ProtocolLib/Readme.md

ProtocolLib 
===========

Certain tasks are impossible to perform with the standard Bukkit API, and may require 
working with and even modify Minecraft directly. A common technique is to modify incoming 
and outgoing [packets](http://www.wiki.vg/Protocol), or inject custom packets into the
stream. This is quite cumbersome to do, however, and most implementations will break 
as soon as a new version of Minecraft has been released, mostly due to obfuscation.

Critically, different plugins that use this approach may _hook_ into the same classes, 
with unpredictable outcomes. More than often this causes plugins to crash, but it may also 
lead to more subtle bugs.


### Resources

* [JavaDoc](http://aadnk.github.com/ProtocolLib/Javadoc/) 


A new API
---------

__ProtocolLib__ attempts to solve this problem by providing a event API, much like Bukkit, 
that allow plugins to monitor, modify or cancel packets sent and received. But more importantly, 
the API also hides all the gritty, obfuscated classes with a simple index based read/write system. 
You no longer have to reference CraftBukkit!


### Using ProtocolLib

To use the library, first add ProtocolLib.jar to your Java build path. Then, add ProtocolLib
as a dependency (or soft-dependency, if you can live without it) to your plugin.yml file:

    depends: [ProtocolLib]

Then get a reference to ProtocolManager in onLoad() and you're good to go.

    private ProtocolManager protocolManager;
    
    public void onLoad() {
        protocolManager = ProtocolLibrary.getProtocolManager();
    }

To listen for packets sent by the server to a client, add a server-side listener:

    // Disable all sound effects
    protocolManager.addPacketListener(
      new PacketAdapter(this, ConnectionSide.SERVER_SIDE, ListenerPriority.NORMAL, 0x3E) {
        @Override
        public void onPacketSending(PacketEvent event) {
            // Item packets
            switch (event.getPacketID()) {
            case 0x3E: // Sound effect
                event.setCancelled(true);
                break;
            }
        }
    });


It's also possible to read and modify the content of these packets. For instance, you can create a global
censor by listening for Packet3Chat events:

    // Censor
    protocolManager.addPacketListener(
      new PacketAdapter(this, ConnectionSide.CLIENT_SIDE, ListenerPriority.NORMAL, 0x03) {
        @Override
        public void onPacketReceiving(PacketEvent event) {
            if (event.getPacketID() == 0x03) {
                try {
                    PacketContainer packet = event.getPacket();
                    String message = packet.getSpecificModifier(String.class).read(0);
                    
                    if (message.contains("shit") || message.contains("damn")) {
                        event.setCancelled(true);
                        event.getPlayer().sendMessage("Bad manners!");
                    }
                    		
                } catch (FieldAccessException e) {
                    getLogger().log(Level.SEVERE, "Couldn't access field.", e);
                }
            }
        }
    });


### Sending packets

Normally, you might have to do something ugly like the following:

    Packet60Explosion fakeExplosion = new Packet60Explosion();
    	
    fakeExplosion.a = player.getLocation().getX();
    fakeExplosion.b = player.getLocation().getY();
    fakeExplosion.c = player.getLocation().getZ();
    fakeExplosion.d = 3.0F;
    fakeExplosion.e = new ArrayList<Object>();

    ((CraftPlayer) player).getHandle().netServerHandler.sendPacket(fakeExplosion);

But with ProtocolLib, you can turn that into something more manageable. Notice that 
you don't have to create an ArrayList this version:

    PacketContainer fakeExplosion = protocolManager.createPacket(60);
    
    fakeExplosion.getSpecificModifier(double.class).
        write(0, player.getLocation().getX()).
        write(1, player.getLocation().getY()).
        write(2, player.getLocation().getZ());
    fakeExplosion.getSpecificModifier(float.class).
        write(0, 3.0F);
    
    protocolManager.sendServerPacket(player, fakeExplosion);


Compatiblity
------------

One of the main goals of this project was to achive maximum compatibility with craftBukkit. And the end
result is quite flexible - in tests I successfully ran an unmodified ProtocolLib on CraftBukkit 1.8.0, and
it should be resiliant against future changes. It's likely that I won't have to update ProtocolLib for
anything but bug and performance fixes. 

How is this possible? It all comes down to reflection in the end. Essentially, no name is hard coded - 
every field, method and class is deduced by looking at field types, package names or parameter
types. It's remarkably consistent across different versions.


### Incompatiblity

The following plugins (to be expanded) are not compatible with ProtocolLib: