Updating TinyProtocol significantly.

Added the ability to send and recieve packets, along with a more 
powerful reflection system. You can now retireve Minecraft classes 
by name.

Examples/TinyProtocol/src/main/java/com/comphenix/tinyprotocol/ExamplePlugin.java

@@ -1,28 +1,62 @@
 package com.comphenix.tinyprotocol;
 
-import net.minecraft.server.v1_7_R1.PacketPlayInChat;
-
+import org.bukkit.Location;
 import org.bukkit.entity.Player;
 import org.bukkit.plugin.java.JavaPlugin;
 
-import com.google.common.base.Function;
+import com.comphenix.tinyprotocol.TinyProtocol.FieldAccessor;
 
 public class ExamplePlugin extends JavaPlugin {
-	private Function<Object, String> CHAT_MESSAGE = TinyProtocol.getFieldAccessor(
-			PacketPlayInChat.class, String.class, 0);
-
+	// Chat packets
+	private FieldAccessor<String> CHAT_MESSAGE = TinyProtocol.getField(
+			"PacketPlayInChat", String.class, 0);
+	
+	// Explosion packet
+	private Class<?> particleClass = TinyProtocol.getMinecraftClass("PacketPlayOutWorldParticles");
+	private FieldAccessor<String> particleName = TinyProtocol.getField(particleClass, String.class, 0);
+	private FieldAccessor<Float> particleX = TinyProtocol.getField(particleClass, float.class, 0);
+	private FieldAccessor<Float> particleY = TinyProtocol.getField(particleClass, float.class, 1);
+	private FieldAccessor<Float> particleZ = TinyProtocol.getField(particleClass, float.class, 2);
+	private FieldAccessor<Integer> particleCount = TinyProtocol.getField(particleClass, int.class, 0);
+	
+	private TinyProtocol protocol;
+	
 	@Override
 	public void onEnable() {
-		new TinyProtocol(this) {
+		protocol = new TinyProtocol(this) {
 			@Override
 			public Object onPacketInAsync(Player sender, Object packet) {
 				// Cancel chat packets
-				if (packet instanceof PacketPlayInChat) {
-					if (CHAT_MESSAGE.apply(packet).contains("dirty"))
+				if (CHAT_MESSAGE.hasField(packet)) {
+					if (CHAT_MESSAGE.get(packet).contains("dirty")) {
+						sendExplosion(sender);
 						return null;
+					}
+				}
+				if (particleName.hasField(packet)) {
+					System.out.println("Sending particle field:" + packet);
 				}
 				return super.onPacketInAsync(sender, packet);
 			}
 		};
 	}
+
+	private void sendExplosion(Player player) {
+		try {
+			// Only visible for the client
+			Object explosionPacket = particleClass.newInstance();
+			Location loc = player.getLocation();
+			particleName.set(explosionPacket, "hugeexplosion");
+			particleX.set(explosionPacket, (float) loc.getX());
+			particleY.set(explosionPacket, (float) loc.getY());
+			particleZ.set(explosionPacket, (float) loc.getZ());
+			particleCount.set(explosionPacket, 1);
+
+			// Send the packet to the player
+			protocol.sendPacket(player, explosionPacket);
+			
+		} catch (Exception e) {
+			throw new RuntimeException("Cannot send packet.", e);
+		}
+	}
 }

Examples/TinyProtocol/src/main/java/com/comphenix/tinyprotocol/TinyProtocol.java

@@ -1,27 +1,41 @@
 package com.comphenix.tinyprotocol;
 
 import java.lang.reflect.Field;
-import javax.annotation.Nullable;
+import java.lang.reflect.Method;
+import java.util.Arrays;
+import java.util.Map;
+import java.util.logging.Level;
 
-import net.minecraft.server.v1_7_R1.NetworkManager;
+// These are not versioned, but they require CraftBukkit
 import net.minecraft.util.io.netty.channel.Channel;
 import net.minecraft.util.io.netty.channel.ChannelDuplexHandler;
 import net.minecraft.util.io.netty.channel.ChannelHandlerContext;
 import net.minecraft.util.io.netty.channel.ChannelPromise;
 
-import org.bukkit.craftbukkit.v1_7_R1.entity.CraftPlayer;
-
+import org.bukkit.Bukkit;
 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.PlayerJoinEvent;
 import org.bukkit.event.server.PluginDisableEvent;
 import org.bukkit.plugin.Plugin;
 
-import com.google.common.base.Function;
+import com.google.common.collect.MapMaker;
 
 public abstract class TinyProtocol implements Listener {
-	private static Function<Object, Channel> CHANNEL_ACCESSOR = getFieldAccessor(NetworkManager.class, Channel.class, 0);
+	// Deduce the net.minecraft.server.v* package
+	private static String OBC_PREFIX = Bukkit.getServer().getClass().getPackage().getName();
+	private static String NMS_PREFIX = OBC_PREFIX.replace("org.bukkit.craftbukkit", "net.minecraft.server");
+	
+	// Used in order to lookup a channel
+	private MethodInvoker getPlayerHandle = getMethod(getCraftBukkitClass("entity.CraftPlayer"), "getHandle");
+	private FieldAccessor<Object> getConnection = getField(getMinecraftClass("EntityPlayer"), "playerConnection", Object.class);
+	private FieldAccessor<Object> getManager = getField(getMinecraftClass("PlayerConnection"), "networkManager", Object.class);
+	private FieldAccessor<Channel> getChannel = getField(getMinecraftClass("NetworkManager"), Channel.class, 0);
+	
+	// Speedup channel lookup
+	private Map<Player, Channel> channelLookup = new MapMaker().weakKeys().makeMap();
 	
 	private boolean closed;
 	private Plugin plugin;
@@ -36,31 +50,32 @@ public abstract class TinyProtocol implements Listener {
 		}
 	}
 	
-	@EventHandler
-	public final void onPlayerJoin(PlayerJoinEvent e) {
-		if (closed) 
-			return;
-		injectPlayer(e.getPlayer());
-	}
-
 	private void injectPlayer(final Player player) {
 		// Inject our packet interceptor
 		getChannel(player).pipeline().addBefore("packet_handler", getHandlerName(), new ChannelDuplexHandler() {
 			@Override
 			public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
-				Object result = onPacketInAsync(player, msg);
+				try {
+					msg = onPacketInAsync(player, msg);
+				} catch (Exception e) {
+					plugin.getLogger().log(Level.SEVERE, "Error in onPacketInAsync().", e);
+				}
 				
-				if (result != null) {
-					super.channelRead(ctx, result);
+				if (msg != null) {
+					super.channelRead(ctx, msg);
 				}
 			}
 			
 			@Override
 			public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
-				Object result = onPacketOutAsync(player, msg);
+				try {
+					msg = onPacketOutAsync(player, msg);
+				} catch (Exception e) {
+					plugin.getLogger().log(Level.SEVERE, "Error in onPacketOutAsync().", e);
+				}
 				
-				if (result != null) {
-					super.write(ctx, result, promise);
+				if (msg != null) {
+					super.write(ctx, msg, promise);
 				}
 			}
 		});
@@ -70,6 +85,13 @@ public abstract class TinyProtocol implements Listener {
 		return "tiny-" + plugin.getName();
 	}
 
+	@EventHandler(priority = EventPriority.LOWEST)
+	public final void onPlayerJoin(PlayerJoinEvent e) {
+		if (closed) 
+			return;
+		injectPlayer(e.getPlayer());
+	}
+	
 	@EventHandler
 	public final void onPluginDisable(PluginDisableEvent e) {
 		if (e.getPlugin().equals(plugin)) {
@@ -77,9 +99,40 @@ public abstract class TinyProtocol implements Listener {
 		}
 	}
 	
+	/**
+	 * Send a packet to a particular player.
+	 * @param player - the destination player.
+	 * @param packet - the packet to send.
+	 */
+	public void sendPacket(Player player, Object packet) {
+		getChannel(player).pipeline().writeAndFlush(packet);
+	}
+	
+	/**
+	 * Pretend that a given packet has been received from a player.
+	 * @param player - the player that sent the packet.
+	 * @param packet - the packet that will be received by the server.
+	 */
+	public void receivePacket(Player player, Object packet) {
+		getChannel(player).pipeline().context("encoder").fireChannelRead(packet);
+	}
+	
+	/**
+	 * Retrieve the Netty channel associated with a player. This is cached.
+	 * @param player - the player.
+	 * @return The Netty channel.
+	 */
 	private Channel getChannel(Player player) {
-		NetworkManager manager = ((CraftPlayer) player.getPlayer()).getHandle().playerConnection.networkManager;
-		return CHANNEL_ACCESSOR.apply(manager);
+		Channel channel = channelLookup.get(player);
+		
+		// Lookup channel again
+		if (channel == null) {
+			Object connection = getConnection.get(getPlayerHandle.invoke(player));
+			Object manager = getManager.get(connection);
+			
+			channelLookup.put(player, channel = getChannel.get(manager));
+		}
+		return channel;
 	}
 	
 	/**
@@ -105,39 +158,8 @@ public abstract class TinyProtocol implements Listener {
 	}
 	
 	/**
-	 * Retrieve a field accessor for a specific field type and index.
-	 * @param target - the target type.
-	 * @param fieldType - the field type.
-	 * @param index - the index.
-	 * @return The field accessor.
+	 * Cease listening for packets. This is called automatically when your plugin is disabled.
 	 */
-	public static <T> Function<Object, T> getFieldAccessor(Class<?> target, Class<T> fieldType, int index) {
-		for (Field field : target.getDeclaredFields()) {
-			if (fieldType.isAssignableFrom(field.getType()) && index-- <= 0) {
-				final Field targetField = field;
-				field.setAccessible(true);
-				
-				// A function for retrieving a specific field value
-				return new Function<Object, T>() {
-					@SuppressWarnings("unchecked")
-					@Override
-					public T apply(@Nullable Object instance) {
-						try {
-							return (T) targetField.get(instance);
-						} catch (IllegalAccessException e) {
-							throw new RuntimeException("Cannot access reflection.", e);
-						}
-					}
-				};
-			}
-		}
-		
-		// Search in parent classes
-		if (target.getSuperclass() != null)
-			return getFieldAccessor(target.getSuperclass(), fieldType, index);
-		throw new IllegalArgumentException("Cannot find field with type " + fieldType);
-	}
-	
 	public final void close() {
 		if (!closed) {
 			closed = true;
@@ -148,4 +170,179 @@ public abstract class TinyProtocol implements Listener {
 			}
 		}
 	}
+	
+	/**
+	 * Retrieve a field accessor for a specific field type and name.
+	 * @param target - the target type.
+	 * @param name - the name of the field, or NULL to ignore.
+	 * @param fieldType - a compatible field type.
+	 * @return The field accessor.
+	 */
+	public static <T> FieldAccessor<T> getField(Class<?> target, String name, Class<T> fieldType) {
+		return getField(target, name, fieldType, 0);
+	}
+	
+	/**
+	 * Retrieve a field accessor for a specific field type and name.
+	 * @param target - the target type.
+	 * @param fieldType - a compatible field type.
+	 * @param index - the number of compatible fields to skip.
+	 * @return The field accessor.
+	 */
+	public static <T> FieldAccessor<T> getField(Class<?> target, Class<T> fieldType, int index) {
+		return getField(target, null, fieldType, index);
+	}
+	
+	/**
+	 * Retrieve a field accessor for a specific field type and name.
+	 * @param nmsTargetClass - the net.minecraft.server class name.
+	 * @param fieldType - a compatible field type.
+	 * @param index - the number of compatible fields to skip.
+	 * @return The field accessor.
+	 */
+	public static <T> FieldAccessor<T> getField(String nmsTargetClass, Class<T> fieldType, int index) {
+		return getField(getMinecraftClass(nmsTargetClass), fieldType, index);
+	}
+	
+	// Common method
+	private static <T> FieldAccessor<T> getField(Class<?> target, String name, Class<T> fieldType, int index) {
+		for (final Field field : target.getDeclaredFields()) {
+			if ((name == null || field.getName().equals(name)) && 
+					fieldType.isAssignableFrom(field.getType()) && index-- <= 0) {
+				field.setAccessible(true);
+				
+				// A function for retrieving a specific field value
+				return new FieldAccessor<T>() {
+					@SuppressWarnings("unchecked")
+					@Override
+					public T get(Object target) {
+						try {
+							return (T) field.get(target);
+						} catch (IllegalAccessException e) {
+							throw new RuntimeException("Cannot access reflection.", e);
+						}
+					}
+					
+					@Override
+					public void set(Object target, Object value) {
+						try {
+							field.set(target, value);
+						} catch (IllegalAccessException e) {
+							throw new RuntimeException("Cannot access reflection.", e);
+						}
+					}
+					
+					@Override
+					public boolean hasField(Object target) {
+						// target instanceof DeclaringClass
+						return field.getDeclaringClass().isAssignableFrom(target.getClass());
+					}
+				};
+			}
+		}
+		
+		// Search in parent classes
+		if (target.getSuperclass() != null)
+			return getField(target.getSuperclass(), name, fieldType, index);
+		throw new IllegalArgumentException("Cannot find field with type " + fieldType);
+	}
+	
+    /**
+     * Search for the first publically and privately defined method of the given name and parameter count.
+     * @param clazz - a class to start with.
+     * @param methodName - the method name, or NULL to skip.
+     * @param params - the expected parameters.
+     * @return An object that invokes this specific method.
+     * @throws IllegalStateException If we cannot find this method.
+     */
+    public static MethodInvoker getMethod(Class<?> clazz, String methodName, Class<?>... params) {
+        for (final Method method : clazz.getDeclaredMethods()) {
+            if ((methodName == null || method.getName().equals(methodName)) &&
+                 Arrays.equals(method.getParameterTypes(), params)) {
+                
+                method.setAccessible(true);
+                return new MethodInvoker() {
+                	@Override
+                	public Object invoke(Object target, Object... arguments) {
+                		try {
+							return method.invoke(target, arguments);
+						} catch (Exception e) {
+							throw new RuntimeException("Cannot invoke method " + method, e);
+						}
+                	}
+                };
+            }
+        }
+        // Search in every superclass
+        if (clazz.getSuperclass() != null)
+            return getMethod(clazz.getSuperclass(), methodName, params);
+        throw new IllegalStateException(String.format(
+            "Unable to find method %s (%s).", methodName, Arrays.asList(params)));
+    }
+	
+	/**
+	 * Retrieve a class in the net.minecraft.server.VERSION.* package.
+	 * @param name - the name of the class, excluding the package.
+	 * @throws IllegalArgumentException If the class doesn't exist.
+	 */
+	public static Class<?> getMinecraftClass(String name) {
+		try {
+			return Class.forName(NMS_PREFIX + "." + name);
+		} catch (ClassNotFoundException e) {
+			throw new IllegalArgumentException("Cannot find nms." + name, e);
+		}
+	}
+	
+	/**
+	 * Retrieve a class in the org.bukkit.craftbukkit.VERSION.* package.
+	 * @param name - the name of the class, excluding the package.
+	 * @throws IllegalArgumentException If the class doesn't exist.
+	 */
+	public static Class<?> getCraftBukkitClass(String name) {
+		try {
+			return Class.forName(OBC_PREFIX + "." + name);
+		} catch (ClassNotFoundException e) {
+			throw new IllegalArgumentException("Cannot find obc." + name, e);
+		}
+	}
+	
+	/**
+	 * An interface for invoking a specific method. 
+	 */
+	public interface MethodInvoker {
+		/**
+		 * Invoke a method on a specific target object.
+		 * @param target - the target object, or NULL for a static method.
+		 * @param arguments - the arguments to pass to the method.
+		 * @return The return value, or NULL if is void.
+		 */
+		public Object invoke(Object target, Object... arguments); 
+	}
+	
+	/**
+	 * An interface for retrieving the field content.
+	 * @param <T> - field type.
+	 */
+	public interface FieldAccessor<T> {
+		/**
+		 * Retrieve the content of a field.
+		 * @param target - the target object, or NULL for a static field.
+		 * @return The value of the field.
+		 */
+		public T get(Object target);
+		
+		/**
+		 * Set the content of a field.
+		 * @param target - the target object, or NULL for a static field.
+		 * @param value - the new value of the field.
+		 */
+		public void set(Object target, Object value);
+		
+		/**
+		 * Determine if the given object has this field.
+		 * @param target - the object to test.
+		 * @return TRUE if it does, FALSE otherwise.
+		 */
+		public boolean hasField(Object target);
+	}
 }