Implements the join command

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

@@ -1,5 +1,11 @@
 package net.knarcraft.dropper.command;
 
+import net.knarcraft.dropper.Dropper;
+import net.knarcraft.dropper.arena.DropperArena;
+import net.knarcraft.dropper.arena.DropperArenaPlayerRegistry;
+import net.knarcraft.dropper.arena.DropperArenaSession;
+import net.knarcraft.dropper.property.ArenaGameMode;
+import net.knarcraft.dropper.util.PlayerTeleporter;
 import org.bukkit.command.Command;
 import org.bukkit.command.CommandExecutor;
 import org.bukkit.command.CommandSender;
@@ -13,16 +19,62 @@ public class JoinArenaCommand implements CommandExecutor {
 
     @Override
     public boolean onCommand(@NotNull CommandSender commandSender, @NotNull Command command, @NotNull String s,
-                             @NotNull String[] strings) {
+                             @NotNull String[] arguments) {
-        if (!(commandSender instanceof Player)) {
+        if (!(commandSender instanceof Player player)) {
             commandSender.sendMessage("This command must be used by a player");
             return false;
         }
-        //TODO: Remember to check if the player is already in an arena first!
+
-        //TODO: Create a new arena session
+        if (arguments.length < 1) {
-        //TODO: Register the session in the arena player registry
+            return false;
-        //TODO: Teleport the player to the arena's start location
+        }
-        return true;
+
+        // Disallow joining if the player is already in a dropper arena
+        DropperArenaSession existingSession = Dropper.getInstance().getPlayerRegistry().getArenaSession(player);
+        if (existingSession != null) {
+            commandSender.sendMessage("You are already in a dropper arena!");
+            return false;
+        }
+
+        // Make sure the arena exists
+        String arenaName = arguments[0].trim();
+        DropperArena specifiedArena = null;
+        for (DropperArena arena : Dropper.getInstance().getArenaHandler().getArenas()) {
+            if (arena.getArenaName().equalsIgnoreCase(arenaName)) {
+                specifiedArena = arena;
+                break;
+            }
+        }
+        if (specifiedArena == null) {
+            commandSender.sendMessage("Unable to find the specified dropper arena.");
+            return false;
+        }
+
+        // Find the specified game-mode
+        ArenaGameMode gameMode;
+        if (arguments.length > 1) {
+            gameMode = ArenaGameMode.matchGamemode(arguments[1]);
+        } else {
+            gameMode = ArenaGameMode.DEFAULT;
+        }
+
+        //TODO: Check if the arena has been beaten if the non-default game-mode has been chosen
+
+        // Register the player's session
+        DropperArenaSession newSession = new DropperArenaSession(specifiedArena, player, gameMode);
+        DropperArenaPlayerRegistry playerRegistry = Dropper.getInstance().getPlayerRegistry();
+        playerRegistry.registerPlayer(player, newSession);
+
+        // Try to teleport the player to the arena
+        boolean teleported = PlayerTeleporter.teleportPlayer(player, specifiedArena.getSpawnLocation(), false);
+        if (!teleported) {
+            commandSender.sendMessage("Unable to teleport you to the dropper arena. Make sure you're not in a vehicle," +
+                    "and is not carrying a passenger!");
+            newSession.triggerQuit();
+            return false;
+        } else {
+            return true;
+        }
     }
 
 }

src/main/java/net/knarcraft/dropper/property/ArenaGameMode.java

@@ -1,5 +1,7 @@
 package net.knarcraft.dropper.property;
 
+import org.jetbrains.annotations.NotNull;
+
 /**
  * A representation of possible arena game-modes
  */
@@ -20,5 +22,23 @@ public enum ArenaGameMode {
      * The least-time game-mode. Player plays until they manage to win. The total time of the session is recorded.
      */
     LEAST_TIME,
+    ;
+
+    /**
+     * Tries to match the correct game-mode according to the given string
+     *
+     * @param gameMode <p>The game-mode string to match</p>
+     * @return <p>The specified arena game-mode</p>
+     */
+    public static @NotNull ArenaGameMode matchGamemode(@NotNull String gameMode) {
+        String sanitized = gameMode.trim().toLowerCase();
+        if (sanitized.matches("(least)?deaths?")) {
+            return ArenaGameMode.LEAST_DEATHS;
+        } else if (sanitized.matches("(least)?time")) {
+            return ArenaGameMode.LEAST_TIME;
+        } else {
+            return ArenaGameMode.DEFAULT;
+        }
+    }
 
 }