/*
 * 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.sk89q.worldedit.math.BlockVector2;
import com.sk89q.worldedit.math.BlockVector3;
import com.sk89q.worldedit.regions.iterator.FlatRegion3DIterator;
import com.sk89q.worldedit.regions.iterator.FlatRegionIterator;
import com.sk89q.worldedit.world.World;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

/**
 * Represents a 2D polygonal region.
 */
public class Polygonal2DRegion extends AbstractRegion implements FlatRegion {

    private List<BlockVector2> points;
    private BlockVector2 min;
    private BlockVector2 max;
    private int minY;
    private int maxY;
    private boolean hasY = false;

    /**
     * Construct the region
     */
    public Polygonal2DRegion() {
        this((World) null);
    }

    /**
     * Construct the region.
     *
     * @param world the world
     */
    public Polygonal2DRegion(World world) {
        this(world, Collections.emptyList(), 0, 0);
        hasY = false;
    }

    /**
     * Construct the region.
     *
     * @param world the world
     * @param points list of points
     * @param minY minimum Y
     * @param maxY maximum Y
     */
    public Polygonal2DRegion(World world, List<BlockVector2> points, int minY, int maxY) {
        super(world);
        this.points = new ArrayList<>(points);
        this.minY = minY;
        this.maxY = maxY;
        hasY = true;
        recalculate();
    }

    /**
     * Make a copy of another region.
     *
     * @param region the other region
     */
    public Polygonal2DRegion(Polygonal2DRegion region) {
        this(region.world, region.points, region.minY, region.maxY);
        hasY = region.hasY;
    }

    /**
     * Get the list of points.
     *
     * @return a list of points
     */
    public List<BlockVector2> getPoints() {
        return Collections.unmodifiableList(points);
    }

    /**
     * Recalculate the bounding box of this polygonal region. This should be
     * called after points have been changed.
     */
    protected void recalculate() {
        if (points.isEmpty()) {
            min = BlockVector2.ZERO;
            minY = 0;
            max = BlockVector2.ZERO;
            maxY = 0;
            return;
        }

        int minX = points.get(0).getBlockX();
        int minZ = points.get(0).getBlockZ();
        int maxX = points.get(0).getBlockX();
        int maxZ = points.get(0).getBlockZ();

        for (BlockVector2 v : points) {
            int x = v.getBlockX();
            int z = v.getBlockZ();
            if (x < minX) minX = x;
            if (z < minZ) minZ = z;
            if (x > maxX) maxX = x;
            if (z > maxZ) maxZ = z;
        }

        int oldMinY = minY;
        int oldMaxY = maxY;
        minY = Math.min(oldMinY, oldMaxY);
        maxY = Math.max(oldMinY, oldMaxY);

        minY = Math.min(Math.max(0, minY), world == null ? 255 : world.getMaxY());
        maxY = Math.min(Math.max(0, maxY), world == null ? 255 : world.getMaxY());

        min = BlockVector2.at(minX, minZ);
        max = BlockVector2.at(maxX, maxZ);
    }

    /**
     * Add a point to the list.
     *
     * @param position the position
     */
    public void addPoint(BlockVector2 position) {
        points.add(position);
        recalculate();
    }

    /**
     * Add a point to the list.
     *
     * @param position the position
     */
    public void addPoint(BlockVector3 position) {
        points.add(BlockVector2.at(position.getBlockX(), position.getBlockZ()));
        recalculate();
    }

    @Override
    public int getMinimumY() {
        return minY;
    }

    /**
     * Set the minimum Y.
     *
     * @param y the Y
     */
    public void setMinimumY(int y) {
        hasY = true;
        minY = y;
        recalculate();
    }

    @Override
    public int getMaximumY() {
        return maxY;
    }

    /**
     * Set the maximum Y.
     *
     * @param y the Y
     */
    public void setMaximumY(int y) {
        hasY = true;
        maxY = y;
        recalculate();
    }

    @Override
    public BlockVector3 getMinimumPoint() {
        return min.toBlockVector3(minY);
    }

    @Override
    public BlockVector3 getMaximumPoint() {
        return max.toBlockVector3(maxY);
    }

    @Override
    public long getVolume() {
        long area = 0;
        int i, j = points.size() - 1;

        for (i = 0; i < points.size(); ++i) {
            long x = points.get(j).getBlockX() + points.get(i).getBlockX();
            long z = points.get(j).getBlockZ() - points.get(i).getBlockZ();
            area += x * z;
            j = i;
        }

        return BigDecimal.valueOf(area)
                .multiply(BigDecimal.valueOf(0.5))
                .abs()
                .setScale(0, RoundingMode.FLOOR)
                .longValue() * (maxY - minY + 1);
    }

    @Override
    public int getWidth() {
        return max.getBlockX() - min.getBlockX() + 1;
    }

    @Override
    public int getHeight() {
        return maxY - minY + 1;
    }

    @Override
    public int getLength() {
        return max.getBlockZ() - min.getBlockZ() + 1;
    }

    @Override
    public void expand(BlockVector3... changes) throws RegionOperationException {
        for (BlockVector3 change : changes) {
            if (change.getBlockX() != 0 || change.getBlockZ() != 0) {
                throw new RegionOperationException("Polygons can only be expanded vertically.");
            }
            int changeY = change.getBlockY();
            if (changeY > 0) {
                maxY += changeY;
            } else {
                minY += changeY;
            }
        }
        recalculate();
    }

    @Override
    public void contract(BlockVector3... changes) throws RegionOperationException {
        for (BlockVector3 change : changes) {
            if (change.getBlockX() != 0 || change.getBlockZ() != 0) {
                throw new RegionOperationException("Polygons can only be contracted vertically.");
            }
            int changeY = change.getBlockY();
            if (changeY > 0) {
                minY += changeY;
            } else {
                maxY += changeY;
            }
        }
        recalculate();
    }

    @Override
    public void shift(BlockVector3 change) throws RegionOperationException {
        final double changeX = change.getX();
        final double changeY = change.getY();
        final double changeZ = change.getZ();

        for (int i = 0; i < points.size(); ++i) {
            BlockVector2 point = points.get(i);
            points.set(i, BlockVector2.at(point.getX() + changeX, point.getZ() + changeZ));
        }

        minY += changeY;
        maxY += changeY;

        recalculate();
    }

    @Override
    public boolean contains(int targetX, int targetZ) {
        boolean inside = false;
        int npoints = points.size();
        int xNew, zNew;
        int xOld, zOld;
        int x1, z1;
        int x2, z2;
        long crossproduct;
        int i;

        xOld = points.get(npoints - 1).getBlockX();
        zOld = points.get(npoints - 1).getBlockZ();

        for (i = 0; i < npoints; ++i) {
            xNew = points.get(i).getBlockX();
            zNew = points.get(i).getBlockZ();
            //Check for corner
            if (xNew == targetX && zNew == targetZ) {
                return true;
            }
            if (xNew > xOld) {
                x1 = xOld;
                x2 = xNew;
                z1 = zOld;
                z2 = zNew;
            } else {
                x1 = xNew;
                x2 = xOld;
                z1 = zNew;
                z2 = zOld;
            }
            if (x1 <= targetX && targetX <= x2) {
                crossproduct = ((long) targetZ - (long) z1) * (long) (x2 - x1)
                        - ((long) z2 - (long) z1) * (long) (targetX - x1);
                if (crossproduct == 0) {
                    if ((z1 <= targetZ) == (targetZ <= z2)) return true; //on edge
                } else if (crossproduct < 0 && (x1 != targetX)) {
                    inside = !inside;
                }
            }
            xOld = xNew;
            zOld = zNew;
        }

        return inside;
    }

    @Override
    public boolean contains(BlockVector3 position) {
        return contains(points, minY, maxY, position);
    }

    /**
     * Checks to see if a point is inside a region.
     *
     * @param points a list of points
     * @param minY the min Y
     * @param maxY the max Y
     * @param pt the position to check
     * @return true if the given polygon contains the given point
     */
    public static boolean contains(List<BlockVector2> points, int minY, int maxY, BlockVector3 pt) {
        if (points.size() < 3) {
            return false;
        }
        int targetX = pt.getBlockX(); //wide
        int targetY = pt.getBlockY(); //height
        int targetZ = pt.getBlockZ(); //depth

        if (targetY < minY || targetY > maxY) {
            return false;
        }

        boolean inside = false;
        int npoints = points.size();
        int xNew, zNew;
        int xOld, zOld;
        int x1, z1;
        int x2, z2;
        long crossproduct;
        int i;

        xOld = points.get(npoints - 1).getBlockX();
        zOld = points.get(npoints - 1).getBlockZ();

        for (i = 0; i < npoints; ++i) {
            xNew = points.get(i).getBlockX();
            zNew = points.get(i).getBlockZ();
            //Check for corner
            if (xNew == targetX && zNew == targetZ) {
                return true;
            }
            if (xNew > xOld) {
                x1 = xOld;
                x2 = xNew;
                z1 = zOld;
                z2 = zNew;
            } else {
                x1 = xNew;
                x2 = xOld;
                z1 = zNew;
                z2 = zOld;
            }
            if (x1 <= targetX && targetX <= x2) {
                crossproduct = ((long) targetZ - (long) z1) * (long) (x2 - x1)
                        - ((long) z2 - (long) z1) * (long) (targetX - x1);
                if (crossproduct == 0) {
                    if ((z1 <= targetZ) == (targetZ <= z2)) return true; //on edge
                } else if (crossproduct < 0 && (x1 != targetX)) {
                    inside = !inside;
                }
            }
            xOld = xNew;
            zOld = zNew;
        }

        return inside;
    }

    /**
     * Return the number of points.
     *
     * @return the number of points
     */
    public int size() {
        return points.size();
    }

    /**
     * Expand the height of the polygon to fit the specified Y.
     *
     * @param y the amount to expand
     * @return true if the area was expanded
     */
    public boolean expandY(int y) {
        if (!hasY) {
            minY = y;
            maxY = y;
            hasY = true;
            return true;
        } else if (y < minY) {
            minY = y;
            return true;
        } else if (y > maxY) {
            maxY = y;
            return true;
        }

        return false;
    }

    @Override
    public Iterator<BlockVector3> iterator() {
        return new FlatRegion3DIterator(this);
    }

    @Override
    public Iterable<BlockVector2> asFlatRegion() {
        return () -> new FlatRegionIterator(Polygonal2DRegion.this);
    }

    /**
     * Returns string representation in the format
     * "(x1, z1) - ... - (xN, zN) * (minY - maxY)"
     *
     * @return string
     */
    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        List<BlockVector2> pts = getPoints();
        Iterator<BlockVector2> it = pts.iterator();
        while (it.hasNext()) {
            BlockVector2 current = it.next();
            sb.append("(").append(current.getBlockX()).append(", ").append(current.getBlockZ()).append(")");
            if (it.hasNext()) sb.append(" - ");
        }
        sb.append(" * (").append(minY).append(" - ").append(maxY).append(")");
        return sb.toString();
    }

    @Override
    public Polygonal2DRegion clone() {
        Polygonal2DRegion clone = (Polygonal2DRegion) super.clone();
        clone.points = new ArrayList<>(points);
        return clone;
    }

    @Override
    public List<BlockVector2> polygonize(int maxPoints) {
        if (maxPoints >= 0 && maxPoints < points.size()) {
            throw new IllegalArgumentException("Cannot polygonize a this Polygonal2DRegion into the amount of points given.");
        }

        return points;
    }

    @Override
    public boolean containsEntireCuboid(int bx, int tx, int by, int ty, int bz, int tz) {
        for (int x = bx; x <= tx; x++) {
            if (!contains(x, 0, bz)) return false;
        }
        for (int x = bx; x <= tx; x++) {
            if (!contains(x, 0, tz)) return false;
        }
        for (int z = bz; z <= tz; z++) {
            if (!contains(bx, 0, z)) return false;
        }
        for (int z = bz; z <= tz; z++) {
            if (!contains(tx, 0, z)) return false;
        }
        return true;
    }
}