API to modify some advanced Minecraft server list data.

ServerListAPI.java

/*
 * ServerListAPI - API to modify some advanced Minecraft server list data
 * Copyright (C) 2013 Minecrell
 * You are not allowed to use this API to fake online players on a production server.
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
import java.net.InetAddress;
import java.util.HashSet;
import java.util.Set;

import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.server.ServerListPingEvent;
import org.bukkit.plugin.Plugin;

import com.comphenix.protocol.Packets;
import com.comphenix.protocol.ProtocolLibrary;
import com.comphenix.protocol.events.ConnectionSide;
import com.comphenix.protocol.events.ListenerPriority;
import com.comphenix.protocol.events.PacketAdapter;
import com.comphenix.protocol.events.PacketContainer;
import com.comphenix.protocol.events.PacketEvent;
import com.comphenix.protocol.injector.GamePhase;
import com.google.common.base.Joiner;
import com.google.common.base.Splitter;
import com.google.common.collect.Iterables;

/**
 * API to modify some advanced Minecraft server list data.
 * If you want to use it with ProtocolLib you have to add ProtocolLib to (soft)depend in your plugin.yml file.
 * @author Minecrell
 */
public class ServerListAPI {
	private final Plugin plugin;

	private Integer onlinePlayers, maxPlayers, snapshotVersion;
	private String motd, serverVersion;
	private boolean hideServerList, lockBannedIPs;
	private final Set<InetAddress> lockedIPs = new HashSet<InetAddress>();

	/**
	 * Creates a new instance of the API.
	 * @param plugin Plugin instance of the Plugin using this API.
	 * @see Plugin
	 */
	public ServerListAPI(final Plugin plugin) {
		this.plugin = plugin;
		plugin.getServer().getPluginManager().registerEvents(new ServerListListener(), plugin);

		final Plugin pLib = plugin.getServer().getPluginManager().getPlugin("ProtocolLib");
		if (pLib != null && (pLib instanceof com.comphenix.protocol.ProtocolLibrary)) {
			new ServerListPacketAdapter();
		}
	}

	/**
	 * Gets the plugin instance of this API.
	 * @return Plugin instance
	 * @see Plugin
	 */
	public Plugin getPlugin() {
		return plugin;
	}

	/**
	 * Resets all changed values on this API.
	 * @return This API object.
	 */
	public ServerListAPI resetData() {
		this.setOnlinePlayers(null);
		this.setMaxPlayers(null);
		this.setSnapshotVersion(null);
		this.setServerVersion(null);
		this.setMotd(null);
		return this;
	}

	/**
	 * Gets the changed online player count.
	 * @return Online player count, or null if not changed.
	 */
	public Integer getOnlinePlayers() {
		return onlinePlayers;
	}

	/**
	 * Sets the online player count for the server.
	 * @param onlinePlayers New online player count or null to reset it.
	 * @return This API object.
	 */
	public ServerListAPI setOnlinePlayers(final Integer onlinePlayers) {
		this.onlinePlayers = onlinePlayers;
		return this;
	}

	/**
	 * Gets the changed max player count.
	 * @return Max player count, or null if not changed.
	 */
	public Integer getMaxPlayers() {
		return maxPlayers;
	}

	/**
	 * Sets the max player count for the server.
	 * @param maxPlayers New max player count or null to reset it.
	 * @return This API object.
	 */
	public ServerListAPI setMaxPlayers(final Integer maxPlayers) {
		this.maxPlayers = maxPlayers;
		return this;
	}

	/**
	 * Gets the changed snapshot version. This should only be changed if you
	 * want to display a custom server version. Remember, nobody can join the
	 * server without a mod or direct connect!
	 * @return Snapshot version or null if not changed.
	 */
	public Integer getSnapshotVersion() {
		return snapshotVersion;
	}

	/**
	 * Sets the snapshot version for the server.
	 * @param snapshotVersion New snapshot version or null to reset it.
	 * @see #getSnapshotVersion()
	 * @return This API object.
	 */
	public ServerListAPI setSnapshotVersion(final Integer snapshotVersion) {
		if (snapshotVersion != null && snapshotVersion < 0)
			throw new IllegalArgumentException("Snapshot version can't be smaller than null.");
		this.snapshotVersion = snapshotVersion;
		return this;
	}

	/**
	 * Gets the changed server version string. The server version is displayed
	 * next to the server ping (or above the player count) when you look at your
	 * server list with a newer or older Minecraft version.
	 * @see #getSnapshotVersion()
	 * @return Server version or null if not changed.
	 */
	public String getServerVersion() {
		return serverVersion;
	}

	/**
	 * Sets the server version for the server. The server version can contain
	 * colors.
	 * @param version Server version string or null to reset it.
	 * @see #getServerVersion()
	 * @return This API object.
	 */
	public ServerListAPI setServerVersion(final String version) {
		serverVersion = version;
		return this;
	}

	/**
	 * Sets the server version for the server. The server version can contain
	 * colors.
	 * @param version Server version string or null to reset it.
	 * @param changeSnapshotVersion If the snapshot version should be set automatically.
	 * @see #setServerVersion(String)
	 * @return This API object.
	 */
	public ServerListAPI setServerVersion(final String version, final boolean changeSnapshotVersion) {
		this.setServerVersion(version);
		if (changeSnapshotVersion)
			snapshotVersion = 255;
		return this;
	}

	/**
	 * Gets the changed <i>Message of the day</i> (MOTD).
	 * @return Motd or null if not changed.
	 */
	public String getMotd() {
		return motd;
	}

	/**
	 * Sets the Motd for the server.
	 * @param motd Motd or null to reset it.
	 * @see #getMotd()
	 * @return This API object.
	 */
	public ServerListAPI setMotd(final String motd) {
		this.motd = motd;
		return this;
	}

	/**
	 * If this is true, the server will show as <i>Communication Error</i> in the server list for everyone.
	 * @return Hide server list entry for everyone?
	 */
	public boolean hideServerList() {
		return hideServerList;
	}

	/**
	 * Sets whether the server should show as <i>Communication Error</i> in the server list for everyone.
	 * @param hideServerList Hide server list entry for everyone?
	 * @return This API object.
	 */
	public ServerListAPI setHideServerList(final boolean hideServerList) {
		this.hideServerList = hideServerList;
		return this;
	}

	/**
	 * If this is true, the API will automatically hide the server status in the server list for every banned IP.
	 * @return Lock banned IPs?
	 */
	public boolean lockBannedIPs() {
		return lockBannedIPs;
	}

	/**
	 * Sets whether the API should automatically hide the server status in the server list for every banned IP.
	 * @param lockBannedIPs Hide server status for banned IPs?
	 * @return This API object.
	 */
	public ServerListAPI setLockBannedIPs(final boolean lockBannedIPs) {
		this.lockBannedIPs = lockBannedIPs;
		return this;
	}

	/**
	 * Lock an IP, so it won't see the server status in the server list anymore. (Server will show as <i>Communication Error</i>)
	 * @param address IP address of the player or service
	 * @return This API object.
	 */
	public ServerListAPI lockIP(final InetAddress address) {
		lockedIPs.add(address);
		return this;
	}

	/**
	 * Unlock an IP, so it will see the server status in the server list again.
	 * @param address IP address of the player or service
	 * @return This API object.
	 */
	public ServerListAPI unlockIP(final InetAddress address) {
		lockedIPs.remove(address);
		return this;
	}

	/**
	 * Returns the set containing all locked IPs for the server list.
	 * @return Set with all locked IPs
	 */
	public Set<InetAddress> getLockedIPs() {
		return lockedIPs;
	}

	/**
	 * Resets all locked IPs. They will all see the server status in the server list again.
	 * @return This API object.
	 */
	public ServerListAPI resetLockedIPs() {
		lockedIPs.clear();
		return this;
	}

	private class ServerListListener implements Listener {

		@EventHandler
		public void onServerListPing(final ServerListPingEvent event) {
			if (maxPlayers != null) event.setMaxPlayers(maxPlayers);
			if (motd != null) event.setMotd(motd);
		}
	}

	private class ServerListPacketAdapter extends PacketAdapter {
		private static final char packetSeperator = '\0';

		private final Splitter packetSplitter = Splitter.on(packetSeperator);
		private final Joiner packetJoiner = Joiner.on(packetSeperator);

		private ServerListPacketAdapter() {
			super(ServerListAPI.this.plugin, ConnectionSide.SERVER_SIDE, ListenerPriority.NORMAL, GamePhase.LOGIN, Packets.Server.KICK_DISCONNECT);
			ProtocolLibrary.getProtocolManager().addPacketListener(this);
		}

		@Override
		public void onPacketSending(final PacketEvent event) {
			if (event.getPacketID() != Packets.Server.KICK_DISCONNECT) return;

			final PacketContainer packet = event.getPacket();
			final String[] data = Iterables.toArray(packetSplitter.split(packet.getStrings().read(0)), String.class);
			if (data.length != 6) return;

			final InetAddress ip = event.getPlayer().getAddress().getAddress();

			if (hideServerList || (lockBannedIPs && plugin.getServer().getIPBans().contains(ip.getHostAddress())) || lockedIPs.contains(ip)) {
				packet.getStrings().write(0, null); return;
			}

			if (onlinePlayers != null) data[4] = onlinePlayers.toString();

			if (snapshotVersion != null) data[1] = snapshotVersion.toString();
			if (serverVersion != null) data[2] = serverVersion;

			packet.getStrings().write(0, packetJoiner.join(data));
		}
	}
}