ProtocolLib/src/main/java/com/comphenix/protocol/wrappers/BlockPosition.java

/**
 *  ProtocolLib - Bukkit server library that allows access to the Minecraft protocol.
 *  Copyright (C) 2015 dmulloy2
 *
 *  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.wrappers;

import com.comphenix.protocol.reflect.EquivalentConverter;
import com.comphenix.protocol.reflect.FieldAccessException;
import com.comphenix.protocol.reflect.StructureModifier;
import com.comphenix.protocol.utility.MinecraftReflection;
import com.google.common.base.Objects;
import org.bukkit.Location;
import org.bukkit.World;
import org.bukkit.util.Vector;

import java.lang.reflect.Constructor;

/**
 * Copies a immutable net.minecraft.server.BlockPosition, which represents a integer 3D vector.
 * 
 * @author dmulloy2
 */
public class BlockPosition {
    
    /**
     * Represents the null (0, 0, 0) origin.
     */
    public static BlockPosition ORIGIN = new BlockPosition(0, 0, 0);
    
    private static Constructor<?> blockPositionConstructor;

    // Use protected members, like Bukkit
    protected final int x;
    protected final int y;
    protected final int z;
    
    // Used to access a BlockPosition, in case it's names are changed
    private static StructureModifier<Integer> intModifier;

    /**
     * Construct an immutable 3D vector.
     * @param x - x coordinate
     * @param y - y coordinate
     * @param z - z coordinate
     */
    public BlockPosition(int x, int y, int z) {
        this.x = x;
        this.y = y;
        this.z = z;
    }
    
    /**
     * Construct an immutable integer 3D vector from a mutable Bukkit vector.
     * @param vector - the mutable real Bukkit vector to copy.
     */
    public BlockPosition(Vector vector) {
        if (vector == null)
            throw new IllegalArgumentException("Vector cannot be NULL.");
        this.x = vector.getBlockX();
        this.y = vector.getBlockY();
        this.z = vector.getBlockZ();
    }

    /**
     * Convert this instance to an equivalent real 3D vector.
     * @return Real 3D vector.
     */
    public Vector toVector() {
        return new Vector(x, y, z);
    }
    
    /**
     * Convert this instance to an equivalent Location.
     * @param world World for the location
     * @return Location
     */
    public Location toLocation(World world) {
        return new Location(world, x, y, z);
    }
    
    /**
     * Retrieve the x-coordinate.
     * @return X coordinate.
     */
    public int getX() {
        return x;
    }
    
    /**
     * Retrieve the y-coordinate.
     * @return Y coordinate.
     */
    public int getY() {
        return y;
    }
    
    /**
     * Retrieve the z-coordinate.
     * @return Z coordinate.
     */
    public int getZ() {
        return z;
    }
    
    /**
     * Adds the current position and a given position together, producing a result position.
     * @param other - the other position.
     * @return The new result position.
     */
    public BlockPosition add(BlockPosition other) {
        if (other == null)
            throw new IllegalArgumentException("other cannot be NULL");
        return new BlockPosition(x + other.x, y + other.y, z + other.z);
    }
    
    /**
     * Adds the current position and a given position together, producing a result position.
     * @param other - the other position.
     * @return The new result position.
     */
    public BlockPosition subtract(BlockPosition other) {
        if (other == null)
            throw new IllegalArgumentException("other cannot be NULL");
        return new BlockPosition(x - other.x, y - other.y, z - other.z);
    }
    
    /**
     * Multiply each dimension in the current position by the given factor.
     * @param factor - multiplier.
     * @return The new result.
     */
    public BlockPosition multiply(int factor) {
        return new BlockPosition(x * factor, y * factor, z * factor);
    }
    
    /**
     * Divide each dimension in the current position by the given divisor.
     * @param divisor - the divisor.
     * @return The new result.
     */
    public BlockPosition divide(int divisor) {
        if (divisor == 0)
            throw new IllegalArgumentException("Cannot divide by null.");
        return new BlockPosition(x / divisor, y / divisor, z / divisor);
    }
    
    /**
     * Used to convert between NMS ChunkPosition and the wrapper instance.
     * @return A new converter.
     */
    public static EquivalentConverter<BlockPosition> getConverter() {
        return new EquivalentConverter<BlockPosition>() {
            @Override
            public Object getGeneric(BlockPosition specific) {
                if (blockPositionConstructor == null) {
                    try {
                        blockPositionConstructor = MinecraftReflection.getBlockPositionClass().
                            getConstructor(int.class, int.class, int.class);
                    } catch (Exception e) {
                        throw new RuntimeException("Cannot find block position constructor.", e);
                    }
                }
                
                // Construct the underlying BlockPosition
                try {
                    return blockPositionConstructor.newInstance(specific.x, specific.y, specific.z);
                } catch (Exception e) {
                    throw new RuntimeException("Cannot construct BlockPosition.", e);
                }
            }
            
            @Override
            public BlockPosition getSpecific(Object generic) {
                if (MinecraftReflection.isBlockPosition(generic)) {
                    // Use a structure modifier
                    intModifier = new StructureModifier<>(generic.getClass(), null, false).withType(int.class);
                    
                    // Damn it all
                    if (intModifier.size() < 3) {
                        throw new IllegalStateException("Cannot read class " + generic.getClass() + " for its integer fields.");
                    }
                    
                    if (intModifier.size() >= 3) {
                        try {
                            StructureModifier<Integer> instance = intModifier.withTarget(generic);
                            return new BlockPosition(instance.read(0), instance.read(1), instance.read(2));
                        } catch (FieldAccessException e) {
                            // This is an exeptional work-around, so we don't want to burden the caller with the messy details
                            throw new RuntimeException("Field access error.", e);
                        }
                    }
                }
                
                // Otherwise, return NULL
                return null;
            }

            // Thanks Java Generics!
            @Override
            public Class<BlockPosition> getSpecificType() {
                return BlockPosition.class;
            }
        };
    }
        
    @Override
    public boolean equals(Object obj) {
        // Fast checks
        if (this == obj) return true;
        if (obj == null) return false;
        
        // Only compare objects of similar type
        if (obj instanceof BlockPosition) {
            BlockPosition other = (BlockPosition) obj;
            return x == other.x && y == other.y && z == other.z;
        }
        return false;
    }
    
    @Override
    public int hashCode() {
        return Objects.hashCode(x, y, z);
    }

    @Override
    public String toString() {
        return "BlockPosition [x=" + x + ", y=" + y + ", z=" + z + "]";
    }
}