HexCoordinate.cs

/// <summary>
/// 
/// </summary>
/// <remarks>
/// https://www.redblobgames.com/grids/hexagons
/// </remarks>
public readonly struct HexCoordinate
{
    private const double SquareRootOfThree = 1.7320508075688772d;
    private const double SquareRootOfThreeHalved = (SquareRootOfThree * 0.5d);

    /// <remarks>
    /// Oblong: (hex) => (hex.Y == 0)
    /// Square: (hex) => (hex.X == 0)
    /// </remarks>
    public static IEnumerable<HexCoordinate> GenerateTileset(int offset, int count, Func<HexCoordinate, bool> predicate) {
        var limit = (offset + count);

        for (var hashCode = offset; (hashCode < limit); ++hashCode) {
            var hexCoordinate = HexCoordinate.New(hashCode);

            if (predicate(hexCoordinate)) {
                yield return hexCoordinate;
            }
        }
    }
    public static HexCoordinate New(int hashCode) {
        var (x, y) = BitwiseHelpers.ElegantUnpair(hashCode);

        return HexCoordinate.New(x, y);
    }
    public static HexCoordinate New(short x, short y) => new HexCoordinate(x, y);

    public static bool operator ==(HexCoordinate left, HexCoordinate right) => ((left.X == right.X) && (left.Y == right.Y));
    public static bool operator !=(HexCoordinate left, HexCoordinate right) => ((left.X != right.X) && (left.Y != right.Y));
    public static HexCoordinate operator +(HexCoordinate left, HexCoordinate right) => New(((short)(left.X + right.X)), ((short)(left.Y + right.Y)));
    public static HexCoordinate operator -(HexCoordinate left, HexCoordinate right) => New(((short)(left.X - right.X)), ((short)(left.Y - right.Y)));
    public static HexCoordinate operator *(HexCoordinate left, HexCoordinate right) => New(((short)(left.X * right.X)), ((short)(left.Y * right.Y)));

    public short X { get; }
    public short Y { get; }
    public short Z => ((short)((-X) - Y));

    private HexCoordinate(short x, short y) {
        X = x;
        Y = y;
    }

    private int GetLength() => ((Math.Abs(X) + Math.Abs(Y) + Math.Abs(Z)) >> 1);

    public bool Equals(HexCoordinate other) => (this == other);
    public override bool Equals(object other) => ((other is null) || ((other is HexCoordinate hexCoordinate) && Equals(hexCoordinate)));
    public HexCoordinate GetDiagonalNeighborNorth() => New(((short)(X + 1)), ((short)(Y + 1)));
    public HexCoordinate GetDiagonalNeighborNorthEast() => New(((short)(X + 2)), ((short)(Y - 1)));
    public HexCoordinate GetDiagonalNeighborNorthWest() => New(((short)(X - 1)), ((short)(Y + 2)));
    public HexCoordinate GetDiagonalNeighborSouthEast() => New(((short)(X + 1)), ((short)(Y - 2)));
    public HexCoordinate GetDiagonalNeighborSouthWest() => New(((short)(X - 2)), ((short)(Y + 1)));
    public HexCoordinate GetDiagonalNeighborSouth() => New(((short)(X - 1)), ((short)(Y - 1)));
    public int GetDistance(HexCoordinate other) => (this - other).GetLength();
    public override int GetHashCode() => BitwiseHelpers.ElegantPair(X, Y);
    public HexCoordinate GetImmediateNeighborEast() => New(((short)(X + 1)), ((short)(Y - 1)));
    public HexCoordinate GetImmediateNeighborNorthEast() => New(((short)(X + 1)), Y);
    public HexCoordinate GetImmediateNeighborNorthWest() => New(X, ((short)(Y + 1)));
    public HexCoordinate GetImmediateNeighborSouthEast() => New(X, ((short)(Y - 1)));
    public HexCoordinate GetImmediateNeighborSouthWest() => New(((short)(X - 1)), Y);
    public HexCoordinate GetImmediateNeighborWest() => New(((short)(X - 1)), ((short)(Y + 1)));
    public (double x, double y) GetPixel(double size) {
        var x = X;
        var y = Z;

        return (
            x: (size * (1.5d * x)),
            y: (size * ((SquareRootOfThreeHalved * x) + (SquareRootOfThree * y)))
        );
    }
    public HexCoordinate RotateLeft() => New(((short)(-Y)), ((short)(-Z)));
    public HexCoordinate RotateRight() => New(((short)(-Z)), ((short)(-X)));
    public override string ToString() => $"({X},{Y},{Z})";
}