/*
 * WorldEdit, a Minecraft world manipulation toolkit
 * Copyright (C) sk89q <http://www.sk89q.com>
 * Copyright (C) WorldEdit team and contributors
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package com.sk89q.worldedit.regions;

import com.boydti.fawe.beta.IChunk;
import com.boydti.fawe.beta.IChunkGet;
import com.boydti.fawe.beta.IChunkSet;
import com.google.common.collect.Iterators;
import com.google.common.collect.Sets;
import com.sk89q.worldedit.math.BlockVector2;
import com.sk89q.worldedit.math.BlockVector3;
import com.sk89q.worldedit.world.World;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

/**
 * An intersection of several other regions. Any location that is contained in one
 * of the child regions is considered as contained by this region.
 *
 * <p>{@link #iterator()} returns a special iterator that will iterate through
 * the iterators of each region in an undefined sequence. Some positions may
 * be repeated if the position is contained in more than one region, but this cannot
 * be guaranteed to occur.</p>
 */
public class RegionIntersection extends AbstractRegion {

    private final List<Region> regions = new ArrayList<>();

    /**
     * Create a new instance with the included list of regions.
     *
     * @param regions a list of regions, which is copied
     */
    public RegionIntersection(List<Region> regions) {
        this(null, regions);
    }

    /**
     * Create a new instance with the included list of regions.
     *
     * @param regions a list of regions, which is copied
     */
    public RegionIntersection(Region... regions) {
        this(null, regions);
    }

    /**
     * Create a new instance with the included list of regions.
     *
     * @param world   the world
     * @param regions a list of regions, which is copied
     */
    public RegionIntersection(World world, List<Region> regions) {
        super(world);
        checkNotNull(regions);
        checkArgument(!regions.isEmpty(), "empty region list is not supported");
        this.regions.addAll(regions);
    }

    /**
     * Create a new instance with the included list of regions.
     *
     * @param world   the world
     * @param regions an array of regions, which is copied
     */
    public RegionIntersection(World world, Region... regions) {
        super(world);
        checkNotNull(regions);
        checkArgument(regions.length > 0, "empty region list is not supported");
        Collections.addAll(this.regions, regions);
    }

    @Override
    public BlockVector3 getMinimumPoint() {
        BlockVector3 minimum = regions.get(0).getMinimumPoint();
        for (int i = 1; i < regions.size(); i++) {
            minimum = regions.get(i).getMinimumPoint().getMinimum(minimum);
        }
        return minimum;
    }

    @Override
    public BlockVector3 getMaximumPoint() {
        BlockVector3 maximum = regions.get(0).getMaximumPoint();
        for (int i = 1; i < regions.size(); i++) {
            maximum = regions.get(i).getMaximumPoint().getMaximum(maximum);
        }
        return maximum;
    }

    @Override
    public void expand(BlockVector3... changes) throws RegionOperationException {
        checkNotNull(changes);
        throw new RegionOperationException("Cannot expand a region intersection");
    }

    @Override
    public void contract(BlockVector3... changes) throws RegionOperationException {
        checkNotNull(changes);
        throw new RegionOperationException("Cannot contract a region intersection");
    }

    @Override
    public boolean contains(BlockVector3 position) {
        checkNotNull(position);

        for (Region region : regions) {
            if (region.contains(position)) {
                return true;
            }
        }

        return false;
    }

    @SuppressWarnings({"unchecked"})
    @Override
    public Iterator<BlockVector3> iterator() {
        Iterator<BlockVector3>[] iterators = (Iterator<BlockVector3>[]) new Iterator[regions.size()];
        for (int i = 0; i < regions.size(); i++) {
            iterators[i] = regions.get(i).iterator();
        }
        return Iterators.concat(iterators);
    }

    @Override
    public boolean containsEntireCuboid(int bx, int tx, int by, int ty, int bz, int tz) {
        for (Region region : regions) {
            if (region.containsEntireCuboid(bx, tx, by, ty, bz, tz)) {
                return true;
            }
        }
        return false;
    }

    @Override
    public IChunkSet processSet(IChunk chunk, IChunkGet get, IChunkSet set) {
        int bx = chunk.getX() << 4;
        int bz = chunk.getZ() << 4;
        int tx = bx + 15;
        int tz = bz + 15;
        for (Region region : regions) {
            BlockVector3 regMin = region.getMinimumPoint();
            BlockVector3 regMax = region.getMaximumPoint();
            if (tx >= regMin.getX() && bx <= regMax.getX() && tz >= regMin.getZ() && bz <= regMax.getZ()) {
                return region.processSet(chunk, get, set);
            }
        }
        return null;
    }

    public List<Region> getRegions() {
        return regions;
    }

    @Override
    public Set<BlockVector2> getChunks() {
        Set<BlockVector2> set = null;
        for (Region region : regions) {
            if (set == null) {
                set = region.getChunks();
            } else {
                set = Sets.union(set, region.getChunks());
            }
        }
        return set;
    }

    @Override
    public Set<BlockVector3> getChunkCubes() {
        Set<BlockVector3> set = null;
        for (Region region : regions) {
            if (set == null) {
                set = region.getChunkCubes();
            } else {
                set = Sets.union(set, region.getChunkCubes());
            }
        }
        return set;
    }

    @Override
    public boolean containsChunk(int chunkX, int chunkZ) {
        for (Region region : regions) if (region.containsChunk(chunkX, chunkZ)) return true;
        return false;
    }

    @Override
    public boolean contains(int x, int z) {
        for (Region region : regions) if (region.contains(x, z)) return true;
        return false;
    }

    @Override
    public boolean contains(int x, int y, int z) {
        for (Region region : regions) if (region.contains(x, y, z)) return true;
        return false;
    }
}