ProtocolLib/src/main/java/com/comphenix/protocol/injector/PacketConstructor.java

/*
 *  ProtocolLib - Bukkit server library that allows access to the Minecraft protocol.
 *  Copyright (C) 2012 Kristian S. Stangeland
 *
 *  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 2 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, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
 *  02111-1307 USA
 */

package com.comphenix.protocol.injector;

import com.comphenix.protocol.PacketType;
import com.comphenix.protocol.error.RethrowErrorReporter;
import com.comphenix.protocol.events.PacketContainer;
import com.comphenix.protocol.injector.packet.PacketRegistry;
import com.comphenix.protocol.reflect.FieldAccessException;
import com.comphenix.protocol.wrappers.BukkitConverters;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import com.google.common.primitives.Primitives;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.List;

/**
 * A packet constructor that uses an internal Minecraft.
 *
 * @author Kristian
 */
public class PacketConstructor {

    /**
     * A packet constructor that automatically converts Bukkit types to their NMS conterpart.
     * <p>
     * Remember to call withPacket().
     */
    public static final PacketConstructor DEFAULT = new PacketConstructor(null);

    // The constructor method that's actually responsible for creating the packet
    private final Constructor<?> constructorMethod;
    // Used to unwrap Bukkit objects
    private final List<Unwrapper> unwrappers;

    // The packet ID
    private PacketType type;
    // Parameters that need to be unwrapped
    private Unwrapper[] paramUnwrapper;

    private PacketConstructor(Constructor<?> constructorMethod) {
        this.constructorMethod = constructorMethod;
        this.unwrappers = Lists.newArrayList(new BukkitUnwrapper(new RethrowErrorReporter()));
        this.unwrappers.addAll(BukkitConverters.getUnwrappers());
    }

    private PacketConstructor(PacketType type, Constructor<?> constructorMethod, List<Unwrapper> unwrappers,
            Unwrapper[] paramUnwrapper) {
        this.type = type;
        this.constructorMethod = constructorMethod;
        this.unwrappers = unwrappers;
        this.paramUnwrapper = paramUnwrapper;
    }

    // Determine if a method with the types 'params' can be called with 'types'
    private static boolean isCompatible(Class<?>[] types, Class<?>[] params) {

        // Determine if the types are similar
        if (params.length == types.length) {
            for (int i = 0; i < params.length; i++) {
                Class<?> inputType = types[i];
                Class<?> paramType = params[i];

                // The input type is always wrapped
                if (!inputType.isPrimitive() && paramType.isPrimitive()) {
                    // Wrap it
                    paramType = Primitives.wrap(paramType);
                }

                // Compare assignability
                if (!paramType.isAssignableFrom(inputType)) {
                    return false;
                }
            }

            return true;
        }

        // Parameter count must match
        return false;
    }

    /**
     * Retrieve the class of an object, or just the class if it already is a class object.
     *
     * @param obj - the object.
     * @return The class of an object.
     */
    public static Class<?> getClass(Object obj) {
        if (obj instanceof Class) {
            return (Class<?>) obj;
        }
        return obj.getClass();
    }

    public ImmutableList<Unwrapper> getUnwrappers() {
        return ImmutableList.copyOf(unwrappers);
    }

    /**
     * Retrieve the id of the packets this constructor creates.
     * <p>
     * Deprecated: Use {@link #getType()} instead.
     *
     * @return The ID of the packets this constructor will create.
     */
    @Deprecated
    public int getPacketID() {
        return type.getCurrentId();
    }

    /**
     * Retrieve the type of the packets this constructor creates.
     *
     * @return The type of the created packets.
     */
    public PacketType getType() {
        return type;
    }

    /**
     * Return a copy of the current constructor with a different list of unwrappers.
     *
     * @param unwrappers - list of unwrappers that convert Bukkit wrappers into the equivalent NMS classes.
     * @return A constructor with a different set of unwrappers.
     */
    public PacketConstructor withUnwrappers(List<Unwrapper> unwrappers) {
        return new PacketConstructor(type, constructorMethod, unwrappers, paramUnwrapper);
    }

    /**
     * Create a packet constructor that creates packets using the given types.
     * <p>
     * Note that if you pass a Class as a value, it will use its type directly.
     *
     * @param type   - the type of the packet to create.
     * @param values - the values that will match each parameter in the desired constructor.
     * @return A packet constructor with these types.
     * @throws IllegalArgumentException If no packet constructor could be created with these types.
     */
    public PacketConstructor withPacket(PacketType type, Object[] values) {
        Class<?>[] types = new Class<?>[values.length];
        Throwable lastException = null;
        Unwrapper[] paramUnwrapper = new Unwrapper[values.length];

        for (int i = 0; i < types.length; i++) {
            // Default type
            if (values[i] != null) {
                types[i] = PacketConstructor.getClass(values[i]);

                for (Unwrapper unwrapper : unwrappers) {
                    Object result = null;

                    try {
                        result = unwrapper.unwrapItem(values[i]);
                    } catch (OutOfMemoryError e) {
                        throw e;
                    } catch (ThreadDeath e) {
                        throw e;
                    } catch (Throwable e) {
                        lastException = e;
                    }

                    // Update type we're searching for
                    if (result != null) {
                        types[i] = PacketConstructor.getClass(result);
                        paramUnwrapper[i] = unwrapper;
                        break;
                    }
                }

            } else {
                // Try it
                types[i] = Object.class;
            }
        }

        Class<?> packetClass = PacketRegistry.getPacketClassFromType(type);

        // Find the correct constructor
        for (Constructor<?> constructor : packetClass.getConstructors()) {
            Class<?>[] params = constructor.getParameterTypes();

            if (isCompatible(types, params)) {
                // Right, we've found our type
                return new PacketConstructor(type, constructor, unwrappers, paramUnwrapper);
            }
        }
        throw new IllegalArgumentException("No suitable constructor could be found.", lastException);
    }

    /**
     * Construct a packet using the special builtin Minecraft constructors.
     *
     * @param values - values containing Bukkit wrapped items to pass to Minecraft.
     * @return The created packet.
     * @throws FieldAccessException     Failure due to a security limitation.
     * @throws IllegalArgumentException Arguments doesn't match the constructor.
     * @throws RuntimeException         Minecraft threw an exception.
     */
    public PacketContainer createPacket(Object... values) throws FieldAccessException {
        try {
            // Convert types that needs to be converted
            for (int i = 0; i < values.length; i++) {
                if (paramUnwrapper[i] != null) {
                    values[i] = paramUnwrapper[i].unwrapItem(values[i]);
                }
            }

            Object nmsPacket = constructorMethod.newInstance(values);
            return new PacketContainer(type, nmsPacket);

        } catch (IllegalArgumentException e) {
            throw e;
        } catch (InstantiationException e) {
            throw new FieldAccessException("Cannot construct an abstract packet.", e);
        } catch (IllegalAccessException e) {
            throw new FieldAccessException("Cannot construct packet due to a security limitation.", e);
        } catch (InvocationTargetException e) {
            throw new RuntimeException("Minecraft error.", e);
        }
    }

    /**
     * Represents a unwrapper for a constructor parameter.
     *
     * @author Kristian
     */
    public static interface Unwrapper {

        /**
         * Convert the given wrapped object to the equivalent net.minecraft.server object.
         * <p>
         * Note that we may pass in a class instead of object - in that case, the unwrapper should return the equivalent NMS
         * class.
         *
         * @param wrappedObject - wrapped object or class.
         * @return The equivalent net.minecraft.server object or class.
         */
        public Object unwrapItem(Object wrappedObject);
    }
}