using System;

namespace FloodSWE.TileGraph
{
    public readonly struct TileId : IEquatable<TileId>
    {
        public readonly int Lod;
        public readonly int X;
        public readonly int Y;

        public TileId(int lod, int x, int y)
        {
            Lod = lod;
            X = x;
            Y = y;
        }

        public bool Equals(TileId other)
        {
            return Lod == other.Lod && X == other.X && Y == other.Y;
        }

        public override bool Equals(object obj)
        {
            return obj is TileId other && Equals(other);
        }

        public override int GetHashCode()
        {
            return HashCode.Combine(Lod, X, Y);
        }

        public override string ToString()
        {
            return $"LOD{Lod} ({X},{Y})";
        }

        public static bool operator ==(TileId a, TileId b)
        {
            return a.Equals(b);
        }

        public static bool operator !=(TileId a, TileId b)
        {
            return !a.Equals(b);
        }

        public TileId Parent()
        {
            return Lod > 0 ? new TileId(Lod - 1, X >> 1, Y >> 1) : this;
        }

        public TileId Child(int childX, int childY)
        {
            return new TileId(Lod + 1, (X << 1) + childX, (Y << 1) + childY);
        }
    }
}