Implements the group set command

src/main/java/net/knarcraft/dropper/arena/DropperArena.java

@@ -2,7 +2,7 @@ package net.knarcraft.dropper.arena;
 
 import net.knarcraft.dropper.Dropper;
 import net.knarcraft.dropper.property.ArenaGameMode;
-import net.knarcraft.dropper.util.ArenaStorageHelper;
+import net.knarcraft.dropper.util.StringSanitizer;
 import org.bukkit.Location;
 import org.bukkit.Material;
 import org.bukkit.World;
@@ -203,7 +203,7 @@ public class DropperArena {
      * @return <p>This arena's sanitized name</p>
      */
     public @NotNull String getArenaNameSanitized() {
-        return ArenaStorageHelper.sanitizeArenaName(this.getArenaName());
+        return StringSanitizer.sanitizeArenaName(this.getArenaName());
     }
 
     /**

src/main/java/net/knarcraft/dropper/arena/DropperArenaGroup.java

@@ -3,7 +3,7 @@ package net.knarcraft.dropper.arena;
 import net.knarcraft.dropper.Dropper;
 import net.knarcraft.dropper.container.SerializableUUID;
 import net.knarcraft.dropper.property.ArenaGameMode;
-import net.knarcraft.dropper.util.ArenaStorageHelper;
+import net.knarcraft.dropper.util.StringSanitizer;
 import org.bukkit.configuration.serialization.ConfigurationSerializable;
 import org.bukkit.entity.Player;
 import org.jetbrains.annotations.NotNull;
@@ -187,7 +187,7 @@ public class DropperArenaGroup implements ConfigurationSerializable {
      * @return <p>The sanitized group name</p>
      */
     public @NotNull String getGroupNameSanitized() {
-        return ArenaStorageHelper.sanitizeArenaName(this.getGroupName());
+        return StringSanitizer.sanitizeArenaName(this.getGroupName());
     }
 
     /**

src/main/java/net/knarcraft/dropper/arena/DropperArenaHandler.java

@@ -2,11 +2,13 @@ package net.knarcraft.dropper.arena;
 
 import net.knarcraft.dropper.Dropper;
 import net.knarcraft.dropper.util.ArenaStorageHelper;
+import net.knarcraft.dropper.util.StringSanitizer;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.io.IOException;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
 import java.util.UUID;
@@ -35,11 +37,27 @@ public class DropperArenaHandler {
      * Sets the group for the given arena
      *
      * @param arenaId    <p>The id of the arena to change</p>
-     * @param arenaGroup <p>The group to add the arena to</p>
+     * @param arenaGroup <p>The group to add the arena to, or null to remove the current group</p>
      */
-    public void setGroup(@NotNull UUID arenaId, @NotNull DropperArenaGroup arenaGroup) {
+    public void setGroup(@NotNull UUID arenaId, @Nullable DropperArenaGroup arenaGroup) {
+        if (arenaGroup == null) {
+            // No need to remove something non-existing
+            if (!this.arenaGroups.containsKey(arenaId)) {
+                return;
+            }
+
+            // Remove the existing group
+            DropperArenaGroup oldGroup = this.arenaGroups.remove(arenaId);
+            oldGroup.removeArena(arenaId);
+        } else {
+            // Make sure to remove the arena from the old group's internal tracking
+            if (this.arenaGroups.containsKey(arenaId)) {
+                this.arenaGroups.remove(arenaId).removeArena(arenaId);
+            }
+
             this.arenaGroups.put(arenaId, arenaGroup);
             arenaGroup.addArena(arenaId);
+        }
         saveGroups();
     }
 
@@ -50,7 +68,7 @@ public class DropperArenaHandler {
      * @return <p>The group, or null if not found</p>
      */
     public @Nullable DropperArenaGroup getGroup(String groupName) {
-        String sanitized = ArenaStorageHelper.sanitizeArenaName(groupName);
+        String sanitized = StringSanitizer.sanitizeArenaName(groupName);
         for (DropperArenaGroup arenaGroup : this.arenaGroups.values()) {
             if (arenaGroup.getGroupNameSanitized().equals(sanitized)) {
                 return arenaGroup;
@@ -59,19 +77,6 @@ public class DropperArenaHandler {
         return null;
     }
 
-    /**
-     * Removes the given arena from its group
-     *
-     * @param arenaId <p>The id of the arena to ungroup</p>
-     */
-    public void removeFromGroup(@NotNull UUID arenaId) {
-        if (this.arenaGroups.containsKey(arenaId)) {
-            this.arenaGroups.get(arenaId).removeArena(arenaId);
-            this.arenaGroups.remove(arenaId);
-            saveGroups();
-        }
-    }
-
     /**
      * Replaces an arena's lookup name
      *
@@ -113,7 +118,7 @@ public class DropperArenaHandler {
      * @return <p>The arena with the given name, or null if not found</p>
      */
     public @Nullable DropperArena getArena(@NotNull String arenaName) {
-        return this.arenas.get(this.arenaNameLookup.get(ArenaStorageHelper.sanitizeArenaName(arenaName)));
+        return this.arenas.get(this.arenaNameLookup.get(StringSanitizer.sanitizeArenaName(arenaName)));
     }
 
     /**
@@ -157,7 +162,7 @@ public class DropperArenaHandler {
      */
     public void saveGroups() {
         try {
-            ArenaStorageHelper.saveDropperArenaGroups((Set<DropperArenaGroup>) this.arenaGroups.values());
+            ArenaStorageHelper.saveDropperArenaGroups(new HashSet<>(this.arenaGroups.values()));
         } catch (IOException e) {
             Dropper.getInstance().getLogger().log(Level.SEVERE, "Unable to save current arena groups! " +
                     "Data loss can occur!");

src/main/java/net/knarcraft/dropper/command/CreateArenaCommand.java

@@ -2,6 +2,7 @@ package net.knarcraft.dropper.command;
 
 import net.knarcraft.dropper.Dropper;
 import net.knarcraft.dropper.arena.DropperArena;
+import net.knarcraft.dropper.util.StringSanitizer;
 import org.bukkit.command.Command;
 import org.bukkit.command.CommandExecutor;
 import org.bukkit.command.CommandSender;
@@ -26,15 +27,20 @@ public class CreateArenaCommand implements CommandExecutor {
             return false;
         }
 
-        DropperArena existingArena = Dropper.getInstance().getArenaHandler().getArena(arguments[0]);
+        // Remove known characters that are likely to cause trouble if used in an arena name
+        String arenaName = StringSanitizer.removeUnwantedCharacters(arguments[0]);
+
+        // An arena name is required
+        if (arenaName.isBlank()) {
+            return false;
+        }
+
+        DropperArena existingArena = Dropper.getInstance().getArenaHandler().getArena(arenaName);
         if (existingArena != null) {
             commandSender.sendMessage("There already exists a dropper arena with that name!");
             return false;
         }
 
-        // Remove known characters that are likely to cause trouble if used in an arena name
-        String arenaName = arguments[0].replaceAll("[§ :=&]", "");
-
         DropperArena arena = new DropperArena(arenaName, player.getLocation());
         Dropper.getInstance().getArenaHandler().addArena(arena);
         commandSender.sendMessage("The arena was successfully created!");

src/main/java/net/knarcraft/dropper/command/GroupSetCommand.java

@@ -1,21 +1,76 @@
 package net.knarcraft.dropper.command;
 
+import net.knarcraft.dropper.Dropper;
+import net.knarcraft.dropper.arena.DropperArena;
+import net.knarcraft.dropper.arena.DropperArenaGroup;
+import net.knarcraft.dropper.arena.DropperArenaHandler;
+import net.knarcraft.dropper.util.StringSanitizer;
+import net.knarcraft.dropper.util.TabCompleteHelper;
 import org.bukkit.command.Command;
-import org.bukkit.command.CommandExecutor;
 import org.bukkit.command.CommandSender;
+import org.bukkit.command.TabExecutor;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
-public class GroupSetCommand implements CommandExecutor {
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * The command for setting the group of an arena
+ */
+public class GroupSetCommand implements TabExecutor {
 
     @Override
     public boolean onCommand(@NotNull CommandSender commandSender, @NotNull Command command, @NotNull String s,
                              @NotNull String[] arguments) {
-        // TODO: Check if the given group is valid
+        if (arguments.length < 2) {
-        // TODO: Try and get the group from ArenaHandler.getGroup
-        // TODO: Create a new group if not found
-        // TODO: Set the group of the arena
-        // TODO: Announce success
             return false;
         }
 
+        DropperArenaHandler arenaHandler = Dropper.getInstance().getArenaHandler();
+
+        DropperArena specifiedArena = arenaHandler.getArena(arguments[0]);
+        if (specifiedArena == null) {
+            commandSender.sendMessage("Unable to find the specified dropper arena.");
+            return false;
+        }
+
+        String groupName = StringSanitizer.removeUnwantedCharacters(arguments[1]);
+
+        if (groupName.isBlank()) {
+            return false;
+        }
+
+        DropperArenaGroup arenaGroup;
+        if (groupName.equalsIgnoreCase("null") || groupName.equalsIgnoreCase("none")) {
+            arenaGroup = null;
+        } else {
+            arenaGroup = arenaHandler.getGroup(groupName);
+            if (arenaGroup == null) {
+                arenaGroup = new DropperArenaGroup(groupName);
+            }
+        }
+
+        arenaHandler.setGroup(specifiedArena.getArenaId(), arenaGroup);
+
+        commandSender.sendMessage("The arena's group has been updated");
+        return true;
+    }
+
+    @Nullable
+    @Override
+    public List<String> onTabComplete(@NotNull CommandSender commandSender, @NotNull Command command, @NotNull String s,
+                                      @NotNull String[] arguments) {
+        if (arguments.length == 1) {
+            return TabCompleteHelper.getArenas();
+        } else if (arguments.length == 2) {
+            List<String> possibleValues = new ArrayList<>();
+            possibleValues.add("none");
+            possibleValues.add("GroupName");
+            return possibleValues;
+        } else {
+            return new ArrayList<>();
+        }
+    }
+
 }

src/main/java/net/knarcraft/dropper/util/ArenaStorageHelper.java

@@ -177,16 +177,6 @@ public final class ArenaStorageHelper {
                 winBlockType.material(), arenaData);
     }
 
-    /**
-     * Sanitizes an arena name for usage as a YAML key
-     *
-     * @param arenaName <p>The arena name to sanitize</p>
-     * @return <p>The sanitized arena name</p>
-     */
-    public static @NotNull String sanitizeArenaName(@NotNull String arenaName) {
-        return arenaName.toLowerCase().trim().replaceAll(" ", "_");
-    }
-
     /**
      * Stores the given arena data to a file
      *

src/main/java/net/knarcraft/dropper/util/StringSanitizer.java

@@ -0,0 +1,37 @@
+package net.knarcraft.dropper.util;
+
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * A helper-class for sanitizing strings
+ */
+public final class StringSanitizer {
+
+    private StringSanitizer() {
+
+    }
+
+    /**
+     * Removes unwanted characters from a string
+     *
+     * <p>This basically removes character that have a special meaning in YML, or ones that cannot be used in the
+     * chat.</p>
+     *
+     * @param input <p>The string to remove from</p>
+     * @return <p>The string with the unwanted characters removed</p>
+     */
+    public static @NotNull String removeUnwantedCharacters(@NotNull String input) {
+        return input.replaceAll("[§ :=&]", "");
+    }
+
+    /**
+     * Sanitizes an arena name for usage as a YAML key
+     *
+     * @param arenaName <p>The arena name to sanitize</p>
+     * @return <p>The sanitized arena name</p>
+     */
+    public static @NotNull String sanitizeArenaName(@NotNull String arenaName) {
+        return arenaName.toLowerCase().trim().replaceAll(" ", "_");
+    }
+
+}