package net.minestom.server.collision;

import net.minestom.server.coordinate.Point;
import net.minestom.server.coordinate.Pos;
import net.minestom.server.coordinate.Vec;
import net.minestom.server.entity.Entity;
import org.jetbrains.annotations.ApiStatus;
import org.jetbrains.annotations.NotNull;

import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

/**
 * See https://wiki.vg/Entity_metadata#Mobs_2
 */
public final class BoundingBox implements Shape {
    private final double width, height, depth;
    private final Point offset;
    private Map<Vec, Vec[]> faces;

    BoundingBox(double width, double height, double depth, Point offset) {
        this.width = width;
        this.height = height;
        this.depth = depth;
        this.offset = offset;
    }

    public BoundingBox(double width, double height, double depth) {
        this(width, height, depth, new Vec(-width / 2, 0, -depth / 2));
    }

    @Override
    @ApiStatus.Experimental
    public boolean intersectBox(@NotNull Point positionRelative, @NotNull BoundingBox boundingBox) {
        return (minX() + positionRelative.x() <= boundingBox.maxX() && maxX() + positionRelative.x() >= boundingBox.minX()) &&
                (minY() + positionRelative.y() <= boundingBox.maxY() && maxY() + positionRelative.y() >= boundingBox.minY()) &&
                (minZ() + positionRelative.z() <= boundingBox.maxZ() && maxZ() + positionRelative.z() >= boundingBox.minZ());
    }

    @Override
    @ApiStatus.Experimental
    public boolean intersectBoxSwept(@NotNull Point rayStart, @NotNull Point rayDirection, @NotNull Point shapePos, @NotNull BoundingBox moving, @NotNull SweepResult finalResult) {
        final boolean isHit = RayUtils.BoundingBoxIntersectionCheck(
                moving, rayStart, rayDirection,
                this,
                shapePos
        );

        if (!isHit) return false;

        SweepResult tempResult = new SweepResult(1, 0, 0, 0, null);
        // Longer check to get result of collision
        RayUtils.SweptAABB(moving, rayStart, rayDirection, this, shapePos, tempResult);
        // Update final result if the temp result collision is sooner than the current final result
        if (tempResult.res < finalResult.res) {
            finalResult.res = tempResult.res;
            finalResult.normalX = tempResult.normalX;
            finalResult.normalY = tempResult.normalY;
            finalResult.normalZ = tempResult.normalZ;
            finalResult.collidedShapePosition = shapePos;
            finalResult.collidedShape = this;
            finalResult.blockType = null;
        }
        return true;
    }

    /**
     * Used to know if this {@link BoundingBox} intersects with the bounding box of an entity.
     *
     * @param entity the entity to check the bounding box
     * @return true if this bounding box intersects with the entity, false otherwise
     */
    @ApiStatus.Experimental
    public boolean intersectEntity(@NotNull Point src, @NotNull Entity entity) {
        return intersectBox(src.sub(entity.getPosition()), entity.getBoundingBox());
    }

    @ApiStatus.Experimental
    public boolean boundingBoxRayIntersectionCheck(Vec start, Vec direction, Pos position) {
        return RayUtils.BoundingBoxRayIntersectionCheck(start, direction, this, position);
    }

    @Override
    public @NotNull Point relativeStart() {
        return offset;
    }

    @Override
    public @NotNull Point relativeEnd() {
        return offset.add(width, height, depth);
    }

    @Override
    public String toString() {
        String result = "BoundingBox";
        result += "\n";
        result += "[" + minX() + " : " + maxX() + "]";
        result += "\n";
        result += "[" + minY() + " : " + maxY() + "]";
        result += "\n";
        result += "[" + minZ() + " : " + maxZ() + "]";
        return result;
    }

    /**
     * Creates a new {@link BoundingBox} linked to the same {@link Entity} with expanded size.
     *
     * @param x the X offset
     * @param y the Y offset
     * @param z the Z offset
     * @return a new {@link BoundingBox} expanded
     */
    public @NotNull BoundingBox expand(double x, double y, double z) {
        return new BoundingBox(this.width + x, this.height + y, this.depth + z);
    }

    /**
     * Creates a new {@link BoundingBox} linked to the same {@link Entity} with contracted size.
     *
     * @param x the X offset
     * @param y the Y offset
     * @param z the Z offset
     * @return a new bounding box contracted
     */
    public @NotNull BoundingBox contract(double x, double y, double z) {
        return new BoundingBox(this.width - x, this.height - y, this.depth - z);
    }

    public double width() {
        return width;
    }

    public double height() {
        return height;
    }

    public double depth() {
        return depth;
    }

    @NotNull Map<Vec, Vec[]> faces() {
        Map<Vec, Vec[]> faces = this.faces;
        if (faces == null) {
            this.faces = faces = retrieveFaces();
        }
        return faces;
    }

    public double minX() {
        return relativeStart().x();
    }

    public double maxX() {
        return relativeEnd().x();
    }

    public double minY() {
        return relativeStart().y();
    }

    public double maxY() {
        return relativeEnd().y();
    }

    public double minZ() {
        return relativeStart().z();
    }

    public double maxZ() {
        return relativeEnd().z();
    }

    private Vec[] buildSet(Collection<Vec> a) {
        return a.toArray(Vec[]::new);
    }

    private Vec[] buildSet(Collection<Vec> a, Collection<Vec> b) {
        Set<Vec> allFaces = new HashSet<>();
        Stream.of(a, b).forEach(allFaces::addAll);
        return allFaces.toArray(Vec[]::new);
    }

    private Vec[] buildSet(Collection<Vec> a, Collection<Vec> b, Collection<Vec> c) {
        Set<Vec> allFaces = new HashSet<>();
        Stream.of(a, b, c).forEach(allFaces::addAll);
        return allFaces.toArray(Vec[]::new);
    }

    private Map<Vec, Vec[]> retrieveFaces() {
        double minX = minX();
        double maxX = maxX();
        double minY = minY();
        double maxY = maxY();
        double minZ = minZ();
        double maxZ = maxZ();

        // Calculate steppings for each axis
        // Start at minimum, increase by step size until we reach maximum
        // This is done to catch all blocks that are part of that axis
        // Since this stops before max point is reached, we add the max point after
        final List<Double> stepsX = IntStream.rangeClosed(0, (int) ((maxX - minX))).mapToDouble(x -> x + minX).boxed().collect(Collectors.toCollection(ArrayList<Double>::new));
        final List<Double> stepsY = IntStream.rangeClosed(0, (int) ((maxY - minY))).mapToDouble(x -> x + minY).boxed().collect(Collectors.toCollection(ArrayList<Double>::new));
        final List<Double> stepsZ = IntStream.rangeClosed(0, (int) ((maxZ - minZ))).mapToDouble(x -> x + minZ).boxed().collect(Collectors.toCollection(ArrayList<Double>::new));

        stepsX.add(maxX);
        stepsY.add(maxY);
        stepsZ.add(maxZ);

        final Set<Vec> bottom = new HashSet<>();
        final Set<Vec> top = new HashSet<>();
        final Set<Vec> left = new HashSet<>();
        final Set<Vec> right = new HashSet<>();
        final Set<Vec> front = new HashSet<>();
        final Set<Vec> back = new HashSet<>();

        CartesianProduct.product(stepsX, stepsY).forEach(cross -> {
            double i = (double) ((List<?>) cross).get(0);
            double j = (double) ((List<?>) cross).get(1);
            front.add(new Vec(i, j, minZ));
            back.add(new Vec(i, j, maxZ));
        });

        CartesianProduct.product(stepsY, stepsZ).forEach(cross -> {
            double j = (double) ((List<?>) cross).get(0);
            double k = (double) ((List<?>) cross).get(1);
            left.add(new Vec(minX, j, k));
            right.add(new Vec(maxX, j, k));
        });

        CartesianProduct.product(stepsX, stepsZ).forEach(cross -> {
            double i = (double) ((List<?>) cross).get(0);
            double k = (double) ((List<?>) cross).get(1);
            bottom.add(new Vec(i, minY, k));
            top.add(new Vec(i, maxY, k));
        });

        // X   -1 left    |  1 right
        // Y   -1 bottom  |  1 top
        // Z   -1 front   |  1 back
        var query = new HashMap<Vec, Vec[]>();
        query.put(new Vec(0, 0, 0), new Vec[0]);

        query.put(new Vec(-1, 0, 0), buildSet(left));
        query.put(new Vec(1, 0, 0), buildSet(right));
        query.put(new Vec(0, -1, 0), buildSet(bottom));
        query.put(new Vec(0, 1, 0), buildSet(top));
        query.put(new Vec(0, 0, -1), buildSet(front));
        query.put(new Vec(0, 0, 1), buildSet(back));

        query.put(new Vec(0, -1, -1), buildSet(bottom, front));
        query.put(new Vec(0, -1, 1), buildSet(bottom, back));
        query.put(new Vec(0, 1, -1), buildSet(top, front));
        query.put(new Vec(0, 1, 1), buildSet(top, back));

        query.put(new Vec(-1, -1, 0), buildSet(left, bottom));
        query.put(new Vec(-1, 1, 0), buildSet(left, top));
        query.put(new Vec(1, -1, 0), buildSet(right, bottom));
        query.put(new Vec(1, 1, 0), buildSet(right, top));

        query.put(new Vec(-1, 0, -1), buildSet(left, front));
        query.put(new Vec(-1, 0, 1), buildSet(left, back));
        query.put(new Vec(1, 0, -1), buildSet(right, front));
        query.put(new Vec(1, 0, 1), buildSet(right, back));

        query.put(new Vec(1, 1, 1), buildSet(right, top, back));
        query.put(new Vec(1, 1, -1), buildSet(right, top, front));
        query.put(new Vec(1, -1, 1), buildSet(right, bottom, back));
        query.put(new Vec(1, -1, -1), buildSet(right, bottom, front));
        query.put(new Vec(-1, 1, 1), buildSet(left, top, back));
        query.put(new Vec(-1, 1, -1), buildSet(left, top, front));
        query.put(new Vec(-1, -1, 1), buildSet(left, bottom, back));
        query.put(new Vec(-1, -1, -1), buildSet(left, bottom, front));

        return query;
    }
}