using Unity.Collections;
using Unity.Mathematics;

namespace DanieleMarotta.RiversongCodeShowcase
{
    public class RoadNetwork : NativeGrid<ushort>
    {
        /// <summary>
        ///     Indicates that the tile is occupied by a road.
        /// </summary>
        private const int TileOccupiedBit = 1 << 15;

        /// <summary>
        ///     Mask selecting the bits indicating in which directions a road tile is connected to another road tile.
        /// </summary>
        private const int ConnectivityBits = 0xFF;

        public RoadNetwork(int2 size) : base(size, Allocator.Persistent)
        {
        }

        public void AddRoadTile(int2 tile)
        {
            SetValue(tile, TileOccupiedBit);
            UpdateRoadTile(tile);
        }

        public void UpdateRoadTile(int2 tile)
        {
            if (!IsRoadTile(tile)) return;

            ushort value = TileOccupiedBit;

            if (tile.x > 0 && GetValue(tile + new int2(-1, 0)) != 0) value |= (ushort)DirectionsMask4.West;

            if (tile.x < Size.x - 1 && GetValue(tile + new int2(1, 0)) != 0) value |= (ushort)DirectionsMask4.East;

            if (tile.y > 0 && GetValue(tile + new int2(0, -1)) != 0) value |= (ushort)DirectionsMask4.South;

            if (tile.y < Size.y - 1 && GetValue(tile + new int2(0, 1)) != 0) value |= (ushort)DirectionsMask4.North;

            SetValue(tile, value);
        }

        public void RemoveRoadTile(int2 tile)
        {
            SetValue(tile, 0);
        }

        public DirectionsMask8 GetConnectivity(int2 tile)
        {
            return (DirectionsMask8)(GetValue(tile) & ConnectivityBits);
        }

        public bool IsRoadTile(int2 tile)
        {
            return GetValue(tile) != 0;
        }
    }
}