using System;
using System.Runtime.CompilerServices;
using Unity.Mathematics;

namespace DanieleMarotta.RiversongCodeShowcase
{
    public static class TileMath
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static int2 Rotate(int2 v, Directions direction)
        {
            switch (direction)
            {
                case Directions.North:
                    return new int2(v.x, v.y);

                case Directions.West:
                    return new int2(v.y, -v.x);

                case Directions.South:
                    return new int2(-v.x, -v.y);

                case Directions.East:
                    return new int2(-v.y, v.x);

                default:
                    throw new ArgumentOutOfRangeException();
            }
        }

        public static TileRect GetBuildingRect(int2 rectCenter, Directions direction, int width, int height)
        {
            int dx;
            int dy;

            var sx = (width - 1) >> 1;
            var sy = (height - 1) >> 1;

            if (width == height || direction == Directions.North)
            {
                dx = -sx;
                dy = -sy;
            }
            else
            {
                switch (direction)
                {
                    case Directions.West:
                        dx = sy - (height - 1);
                        dy = -sx;
                        (width, height) = (height, width);
                        break;

                    case Directions.South:
                        dx = sx - (width - 1);
                        dy = sy - (height - 1);
                        break;

                    case Directions.East:
                        dx = -sy;
                        dy = sx - (width - 1);
                        (width, height) = (height, width);
                        break;

                    default:
                        throw new ArgumentOutOfRangeException();
                }
            }

            return new TileRect(rectCenter + new int2(dx, dy), width, height);
        }

        public static void WalkLine(int2 startTile, int2 endTile, Action<int2> tileAction)
        {
            var dx = endTile.x - startTile.x;
            var dy = endTile.y - startTile.y;
            if (math.abs(dx) >= math.abs(dy))
                endTile.y = startTile.y;
            else
                endTile.x = startTile.x;

            var tile = startTile;
            var d = math.sign(endTile - startTile);

            while (true)
            {
                tileAction.Invoke(tile);

                if (math.all(tile == endTile)) break;

                tile += d;
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static int StepCount(int2 tile, int2 otherTile)
        {
            var delta = math.abs(tile - otherTile);
            return math.max(delta.x, delta.y);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static int StepCount(int2 tile, in TileRect rect)
        {
            var left = math.max(rect.Min.x - tile.x, 0);
            var right = math.max(tile.x - rect.Max.x, 0);
            var dx = math.max(left, right);

            var bottom = math.max(rect.Min.y - tile.y, 0);
            var top = math.max(tile.y - rect.Max.y, 0);
            var dy = math.max(bottom, top);

            return math.max(dx, dy);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static int StepCount(in TileRect rect, int2 tile)
        {
            return StepCount(tile, rect);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static int StepCount(in TileRect rect, in TileRect otherRect)
        {
            var left = math.max(otherRect.Min.x - rect.Max.x, 0);
            var right = math.max(rect.Min.x - otherRect.Max.x, 0);
            var dx = math.max(left, right);

            var bottom = math.max(otherRect.Min.y - rect.Max.y, 0);
            var top = math.max(rect.Min.y - otherRect.Max.y, 0);
            var dy = math.max(bottom, top);

            return math.max(dx, dy);
        }
    }
}