using Unity.Mathematics;

namespace GameCommon.Spatial
{
    public struct SpatialHash
    {
        public const int Goffset = 10000;
        public const int Max = 20480;

        public int CellSize;
        public float ConvFactor;
        public int Width;

        public static SpatialHash Default
        {
            get
            {
                return new SpatialHash(100);
            }
        }

        public SpatialHash(int cellSize)
        {
            CellSize = cellSize;
            ConvFactor = 1.0f / CellSize;
            Width = Max / CellSize;
        }

        public int HashWithOffset(float x, float y)
        {
            x += Goffset;
            y += Goffset;
            return Hash(x, y);
        }

        public int Hash(float x, float y)
        {
            return (int)((x * ConvFactor)) + (int)((y * ConvFactor)) * Width;
        }


        public bool InRangeOf(float x0, float y0, float x1, float y1)
        {
            int otherHash = HashWithOffset(x1, y1);
            x0 += Goffset;
            y0 += Goffset;
            SetStartEnd(x0, y0, out int2 start, out int2 end);

            for (int rowNum = start.x; rowNum <= end.x; rowNum += CellSize)
            {
                for (int colNum = start.y; colNum <= end.y; colNum += CellSize)
                {
                    if (rowNum >= 0 && colNum >= 0)
                    {
                        int hash = Hash(rowNum, colNum);
                        if (hash == otherHash)
                        {
                            return true;
                        }
                    }
                }
            }
            return false;
        }

        public int CellsWithinBounds(float x, float y, int[] cells)
        {
            int index = 0;
            x += Goffset;
            y += Goffset;

            SetStartEnd(x, y, out int2 start, out int2 end);

            for (int rowNum = start.x; rowNum <= end.x; rowNum += CellSize)
            {
                for (int colNum = start.y; colNum <= end.y; colNum += CellSize)
                {
                    if (rowNum >= 0 && colNum >= 0)
                    {
                        cells[index] = Hash(rowNum, colNum);
                        index++;
                    }
                }
            }
            return index;
        }

        public void SetStartEnd(float x, float y, out int2 start, out int2 end)
        {
            start = new int2
            {
                x = (int)(x - CellSize),
                y = (int)(y - CellSize)
            };

            end = new int2
            {
                x = (int)(x + CellSize),
                y = (int)(y + CellSize)
            };
        }

    }

}