Remove ability to unload default worlds.

Small WorldManager updates

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

@@ -174,6 +174,16 @@ public interface MVWorldManager {
      */
     MultiverseWorld getMVWorld(String name);
 
+    /**
+     * Returns a {@link MultiverseWorld} if the world with name given exists, and null if it does not.
+     * This will search optionally for alias names.
+     *
+     * @param name          The name or optionally the alias of the world to get.
+     * @param checkAliases  Indicates whether to check for world alias name.
+     * @return A {@link MultiverseWorld} or null.
+     */
+    MultiverseWorld getMVWorld(String name, boolean checkAliases);
+
     /**
      * Returns a {@link MultiverseWorld} if it exists, and null if it does not.
      *
@@ -183,13 +193,24 @@ public interface MVWorldManager {
     MultiverseWorld getMVWorld(World world);
 
     /**
-     * Checks to see if the given name is a valid {@link MultiverseWorld}.
+     * Checks to see if the given name is a valid {@link MultiverseWorld}
+     * Searches based on world name AND alias.
      *
      * @param name The name or alias of the world to check.
      * @return True if the world exists, false if not.
      */
     boolean isMVWorld(String name);
 
+    /**
+     * Checks to see if the given name is a valid {@link MultiverseWorld}.
+     * Optionally searches by alias is specified.
+     *
+     * @param name          The name or alias of the world to check.
+     * @param checkAliases  Indicates whether to check for world alias name.
+     * @return True if the world exists, false if not.
+     */
+    boolean isMVWorld(String name, boolean checkAliases);
+
     /**
      * Checks to see if the given world is a valid {@link MultiverseWorld}.
      *
@@ -198,6 +219,38 @@ public interface MVWorldManager {
      */
     boolean isMVWorld(World world);
 
+    /**
+     * Checks if a world name is the servers default world.
+     *
+     * Generally, default world is defined in level-name of server properties file along with
+     * it's 2 dimensions: [world]_nether, [world]_the_end.
+     *
+     * @param world The world to check.
+     * @return True if world name is a default world, else false.
+     */
+    boolean isDefaultWorld(MultiverseWorld world);
+
+    /**
+     * Checks if a world name is the servers default world.
+     *
+     * Generally, default world is defined in level-name of server properties file along with
+     * it's 2 dimensions: [world]_nether, [world]_the_end.
+     *
+     * @param worldName The name of the world to check.
+     * @return True if world name is a default world, else false.
+     */
+    boolean isDefaultWorld(String worldName);
+
+    /**
+     * Gets all the default world names of the server.
+     *
+     * Generally, default world is defined in level-name of server properties file along with
+     * it's 2 dimensions: [world]_nether, [world]_the_end.
+     *
+     * @return Collection of default world names.
+     */
+    Collection<String> getDefaultWorldNames();
+
     /**
      * Load the Worlds &amp; Settings from the configuration file.
      *
@@ -314,4 +367,11 @@ public interface MVWorldManager {
      * does not exist. {@code includeLoaded} if the world exists and is loaded.
      */
     boolean hasUnloadedWorld(String name, boolean includeLoaded);
+
+    /**
+     * Get all the possible worlds that Multiverse has detected to be importable.
+     *
+     * @return A collection of world names that are deemed importable.
+     */
+    Collection<String> getPotentialWorlds();
 }

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

@@ -8,12 +8,7 @@
 package com.onarandombox.MultiverseCore.commands;
 
 import com.onarandombox.MultiverseCore.MultiverseCore;
-import com.onarandombox.MultiverseCore.api.Core;
 import com.onarandombox.MultiverseCore.api.MVWorldManager;
-import com.onarandombox.MultiverseCore.commandtools.flag.CoreFlags;
-import com.onarandombox.MultiverseCore.commandtools.flag.FlagGroup;
-import com.onarandombox.MultiverseCore.commandtools.flag.FlagParseFailedException;
-import com.onarandombox.MultiverseCore.commandtools.flag.FlagResult;
 import com.pneumaticraft.commandhandler.CommandHandler;
 import org.bukkit.ChatColor;
 import org.bukkit.World.Environment;
@@ -31,16 +26,7 @@ import java.util.List;
  * Creates a new world and loads it.
  */
 public class CreateCommand extends MultiverseCommand {
-
-    private static final FlagGroup FLAG_GROUP = FlagGroup.of(
-            CoreFlags.SEED,
-            CoreFlags.WORLD_TYPE,
-            CoreFlags.GENERATOR,
-            CoreFlags.GENERATE_STRUCTURES,
-            CoreFlags.SPAWN_ADJUST
-    );
-
-    private final MVWorldManager worldManager;
+    private MVWorldManager worldManager;
 
     public CreateCommand(MultiverseCore plugin) {
         super(plugin);
@@ -64,7 +50,22 @@ public class CreateCommand extends MultiverseCommand {
     @Override
     public void runCommand(CommandSender sender, List<String> args) {
         String worldName = args.get(0);
+        File worldFile = new File(this.plugin.getServer().getWorldContainer(), worldName);
         String env = args.get(1);
+        String seed = CommandHandler.getFlag("-s", args);
+        String generator = CommandHandler.getFlag("-g", args);
+        boolean allowStructures = true;
+        String structureString = CommandHandler.getFlag("-a", args);
+        if (structureString != null) {
+            allowStructures = Boolean.parseBoolean(structureString);
+        }
+        String typeString = CommandHandler.getFlag("-t", args);
+        boolean useSpawnAdjust = true;
+        for (String s : args) {
+            if (s.equalsIgnoreCase("-n")) {
+                useSpawnAdjust = false;
+            }
+        }
 
         if (this.worldManager.isMVWorld(worldName)) {
             sender.sendMessage(ChatColor.RED + "Multiverse cannot create " + ChatColor.GOLD + ChatColor.UNDERLINE
@@ -72,7 +73,6 @@ public class CreateCommand extends MultiverseCommand {
             return;
         }
 
-        File worldFile = new File(this.plugin.getServer().getWorldContainer(), worldName);
         if (worldFile.exists()) {
             sender.sendMessage(ChatColor.RED + "A Folder/World already exists with this name!");
             sender.sendMessage(ChatColor.RED + "If you are confident it is a world you can import with /mvimport");
@@ -86,28 +86,35 @@ public class CreateCommand extends MultiverseCommand {
             return;
         }
 
-        FlagResult flags;
-        try {
-            flags = FLAG_GROUP.calculateResult(args.subList(2, args.size()).toArray(new String[0]));
-        } catch (FlagParseFailedException e) {
-            sender.sendMessage(String.format("%sError: %s", ChatColor.RED, e.getMessage()));
+        // If they didn't specify a type, default to NORMAL
+        if (typeString == null) {
+            typeString = "NORMAL";
+        }
+        WorldType type = EnvironmentCommand.getWorldTypeFromString(typeString);
+        if (type == null) {
+            sender.sendMessage(ChatColor.RED + "That is not a valid World Type.");
+            EnvironmentCommand.showWorldTypes(sender);
             return;
         }
-
+        // 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) {
+                // We have an invalid generator.
+                sender.sendMessage("Invalid generator! '" + generator + "'. " + ChatColor.RED + "Aborting world creation.");
+                return;
+            }
+        }
         Command.broadcastCommandMessage(sender, "Starting creation of world '" + worldName + "'...");
 
-        if (this.worldManager.addWorld(
-                worldName,
-                environment,
-                flags.getValue(CoreFlags.SEED),
-                flags.getValue(CoreFlags.WORLD_TYPE),
-                flags.getValue(CoreFlags.GENERATE_STRUCTURES),
-                flags.getValue(CoreFlags.GENERATOR),
-                flags.getValue(CoreFlags.SPAWN_ADJUST))) {
-
+        if (this.worldManager.addWorld(worldName, environment, seed, type, allowStructures, generator, useSpawnAdjust)) {
             Command.broadcastCommandMessage(sender, "Complete!");
-            return;
+        } else {
+            Command.broadcastCommandMessage(sender, "FAILED.");
         }
-        Command.broadcastCommandMessage(sender, "FAILED.");
     }
 }

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

@@ -9,7 +9,7 @@ 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;
@@ -18,8 +18,6 @@ import org.bukkit.command.CommandSender;
 import org.bukkit.permissions.PermissionDefault;
 
 import java.io.File;
-import java.io.FilenameFilter;
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 
@@ -45,55 +43,17 @@ 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) {
-            return "";
-        }
-        File[] files = worldFolder.listFiles();
-        String worldList = "";
-        Collection<MultiverseWorld> worlds = this.worldManager.getMVWorlds();
-        List<String> worldStrings = new ArrayList<String>();
-        for (MultiverseWorld world : worlds) {
-            worldStrings.add(world.getName());
-        }
-        for (String world : this.worldManager.getUnloadedWorlds()) {
-            worldStrings.add(world);
-        }
+    private String getPotentialWorldStrings() {
+        final Collection<String> potentialWorlds = this.worldManager.getPotentialWorlds();
+        StringBuilder worldList = new StringBuilder();
         ChatColor currColor = ChatColor.WHITE;
-        for (File file : files) {
-            if (file.isDirectory() && checkIfIsWorld(file) && !worldStrings.contains(file.getName())) {
-                worldList += currColor + file.getName() + " ";
-                if (currColor == ChatColor.WHITE) {
-                    currColor = ChatColor.YELLOW;
-                } else {
-                    currColor = ChatColor.WHITE;
-                }
-            }
+
+        for (String world : potentialWorlds) {
+            worldList.append(currColor).append(world).append(' ');
+            currColor = currColor == ChatColor.WHITE ? ChatColor.YELLOW : ChatColor.WHITE;
         }
-        return worldList;
+
+        return worldList.toString();
     }
     
     private String trimWorldName(String userInput) {
@@ -106,7 +66,7 @@ public class ImportCommand extends MultiverseCommand {
         String worldName = trimWorldName(args.get(0));
 
         if (worldName.toLowerCase().equals("--list") || worldName.toLowerCase().equals("-l")) {
-            String worldList = this.getPotentialWorlds();
+            String worldList = this.getPotentialWorldStrings();
             if (worldList.length() > 2) {
                 sender.sendMessage(ChatColor.AQUA + "====[ These look like worlds ]====");
                 sender.sendMessage(worldList);
@@ -149,10 +109,10 @@ public class ImportCommand extends MultiverseCommand {
 
         if (!worldFile.exists()) {
             sender.sendMessage(ChatColor.RED + "FAILED.");
-            String worldList = this.getPotentialWorlds();
+            String worldList = this.getPotentialWorldStrings();
             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/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/commandtools/flag/CommandFlag.java

@@ -1,136 +0,0 @@
-package com.onarandombox.MultiverseCore.commandtools.flag;
-
-import org.jetbrains.annotations.NotNull;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-
-/**
- * <p>Represents a flag that can be used in commands. This works as a key value pair.</p>
- *
- * <p>Key is the {@link #identifier} and {@link #aliases} set.</p>
- * <p>Value is the {@link T} parsed based on 3 scenarios during command input:</p>
- * <ol>
- *     <li>Flag completely not present. {@link #getDefaultValue()}</li>
- *     <li>Flag key present but no value. {@link #getValue()}</li>
- *     <li>Flag key and value present. {@link #getValue(String)}</li>
- * </ol>
- *
- * @param <T>   The flag Type.
- */
-public abstract class CommandFlag<T> {
-
-    protected final String name;
-    protected final String identifier;
-    protected final Class<T> type;
-    protected final Collection<String> aliases;
-
-    /**
-     * @param name          Readable name for the flag.
-     * @param identifier    Unique key to identify the flag in command arguments.
-     * @param type          The type of value this flag represents.
-     */
-    protected CommandFlag(@NotNull String name,
-                          @NotNull String identifier,
-                          @NotNull Class<T> type) {
-
-        this.name = name;
-        this.identifier = identifier;
-        this.type = type;
-        this.aliases = new ArrayList<>();
-    }
-
-    /**
-     * Gets name of the Command Flag.
-     *
-     * @return The Command Flag name.
-     */
-    @NotNull
-    public String getName() {
-        return this.name;
-    }
-
-    /**
-     * Gets identifier of the Command Flag.
-     *
-     * @return The Command Flag identifier.
-     */
-    @NotNull
-    public String getIdentifier() {
-        return this.identifier;
-    }
-
-    /**
-     * Gets {@link T} Type of the Command Flag.
-     *
-     * @return The Command Flag type.
-     */
-    @NotNull
-    public Class<T> getType() {
-        return this.type;
-    }
-
-    /**
-     * Gets all the alternative key identifiers set for this Command Flag.
-     *
-     * @return Collection of aliases.
-     */
-    @NotNull
-    public Collection<String> getAliases() {
-        return this.aliases;
-    }
-
-    /**
-     * Add alternative key identifiers for this Command Flag.
-     *
-     * @param aliases   Alias(es) to be added.
-     * @return A {@link CommandFlag}.
-     */
-    public CommandFlag<T> addAliases(String...aliases) {
-        Collections.addAll(this.aliases, aliases);
-        return this;
-    }
-
-    /**
-     * Tab-complete suggestion for this Command Flag values.
-     *
-     * @return Collection of suggested values available.
-     */
-    public abstract Collection<String> suggestValue();
-
-    /**
-     * When this Command Flag can get value by a user input.
-     *
-     * @return The {@link T} value.
-     */
-    public abstract T getValue(@NotNull String input) throws FlagParseFailedException;
-
-    /**
-     * When this Command Flag user input value is null/not present.
-     *
-     * @return The {@link T} value.
-     */
-    public T getValue() throws FlagParseFailedException {
-        return null;
-    }
-
-    /**
-     * When this Command Flag is not present in command input.
-     *
-     * @return The {@link T} value.
-     */
-    public T getDefaultValue() {
-        return null;
-    }
-
-    @Override
-    public String toString() {
-        return "CommandFlag{" +
-                "name='" + name + '\'' +
-                ", identifier='" + identifier + '\'' +
-                ", type=" + type +
-                ", aliases=" + aliases +
-                '}';
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/commandtools/flag/CoreFlags.java

@@ -1,217 +0,0 @@
-package com.onarandombox.MultiverseCore.commandtools.flag;
-
-import com.onarandombox.MultiverseCore.MultiverseCore;
-import com.onarandombox.MultiverseCore.utils.webpaste.PasteServiceType;
-import org.bukkit.Bukkit;
-import org.bukkit.WorldType;
-import org.bukkit.plugin.Plugin;
-import org.jetbrains.annotations.NotNull;
-
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Random;
-import java.util.stream.Collectors;
-
-public class CoreFlags {
-
-    private static MultiverseCore multiverse;
-
-    public static void setCoreInstance(MultiverseCore plugin) {
-        multiverse = plugin;
-    }
-
-    /**
-     * Flag for custom seed.
-     */
-    public static final CommandFlag<String> SEED = new RequiredCommandFlag<String>
-            ("Seed", "--seed", String.class) {
-        @Override
-        public Collection<String> suggestValue() {
-            return Collections.singleton(String.valueOf(new Random().nextLong()));
-        }
-
-        @Override
-        public String getValue(@NotNull String input) throws FlagParseFailedException {
-            return input;
-        }
-    }.addAliases("-s");
-
-    /**
-     * Flag for custom seed. No value means random seed.
-     */
-    public static final CommandFlag<String> RANDOM_SEED = new OptionalCommandFlag<String>
-            ("Seed", "--seed", String.class) {
-        @Override
-        public Collection<String> suggestValue() {
-            return Collections.singletonList(String.valueOf(new Random().nextLong()));
-        }
-
-        @Override
-        public String getValue(@NotNull String input) throws FlagParseFailedException {
-            return input;
-        }
-    }.addAliases("-s");
-
-    /**
-     * Flag for world type used.
-     */
-    public static final CommandFlag<WorldType> WORLD_TYPE = new RequiredCommandFlag<WorldType>
-            ("WorldType", "--type", WorldType.class) {
-
-        private final Map<String, String> typeAlias = new HashMap<String, String>(4){{
-            put("normal", "NORMAL");
-            put("flat", "FLAT");
-            put("largebiomes", "LARGE_BIOMES");
-            put("amplified", "AMPLIFIED");
-        }};
-
-        @Override
-        public Collection<String> suggestValue() {
-            return typeAlias.keySet();
-        }
-
-        @Override
-        public WorldType getValue(@NotNull String input) throws FlagParseFailedException {
-            String typeName = typeAlias.getOrDefault(input, input);
-            try {
-                return WorldType.valueOf(input.toUpperCase());
-            }
-            catch (IllegalArgumentException e) {
-                throw new FlagParseFailedException("'%s' is not a valid World Type. See /mv env for available World Types.", input);
-            }
-        }
-
-        @Override
-        public WorldType getDefaultValue() {
-            return WorldType.NORMAL;
-        }
-    }.addAliases("-t");
-
-    /**
-     * Flag for world generator.
-     */
-    public static final CommandFlag<String> GENERATOR = new RequiredCommandFlag<String>
-            ("Generator", "--gen", String.class) {
-        @Override
-        public Collection<String> suggestValue() {
-            return Arrays.stream(Bukkit.getServer().getPluginManager().getPlugins())
-                    .filter(Plugin::isEnabled)
-                    .filter(plugin -> multiverse.getUnsafeCallWrapper().wrap(
-                            () -> plugin.getDefaultWorldGenerator("world", ""),
-                            plugin.getName(),
-                            "Get generator"
-                    ) != null)
-                    .map(plugin -> plugin.getDescription().getName())
-                    .collect(Collectors.toList());
-        }
-
-        @Override
-        public String getValue(@NotNull String input) throws FlagParseFailedException {
-            String[] genArray = input.split(":");
-            String generator = genArray[0];
-            String generatorId = (genArray.length > 1) ? genArray[1] : "";
-            try {
-                if (multiverse.getMVWorldManager().getChunkGenerator(generator, generatorId, "test") == null) {
-                    throw new Exception();
-                }
-            } catch (Exception e) {
-                throw new FlagParseFailedException("Invalid generator string '%s'. See /mv gens for available generators.", input);
-            }
-            return input;
-        }
-    }.addAliases("-g");
-
-    /**
-     * Flag to toggle if world should generate structures.
-     */
-    public static final CommandFlag<Boolean> GENERATE_STRUCTURES = new RequiredCommandFlag<Boolean>
-            ("GenerateStructures", "--structures", Boolean.class) {
-        @Override
-        public Collection<String> suggestValue() {
-            return Arrays.asList("true", "false");
-        }
-
-        @Override
-        public Boolean getValue(@NotNull String input) throws FlagParseFailedException {
-            return input.equalsIgnoreCase("true");
-        }
-
-        @Override
-        public Boolean getDefaultValue() {
-            return true;
-        }
-    }.addAliases("--structure", "-a");
-
-    /**
-     * Flag to toggle if world spawn should be adjusted.
-     */
-    public static final CommandFlag<Boolean> SPAWN_ADJUST = new NoValueCommandFlag<Boolean>
-            ("AdjustSpawn", "--dont-adjust-spawn", Boolean.class) {
-        @Override
-        public Boolean getValue() throws FlagParseFailedException {
-            return false;
-        }
-
-        @Override
-        public Boolean getDefaultValue() {
-            return true;
-        }
-    }.addAliases("-n");
-
-    /**
-     * Flag to specify a paste service.
-     */
-    public static final CommandFlag<PasteServiceType> PASTE_SERVICE_TYPE = new OptionalCommandFlag<PasteServiceType>
-            ("PasteServiceType", "--paste", PasteServiceType.class) {
-
-        private final List<String> pasteTypes = Arrays.stream(PasteServiceType.values())
-                .filter(pt -> pt != PasteServiceType.NONE)
-                .map(p -> p.toString().toLowerCase())
-                .collect(Collectors.toList());
-
-        @Override
-        public Collection<String> suggestValue() {
-            return pasteTypes;
-        }
-
-        @Override
-        public PasteServiceType getValue(@NotNull String input) throws FlagParseFailedException {
-            try {
-                return PasteServiceType.valueOf(input.toUpperCase());
-            }
-            catch (IllegalArgumentException e) {
-                throw new FlagParseFailedException(String.format("Invalid paste service type '%s'.", input));
-            }
-        }
-
-        @Override
-        public PasteServiceType getValue() throws FlagParseFailedException {
-            return PasteServiceType.PASTEGG;
-        }
-
-        @Override
-        public PasteServiceType getDefaultValue() {
-            return PasteServiceType.NONE;
-        }
-    }.addAliases("-p");
-
-    /**
-     * Flag to toggle if plugin list should be included.
-     */
-    public static final CommandFlag<Boolean> INCLUDE_PLUGIN_LIST = new NoValueCommandFlag<Boolean>
-            ("IncludePlugins", "--include-plugin-list", Boolean.class) {
-        @Override
-        public Boolean getValue() throws FlagParseFailedException {
-            return true;
-        }
-
-        @Override
-        public Boolean getDefaultValue() {
-            return true;
-        }
-    }.addAliases("-pl");
-}

src/main/java/com/onarandombox/MultiverseCore/commandtools/flag/FlagGroup.java

@@ -1,96 +0,0 @@
-package com.onarandombox.MultiverseCore.commandtools.flag;
-
-import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
-/**
- * A group of {@link CommandFlag}, with indexed keys for efficient lookup.
- */
-public class FlagGroup {
-
-    /**
-     * Create a new Flag Group with multiple {@link CommandFlag}.
-     *
-     * @param flags Multiple flags.
-     * @return A new {@link FlagGroup} generated from the flags.
-     */
-    public static FlagGroup of(CommandFlag<?>...flags) {
-        return new FlagGroup(flags);
-    }
-
-    private final List<String> identifiers;
-    private final Map<String, CommandFlag<?>> keyMap;
-
-    /**
-     * Create a new Flag Group with multiple {@link CommandFlag}.
-     *
-     * @param commandFlags Array of flags
-     */
-    public FlagGroup(CommandFlag<?>[] commandFlags) {
-        this.identifiers = new ArrayList<>(commandFlags.length);
-        this.keyMap = new HashMap<>();
-        for (CommandFlag<?> flag : commandFlags) {
-            addFlag(flag);
-        }
-    }
-
-    /**
-     * Add and indexes a flag.
-     *
-     * @param flag  The flag to add.
-     */
-    private void addFlag(CommandFlag<?> flag) {
-        this.identifiers.add(flag.getIdentifier());
-        this.keyMap.put(flag.getIdentifier(), flag);
-        for (String flagAlias : flag.getAliases()) {
-            this.keyMap.put(flagAlias, flag);
-        }
-    }
-
-    /**
-     * Parse the arguments to get it's flag values.
-     *
-     * @param args  The arguments to parse.
-     * @return A {@link FlagResult} containing value results.
-     * @throws FlagParseFailedException When there is an error parsing, such as invalid format.
-     */
-    @NotNull
-    public FlagResult calculateResult(String[] args) throws FlagParseFailedException {
-        return FlagResult.parse(args,this);
-    }
-
-    /**
-     * Gets flag from pre-indexed key mapping.
-     *
-     * @param key   The target key.
-     * @return A {@link CommandFlag} if found, else null.
-     */
-    @Nullable
-    public CommandFlag<?> getByKey(String key) {
-        return this.keyMap.get(key);
-    }
-
-    /**
-     * Suggest possible identifiers available for this Flag Group.
-     *
-     * @return A collection of identifier strings.
-     */
-    @NotNull
-    public Collection<String> suggestIdentifiers() {
-        return identifiers;
-    }
-
-    @Override
-    public String toString() {
-        return "FlagGroup{" +
-                "flagIdentifiers=" + identifiers +
-                ", keyFlagMap=" + keyMap +
-                '}';
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/commandtools/flag/FlagParseFailedException.java

@@ -1,27 +0,0 @@
-package com.onarandombox.MultiverseCore.commandtools.flag;
-
-/**
- * Thrown when there is an issue with parsing flags from string arguments.
- */
-//TODO: extend this from ACF CommandArgumentFailed exception class.
-public class FlagParseFailedException extends Exception {
-
-    public FlagParseFailedException() {
-    }
-
-    public FlagParseFailedException(String message, Object...replacements) {
-        super(String.format(message, replacements));
-    }
-
-    public FlagParseFailedException(String message, Throwable cause) {
-        super(message, cause);
-    }
-
-    public FlagParseFailedException(Throwable cause) {
-        super(cause);
-    }
-
-    public FlagParseFailedException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
-        super(message, cause, enableSuppression, writableStackTrace);
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/commandtools/flag/FlagResult.java

@@ -1,198 +0,0 @@
-package com.onarandombox.MultiverseCore.commandtools.flag;
-
-import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
-
-import java.util.HashMap;
-import java.util.Map;
-
-/**
- * Represents the value result parsed from command arguments.
- */
-public class FlagResult {
-
-    /**
-     * Parse arguments into its flag key and values.
-     *
-     * @param args      The arguments to parse.
-     * @param flagGroup The flags available to parse into.
-     * @return The {@link FlagResult} from the parse.
-     * @throws FlagParseFailedException there is an issue with parsing flags from string arguments.
-     */
-    public static FlagResult parse(@Nullable String[] args,
-                                   @NotNull FlagGroup flagGroup) throws FlagParseFailedException {
-
-        FlagResult flagResult = new FlagResult();
-
-        // No args to parse.
-        if (args == null || args.length <= 0) {
-            return flagResult;
-        }
-
-        // First arg must be a flag.
-        CommandFlag<?> currentFlag = flagGroup.getByKey(args[0]);
-        boolean completed = false;
-
-        // Parse the arguments.
-        for (int i = 1, argsLength = args.length; i <= argsLength; i++) {
-            if (currentFlag == null) {
-                throw new FlagParseFailedException("%s is not a valid flag.", args[i-1]);
-            }
-            // This ensures that flag is not null during final parse.
-            if (i >= argsLength) {
-                break;
-            }
-
-            String arg = args[i];
-            if (arg == null) {
-                throw new FlagParseFailedException("Arguments cannot be null!");
-            }
-
-            CommandFlag<?> nextFlag = flagGroup.getByKey(arg);
-
-            // Arg must be a flag key.
-            if (currentFlag instanceof NoValueCommandFlag) {
-                flagResult.add(currentFlag, currentFlag.getValue(), false);
-                currentFlag = nextFlag;
-                continue;
-            }
-
-            // Arg can be a flag key or value.
-            if (currentFlag instanceof OptionalCommandFlag) {
-                if (nextFlag != null) {
-                    // It's a key.
-                    flagResult.add(currentFlag, currentFlag.getValue(), false);
-                    currentFlag = nextFlag;
-                    continue;
-                }
-                // It's a value.
-                flagResult.add(currentFlag, currentFlag.getValue(arg), true);
-                if (i == argsLength - 1) {
-                    completed = true;
-                    break;
-                }
-                currentFlag = flagGroup.getByKey(args[++i]);
-                continue;
-            }
-
-            // Arg must be a flag value.
-            if (currentFlag instanceof RequiredCommandFlag) {
-                if (nextFlag != null) {
-                    // It's a key, error!
-                    throw new FlagParseFailedException("%s flag '%s' requires a value input.",
-                            currentFlag.getName(), currentFlag.getIdentifier());
-                }
-                // It's a value.
-                flagResult.add(currentFlag, currentFlag.getValue(arg), true);
-                if (i == argsLength - 1) {
-                    completed = true;
-                    break;
-                }
-                currentFlag = flagGroup.getByKey(args[++i]);
-            }
-        }
-
-        // Parse last flag.
-        if (!completed) {
-            if (currentFlag instanceof RequiredCommandFlag) {
-                throw new FlagParseFailedException("%s flag '%s' requires a value input.",
-                        currentFlag.getName(), currentFlag.getIdentifier());
-            }
-            flagResult.add(currentFlag, currentFlag.getValue(), false);
-        }
-
-        return flagResult;
-    }
-
-    private final Map<CommandFlag<?>, SingleFlagResult<?>> resultMap;
-
-    private FlagResult() {
-        resultMap = new HashMap<>();
-    }
-
-    /**
-     * Add a new value result from parsing arguments.
-     *
-     * @param flag      The flag that the value represents.
-     * @param value     The value of the flag.
-     * @param fromInput Denotes if flag was parsed by a user input.
-     */
-    private void add(CommandFlag<?> flag, Object value, boolean fromInput) {
-        resultMap.put(flag, new SingleFlagResult<>(value, fromInput));
-    }
-
-    /**
-     * Gets value of a flag.
-     *
-     * @param flag  The flag to get value from.
-     * @param <T>   The type of value.
-     * @return The value which is associated with the flag.
-     */
-    public <T> T getValue(CommandFlag<T> flag) {
-        SingleFlagResult<?> result = resultMap.get(flag);
-        if (result == null) {
-            return flag.getDefaultValue();
-        }
-        return (T) result.value;
-    }
-
-    /**
-     * Gets if the flag value is by a user input.
-     *
-     * @param flag  The flag to check against.
-     * @return True if value is by user input, else false.
-     */
-    public boolean isByUserInput(CommandFlag<?> flag) {
-        SingleFlagResult<?> result = resultMap.get(flag);
-        if (result == null) {
-            return false;
-        }
-        return result.isFromUserInput;
-    }
-
-    /**
-     * Gets if the flag is a default value, and key was not present in user's command arguments.
-     * i.e. Not in the {@link #resultMap}.
-     *
-     * @param flag  The flag to check against.
-     * @return True if flag was not present in user's command arguments, else false.
-     */
-    public boolean isDefaulted(CommandFlag<?> flag) {
-        return resultMap.get(flag) != null;
-    }
-
-    @Override
-    public String toString() {
-        return "FlagResult{" +
-                "resultMap=" + resultMap +
-                '}';
-    }
-
-    /**
-     * Represents a single value result parsed.
-     * Stores value and addition data such as if value is by user input.
-     *
-     * @param <T>   The type of value.
-     */
-    private static class SingleFlagResult<T> {
-        private final T value;
-        private final boolean isFromUserInput;
-
-        /**
-         * @param value     The resultant value from argument parsing.
-         * @param fromInput Indicates if value is parsed by user input.
-         */
-        private SingleFlagResult(T value, boolean fromInput) {
-            this.value = value;
-            this.isFromUserInput = fromInput;
-        }
-
-        @Override
-        public String toString() {
-            return "SingleFlagResult{" +
-                    "value=" + value +
-                    ", isFromUserInput=" + isFromUserInput +
-                    '}';
-        }
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/commandtools/flag/NoValueCommandFlag.java

@@ -1,39 +0,0 @@
-package com.onarandombox.MultiverseCore.commandtools.flag;
-
-import org.jetbrains.annotations.NotNull;
-
-import java.util.Collection;
-import java.util.Collections;
-
-/**
- * This flag will always not require a user input to parse value.
- *
- * @param <T>   The flag Type.
- */
-public abstract class NoValueCommandFlag<T> extends CommandFlag<T> {
-
-    /**
-     * {@inheritDoc}
-     */
-    public NoValueCommandFlag(String name, String identifier, Class<T> type) {
-        super(name, identifier, type);
-    }
-
-    /**
-     * {@link NoValueCommandFlag} will always not require a user input to parse value.
-     * Thus, no value suggestion needed.
-     */
-    @Override
-    public final Collection<String> suggestValue() {
-        return Collections.emptyList();
-    }
-
-    /**
-     * {@link NoValueCommandFlag} will always not require a user input to parse value.
-     * Thus, this operation is not allowed.
-     */
-    @Override
-    public final T getValue(@NotNull String input) throws FlagParseFailedException {
-        throw new FlagParseFailedException("%s flag '%s' does not require a value.", this.name, this.identifier);
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/commandtools/flag/OptionalCommandFlag.java

@@ -1,16 +0,0 @@
-package com.onarandombox.MultiverseCore.commandtools.flag;
-
-/**
- * Command Flag that optionally allows a user input value.
- *
- * @param <T>   The flag Type.
- */
-public abstract class OptionalCommandFlag<T> extends CommandFlag<T> {
-
-    /**
-     * {@inheritDoc}
-     */
-    public OptionalCommandFlag(String name, String identifier, Class<T> type) {
-        super(name, identifier, type);
-    }
-}

src/main/java/com/onarandombox/MultiverseCore/commandtools/flag/RequiredCommandFlag.java

@@ -1,25 +0,0 @@
-package com.onarandombox.MultiverseCore.commandtools.flag;
-
-/**
- * This flag will always require a user input to parse value.
- *
- * @param <T>   The flag Type.
- */
-public abstract class RequiredCommandFlag<T> extends CommandFlag<T> {
-
-    /**
-     * {@inheritDoc}
-     */
-    public RequiredCommandFlag(String name, String identifier, Class<T> type) {
-        super(name, identifier, type);
-    }
-
-    /**
-     * {@link RequiredCommandFlag} will always require a user input to parse value.
-     * Thus, this operation is not allowed.
-     */
-    @Override
-    public final T getValue() throws FlagParseFailedException {
-        throw new FlagParseFailedException("%s flag '%s' requires a value input.", this.name, this.identifier);
-    }
-}

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

@@ -11,16 +11,27 @@ 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.Collection;
 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 +47,59 @@ 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.
@@ -101,4 +165,8 @@ public class DestinationFactory {
         this.teleportCommand.addAdditonalPermission(other);
         return true;
     }
+    
+    public Collection<String> getRegisteredIdentifiers() {
+        return this.destList.keySet();
+    }
 }

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}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[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

@@ -36,19 +36,20 @@ import java.io.File;
 import java.io.FilenameFilter;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Random;
 import java.util.Set;
 import java.util.Stack;
-import java.util.Arrays;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.logging.Level;
-import java.util.regex.Matcher;
 import java.util.regex.Pattern;
+import java.util.stream.Collectors;
 
 /**
  * Public facing API to add/remove Multiverse worlds.
@@ -59,6 +60,7 @@ public class WorldManager implements MVWorldManager {
     private final WorldPurger worldPurger;
     private final Map<String, MultiverseWorld> worlds;
     private Map<String, WorldProperties> worldsFromTheConfig;
+    private Set<String> defaultWorldNames;
     private FileConfiguration configWorlds = null;
     private Map<String, String> defaultGens;
     private String firstSpawn;
@@ -130,7 +132,7 @@ 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 +240,9 @@ 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;
         }
 
@@ -381,6 +385,11 @@ public class WorldManager implements MVWorldManager {
      */
     @Override
     public boolean unloadWorld(String name, boolean unloadBukkit) {
+        if (this.isDefaultWorld(name)) {
+            Logging.warning("You cannot unload the default worlds.");
+            Logging.warning("Default worlds on your server are: %s", this.defaultWorldNames);
+            return false;
+        }
         if (this.worlds.containsKey(name)) {
             this.worldsFromTheConfig.get(name).cacheVirtualProperties();
             if (unloadBukkit && this.unloadWorldFromBukkit(name, true)) {
@@ -424,21 +433,6 @@ 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 + "'");
@@ -630,6 +624,14 @@ public class WorldManager implements MVWorldManager {
      */
     @Override
     public MultiverseWorld getMVWorld(String name) {
+        return this.getMVWorld(name, true);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public MultiverseWorld getMVWorld(String name, boolean checkAliases) {
         if (name == null) {
             return null;
         }
@@ -637,7 +639,7 @@ public class WorldManager implements MVWorldManager {
         if (world != null) {
             return world;
         }
-        return this.getMVWorldByAlias(name);
+        return (checkAliases) ? this.getMVWorldByAlias(name) : null;
     }
 
     /**
@@ -646,7 +648,7 @@ public class WorldManager implements MVWorldManager {
     @Override
     public MultiverseWorld getMVWorld(World world) {
         if (world != null) {
-            return this.getMVWorld(world.getName());
+            return this.getMVWorld(world.getName(), false);
         }
         return null;
     }
@@ -671,7 +673,15 @@ public class WorldManager implements MVWorldManager {
      */
     @Override
     public boolean isMVWorld(final String name) {
-        return (this.worlds.containsKey(name) || isMVWorldAlias(name));
+        return this.isMVWorld(name, true);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public boolean isMVWorld(final String name, boolean checkAliases) {
+        return this.worlds.containsKey(name) || (checkAliases && this.isMVWorldAlias(name));
     }
 
     /**
@@ -704,6 +714,7 @@ public class WorldManager implements MVWorldManager {
     public void loadDefaultWorlds() {
         this.ensureConfigIsPrepared();
         List<World> myWorlds = this.plugin.getServer().getWorlds();
+        this.defaultWorldNames = new HashSet<>(myWorlds.size());
         for (World w : myWorlds) {
             String name = w.getName();
             if (!worldsFromTheConfig.containsKey(name)) {
@@ -711,9 +722,15 @@ public class WorldManager implements MVWorldManager {
                 if (this.defaultGens.containsKey(name)) {
                     generator = this.defaultGens.get(name);
                 }
-                this.addWorld(name, w.getEnvironment(), String.valueOf(w.getSeed()), w.getWorldType(), w.canGenerateStructures(), generator);
+                if (!this.addWorld(name, w.getEnvironment(), String.valueOf(w.getSeed()), w.getWorldType(), w.canGenerateStructures(), generator)) {
+                    Logging.warning("Error loading default world '%s'!", w.getName());
+                    continue;
+                }
             }
+            this.defaultWorldNames.add(name);
         }
+        this.defaultWorldNames = Collections.unmodifiableSet(this.defaultWorldNames);
+        Logging.fine("Loaded default worlds: %s", this.defaultWorldNames);
     }
 
     private void ensureConfigIsPrepared() {
@@ -723,6 +740,21 @@ public class WorldManager implements MVWorldManager {
         }
     }
 
+    @Override
+    public boolean isDefaultWorld(MultiverseWorld world) {
+        return world != null && this.isDefaultWorld(world.getName());
+    }
+
+    @Override
+    public boolean isDefaultWorld(String worldName) {
+        return this.defaultWorldNames != null && this.defaultWorldNames.contains(worldName);
+    }
+
+    @Override
+    public Collection<String> getDefaultWorldNames() {
+        return this.defaultWorldNames;
+    }
+
     /**
      * {@inheritDoc}
      */
@@ -953,4 +985,21 @@ public class WorldManager implements MVWorldManager {
 		}
 		return false;
 	}
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+	public Collection<String> getPotentialWorlds() {
+        File worldContainer = this.plugin.getServer().getWorldContainer();
+        if (worldContainer == null) {
+            return Collections.emptyList();
+        }
+        return Arrays.stream(worldContainer.listFiles())
+                .filter(File::isDirectory)
+                .filter(folder -> !this.isMVWorld(folder.getName(), false))
+                .filter(WorldNameChecker::isValidWorldFolder)
+                .map(File::getName)
+                .collect(Collectors.toList());
+    }
 }

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/main/java/com/onarandombox/MultiverseCore/utils/webpaste/PasteServiceType.java

@@ -22,9 +22,5 @@ public enum PasteServiceType {
     /**
      * @see GitHubPasteService
      */
-    GITHUB,
-    /**
-     * No paste service used.
-     */
-    NONE
+    GITHUB
 }

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("§cError: Invalid generator string 'BogusGen'. See /mv gens for available generators.");
+        verify(mockCommandSender).sendMessage("Invalid generator! 'BogusGen'. " + ChatColor.RED + "Aborting world creation.");
     }
 
     @Test