Implements the group swap command

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

@@ -23,6 +23,19 @@ public class DropperArenaHandler {
     private Map<UUID, DropperArenaGroup> arenaGroups = new HashMap<>();
     private Map<String, UUID> arenaNameLookup = new HashMap<>();
 
+    /**
+     * Gets all arenas that are within a group
+     *
+     * @return <p>All arenas in a group</p>
+     */
+    public @NotNull Set<DropperArena> getArenasInAGroup() {
+        Set<DropperArena> arenas = new HashSet<>();
+        for (UUID arenaId : arenaGroups.keySet()) {
+            arenas.add(this.arenas.get(arenaId));
+        }
+        return arenas;
+    }
+
     /**
      * Gets a copy of all dropper groups
      *

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

@@ -1,23 +1,102 @@
 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 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 GroupSwapCommand implements CommandExecutor {
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+
+/**
+ * The command for swapping the order of two arenas in a group
+ */
+public class GroupSwapCommand implements TabExecutor {
 
     @Override
     public boolean onCommand(@NotNull CommandSender commandSender, @NotNull Command command, @NotNull String s,
                              @NotNull String[] arguments) {
-        // TODO: Make sure the two arenas exist
-        // TODO: Make sure the two arenas belong to the same group
-        // TODO: Swap the order of the two groups
-        // TODO: Announce success
-        return false;
+        if (arguments.length < 2) {
+            return false;
+        }
+
+        DropperArenaHandler arenaHandler = Dropper.getInstance().getArenaHandler();
+
+        DropperArena arena1 = arenaHandler.getArena(arguments[0]);
+        if (arena1 == null) {
+            commandSender.sendMessage("Unable to find the first specified dropper arena.");
+            return false;
+        }
+
+        DropperArena arena2 = arenaHandler.getArena(arguments[1]);
+        if (arena2 == null) {
+            commandSender.sendMessage("Unable to find the second specified dropper arena.");
+            return false;
+        }
+
+        DropperArenaGroup arena1Group = arenaHandler.getGroup(arena1.getArenaId());
+        DropperArenaGroup arena2Group = arenaHandler.getGroup(arena2.getArenaId());
+        if (arena1Group == null || !arena1Group.equals(arena2Group)) {
+            commandSender.sendMessage("You cannot swap arenas in different groups!");
+            return false;
+        }
+
+        arena1Group.swapArenas(arena1Group.getArenas().indexOf(arena1.getArenaId()),
+                arena1Group.getArenas().indexOf(arena2.getArenaId()));
+        commandSender.sendMessage("The arenas have been swapped!");
+        return true;
     }
 
-    // Tab-completion TODO: Only give arenas with a group for the first value. Only give arenas within the same group
-    //  for the second value
+    @Nullable
+    @Override
+    public List<String> onTabComplete(@NotNull CommandSender commandSender, @NotNull Command command, @NotNull String s,
+                                      @NotNull String[] arguments) {
+        DropperArenaHandler arenaHandler = Dropper.getInstance().getArenaHandler();
+        if (arguments.length == 1) {
+            List<String> arenaNames = new ArrayList<>();
+            for (DropperArena dropperArena : arenaHandler.getArenasInAGroup()) {
+                arenaNames.add(dropperArena.getArenaName());
+            }
+            return arenaNames;
+        } else if (arguments.length == 2) {
+            return getArenaNamesInSameGroup(arguments[0]);
+        } else {
+            return new ArrayList<>();
+        }
+    }
+
+    /**
+     * Gets the names of all arenas in the same group as the specified arena
+     *
+     * @param arenaName <p>The name of the specified arena</p>
+     * @return <p>The names of the arenas in the same group</p>
+     */
+    private List<String> getArenaNamesInSameGroup(String arenaName) {
+        DropperArenaHandler arenaHandler = Dropper.getInstance().getArenaHandler();
+        DropperArena arena1 = arenaHandler.getArena(arenaName);
+        if (arena1 == null) {
+            return new ArrayList<>();
+        }
+
+        // Only display other arenas in the selected group
+        List<String> arenaNames = new ArrayList<>();
+        DropperArenaGroup group = arenaHandler.getGroup(arena1.getArenaId());
+        if (group == null) {
+            return new ArrayList<>();
+        }
+        for (UUID arenaId : group.getArenas()) {
+            DropperArena arena = arenaHandler.getArena(arenaId);
+            if (arena != null && arena.getArenaId() != arena1.getArenaId()) {
+                arenaNames.add(arena.getArenaName());
+            }
+        }
+        return arenaNames;
+    }
 
 }