenerator("world", "") != null) {
-                generators.add(p.getDescription().getName());
-            }
+        if (args.size() == 0) {
+            listKnownGenerators(sender);
+            return;
         }
+        showGeneratorDetails(sender, args.get(0));
+    }
+
+    private void listKnownGenerators(CommandSender sender) {
         sender.sendMessage(ChatColor.AQUA + "--- Loaded Generator Plugins ---");
-        String loadedGens = "";
+        StringBuilder loadedGens = new StringBuilder();
         boolean altColor = false;
-        for (String s : generators) {
-            loadedGens += (altColor ? ChatColor.YELLOW : ChatColor.WHITE) + s + " ";
+        for (String s : this.plugin.getMVGeneratorManager().getGeneratorPluginNames()) {
+            loadedGens.append(altColor ? ChatColor.YELLOW : ChatColor.WHITE).append(s).append(' ');
             altColor = !altColor;
         }
         if (loadedGens.length() == 0) {
-            loadedGens = ChatColor.RED + "No Generator Plugins found.";
+            loadedGens.append(ChatColor.RED).append("No Generator Plugins found.");
+        }
+        sender.sendMessage(loadedGens.toString());
+    }
+
+    private void showGeneratorDetails(CommandSender sender, String pluginName) {
+        Plugin genPlugin = Bukkit.getPluginManager().getPlugin(pluginName);
+        if (genPlugin == null) {
+            sender.sendMessage(ChatColor.RED + "You do not have a plugin named '"+ pluginName + "' on your server.");
+            return;
+        }
+
+        GeneratorPlugin generatorPlugin = this.plugin.getMVGeneratorManager().getGeneratorPlugin(genPlugin);
+        if (generatorPlugin == null) {
+            sender.sendMessage(ChatColor.RED + "'" + pluginName + "' does not look like a generator plugin.");
+            return;
+        }
+
+        sender.sendMessage(ChatColor.AQUA + "--- Info on " + generatorPlugin.getPlugin().getName() + " ---");
+        boolean hasAddInfo = false;
+
+        Collection<String> exampleUsages = generatorPlugin.getExampleUsages();
+        if (exampleUsages != null && exampleUsages.size() > 0) {
+            hasAddInfo = true;
+            sender.sendMessage("Usages:");
+            exampleUsages.forEach(sender::sendMessage);
+        }
+        String infoLink = generatorPlugin.getInfoLink();
+        if (infoLink != null) {
+            hasAddInfo = true;
+            sender.sendMessage("More Info: " + infoLink);
+        }
+
+        if (!hasAddInfo) {
+            sender.sendMessage(ChatColor.RED + "'" + pluginName + "' did not provide additional info to Multiverse.");
         }
-        sender.sendMessage(loadedGens);
     }
 }

src/main/java/com/onarandombox/MultiverseCore/commands/ImportCommand.java

@@ -10,6 +10,7 @@ package com.onarandombox.MultiverseCore.commands;
 import com.onarandombox.MultiverseCore.MultiverseCore;
 import com.onarandombox.MultiverseCore.api.MVWorldManager;
 import com.onarandombox.MultiverseCore.api.MultiverseWorld;
+import com.onarandombox.MultiverseCore.utils.WorldNameChecker;
 import com.pneumaticraft.commandhandler.CommandHandler;
 import org.bukkit.ChatColor;
 import org.bukkit.World.Environment;
@@ -45,28 +46,6 @@ public class ImportCommand extends MultiverseCommand {
         this.worldManager = this.plugin.getMVWorldManager();
     }
 
-    /**
-     * A very basic check to see if a folder has a level.dat file.
-     * If it does, we can safely assume it's a world folder.
-     *
-     * @param worldFolder The File that may be a world.
-     * @return True if it looks like a world, false if not.
-     */
-    private static boolean checkIfIsWorld(File worldFolder) {
-        if (worldFolder.isDirectory()) {
-            File[] files = worldFolder.listFiles(new FilenameFilter() {
-                @Override
-                public boolean accept(File file, String name) {
-                    return name.toLowerCase().endsWith(".dat");
-                }
-            });
-            if (files != null && files.length > 0) {
-                return true;
-            }
-        }
-        return false;
-    }
-
     private String getPotentialWorlds() {
         File worldFolder = this.plugin.getServer().getWorldContainer();
         if (worldFolder == null) {
@@ -84,7 +63,7 @@ public class ImportCommand extends MultiverseCommand {
         }
         ChatColor currColor = ChatColor.WHITE;
         for (File file : files) {
-            if (file.isDirectory() && checkIfIsWorld(file) && !worldStrings.contains(file.getName())) {
+            if (file.isDirectory() && WorldNameChecker.isValidWorldFolder(file) && !worldStrings.contains(file.getName())) {
                 worldList += currColor + file.getName() + " ";
                 if (currColor == ChatColor.WHITE) {
                     currColor = ChatColor.YELLOW;
@@ -152,7 +131,7 @@ public class ImportCommand extends MultiverseCommand {
             String worldList = this.getPotentialWorlds();
             sender.sendMessage("That world folder does not exist. These look like worlds to me:");
             sender.sendMessage(worldList);
-        } else if (!checkIfIsWorld(worldFile)) {
+        } else if (!WorldNameChecker.isValidWorldFolder(worldFile)) {
             sender.sendMessage(ChatColor.RED + "FAILED.");
             sender.sendMessage(String.format("'%s' does not appear to be a world. It is lacking a .dat file.",
                                              worldName));

src/main/java/com/onarandombox/MultiverseCore/commands/ListCommand.java

@@ -9,111 +9,122 @@ package com.onarandombox.MultiverseCore.commands;
 
 import com.onarandombox.MultiverseCore.MultiverseCore;
 import com.onarandombox.MultiverseCore.api.MultiverseWorld;
-import com.onarandombox.MultiverseCore.display.ColorAlternator;
-import com.onarandombox.MultiverseCore.display.ContentDisplay;
-import com.onarandombox.MultiverseCore.display.ContentFilter;
-import com.onarandombox.MultiverseCore.display.DisplayHandlers;
-import com.onarandombox.MultiverseCore.display.settings.PagedDisplaySettings;
 import org.bukkit.ChatColor;
-import org.bukkit.World;
+import org.bukkit.World.Environment;
 import org.bukkit.command.CommandSender;
 import org.bukkit.entity.Player;
 import org.bukkit.permissions.PermissionDefault;
-import org.jetbrains.annotations.NotNull;
 
-import java.util.Collection;
+import java.util.ArrayList;
 import java.util.List;
-import java.util.stream.Collectors;
 
 /**
  * Displays a listing of all worlds that a player can enter.
  */
-public class ListCommand extends MultiverseCommand {
+public class ListCommand extends PaginatedCoreCommand<String> {
 
     public ListCommand(MultiverseCore plugin) {
         super(plugin);
         this.setName("World Listing");
-        this.setCommandUsage("/mv list [filter] [page]");
+        this.setCommandUsage("/mv list [page]");
         this.setArgRange(0, 2);
         this.addKey("mvlist");
         this.addKey("mvl");
         this.addKey("mv list");
         this.setPermission("multiverse.core.list.worlds", "Displays a listing of all worlds that you can enter.", PermissionDefault.OP);
+        this.setItemsPerPage(8); // SUPPRESS CHECKSTYLE: MagicNumberCheck
+    }
+
+    private List<String> getFancyWorldList(Player p) {
+        List<String> worldList = new ArrayList<String>();
+        for (MultiverseWorld world : this.plugin.getMVWorldManager().getMVWorlds()) {
+
+            if (p != null && (!this.plugin.getMVPerms().canEnterWorld(p, world))) {
+                continue;
+            }
+
+            ChatColor color = ChatColor.GOLD;
+            Environment env = world.getEnvironment();
+            if (env == Environment.NETHER) {
+                color = ChatColor.RED;
+            } else if (env == Environment.NORMAL) {
+                color = ChatColor.GREEN;
+            } else if (env == Environment.THE_END) {
+                color = ChatColor.AQUA;
+            }
+            StringBuilder builder = new StringBuilder();
+            builder.append(world.getColoredWorldString()).append(ChatColor.WHITE);
+            builder.append(" - ").append(color).append(world.getEnvironment());
+            if (world.isHidden()) {
+                if (p == null || this.plugin.getMVPerms().hasPermission(p, "multiverse.core.modify", true)) {
+                    // Prefix hidden worlds with an "[H]"
+                    worldList.add(ChatColor.GRAY + "[H]" + builder.toString());
+                }
+            } else {
+                worldList.add(builder.toString());
+            }
+        }
+        for (String name : this.plugin.getMVWorldManager().getUnloadedWorlds()) {
+            if (p == null || this.plugin.getMVPerms().hasPermission(p, "multiverse.access." + name, true)) {
+                worldList.add(ChatColor.GRAY + name + " - UNLOADED");
+            }
+        }
+        return worldList;
+    }
+
+    @Override
+    protected List<String> getFilteredItems(List<String> availableItems, String filter) {
+        List<String> filtered = new ArrayList<String>();
+
+        for (String s : availableItems) {
+            if (s.matches("(?i).*" + filter + ".*")) {
+                filtered.add(s);
+            }
+        }
+        return filtered;
+    }
+
+    @Override
+    protected String getItemText(String item) {
+        return item;
     }
 
     @Override
     public void runCommand(CommandSender sender, List<String> args) {
-        ContentFilter filter = ContentFilter.DEFAULT;
-        int page = 1;
+        sender.sendMessage(ChatColor.LIGHT_PURPLE + "====[ Multiverse World List ]====");
+        Player p = null;
+        if (sender instanceof Player) {
+            p = (Player) sender;
+        }
 
-        // Either page or filter.
-        if (args.size() == 1) {
-            try {
-                page = Integer.parseInt(args.get(0));
-            } catch (NumberFormatException ignore) {
-                filter = new ContentFilter(args.get(0));
+
+        FilterObject filterObject = this.getPageAndFilter(args);
+
+        List<String> availableWorlds = new ArrayList<String>(this.getFancyWorldList(p));
+        if (filterObject.getFilter().length() > 0) {
+            availableWorlds = this.getFilteredItems(availableWorlds, filterObject.getFilter());
+            if (availableWorlds.size() == 0) {
+                sender.sendMessage(ChatColor.RED + "Sorry... " + ChatColor.WHITE
+                        + "No worlds matched your filter: " + ChatColor.AQUA + filterObject.getFilter());
+                return;
             }
         }
 
-        // Filter then page.
-        if (args.size() == 2) {
-            filter = new ContentFilter(args.get(0));
-            try {
-                page = Integer.parseInt(args.get(1));
-            } catch (NumberFormatException ignore) {
-                sender.sendMessage(ChatColor.RED + args.get(1) + " is not valid number!");
+        if (!(sender instanceof Player)) {
+            for (String c : availableWorlds) {
+                sender.sendMessage(c);
             }
+            return;
         }
 
-        ContentDisplay.forContent(getListContents(sender))
-                .header("%s====[ Multiverse World List ]====", ChatColor.GOLD)
-                .displayHandler(DisplayHandlers.PAGE_LIST)
-                .colorTool(ColorAlternator.with(ChatColor.AQUA, ChatColor.GOLD))
-                .filter(filter)
-                .setting(PagedDisplaySettings.SHOW_PAGE, page)
-                .show(sender);
-    }
+        int totalPages = (int) Math.ceil(availableWorlds.size() / (this.itemsPerPage + 0.0));
 
-    private Collection<String> getListContents(@NotNull CommandSender sender) {
-        Player player = (sender instanceof Player) ? (Player) sender : null;
-
-        List<String> worldList = this.plugin.getMVWorldManager().getMVWorlds().stream()
-                .filter(world -> player == null || plugin.getMVPerms().canEnterWorld(player, world))
-                .filter(world -> canSeeWorld(player, world))
-                .map(world -> hiddenText(world) + world.getColoredWorldString() + " - " + parseColouredEnvironment(world.getEnvironment()))
-                .collect(Collectors.toList());
-
-        this.plugin.getMVWorldManager().getUnloadedWorlds().stream()
-                .filter(world -> plugin.getMVPerms().hasPermission(sender, "multiverse.access." + world, true))
-                .map(world -> ChatColor.GRAY + world + " - UNLOADED")
-                .forEach(worldList::add);
-        
-        return worldList;
-    }
-
-    private boolean canSeeWorld(Player player, MultiverseWorld world) {
-        return !world.isHidden()
-                || player == null
-                || this.plugin.getMVPerms().hasPermission(player, "multiverse.core.modify", true);
-    }
-
-    private String hiddenText(MultiverseWorld world) {
-        return (world.isHidden()) ? String.format("%s[H] ", ChatColor.GRAY) : "";
-    }
-
-    private String parseColouredEnvironment(World.Environment env) {
-        ChatColor color = ChatColor.GOLD;
-        switch (env) {
-            case NETHER:
-                color = ChatColor.RED;
-                break;
-            case NORMAL:
-                color = ChatColor.GREEN;
-                break;
-            case THE_END:
-                color = ChatColor.AQUA;
-                break;
+        if (filterObject.getPage() > totalPages) {
+            filterObject.setPage(totalPages);
         }
-        return color + env.toString();
+
+        sender.sendMessage(ChatColor.AQUA + " Page " + filterObject.getPage() + " of " + totalPages);
+
+        this.showPage(filterObject.getPage(), sender, availableWorlds);
     }
 }

src/main/java/com/onarandombox/MultiverseCore/commands/SpawnCommand.java

@@ -9,6 +9,7 @@ package com.onarandombox.MultiverseCore.commands;
 
 import com.onarandombox.MultiverseCore.MultiverseCore;
 import com.onarandombox.MultiverseCore.api.MultiverseWorld;
+import com.onarandombox.MultiverseCore.utils.PlayerFinder;
 import org.bukkit.ChatColor;
 import org.bukkit.Location;
 import org.bukkit.command.CommandSender;
@@ -50,7 +51,7 @@ public class SpawnCommand extends MultiverseCommand {
                 sender.sendMessage("You don't have permission to teleport another player to spawn. (multiverse.core.spawn.other)");
                 return;
             }
-            Player target = this.plugin.getServer().getPlayerExact(args.get(0));
+            Player target = PlayerFinder.get(args.get(0), sender);
             if (target != null) {
                 target.sendMessage("Teleporting to this world's spawn...");
                 spawnAccurately(target);

src/main/java/com/onarandombox/MultiverseCore/commands/TeleportCommand.java

@@ -18,6 +18,7 @@ import com.onarandombox.MultiverseCore.destination.WorldDestination;
 import com.onarandombox.MultiverseCore.enums.TeleportResult;
 import com.onarandombox.MultiverseCore.event.MVTeleportEvent;
 import com.onarandombox.MultiverseCore.api.SafeTTeleporter;
+import com.onarandombox.MultiverseCore.utils.PlayerFinder;
 import org.bukkit.ChatColor;
 import org.bukkit.Location;
 import org.bukkit.World;
@@ -28,7 +29,6 @@ import org.bukkit.permissions.PermissionDefault;
 
 import java.util.ArrayList;
 import java.util.List;
-import java.util.logging.Level;
 
 /**
  * Used to teleport players.
@@ -59,7 +59,7 @@ public class TeleportCommand extends MultiverseCommand {
         String destinationName;
 
         if (args.size() == 2) {
-            teleportee = this.plugin.getServer().getPlayerExact(args.get(0));
+            teleportee = PlayerFinder.get(args.get(0), sender);
             if (teleportee == null) {
                 this.messaging.sendMessage(sender, String.format("Sorry, I couldn't find player: %s%s",
                         ChatColor.GOLD, args.get(0)), false);
@@ -75,22 +75,9 @@ public class TeleportCommand extends MultiverseCommand {
             }
             teleportee = (Player) sender;
         }
-        // Special case for cannons:
-        if (destinationName.matches("(?i)cannon-[\\d]+(\\.[\\d]+)?")) {
-            String[] cannonSpeed = destinationName.split("-");
-            try {
-                double speed = Double.parseDouble(cannonSpeed[1]);
-                destinationName = "ca:" + teleportee.getWorld().getName() + ":" + teleportee.getLocation().getX()
-                        + "," + teleportee.getLocation().getY() + "," + teleportee.getLocation().getZ() + ":"
-                        + teleportee.getLocation().getPitch() + ":" + teleportee.getLocation().getYaw() + ":" + speed;
-            } catch (Exception e) {
-                destinationName = "i:invalid";
-            }
 
-        }
         DestinationFactory df = this.plugin.getDestFactory();
-        MVDestination d = df.getDestination(destinationName);
-
+        MVDestination d = df.getPlayerAwareDestination(teleportee, destinationName);
 
         MVTeleportEvent teleportEvent = new MVTeleportEvent(d, teleportee, teleporter, true);
         this.plugin.getServer().getPluginManager().callEvent(teleportEvent);

src/main/java/com/onarandombox/MultiverseCore/destination/DestinationFactory.java

@@ -11,16 +11,26 @@ import com.onarandombox.MultiverseCore.MultiverseCore;
 import com.onarandombox.MultiverseCore.api.MVDestination;
 import com.onarandombox.MultiverseCore.commands.TeleportCommand;
 import com.onarandombox.MultiverseCore.utils.PermissionTools;
+import com.onarandombox.MultiverseCore.utils.PlayerFinder;
 import com.pneumaticraft.commandhandler.Command;
+import org.bukkit.Bukkit;
+import org.bukkit.command.CommandSender;
+import org.bukkit.entity.Player;
 import org.bukkit.permissions.Permission;
 import org.bukkit.permissions.PermissionDefault;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.regex.Pattern;
 
 /** A factory class that will create destinations from specific strings. */
 public class DestinationFactory {
+
+    private static final Pattern CANNON_PATTERN = Pattern.compile("(?i)cannon-[\\d]+(\\.[\\d]+)?");
+
     private MultiverseCore plugin;
     private Map<String, Class<? extends MVDestination>> destList;
     private Command teleportCommand;
@@ -36,6 +46,59 @@ public class DestinationFactory {
         }
     }
 
+    /**
+     * Parse a destination that has relation to sender, such as a cannon or player destination.
+     *
+     * @param teleportee        The player that is going to be teleported.
+     * @param destinationName   The destination to parse.
+     * @return A non-null MVDestination
+     */
+    @NotNull
+    public MVDestination getPlayerAwareDestination(@NotNull Player teleportee,
+                                                   @NotNull String destinationName) {
+
+        // Prioritise world, in the event that a world is named after a player online.
+        if (Bukkit.getWorld(destinationName) != null) {
+            return getDestination(destinationName);
+        }
+
+        Player targetPlayer = PlayerFinder.get(destinationName, teleportee);
+        if (targetPlayer != null) {
+            return getDestination("pl:" + targetPlayer.getName());
+        }
+
+        if (CANNON_PATTERN.matcher(destinationName).matches()) {
+            return getDestination(parseCannonDest(teleportee, destinationName));
+        }
+
+        return getDestination(destinationName);
+    }
+
+    /**
+     * Parses a cannon destination.
+     *
+     * @param teleportee        The player that is going to be teleported.
+     * @param destinationName   The destination to parse.
+     * @return A destination string.
+     */
+    @NotNull
+    private String parseCannonDest(@NotNull Player teleportee,
+                                   @NotNull String destinationName) {
+
+        String[] cannonSpeed = destinationName.split("-");
+        try {
+            double speed = Double.parseDouble(cannonSpeed[1]);
+            destinationName = "ca:" + teleportee.getWorld().getName() + ":" + teleportee.getLocation().getX()
+                    + "," + teleportee.getLocation().getY() + "," + teleportee.getLocation().getZ() + ":"
+                    + teleportee.getLocation().getPitch() + ":" + teleportee.getLocation().getYaw() + ":" + speed;
+        }
+        catch (Exception e) {
+            destinationName = "i:invalid";
+        }
+
+        return destinationName;
+    }
+
     /**
      * Gets a new destination from a string.
      * Returns a new InvalidDestination if the string could not be parsed.

src/main/java/com/onarandombox/MultiverseCore/display/ColorAlternator.java

@@ -1,62 +0,0 @@
-package com.onarandombox.MultiverseCore.display;
-
-import org.bukkit.ChatColor;
-import org.jetbrains.annotations.NotNull;
-
-/**
- * Helper class to switch between 2 {@link ChatColor}.
- */
-public class ColorAlternator implements ColorTool {
-
-    /**
-     * Creates a new {@link ColorAlternator} with 2 {@link ChatColor}s.
-     *
-     * @param colorThis The first color.
-     * @param colorThat The second color.
-     * @return The {@link ColorAlternator} created for you.
-     */
-    public static ColorAlternator with(@NotNull ChatColor colorThis,
-                                       @NotNull ChatColor colorThat) {
-
-        return new ColorAlternator(colorThis, colorThat);
-    }
-
-    private boolean switcher;
-    private final ChatColor thisColor;
-    private final ChatColor thatColor;
-
-    /**
-     * @param colorThis The first color.
-     * @param colorThat The second color.
-     */
-    public ColorAlternator(@NotNull ChatColor colorThis,
-                           @NotNull ChatColor colorThat) {
-
-        this.thisColor = colorThis;
-        this.thatColor = colorThat;
-    }
-
-    /**
-     * Gets the color. Everytime this method is called, it swaps the color that it returns.
-     *
-     * @return The color.
-     */
-    @Override
-    public ChatColor get() {
-        return (this.switcher ^= true) ? this.thisColor : this.thatColor;
-    }
-
-    /**
-     * @return The first color.
-     */
-    public ChatColor getThisColor() {
-        return thisColor;
-    }
-
-    /**
-     * @return The second color.
-     */
-    public ChatColor getThatColor() {
-        return thatColor;
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/display/ColorTool.java

@@ -1,22 +0,0 @@
-package com.onarandombox.MultiverseCore.display;
-
-import org.bukkit.ChatColor;
-
-/**
- * Tools to allow customisation.
- */
-@FunctionalInterface
-public interface ColorTool {
-
-    /**
-     * Gets a chat color.
-     *
-     * @return The color.
-     */
-    ChatColor get();
-
-    /**
-     * Default implementation of this interface. Returns a default white color.
-     */
-    ColorTool DEFAULT = () -> ChatColor.WHITE;
-}

src/main/java/com/onarandombox/MultiverseCore/display/ContentDisplay.java

@@ -1,268 +0,0 @@
-package com.onarandombox.MultiverseCore.display;
-
-import com.onarandombox.MultiverseCore.display.settings.DisplaySetting;
-import org.bukkit.ChatColor;
-import org.bukkit.command.CommandSender;
-import org.jetbrains.annotations.NotNull;
-
-import java.util.Collection;
-import java.util.Map;
-import java.util.Objects;
-import java.util.WeakHashMap;
-
-/**
- * Helps to display contents such as list and maps in a nicely formatted fashion.
- *
- * @param <T>   Type of content to display.
- */
-public class ContentDisplay<T> {
-
-    public static final String LINE_BREAK = "%br%";
-
-    /**
-     * Creates a ContentDisplay.Builder for the given content.
-     *
-     * @param content The content to be displayed.
-     * @param <T> The type of the content which can be inferred.
-     * @return A new Builder.
-     */
-    public static <T> Builder<T> forContent(T content) {
-        return new Builder<>(content);
-    }
-
-    /**
-     * Creates a ContentDisplay.Builder for the given collection of content.
-     *
-     * @param content The content to be displayed.
-     * @return A new Builder.
-     */
-    public static Builder<Collection<String>> forContent(Collection<String> content) {
-        return new Builder<>(content).displayHandler(DisplayHandlers.LIST);
-    }
-
-    /**
-     * Creates a ContentDisplay.Builder for the given map of content.
-     *
-     * @param content The content to be displayed.
-     * @return A new Builder.
-     */
-    public static Builder<Map<String, Object>> forContent(Map<String, Object> content) {
-        return new Builder<>(content).displayHandler(DisplayHandlers.INLINE_MAP);
-    }
-
-    private final T contents;
-
-    private String header;
-    private String emptyMessage = "No matching content to display.";
-    private DisplayHandler<T> displayHandler;
-    private ColorTool colorTool = ColorTool.DEFAULT;
-    private ContentFilter filter = ContentFilter.DEFAULT;
-    private final Map<DisplaySetting<?>, Object> settingsMap = new WeakHashMap<>();
-
-    private ContentDisplay(T contents) {
-        this.contents = contents;
-    }
-
-    /**
-     * Do the actual displaying of contents to the sender.
-     *
-     * @param sender The CommandSender to show the display to.
-     */
-    public void show(@NotNull CommandSender sender) {
-        Collection<String> formattedContent;
-        try {
-            formattedContent = (this.contents == null) ? null : this.displayHandler.format(sender, this);
-        } catch (DisplayFormatException e) {
-            sender.sendMessage(String.format("%sError: %s", ChatColor.RED, e.getMessage()));
-            return;
-        }
-        this.displayHandler.sendHeader(sender, this);
-        this.displayHandler.sendSubHeader(sender, this);
-        this.displayHandler.sendBody(sender, this, formattedContent);
-    }
-
-    /**
-     * @return Gets the header to display.
-     */
-    public String getHeader() {
-        return header;
-    }
-
-    /**
-     * Sets the header text.
-     */
-    public void setHeader(@NotNull String header) {
-        this.header = header;
-    }
-
-    /**
-     * @return Gets the contents to display.
-     */
-    public T getContents() {
-        return contents;
-    }
-
-    /**
-     * @return Gets the message to display when no content is shown.
-     */
-    @NotNull
-    public String getEmptyMessage() {
-        return emptyMessage;
-    }
-
-    /**
-     * @return Gets the display handler that formats and sends content to sender.
-     */
-    @NotNull
-    public DisplayHandler<T> getDisplayHandler() {
-        return displayHandler;
-    }
-
-    /**
-     * @return Gets the color tool used.
-     */
-    @NotNull
-    public ColorTool getColorTool() {
-        return colorTool;
-    }
-
-    /**
-     * @return Gets the filter used.
-     */
-    @NotNull
-    public ContentFilter getFilter() {
-        return filter;
-    }
-
-    /**
-     * Gets the value for a given setting option.
-     *
-     * @param setting   The setting option.
-     * @param <S>       The setting type.
-     * @return Value set for the given setting.
-     */
-    public <S> S getSetting(@NotNull DisplaySetting<S> setting) {
-        return (S) settingsMap.getOrDefault(setting, setting.defaultValue());
-    }
-
-    /**
-     * Sets other specific settings that may be used by the {@link DisplayHandler}.
-     *
-     * @param setting   The settings option.
-     * @param value     The value to set.
-     * @param <S>       The type of setting.
-     */
-    public <S> void setSetting(@NotNull DisplaySetting<S> setting, S value) {
-        this.settingsMap.put(setting, value);
-    }
-
-    /**
-     * Builds a {@link ContentDisplay}.
-     *
-     * @param <T>   Type of content to display.
-     */
-    public static class Builder<T> {
-
-        private final ContentDisplay<T> display;
-
-        private Builder(T content) {
-            this.display = new ContentDisplay<>(content);
-        }
-
-        /**
-         * Sets header to be displayed.
-         *
-         * @param header        The header text.
-         * @param replacements  String formatting replacements.
-         * @return The builder.
-         */
-        @NotNull
-        public Builder<T> header(@NotNull String header, Object...replacements) {
-            this.display.header = String.format(header, replacements);
-            return this;
-        }
-
-        /**
-         * Sets the message to show when no content is available for display.
-         *
-         * @param emptyMessage  The message text.
-         * @param replacements  String formatting replacements.
-         * @return The builder.
-         */
-        @NotNull
-        public Builder<T> emptyMessage(@NotNull String emptyMessage, Object...replacements) {
-            this.display.emptyMessage = String.format(emptyMessage, replacements);
-            return this;
-        }
-
-        /**
-         * Sets the display handler that does the formatting and sending of content. <b>Required.</b>
-         *
-         * @param displayHandler    The display handler for the given content type.
-         * @return The builder.
-         */
-        @NotNull
-        public Builder<T> displayHandler(@NotNull DisplayHandler<T> displayHandler) {
-            this.display.displayHandler = displayHandler;
-            return this;
-        }
-
-        /**
-         * Sets the color tool used to make messages more colourful.
-         *
-         * @param colorTool The color tool to use.
-         * @return The builder.
-         */
-        @NotNull
-        public Builder<T> colorTool(@NotNull ColorTool colorTool) {
-            this.display.colorTool = colorTool;
-            return this;
-        }
-
-        /**
-         * Sets content filter used to match specific content to be displayed.
-         *
-         * @param filter    The filter to use.
-         * @return The builder.
-         */
-        @NotNull
-        public Builder<T> filter(@NotNull ContentFilter filter) {
-            this.display.filter = filter;
-            return this;
-        }
-
-        /**
-         * Sets other specific settings that may be used by the {@link DisplayHandler}.
-         *
-         * @param setting   The settings option.
-         * @param value     The value to set.
-         * @param <S>       The type of setting.
-         * @return The builder.
-         */
-        @NotNull
-        public <S> Builder<T> setting(@NotNull DisplaySetting<S> setting, S value) {
-            this.display.settingsMap.put(setting, value);
-            return this;
-        }
-
-        /**
-         * Validates and build the content display.
-         *
-         * @return The content display.
-         */
-        @NotNull
-        public ContentDisplay<T> build() {
-            Objects.requireNonNull(this.display.displayHandler);
-            return this.display;
-        }
-
-        /**
-         * Build and show the content to the sender.
-         *
-         * @param sender The CommandSender to show the display to.
-         */
-        public void show(CommandSender sender) {
-            this.build().show(sender);
-        }
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/display/ContentFilter.java

@@ -1,153 +0,0 @@
-package com.onarandombox.MultiverseCore.display;
-
-import com.dumptruckman.minecraft.util.Logging;
-import org.bukkit.ChatColor;
-import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
-
-import java.util.regex.Pattern;
-import java.util.regex.PatternSyntaxException;
-
-/**
- * <p>Filter content and text based on regex matching.</p>
- *
- * <p>Compile regex pattern based on {@link ContentFilter#filterString}. When prefixed with 'r=',
- * use {@link ContentFilter#filterString} as the full regex pattern. Else, set to any match that
- * contains the {@link ContentFilter#filterString}.<p>
- */
-public class ContentFilter {
-
-    public static final ContentFilter DEFAULT = new ContentFilter();
-    private static final Pattern REGEX_SPECIAL_CHARS = Pattern.compile("[.+*?\\[^\\]$(){}=!<>|:-\\\\]");
-
-    private String filterString;
-    private Pattern filterPattern;
-    private boolean exactMatch;
-
-    private ContentFilter() {
-    }
-
-    /**
-     * @param filterString  The text to do matching, either plaintext or regex.
-     */
-    public ContentFilter(@NotNull String filterString) {
-        this(filterString, false);
-    }
-
-    /**
-     * @param filterString  The text to do matching, else plaintext or regex.
-     * @param exactMatch    Should check for exact match when doing regex matching.
-     */
-    public ContentFilter(@NotNull String filterString,
-                         boolean exactMatch) {
-
-        this.filterString = filterString;
-        this.exactMatch = exactMatch;
-        parseFilter();
-    }
-
-    private void parseFilter() {
-        if (filterString == null) {
-            return;
-        }
-        if (filterString.startsWith("r=")) {
-            convertToMatcher(filterString.substring(2));
-            return;
-        }
-        String cleanedFilter = REGEX_SPECIAL_CHARS.matcher(filterString.toLowerCase()).replaceAll("\\\\$0");
-        convertToMatcher("(?i).*" + cleanedFilter + ".*");
-    }
-
-    /**
-     * Compile and store the regex into a {@link Pattern}.
-     *
-     * @param regex The regex text.
-     */
-    private void convertToMatcher(@NotNull String regex) {
-        try {
-            this.filterPattern = Pattern.compile(regex);
-            Logging.finest("Parsed regex pattern: %s", this.filterPattern.toString());
-        }
-        catch (PatternSyntaxException ignored) {
-            Logging.warning("Error parsing regex: %s", filterString);
-        }
-    }
-
-    /**
-     * Do regex matching.
-     *
-     * @param text String to check regex on.
-     * @return True of matches regex pattern, false otherwise.
-     */
-    public boolean checkMatch(@Nullable Object text) {
-        if (!hasFilter()) {
-            return true;
-        }
-        if (text == null || !hasValidPattern()) {
-            return false;
-        }
-        text = ChatColor.stripColor(String.valueOf(text));
-        return (exactMatch)
-                ? filterPattern.matcher((CharSequence) text).matches()
-                : filterPattern.matcher((CharSequence) text).find();
-    }
-
-    /**
-     * Checks if a filter string is present.
-     *
-     * @return True if there is a filter string, else false.
-     */
-    public boolean hasFilter() {
-        return filterString != null;
-    }
-
-    /**
-     * Checks if regex pattern syntax is valid.
-     *
-     * @return True if valid, else false.
-     */
-    public boolean hasValidPattern() {
-        return filterPattern != null;
-    }
-
-    /**
-     * @return The filter string.
-     */
-    @Nullable
-    public String getString() {
-        return filterString;
-    }
-
-    /**
-     * @return The regex pattern.
-     */
-    @Nullable
-    public Pattern getPattern() {
-        return filterPattern;
-    }
-
-    /**
-     * @return True if filter is set to do exact matching, else false.
-     */
-    public boolean isExactMatch() {
-        return exactMatch;
-    }
-
-    /**
-     * Nicely format the filter string to be used for showing the sender.
-     *
-     * @return The formatted filter string.
-     */
-    public @NotNull String getFormattedString() {
-        return String.format("%sFilter: '%s'", ChatColor.ITALIC, filterString);
-    }
-
-    @Override
-    public String toString() {
-        return "ContentFilter{" +
-                "filterString='" + filterString + '\'' +
-                ", filterPattern=" + filterPattern +
-                ", exactMatch=" + exactMatch +
-                '}';
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/display/DisplayFormatException.java

@@ -1,25 +0,0 @@
-package com.onarandombox.MultiverseCore.display;
-
-/**
- * Thrown when an issue occur while formatting content.
- */
-public class DisplayFormatException extends Exception {
-    public DisplayFormatException() {
-    }
-
-    public DisplayFormatException(String message) {
-        super(message);
-    }
-
-    public DisplayFormatException(String message, Throwable cause) {
-        super(message, cause);
-    }
-
-    public DisplayFormatException(Throwable cause) {
-        super(cause);
-    }
-
-    public DisplayFormatException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
-        super(message, cause, enableSuppression, writableStackTrace);
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/display/DisplayHandler.java

@@ -1,68 +0,0 @@
-package com.onarandombox.MultiverseCore.display;
-
-import com.google.common.base.Strings;
-import org.bukkit.ChatColor;
-import org.bukkit.command.CommandSender;
-import org.jetbrains.annotations.NotNull;
-
-import java.util.Collection;
-
-/**
- * Handles the formatting and sending of all content by the {@link ContentDisplay}.
- *
- * @param <T>   Type of content to display.
- */
-@FunctionalInterface
-public interface DisplayHandler<T> {
-
-    /**
-     * Formats the raw content into a {@link Collection<String>} for displaying to the given sender.
-     *
-     * @param sender The {@link CommandSender} who will the content will be displayed to.
-     * @param display The responsible {@link ContentDisplay}.
-     * @return The formatted content.
-     * @throws DisplayFormatException Issue occurred while formatting content. E.g. invalid page.
-     */
-    Collection<String> format(@NotNull CommandSender sender, @NotNull ContentDisplay<T> display)
-            throws DisplayFormatException;
-
-    /**
-     * Sends the header.
-     *
-     * @param sender The {@link CommandSender} who will the header will be displayed to.
-     * @param display The responsible {@link ContentDisplay}.
-     */
-    default void sendHeader(@NotNull CommandSender sender, @NotNull ContentDisplay<T> display) {
-        if (!Strings.isNullOrEmpty(display.getHeader())) {
-            sender.sendMessage(display.getHeader());
-        }
-    }
-
-    /**
-     * Sends info such as filter and page.
-     *
-     * @param sender The {@link CommandSender} who will the sub header will be displayed to.
-     * @param display The responsible {@link ContentDisplay}.
-     */
-    default void sendSubHeader(@NotNull CommandSender sender, @NotNull ContentDisplay<T> display) {
-        if (display.getFilter().hasFilter()) {
-            sender.sendMessage(String.format("%s[ %s ]", ChatColor.GRAY, display.getFilter().getFormattedString()));
-        }
-    }
-
-    /**
-     * Sends the content.
-     *
-     * @param sender The {@link CommandSender} who will the body will be displayed to.
-     * @param display The responsible {@link ContentDisplay}.
-     * @param formattedContent The content after being formatted by {@link #format(CommandSender, ContentDisplay)}
-     */
-    default void sendBody(@NotNull CommandSender sender, @NotNull ContentDisplay<T> display,
-                          Collection<String> formattedContent) {
-        if (formattedContent == null || formattedContent.size() == 0) {
-            sender.sendMessage(display.getEmptyMessage());
-            return;
-        }
-        sender.sendMessage(formattedContent.toArray(new String[0]));
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/display/DisplayHandlers.java

@@ -1,47 +0,0 @@
-package com.onarandombox.MultiverseCore.display;
-
-import com.onarandombox.MultiverseCore.display.handlers.InlineListDisplayHandler;
-import com.onarandombox.MultiverseCore.display.handlers.InlineMapDisplayHandler;
-import com.onarandombox.MultiverseCore.display.handlers.ListDisplayHandler;
-import com.onarandombox.MultiverseCore.display.handlers.PagedListDisplayHandler;
-import com.onarandombox.MultiverseCore.display.settings.InlineDisplaySettings;
-import com.onarandombox.MultiverseCore.display.settings.PagedDisplaySettings;
-import com.onarandombox.MultiverseCore.display.settings.MapDisplaySettings;
-
-import java.util.Collection;
-import java.util.Map;
-
-/**
- * Various implementations of {@link DisplayHandler}.
- */
-public class DisplayHandlers {
-
-    /**
-     * Standard list display.
-     *
-     * Supported settings: none.
-     */
-    public static final DisplayHandler<Collection<String>> LIST = new ListDisplayHandler();
-
-    /**
-     * List display with paging.
-     *
-     * Supported settings: {@link PagedDisplaySettings#SHOW_PAGE}, {@link PagedDisplaySettings#LINES_PER_PAGE},
-     * {@link PagedDisplaySettings#PAGE_IN_CONSOLE}, {@link PagedDisplaySettings#DO_END_PADDING}.
-     */
-    public static final DisplayHandler<Collection<String>> PAGE_LIST = new PagedListDisplayHandler();
-
-    /**
-     * Display a list inline.
-     *
-     * Supported settings: {@link InlineDisplaySettings#SEPARATOR}.
-     */
-    public static final DisplayHandler<Collection<String>> INLINE_LIST = new InlineListDisplayHandler();
-
-    /**
-     * Display key value pair inline.
-     *
-     * Supported settings: {@link InlineDisplaySettings#SEPARATOR}, {@link MapDisplaySettings#OPERATOR}.
-     */
-    public static final DisplayHandler<Map<String, Object>> INLINE_MAP = new InlineMapDisplayHandler();
-}

src/main/java/com/onarandombox/MultiverseCore/display/handlers/InlineListDisplayHandler.java

@@ -1,36 +0,0 @@
-package com.onarandombox.MultiverseCore.display.handlers;
-
-import com.onarandombox.MultiverseCore.display.ContentDisplay;
-import com.onarandombox.MultiverseCore.display.DisplayFormatException;
-import com.onarandombox.MultiverseCore.display.DisplayHandler;
-import com.onarandombox.MultiverseCore.display.settings.InlineDisplaySettings;
-import org.bukkit.command.CommandSender;
-import org.jetbrains.annotations.NotNull;
-
-import java.util.Collection;
-import java.util.Collections;
-import java.util.Iterator;
-
-public class InlineListDisplayHandler implements DisplayHandler<Collection<String>> {
-
-    @Override
-    public Collection<String> format(@NotNull CommandSender sender, @NotNull ContentDisplay<Collection<String>> display)
-            throws DisplayFormatException {
-        StringBuilder builder = new StringBuilder();
-        String separator = display.getSetting(InlineDisplaySettings.SEPARATOR);
-
-        for (Iterator<String> iterator = display.getContents().iterator(); iterator.hasNext(); ) {
-            String content = iterator.next();
-            if (!display.getFilter().checkMatch(content)) {
-                continue;
-            }
-            builder.append(display.getColorTool().get()).append(content);
-            if (iterator.hasNext()) {
-                builder.append(separator);
-            }
-        }
-        return (builder.length() == 0)
-                ? Collections.singletonList(display.getEmptyMessage())
-                : Collections.singleton(builder.toString());
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/display/handlers/InlineMapDisplayHandler.java

@@ -1,44 +0,0 @@
-package com.onarandombox.MultiverseCore.display.handlers;
-
-import com.onarandombox.MultiverseCore.display.ContentDisplay;
-import com.onarandombox.MultiverseCore.display.DisplayFormatException;
-import com.onarandombox.MultiverseCore.display.DisplayHandler;
-import com.onarandombox.MultiverseCore.display.settings.InlineDisplaySettings;
-import com.onarandombox.MultiverseCore.display.settings.MapDisplaySettings;
-import org.bukkit.command.CommandSender;
-import org.jetbrains.annotations.NotNull;
-
-import java.util.Collection;
-import java.util.Collections;
-import java.util.Iterator;
-import java.util.Map;
-
-public class InlineMapDisplayHandler implements DisplayHandler<Map<String, Object>> {
-
-    @Override
-    public Collection<String> format(@NotNull CommandSender sender,
-                                     @NotNull ContentDisplay<Map<String, Object>> display)
-            throws DisplayFormatException {
-        StringBuilder builder = new StringBuilder();
-        String separator = display.getSetting(InlineDisplaySettings.SEPARATOR);
-        String operator = display.getSetting(MapDisplaySettings.OPERATOR);
-
-        for (Iterator<Map.Entry<String, Object>> iterator = display.getContents().entrySet().iterator(); iterator.hasNext(); ) {
-            Map.Entry<String, Object> entry = iterator.next();
-            if (!display.getFilter().checkMatch(entry.getKey()) && !display.getFilter().checkMatch(entry.getValue())) {
-                continue;
-            }
-            builder.append(display.getColorTool().get())
-                    .append(entry.getKey())
-                    .append(operator)
-                    .append(display.getColorTool().get())
-                    .append(entry.getValue());
-            if (iterator.hasNext()) {
-                builder.append(separator);
-            }
-        }
-        return (builder.length() == 0)
-                ? Collections.singletonList(display.getEmptyMessage())
-                : Collections.singleton(builder.toString());
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/display/handlers/ListDisplayHandler.java

@@ -1,22 +0,0 @@
-package com.onarandombox.MultiverseCore.display.handlers;
-
-import com.onarandombox.MultiverseCore.display.ContentDisplay;
-import com.onarandombox.MultiverseCore.display.DisplayFormatException;
-import com.onarandombox.MultiverseCore.display.DisplayHandler;
-import org.bukkit.command.CommandSender;
-import org.jetbrains.annotations.NotNull;
-
-import java.util.Collection;
-import java.util.stream.Collectors;
-
-public class ListDisplayHandler implements DisplayHandler<Collection<String>> {
-
-    @Override
-    public Collection<String> format(@NotNull CommandSender sender, @NotNull ContentDisplay<Collection<String>> display)
-            throws DisplayFormatException {
-        return display.getContents().stream()
-                .filter(display.getFilter()::checkMatch)
-                .map(s -> (ContentDisplay.LINE_BREAK.equals(s)) ? "" : display.getColorTool().get() + s)
-                .collect(Collectors.toList());
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/display/handlers/PagedListDisplayHandler.java

@@ -1,105 +0,0 @@
-package com.onarandombox.MultiverseCore.display.handlers;
-
-import com.onarandombox.MultiverseCore.display.ContentDisplay;
-import com.onarandombox.MultiverseCore.display.DisplayFormatException;
-import com.onarandombox.MultiverseCore.display.settings.PagedDisplaySettings;
-import org.bukkit.ChatColor;
-import org.bukkit.command.CommandSender;
-import org.bukkit.command.ConsoleCommandSender;
-import org.jetbrains.annotations.NotNull;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.List;
-import java.util.stream.IntStream;
-
-public class PagedListDisplayHandler extends ListDisplayHandler {
-
-    @Override
-    public Collection<String> format(@NotNull CommandSender sender, @NotNull ContentDisplay<Collection<String>> display)
-            throws DisplayFormatException {
-        if (dontNeedPaging(sender, display)) {
-            return super.format(sender, display);
-        }
-
-        int pages = 1;
-        int currentLength = 0;
-        int targetPage = display.getSetting(PagedDisplaySettings.SHOW_PAGE);
-        int linesPerPage = display.getSetting(PagedDisplaySettings.LINES_PER_PAGE);
-        List<String> content = new ArrayList<>(linesPerPage);
-
-        // Calculate the paging.
-        for (String line : display.getContents()) {
-            if (!display.getFilter().checkMatch(line)) {
-                continue;
-            }
-            // When it's the next page.
-            boolean isLineBreak = ContentDisplay.LINE_BREAK.equals(line);
-            if (isLineBreak || ++currentLength > linesPerPage) {
-                pages++;
-                currentLength = 0;
-                if (isLineBreak) {
-                    continue;
-                }
-            }
-            if (pages == targetPage) {
-                // Let first line be the header when no header is defined.
-                if (display.getHeader() == null) {
-                    display.setHeader(line);
-                    currentLength--;
-                    continue;
-                }
-                content.add(display.getColorTool().get() + line);
-            }
-        }
-
-        // Page out of range.
-        if (targetPage < 1 || targetPage > pages) {
-            if (pages == 1) {
-                throw new DisplayFormatException("There is only 1 page!");
-            }
-            throw new DisplayFormatException("Please enter a page from 1 to " + pages + ".");
-        }
-
-        // No content
-        if (content.size() == 0) {
-            content.add(display.getEmptyMessage());
-        }
-
-        // Add empty lines to make output length consistent.
-        if (display.getSetting(PagedDisplaySettings.DO_END_PADDING)) {
-            IntStream.range(0, linesPerPage - content.size()).forEach(i -> content.add(""));
-        }
-        display.setSetting(PagedDisplaySettings.TOTAL_PAGE, pages);
-
-        return content;
-    }
-
-    @Override
-    public void sendSubHeader(@NotNull CommandSender sender, @NotNull ContentDisplay<Collection<String>> display) {
-        if (dontNeedPaging(sender, display)) {
-            super.sendSubHeader(sender, display);
-            return;
-        }
-
-        if (display.getFilter().hasFilter()) {
-            sender.sendMessage(String.format("%s[ Page %s of %s, %s ]",
-                    ChatColor.GRAY,
-                    display.getSetting(PagedDisplaySettings.SHOW_PAGE),
-                    display.getSetting(PagedDisplaySettings.TOTAL_PAGE),
-                    display.getFilter().getFormattedString())
-            );
-            return;
-        }
-        sender.sendMessage(String.format("%s[ Page %s of %s ]",
-                ChatColor.GRAY,
-                display.getSetting(PagedDisplaySettings.SHOW_PAGE),
-                display.getSetting(PagedDisplaySettings.TOTAL_PAGE))
-        );
-    }
-
-    private boolean dontNeedPaging(CommandSender sender, ContentDisplay<Collection<String>> display) {
-        return sender instanceof ConsoleCommandSender
-                && !display.getSetting(PagedDisplaySettings.PAGE_IN_CONSOLE);
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/display/settings/DisplaySetting.java

@@ -1,19 +0,0 @@
-package com.onarandombox.MultiverseCore.display.settings;
-
-import com.onarandombox.MultiverseCore.display.DisplayHandler;
-
-/**
- * Represents a setting option that can be used by {@link DisplayHandler}.
- *
- * @param <T>
- */
-@FunctionalInterface
-public interface DisplaySetting<T> {
-
-     /**
-      * Gets the default value of this Display Setting.
-      *
-      * @return The default value.
-      */
-     T defaultValue();
-}

src/main/java/com/onarandombox/MultiverseCore/display/settings/InlineDisplaySettings.java

@@ -1,15 +0,0 @@
-package com.onarandombox.MultiverseCore.display.settings;
-
-import com.onarandombox.MultiverseCore.display.DisplayHandler;
-import org.bukkit.ChatColor;
-
-/**
- * Collection of {@link DisplaySetting} that are used by various {@link DisplayHandler}.
- */
-public class InlineDisplaySettings {
-
-    /**
-     * Inline separator. E.g. '1, 2, 3'
-     */
-    public static final DisplaySetting<String> SEPARATOR = () -> ChatColor.WHITE + ", ";
-}

src/main/java/com/onarandombox/MultiverseCore/display/settings/MapDisplaySettings.java

@@ -1,15 +0,0 @@
-package com.onarandombox.MultiverseCore.display.settings;
-
-import com.onarandombox.MultiverseCore.display.DisplayHandler;
-import org.bukkit.ChatColor;
-
-/**
- * Collection of {@link DisplaySetting} that are used by various {@link DisplayHandler}.
- */
-public class MapDisplaySettings {
-
-    /**
-     * The thing between a key value pair. E.g. 'Me = Smart'
-     */
-    public static final DisplaySetting<String> OPERATOR = () -> ChatColor.WHITE + " = ";
-}

src/main/java/com/onarandombox/MultiverseCore/display/settings/PagedDisplaySettings.java

@@ -1,30 +0,0 @@
-package com.onarandombox.MultiverseCore.display.settings;
-
-public class PagedDisplaySettings {
-
-    /**
-     * Page to display.
-     */
-    public static final DisplaySetting<Integer> SHOW_PAGE = () -> 1;
-
-    /**
-     * Total pages available to display.
-     */
-    public static final DisplaySetting<Integer> TOTAL_PAGE = () -> 1;
-
-    /**
-     * The max number of lines per page. This excludes header.
-     */
-    public static final DisplaySetting<Integer> LINES_PER_PAGE = () -> 8;
-
-    /**
-     * Should add empty lines if content lines shown is less that {@link #LINES_PER_PAGE}.
-     */
-    public static final DisplaySetting<Boolean> DO_END_PADDING = () -> true;
-
-    /**
-     * Should display with paging when it's sent to console.
-     */
-    public static final DisplaySetting<Boolean> PAGE_IN_CONSOLE = () -> false;
-
-}

src/main/java/com/onarandombox/MultiverseCore/generators/GeneratorManager.java

@@ -0,0 +1,311 @@
+package com.onarandombox.MultiverseCore.generators;
+
+import com.dumptruckman.minecraft.util.Logging;
+import com.onarandombox.MultiverseCore.MultiverseCore;
+import com.onarandombox.MultiverseCore.api.GeneratorPlugin;
+import com.onarandombox.MultiverseCore.api.MVGeneratorManager;
+import org.bukkit.Bukkit;
+import org.bukkit.configuration.file.FileConfiguration;
+import org.bukkit.configuration.file.YamlConfiguration;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.server.PluginDisableEvent;
+import org.bukkit.event.server.PluginEnableEvent;
+import org.bukkit.generator.ChunkGenerator;
+import org.bukkit.plugin.Plugin;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.File;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.Callable;
+
+/**
+ * Default implementation of {@link MVGeneratorManager} to facilitate the detection and management of generator
+ * plugins installed on user's server.
+ */
+public class GeneratorManager implements MVGeneratorManager {
+
+    private final MultiverseCore plugin;
+    private final Map<String, String> defaultGens;
+    private Map<String, GeneratorPlugin> generatorPluginMap;
+
+    public GeneratorManager(MultiverseCore plugin) {
+        this.plugin = plugin;
+        this.defaultGens = new HashMap<>();
+        loadDefaultWorldGenerators();
+        findAndRegisterAllGeneratorPlugins();
+        Bukkit.getPluginManager().registerEvents(new GeneratorListener(), this.plugin);
+    }
+
+    /**
+     * Loads default generator strings defined in 'bukkit.yml'.
+     */
+    private void loadDefaultWorldGenerators() {
+        this.generatorPluginMap = new HashMap<>();
+
+        File[] files = this.plugin.getServerFolder().listFiles((file, s) -> s.equalsIgnoreCase("bukkit.yml"));
+        if (files == null || files.length != 1) {
+            Logging.fine("Could not read 'bukkit.yml'. Any Default worldgenerators will not be loaded!");
+            return;
+        }
+
+        FileConfiguration bukkitConfig = YamlConfiguration.loadConfiguration(files[0]);
+        if (!bukkitConfig.isConfigurationSection("worlds")) {
+            Logging.fine("'bukkit.yml' missing worlds config section. No default generators found!");
+            return;
+        }
+
+        Set<String> keys = bukkitConfig.getConfigurationSection("worlds").getKeys(false);
+        for (String key : keys) {
+            this.defaultGens.put(key, bukkitConfig.getString("worlds." + key + ".generator", ""));
+        }
+
+        this.generatorPluginMap = Collections.unmodifiableMap(this.generatorPluginMap);
+    }
+
+    /**
+     * Register all generator plugins detected.
+     */
+    private void findAndRegisterAllGeneratorPlugins() {
+        Arrays.stream(Bukkit.getPluginManager().getPlugins()).forEach(this::register);
+    }
+
+    /**
+     * Attempts to register a plugin as {@link SimpleGeneratorPlugin}.
+     *
+     * @param genPlugin The plugin to register.
+     * @return True if registered successfully, else false.
+     */
+    private boolean register(@NotNull Plugin genPlugin) {
+        return this.register(genPlugin, SimpleGeneratorPlugin.DEFAULT_TEST_ID);
+    }
+
+    /**
+     * Attempts to register a plugin as {@link SimpleGeneratorPlugin}.
+     *
+     * @param genPlugin The plugin to register.
+     * @param id        Generator Id to test for valid chunk generator.
+     * @return True if registered successfully, else false.
+     */
+    private boolean register(@NotNull Plugin genPlugin, String id) {
+        Logging.finer("Attempting to register %s as a generator...", genPlugin.getName());
+        if (this.isGeneratorPlugin(genPlugin)) {
+            return false;
+        }
+        if (!simpleTestGen(genPlugin, id)) {
+            Logging.finer("%s is probably not a generator plugin!", genPlugin.getName());
+            return false;
+        }
+        this.generatorPluginMap.put(genPlugin.getName(), new SimpleGeneratorPlugin(genPlugin));
+        Logging.finer("Registered %s as a simple generator plugin.", genPlugin.getName());
+        return true;
+    }
+
+    /**
+     * Basic test to see if plugin is a valid generator.
+     *
+     * @param generator The potential generator plugin.
+     * @param id        Generator Id to test for valid chunk generator.
+     * @return True if plugin is a valid generator, else false.
+     */
+    private boolean simpleTestGen(@Nullable Plugin generator, String id) {
+        if (generator == null) {
+            return false;
+        }
+
+        // Since we are unsure if the plugin is even suppose to be a generator, we assume any error means its
+        // not a generator plugin.
+        try {
+            return generator.getDefaultWorldGenerator(SimpleGeneratorPlugin.TEST_WORLDNAME, id) != null;
+        } catch (Exception ignore) {
+            return false;
+        }
+    }
+
+    /**
+     * Unregisters a plugin.
+     *
+     * @param genPlugin The plugin to unregister.
+     * @return True if the plugin was present and now unregistered, else false.
+     */
+    private boolean unregister(@NotNull Plugin genPlugin) {
+        return this.generatorPluginMap.remove(genPlugin.getName()) != null;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public boolean register(@NotNull GeneratorPlugin generatorPlugin) {
+        Plugin genPlugin = generatorPlugin.getPlugin();
+
+        // Make sure not registered before.
+        GeneratorPlugin registeredGeneratorPlugin = this.getGeneratorPlugin(genPlugin);
+        if (registeredGeneratorPlugin != null) {
+            if (!(registeredGeneratorPlugin instanceof SimpleGeneratorPlugin)) {
+                throw new IllegalStateException("You cannot register plugin for '" + genPlugin.getName() + "' twice!");
+            }
+            // If it's auto registration by MV, we can remove in favour of the custom one.
+            this.unregister(genPlugin);
+        }
+
+        if (this.safelyTestGenerator(genPlugin, generatorPlugin::getDefaultChunkGenerator) != TestResult.VALID) {
+            return false;
+        }
+
+        this.generatorPluginMap.put(genPlugin.getName(), generatorPlugin);
+        Logging.fine("Registered %s as a simple generator plugin.", genPlugin.getName());
+        return true;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public boolean isValidGenerator(@NotNull String genString, @NotNull String worldName) {
+        return validateGenerator(genString, worldName) == TestResult.VALID;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    @NotNull
+    public TestResult validateGenerator(@NotNull String genString, @NotNull String worldName) {
+        String[] genArray = genString.split(":", 2);
+        String pluginName = genArray[0];
+        String id = (genArray.length == 1) ? "" : genArray[1];
+
+        Plugin genPlugin = Bukkit.getPluginManager().getPlugin(pluginName);
+        if (genPlugin == null) {
+            return TestResult.PLUGIN_DOES_NOT_EXIST;
+        }
+
+        if (!this.isGeneratorPlugin(genPlugin)) {
+            // Tries to register again with specific Id defined.
+            if (!this.register(genPlugin, id)) {
+                return TestResult.INVALID_GENERATOR;
+            }
+        }
+
+        GeneratorPlugin generatorPlugin = this.getGeneratorPlugin(genPlugin);
+        if (generatorPlugin == null) {
+            return TestResult.INVALID_GENERATOR;
+        }
+
+        TestResult testResult = safelyTestGenerator(generatorPlugin.getPlugin(), () -> generatorPlugin.getChunkGenerator(id, worldName));
+        if (testResult == TestResult.VALID && generatorPlugin instanceof SimpleGeneratorPlugin) {
+            ((SimpleGeneratorPlugin) generatorPlugin).addKnownWorkingId(id);
+        }
+        return testResult;
+    }
+
+    /**
+     * Tries to get chunk generator with wrapper to catch any exceptions that may occur.
+     *
+     * @param genPlugin The generator plugin.
+     * @param genGetter Logic to get the chunk generator.
+     * @return VALID if successfully got a not-null chunk generator, INVALID_GENERATOR if null,
+     * ERRORS if exception is thrown.
+     */
+    @NotNull
+    private TestResult safelyTestGenerator(Plugin genPlugin, Callable<ChunkGenerator> genGetter) {
+        TestResult result = this.plugin.getUnsafeCallWrapper().wrap(
+                () -> genGetter.call() == null ? TestResult.INVALID_GENERATOR : TestResult.VALID,
+                genPlugin.getName(),
+                "Failed to get the chunk generator: %s"
+        );
+        return (result == null) ? TestResult.ERRORS : result;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public boolean isGeneratorPlugin(@NotNull Plugin genPlugin) {
+        return this.isGeneratorPlugin(genPlugin.getName());
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public boolean isGeneratorPlugin(@NotNull String pluginName) {
+        return this.generatorPluginMap.containsKey(pluginName);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    @Nullable
+    public GeneratorPlugin getGeneratorPlugin(@NotNull Plugin genPlugin) {
+        return this.getGeneratorPlugin(genPlugin.getName());
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    @Nullable
+    public GeneratorPlugin getGeneratorPlugin(@NotNull String pluginName) {
+        return this.generatorPluginMap.get(pluginName);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    @NotNull
+    public Collection<GeneratorPlugin> getGeneratorPlugins() {
+        return this.generatorPluginMap.values();
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    @NotNull
+    public Collection<String> getGeneratorPluginNames() {
+        return this.generatorPluginMap.keySet();
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    @Nullable
+    public String getDefaultWorldGen(String worldName) {
+        return this.defaultGens.get(worldName);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    @NotNull
+    public Map<String, String> getDefaultWorldGens() {
+        return this.defaultGens;
+    }
+
+    /**
+     * Listen to when a plugin enables/disable to register and unregister accordingly.
+     */
+    private class GeneratorListener implements Listener {
+        @EventHandler
+        public void onEnable(PluginEnableEvent event) {
+            register(event.getPlugin());
+        }
+
+        @EventHandler
+        public void onDisable(PluginDisableEvent event) {
+            unregister(event.getPlugin());
+        }
+    }
+}

src/main/java/com/onarandombox/MultiverseCore/generators/SimpleGeneratorPlugin.java

@@ -0,0 +1,94 @@
+package com.onarandombox.MultiverseCore.generators;
+
+import com.onarandombox.MultiverseCore.api.GeneratorPlugin;
+import org.bukkit.generator.ChunkGenerator;
+import org.bukkit.plugin.Plugin;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+/**
+ * A default implementation of {@link GeneratorPlugin} for those generator plugins that do not provide their own
+ * custom {@link GeneratorPlugin} implementation to Multiverse.
+ */
+public class SimpleGeneratorPlugin implements GeneratorPlugin {
+
+    public static String TEST_WORLDNAME = "test";
+    public static String DEFAULT_TEST_ID = "";
+
+    private final Plugin plugin;
+    private final List<String> workingIds;
+
+    SimpleGeneratorPlugin(Plugin plugin) {
+        this(plugin, DEFAULT_TEST_ID);
+    }
+
+    SimpleGeneratorPlugin(Plugin plugin, String testedId) {
+        this.plugin = plugin;
+        this.workingIds = new ArrayList<>();
+        this.workingIds.add(testedId);
+    }
+
+    /**
+     * Adds a known generator id that was tested to be working.
+     *
+     * @param id The known working generator id.
+     */
+    void addKnownWorkingId(String id) {
+        if (!this.workingIds.contains(id)) {
+            this.workingIds.add(id);
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public @NotNull Collection<String> suggestIds(@Nullable String currentIdInput) {
+        return this.workingIds;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public @Nullable ChunkGenerator getDefaultChunkGenerator() throws Exception {
+        return this.plugin.getDefaultWorldGenerator(TEST_WORLDNAME, this.workingIds.get(0));
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public @Nullable ChunkGenerator getChunkGenerator(String id, String worldName) throws Exception {
+        return this.plugin.getDefaultWorldGenerator(worldName, id);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public @Nullable Collection<String> getExampleUsages() {
+        return null;
+    }
+
+    /**
+     * {@inheritDoc}
+     * @return
+     */
+    @Override
+    public @Nullable String getInfoLink() {
+        return null;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public @NotNull Plugin getPlugin() {
+        return this.plugin;
+    }
+}

src/main/java/com/onarandombox/MultiverseCore/utils/PlayerFinder.java

@@ -0,0 +1,176 @@
+package com.onarandombox.MultiverseCore.utils;
+
+import com.dumptruckman.minecraft.util.Logging;
+import org.bukkit.Bukkit;
+import org.bukkit.command.CommandSender;
+import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
+/**
+ * Helper class to get {@link Player} from name, UUID or Selectors.
+ */
+public class PlayerFinder {
+
+    private static final Pattern UUID_REGEX = Pattern.compile("[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[34][0-9a-fA-F]{3}-[89ab][0-9a-fA-F]{3}-[0-9a-fA-F]{12}");
+    private static final Pattern COMMA_SPLIT = Pattern.compile(",");
+
+    /**
+     * Get a {@link Player} based on an identifier of name UUID or selector.
+     *
+     * @param playerIdentifier  An identifier of name UUID or selector.
+     * @param sender            Target sender for selector.
+     * @return The player if found, else null.
+     */
+    @Nullable
+    public static Player get(@NotNull String playerIdentifier,
+                             @NotNull CommandSender sender) {
+
+        Player targetPlayer = getByName(playerIdentifier);
+        if (targetPlayer != null) {
+            return targetPlayer;
+        }
+        targetPlayer = getByUuid(playerIdentifier);
+        if (targetPlayer != null) {
+            return targetPlayer;
+        }
+        return getBySelector(playerIdentifier, sender);
+    }
+
+    /**
+     * Get multiple {@link Player} based on many identifiers of name UUID or selector.
+     *
+     * @param playerIdentifiers An identifier of multiple names, UUIDs or selectors, separated by comma.
+     * @param sender            Target sender for selector.
+     * @return A list of all the {@link Player} found.
+     */
+    @Nullable
+    public static List<Player> getMulti(@NotNull String playerIdentifiers,
+                                        @NotNull CommandSender sender) {
+
+        String[] playerIdentifierArray = COMMA_SPLIT.split(playerIdentifiers);
+        if (playerIdentifierArray == null || playerIdentifierArray.length == 0) {
+            return null;
+        }
+
+        List<Player> playerResults = new ArrayList<>();
+        for (String playerIdentifier : playerIdentifierArray) {
+            Player targetPlayer = getByName(playerIdentifier);
+            if (targetPlayer != null) {
+                playerResults.add(targetPlayer);
+                continue;
+            }
+            targetPlayer = getByUuid(playerIdentifier);
+            if (targetPlayer != null) {
+                playerResults.add(targetPlayer);
+                continue;
+            }
+            List<Player> targetPlayers = getMultiBySelector(playerIdentifier, sender);
+            if (targetPlayers != null) {
+                playerResults.addAll(targetPlayers);
+            }
+        }
+        return playerResults;
+    }
+
+    /**
+     * Get a {@link Player} based on player name.
+     *
+     * @param playerName    Name of a {@link Player}.
+     * @return The player if found, else null.
+     */
+    @Nullable
+    public static Player getByName(@NotNull String playerName) {
+        return Bukkit.getPlayerExact(playerName);
+    }
+
+    /**
+     * Get a {@link Player} based on player UUID.
+     *
+     * @param playerUuid    UUID of a player.
+     * @return The player if found, else null.
+     */
+    @Nullable
+    public static Player getByUuid(@NotNull String playerUuid) {
+        if (!UUID_REGEX.matcher(playerUuid).matches()) {
+            return null;
+        }
+        UUID uuid;
+        try {
+            uuid = UUID.fromString(playerUuid);
+        } catch (Exception e) {
+            return null;
+        }
+        return getByUuid(uuid);
+    }
+
+    /**
+     * Get a {@link Player} based on playerUUID.
+     *
+     * @param playerUuid    UUID of a player.
+     * @return The player if found, else null.
+     */
+    @Nullable
+    public static Player getByUuid(@NotNull UUID playerUuid) {
+        return Bukkit.getPlayer(playerUuid);
+    }
+
+    /**
+     * Get a {@link Player} based on vanilla selectors.
+     * https://minecraft.gamepedia.com/Commands#Target_selectors
+     *
+     * @param playerSelector    A target selector, usually starts with an '@'.
+     * @param sender            Target sender for selector.
+     * @return The player if only one found, else null.
+     */
+    @Nullable
+    public static Player getBySelector(@NotNull String playerSelector,
+                                       @NotNull CommandSender sender) {
+
+        List<Player> matchedPlayers = getMultiBySelector(playerSelector, sender);
+        if (matchedPlayers == null || matchedPlayers.isEmpty()) {
+            Logging.warning("No player found with selector '%s' for %s.", playerSelector, sender.getName());
+            return null;
+        }
+        if (matchedPlayers.size() > 1) {
+            Logging.warning("Ambiguous selector result '%s' for %s (more than one player matched) - %s",
+                    playerSelector, sender.getName(), matchedPlayers.toString());
+            return null;
+        }
+        return matchedPlayers.get(0);
+    }
+
+    /**
+     * Get multiple {@link Player} based on selector.
+     * https://minecraft.gamepedia.com/Commands#Target_selectors
+     *
+     * @param playerSelector    A target selector, usually starts with an '@'.
+     * @param sender            Target sender for selector.
+     * @return A list of all the {@link Player} found.
+     */
+    @Nullable
+    public static List<Player> getMultiBySelector(@NotNull String playerSelector,
+                                                  @NotNull CommandSender sender) {
+
+        if (playerSelector.charAt(0) != '@') {
+            return null;
+        }
+        try {
+            return Bukkit.selectEntities(sender, playerSelector).stream()
+                    .filter(e -> e instanceof Player)
+                    .map(e -> ((Player) e))
+                    .collect(Collectors.toList());
+        } catch (IllegalArgumentException e) {
+            Logging.warning("An error occurred while parsing selector '%s' for %s. Is it is the correct format?",
+                    playerSelector, sender.getName());
+            e.printStackTrace();
+            return null;
+        }
+    }
+}

src/main/java/com/onarandombox/MultiverseCore/utils/ReflectHelper.java

@@ -0,0 +1,140 @@
+package com.onarandombox.MultiverseCore.utils;
+
+import org.jetbrains.annotations.Nullable;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+
+/**
+ * Utility class used to help in doing various reflection actions.
+ */
+public class ReflectHelper {
+
+    /**
+     * Try to get the {@link Class} based on its classpath.
+     *
+     * @param classPath The target classpath.
+     * @return A {@link Class} if found, else null.
+     */
+    @Nullable
+    public static Class<?> getClass(String classPath) {
+        try {
+            return Class.forName(classPath);
+        } catch (ClassNotFoundException e) {
+            return null;
+        }
+    }
+
+    /**
+     * Check if the {@link Class} for a give classpath is present/valid.
+     *
+     * @param classPath Target classpath.
+     * @return True if class path is a valid class, else false.
+     */
+    public static boolean hasClass(String classPath) {
+        return getClass(classPath) != null;
+    }
+
+    /**
+     * Try to get a {@link Method} from a given class.
+     *
+     * @param clazz             The class to search the method on.
+     * @param methodName        Name of the method to get.
+     * @param parameterTypes    Parameters present for that method.
+     * @param <C>               The class type.
+     * @return A {@link Method} if found, else null.
+     */
+    @Nullable
+    public static <C> Method getMethod(Class<C> clazz, String methodName, Class<?>... parameterTypes) {
+        try {
+            Method method = clazz.getDeclaredMethod(methodName, parameterTypes);
+            method.setAccessible(true);
+            return method;
+        } catch (NoSuchMethodException e) {
+            return null;
+        }
+    }
+
+    /**
+     * Try to get a {@link Method} from a given class.
+     *
+     * @param classInstance     Instance of the class to search the method on.
+     * @param methodName        Name of the method to get.
+     * @param parameterTypes    Parameters present for that method.
+     * @param <C>               The class type.
+     * @return A {@link Method} if found, else null.
+     */
+    @Nullable
+    public static <C> Method getMethod(C classInstance, String methodName, Class<?>... parameterTypes) {
+        return getMethod(classInstance.getClass(), methodName, parameterTypes);
+    }
+
+    /**
+     * Calls a {@link Method}.
+     *
+     * @param classInstance Instance of the class responsible for the method.
+     * @param method        The method to call.
+     * @param parameters    Parameters needed when calling the method.
+     * @param <C>           The class type.
+     * @param <R>           The return type.
+     * @return Return value of the method call if any, else null.
+     */
+    @Nullable
+    public static <C, R> R invokeMethod(C classInstance, Method method, Object...parameters) {
+        try {
+            return (R) method.invoke(classInstance, parameters);
+        } catch (Exception e) {
+            return null;
+        }
+    }
+
+    /**
+     * Try to get a {@link Field} from a given class.
+     *
+     * @param clazz     The class to search the field on.
+     * @param fieldName Name of the field to get.
+     * @param <C>       The class type.
+     * @return A {@link Field} if found, else null.
+     */
+    @Nullable
+    public static <C> Field getField(Class<C> clazz, String fieldName) {
+        try {
+            Field field = clazz.getDeclaredField(fieldName);
+            field.setAccessible(true);
+            return field;
+        } catch (NoSuchFieldException e) {
+            return null;
+        }
+    }
+
+    /**
+     * Try to get a {@link Field} from a given class.
+     *
+     * @param classInstance Instance of the class to search the field on.
+     * @param fieldName     Name of the field to get.
+     * @param <C>           The class type.
+     * @return A {@link Field} if found, else null.
+     */
+    @Nullable
+    public static <C> Field getField(C classInstance, String fieldName) {
+        return getField(classInstance.getClass(), fieldName);
+    }
+
+    /**
+     * Gets the value of an {@link Field} from an instance of the class responsible.
+     *
+     * @param classInstance Instance of the class to get the field value from.
+     * @param field         The field to get value from.
+     * @param <C>           The class type.
+     * @param <V>           The field value type.
+     * @return The field value if any, else null.
+     */
+    @Nullable
+    public static <C, V> V getFieldValue(C classInstance, Field field)  {
+        try {
+            return (V) field.get(classInstance);
+        } catch (IllegalAccessException e) {
+            return null;
+        }
+    }
+}

src/main/java/com/onarandombox/MultiverseCore/utils/WorldManager.java

@@ -74,6 +74,7 @@ public class WorldManager implements MVWorldManager {
      * {@inheritDoc}
      */
     @Override
+    @Deprecated
     public void getDefaultWorldGenerators() {
         this.defaultGens = new HashMap<String, String>();
         File[] files = this.plugin.getServerFolder().listFiles(new FilenameFilter() {
@@ -130,7 +131,7 @@ public class WorldManager implements MVWorldManager {
         }
 
         // Check for valid world name
-        if (!(isValidWorldName(oldName) && isValidWorldName(newName))) {
+        if (!(WorldNameChecker.isValidWorldName(oldName) && WorldNameChecker.isValidWorldName(oldName))) {
             return false;
         }
 
@@ -238,7 +239,9 @@ public class WorldManager implements MVWorldManager {
             return false;
         }
 
-        if (!isValidWorldName(name)) {
+        if (!WorldNameChecker.isValidWorldName(name)) {
+            Logging.warning("Invalid world name '" + name + "'");
+            Logging.warning("World name should not contain spaces or special characters!");
             return false;
         }
 
@@ -299,6 +302,7 @@ public class WorldManager implements MVWorldManager {
      * {@inheritDoc}
      */
     @Override
+    @Deprecated
     public ChunkGenerator getChunkGenerator(String generator, final String generatorID, final String worldName) {
         if (generator == null) {
             return null;
@@ -424,21 +428,6 @@ public class WorldManager implements MVWorldManager {
         }
     }
 
-    /**
-     * Check if the world name is allowed
-     *
-     * @param name   Name of the world
-     * @return True if the world world name is valid based on regex
-     */
-    private boolean isValidWorldName(String name) {
-        if (!worldNamePattern.matcher(name).matches()) {
-            Logging.warning("Invalid world name '" + name + "'");
-            Logging.warning("World name should not contain spaces or special characters!");
-            return false;
-        }
-        return true;
-    }
-
     private void brokenWorld(String name) {
         Logging.severe("The world '" + name + "' could NOT be loaded because it contains errors and is probably corrupt!");
         Logging.severe("Try using Minecraft Region Fixer to repair your world! '" + name + "'");
@@ -707,10 +696,7 @@ public class WorldManager implements MVWorldManager {
         for (World w : myWorlds) {
             String name = w.getName();
             if (!worldsFromTheConfig.containsKey(name)) {
-                String generator = null;
-                if (this.defaultGens.containsKey(name)) {
-                    generator = this.defaultGens.get(name);
-                }
+                String generator = this.plugin.getMVGeneratorManager().getDefaultWorldGen(name);
                 this.addWorld(name, w.getEnvironment(), String.valueOf(w.getSeed()), w.getWorldType(), w.canGenerateStructures(), generator);
             }
         }

src/main/java/com/onarandombox/MultiverseCore/utils/WorldNameChecker.java

@@ -0,0 +1,159 @@
+package com.onarandombox.MultiverseCore.utils;
+
+import org.bukkit.Bukkit;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.File;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.regex.Pattern;
+
+/**
+ * <p>Utility class in helping to check the status of a world name and it's associated world folder.</p>
+ *
+ * <p>Note this is for preliminary checks and better command output. A valid result will suggest but not
+ * 100% determine that a world name can be created, loaded or imported.</p>
+ */
+public class WorldNameChecker {
+
+    private static final Pattern WORLD_NAME_PATTERN = Pattern.compile("[a-zA-Z0-9/._-]+");
+    private static final Set<String> BLACKLIST_NAMES = Collections.unmodifiableSet(new HashSet<String>() {{
+        add("plugins");
+        add("logs");
+        add("cache");
+        add("crash-reports");
+    }});
+
+    /**
+     * Checks if a world name is valid.
+     *
+     * @param worldName The world name to check on.
+     * @return True if check result is valid, else false.
+     */
+    public static boolean isValidWorldName(@Nullable String worldName) {
+        return checkName(worldName) == NameStatus.VALID;
+    }
+
+    /**
+     * Checks the current validity status of a world name.
+     *
+     * @param worldName The world name to check on.
+     * @return The resulting name status.
+     */
+    @NotNull
+    public static NameStatus checkName(@Nullable String worldName) {
+        if (BLACKLIST_NAMES.contains(worldName)) {
+            return NameStatus.BLACKLISTED;
+        }
+        if (worldName == null || !WORLD_NAME_PATTERN.matcher(worldName).matches()) {
+            return NameStatus.INVALID_CHARS;
+        }
+        return NameStatus.VALID;
+    }
+
+    /**
+     * Checks if a world name has a valid world folder.
+     *
+     * @param worldName The world name to check on.
+     * @return True if check result is valid, else false.
+     */
+    public static boolean isValidWorldFolder(@Nullable String worldName) {
+        return checkFolder(worldName) == FolderStatus.VALID;
+    }
+
+    /**
+     * Checks if a world folder is valid.
+     *
+     * @param worldFolder   The world folder to check on.
+     * @return True if check result is valid, else false.
+     */
+    public static boolean isValidWorldFolder(@Nullable File worldFolder) {
+        return checkFolder(worldFolder) == FolderStatus.VALID;
+    }
+
+    /**
+     * Checks the current folder status for a world name.
+     *
+     * @param worldName The world name to check on.
+     * @return The resulting folder status.
+     */
+    @NotNull
+    public static FolderStatus checkFolder(@Nullable String worldName) {
+        if (worldName == null) {
+            return FolderStatus.DOES_NOT_EXIST;
+        }
+        File worldFolder = new File(Bukkit.getWorldContainer(), worldName);
+        return checkFolder(worldFolder);
+    }
+
+    /**
+     * Checks the current folder status.
+     *
+     * @param worldFolder   The world folder to check on.
+     * @return The resulting folder status.
+     */
+    @NotNull
+    public static FolderStatus checkFolder(@Nullable File worldFolder) {
+        if (worldFolder == null || !worldFolder.exists() || !worldFolder.isDirectory()) {
+            return FolderStatus.DOES_NOT_EXIST;
+        }
+        if (!folderHasDat(worldFolder)) {
+            return FolderStatus.NOT_A_WORLD;
+        }
+        return FolderStatus.VALID;
+    }
+
+    /**
+     * A very basic check to see if a folder has a level.dat file. If it does, we can safely assume
+     * it's a world folder.
+     *
+     * @param worldFolder   The File that may be a world.
+     * @return True if it looks like a world, else false.
+     */
+    private static boolean folderHasDat(@NotNull File worldFolder) {
+        File[] files = worldFolder.listFiles((file, name) -> name.toLowerCase().endsWith(".dat"));
+        return files != null && files.length > 0;
+    }
+
+    /**
+     * Result after checking validity of world name.
+     */
+    public enum NameStatus {
+        /**
+         * Name is valid.
+         */
+        VALID,
+
+        /**
+         * Name not valid as it contains invalid characters.
+         */
+        INVALID_CHARS,
+
+        /**
+         * Name not valid as it is deemed blacklisted.
+         */
+        BLACKLISTED
+    }
+
+    /**
+     * Result after checking validity of world folder.
+     */
+    public enum FolderStatus {
+        /**
+         * Folder is valid.
+         */
+        VALID,
+
+        /**
+         * Folder exist, but contents in it doesnt look like a world.
+         */
+        NOT_A_WORLD,
+
+        /**
+         * Folder does not exist.
+         */
+        DOES_NOT_EXIST
+    }
+}

src/test/java/com/onarandombox/MultiverseCore/TestWorldStuff.java

@@ -207,7 +207,7 @@ public class TestWorldStuff {
         assertEquals(0, creator.getCore().getMVWorldManager().getMVWorlds().size());
 
         // Verify
-        verify(mockCommandSender).sendMessage("Invalid generator! 'BogusGen'. " + ChatColor.RED + "Aborting world creation.");
+        verify(mockCommandSender).sendMessage("That generator plugin is not installed on your server!");
     }
 
     @Test