Citizens2/main/src/main/java/net/citizensnpcs/ProtocolLibListener.java

package net.citizensnpcs;

import java.util.Set;

import org.bukkit.entity.Entity;

import com.comphenix.protocol.PacketType;
import com.comphenix.protocol.PacketType.Play.Server;
import com.comphenix.protocol.ProtocolLibrary;
import com.comphenix.protocol.ProtocolManager;
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.reflect.FieldAccessException;
import com.comphenix.protocol.reflect.StructureModifier;
import com.comphenix.protocol.utility.MinecraftReflection;
import com.comphenix.protocol.wrappers.EnumWrappers;

import net.citizensnpcs.api.npc.NPC;
import net.citizensnpcs.api.util.Messaging;
import net.citizensnpcs.npc.ai.NPCHolder;
import net.citizensnpcs.trait.RotationTrait;
import net.citizensnpcs.trait.RotationTrait.PacketRotationSession;

public class ProtocolLibListener {
    private final Class<?> flagsClass;
    private final ProtocolManager manager;
    private final Citizens plugin;

    public ProtocolLibListener(Citizens plugin) {
        this.plugin = plugin;
        this.manager = ProtocolLibrary.getProtocolManager();
        flagsClass = MinecraftReflection.getMinecraftClass("EnumPlayerTeleportFlags",
                "PacketPlayOutPosition$EnumPlayerTeleportFlags",
                "network.protocol.game.PacketPlayOutPosition$EnumPlayerTeleportFlags");

        manager.addPacketListener(
                new PacketAdapter(plugin, ListenerPriority.MONITOR, Server.ENTITY_HEAD_ROTATION, Server.ENTITY_LOOK) {
                    @Override
                    public void onPacketSending(PacketEvent event) {
                        NPC npc = getNPCFromPacket(event);
                        if (npc == null)
                            return;

                        RotationTrait trait = npc.getTraitNullable(RotationTrait.class);
                        if (trait == null)
                            return;

                        PacketRotationSession session = trait.getPacketSession(event.getPlayer());
                        if (session == null || !session.isActive())
                            return;

                        PacketContainer packet = event.getPacket();
                        PacketType type = event.getPacketType();
                        if (type == Server.ENTITY_HEAD_ROTATION) {
                            packet.getBytes().write(0, degToByte(session.getHeadYaw()));
                        } else if (type == Server.ENTITY_LOOK) {
                            packet.getBytes().write(0, degToByte(session.getBodyYaw()));
                            packet.getBytes().write(1, degToByte(session.getPitch()));
                        } else if (type == Server.ENTITY_MOVE_LOOK || type == Server.REL_ENTITY_MOVE_LOOK) {
                            packet.getBytes().write(0, degToByte(session.getBodyYaw()));
                            packet.getBytes().write(1, degToByte(session.getPitch()));
                        } else if (type == Server.POSITION) {
                            Set<PlayerTeleportFlag> rel = getFlagsModifier(packet).read(0);
                            rel.remove(PlayerTeleportFlag.ZYAW);
                            rel.remove(PlayerTeleportFlag.ZPITCH);
                            getFlagsModifier(packet).write(0, rel);
                            packet.getFloat().write(0, session.getBodyYaw());
                            packet.getFloat().write(1, session.getPitch());
                        }
                    }
                });
    }

    private StructureModifier<Set<PlayerTeleportFlag>> getFlagsModifier(PacketContainer handle) {
        return handle.getSets(EnumWrappers.getGenericConverter(flagsClass, PlayerTeleportFlag.class));
    }

    private NPC getNPCFromPacket(PacketEvent event) {
        PacketContainer packet = event.getPacket();
        Entity entity = null;
        try {
            Integer id = packet.getIntegers().readSafely(0);
            if (id == null)
                return null;
            entity = manager.getEntityFromID(event.getPlayer().getWorld(), id);
        } catch (FieldAccessException | IllegalArgumentException ex) {
            if (!LOGGED_ERROR) {
                Messaging.severe(
                        "Error retrieving entity from ID: ProtocolLib error? Suppressing further exceptions unless debugging.");
                ex.printStackTrace();
                LOGGED_ERROR = true;
            } else if (Messaging.isDebugging()) {
                ex.printStackTrace();
            }
            return null;
        }

        return entity instanceof NPCHolder ? ((NPCHolder) entity).getNPC() : null;
    }

    public enum PlayerTeleportFlag {
        X,
        Y,
        Z,
        ZPITCH,
        ZYAW,
    }

    private static byte degToByte(float in) {
        return (byte) (in * 256.0F / 360.0F);
    }

    private static boolean LOGGED_ERROR = false;
}