AdventOfCode23/Day16/IRay.cs

namespace Day16;

public interface IRay
{
    bool IsHorizontal { get; }
    bool IsVertical { get; }
    (int X, int Y) Apply(Tile t);
    IRay Rotate();
    IRay AntiRotate();
}

public static class Rays
{
    public static IRay North { get; } = new Ray(0, -1);
    public static IRay East { get; } = new Ray(1, 0);
    public static IRay South { get; } = new Ray(0, 1);
    public static IRay West { get; } = new Ray(-1, 0);
    private static readonly IList<IRay> _rays = new List<IRay> { North, West, South, East };
    
    private class Ray : IRay
    {
        private readonly int _dX;
        private readonly int _dY;

        public bool IsHorizontal => _dX != 0;
        public bool IsVertical => _dY != 0;

        public Ray(int dX, int dY)
        {
            _dX = dX;
            _dY = dY;
        }
        
        public (int X, int Y) Apply(Tile t)
        {
            return (t.X + _dX, t.Y + _dY);
        }

        public IRay Rotate()
        {
            var index = _rays.IndexOf(this);
            return _rays[(index + 1) % _rays.Count];
        }

        public IRay AntiRotate()
        {
            var index = _rays.IndexOf(this);
            return _rays[(index + _rays.Count - 1) % _rays.Count];
        }
    }
}