Using the new synchronous client packet listeners

SynchronousCensor.java

package com.comphenix.example;

import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;

import org.bukkit.entity.Player;
import org.bukkit.event.Listener;
import org.bukkit.plugin.java.JavaPlugin;

import com.comphenix.protocol.Packets;
import com.comphenix.protocol.ProtocolLibrary;
import com.comphenix.protocol.ProtocolManager;
import com.comphenix.protocol.events.ConnectionSide;
import com.comphenix.protocol.events.PacketAdapter;
import com.comphenix.protocol.events.PacketEvent;
import com.comphenix.protocol.reflect.FieldAccessException;

public class SynchronousCensor extends JavaPlugin implements Listener {

    private static final int TICKS_PER_SECOND = 20;
    
    private ProtocolManager manager;
    
    public void onLoad() {
        manager = ProtocolLibrary.getProtocolManager();
    }
    
    @Override
    public void onEnable() {
        final Thread mainThread = Thread.currentThread();
        
        manager.getAsynchronousManager().registerAsyncHandler(
                new PacketAdapter(this, ConnectionSide.CLIENT_SIDE, Packets.Client.CHAT) {
            @Override
            public void onPacketReceiving(final PacketEvent event) {
                try {
                    // Proof that we're running on the main thread
                    if (Thread.currentThread().getId() == mainThread.getId()) {
                        if (!event.getPlayer().hasPermission("chat.offensive")) {
                            String message = event.getPacket().getStrings().read(0);

                            if (message.contains("shit") || message.contains("fuck")) {
                                event.getPlayer().sendMessage("Bad manners!");
                                event.setCancelled(true);
                            }
                        }
                        
                        // Add a delay of 2 seconds
                        if (!event.isCancelled()) {
                            event.getAsyncMarker().incrementProcessingDelay();
                            
                            getServer().getScheduler().scheduleSyncDelayedTask(ExampleMod.this, new Runnable() {
                                @Override
                                public void run() {
                                    manager.getAsynchronousManager().signalPacketTransmission(event);
                                }
                            }, TICKS_PER_SECOND * 2);
                        }
                        
                        System.out.println("Processed on the main thread. Cancelled: " + event.isCancelled());
                    } else {
                        System.out.println("Something bad happened.");
                    }
                    
                } catch (FieldAccessException e) {
                    // Error
                    e.printStackTrace();
                }
            }
            
            // Remember this!
        }).syncStart();
    }
}