QuickChatCommandsDemo for MC/Spigot 1.3.2

package net.experimentalidea.quickchatcommands;

import java.util.ArrayList;
import java.util.List;

import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.Sound;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.EventPriority;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerItemHeldEvent;
import org.bukkit.event.player.PlayerQuitEvent;
import org.bukkit.event.player.PlayerSwapHandItemsEvent;
import org.bukkit.plugin.java.JavaPlugin;

/** QuickChatCommandsDemo for MC/Spigot 1.3.2:
 * A demonstration on how an effective "voice command" system (like in Team Fortress 2 and CS:GO)
 * could be implemented in Minecraft via a server-side plugin with no client-side mods needed.
 * <p>
 * The code written here is to simply demonstrate this concept and doesn't necessarily follow best practices.
 * <p>
 * How it works: <br>
 * Player presses their "Swap Item In Hands" (default 'F') hotkey.
 * The server cancels the event generated by this action and sets the player's hotbar to the first slot.
 * Next a menu is sent to the player with up to 8 options - corresponding with slots 2 through 9 on their hotbar.
 * Once the player presses one of their number keys (from 2 to 9),
 * the server sends a message in chat under the player's name and plays a sound effect.
 * <p>
 * Other Notes: <br>
 * - Implementing this system would mean removing the player's ability to quickly swap an item
 *   from their main hand to their off hand via the "Swap Item In Hands" (default 'F') hotkey.
 *   Making this something best implemented in a mini-game where the player would typically
 *   not be able to use this function anyways.
 *  <p>
 * - It probably would be better to show the menu in the scoreboard rather than ruining visibility of the chat by putting it in there.
 * <p>
 * - This relies on dual wielding, i.e. Minecraft versions after 1.8. If your stuck on 1.8,
 *   then you may be able to implement this on the packet level for newer Minecraft clients.
 *   But players connecting with 1.8 clients wouldn't be able to benefit from this feature.
 *   As much as I'd like mainstream servers to pick up on this, I doubt it'd be worth the effort until they
 *   update to the latest version of the game. (Ha. Fat chance I know - with 1.8 being the go-to PVP version of the game)
 * <p>
 *
 * I hope you found this little demo project interesting.
 * You can find me online both at YouTube and Twitter.
 * If you end up implementing this concept into your own project,
 * feel free to drop me a message/comment, I'd love to see how you use it.
 * <br> https://www.youtube.com/c/ExperimentalIdea
 * <br> https://twitter.com/ExperimentIdea
 * <p>
 * Video: https://youtu.be/DItXvV38NrM */
public class QuickChatCommandsDemo extends JavaPlugin implements Listener {

    // Player's which have QCC active.
    private static List<Player> cmdActive = new ArrayList<Player>();

    // The menu message sent to the player when they activate QCC.
    private String cmdMenu = ChatColor.GRAY
                             + "2. Help!\n"
                             + "3. Thanks!\n"
                             + "4. Go!\n"
                             + "5. Move Up!\n"
                             + "6. Dispenser Here!\n"
                             + "7. Good Job!\n"
                             + "8. Jeers\n"
                             + "9. Negative\n";

    // The message sent by the player when they use QCC.
    private String[] cmdMsg =  {"(QCC) Need Help!",
                                "(QCC) Thanks Mate!",
                                "(QCC) Let's Go!",
                                "(QCC) Move That Gear Up!",
                                "(QCC) Need A Dispenser Here!",
                                "(QCC) Nicely Done!",
                                "(QCC) Well This Sucks!",
                                "(QCC) We are Screwed!"};

    // The sound played when the player uses QCC.
    // In my video I had a custom resource pack that replaced
    // these sounds with voice lines from The Scout in Team Fortress 2
    // I didn't include that resource pack, since it contained Valve's IP.
    // So I'll leave it up to you to change these sounds to whatever you like.
    private Sound[] cmdSound = {Sound.ENTITY_GHAST_DEATH, // 2. Help
                                Sound.BLOCK_ANVIL_LAND, // 3. Thanks
                                Sound.BLOCK_ANVIL_USE, // 4. Go
                                Sound.ENTITY_BLAZE_DEATH, // 5. Move Up
                                Sound.ENTITY_ZOMBIE_PIGMAN_DEATH, // 6. Dispenser Here!
                                Sound.ENTITY_SKELETON_DEATH, // 7. Good Job
                                Sound.ENTITY_BAT_DEATH, // 8. Jeers
                                Sound.ENTITY_CREEPER_DEATH}; // 9. Negative

    @Override
    public void onEnable(){
        Bukkit.getPluginManager().registerEvents(this, this);
        this.getLogger().info("QuickChatCommandsDemo by Duke @ ExperimentalIdea.");
        this.getLogger().info("Youtube: https://www.youtube.com/c/ExperimentalIdea");
        this.getLogger().info("Twitter: https://twitter.com/ExperimentIdea");
        this.getLogger().info("Video: https://youtu.be/DItXvV38NrM");
    }

    @Override
    public void onDisable(){
        cmdActive.clear();
    }

    // When the player presses their "Swap Item In Hands" (default 'F') hotkey.
    // This event is fired, even when both the player's hands are empty.
    @EventHandler(priority = EventPriority.NORMAL)
    public void onPlayerSwapItems(PlayerSwapHandItemsEvent event) {
        event.setCancelled(true);

        Player player = event.getPlayer();

        if(!cmdActive.contains(player)) {
            player.sendMessage(this.cmdMenu);
            player.getInventory().setHeldItemSlot(0);
            cmdActive.add(player);
        }else {
            player.sendMessage(ChatColor.GRAY + "Quick Chat Command cancelled.");
            cmdActive.remove(player);
        }
    }

    // When the player has QCC active, listen for what command they choose.
    @EventHandler(priority = EventPriority.NORMAL)
    public void onPlayer(PlayerItemHeldEvent event) {
        Player player = event.getPlayer();

        if(cmdActive.contains(player)) {
            int slot = event.getNewSlot();
            if(slot < 9 && slot != 0) {
                int index = slot - 1;
                player.chat(this.cmdMsg[index]);
                player.getWorld().playSound(player.getLocation(), this.cmdSound[index], 1.5F, 1.0F);
                cmdActive.remove(player);
            }
        }
    }

    // Cleanup - Don't leak memory by keeping an QCC active player in the list.
    @EventHandler(priority = EventPriority.NORMAL)
    public void onPlayerQuit(PlayerQuitEvent event) {
        cmdActive.remove(event.getPlayer());
    }

}