namespace Coilgarden;

/// <summary>The four headings a snake can travel. Ordered clockwise from up.</summary>
public enum Direction
{
	Up,
	Right,
	Down,
	Left
}

public static class DirectionExtensions
{
	/// <summary>The cell offset one step in this direction.</summary>
	public static GridPos Delta( this Direction direction ) => direction switch
	{
		Direction.Up => new GridPos( 0, 1 ),
		Direction.Right => new GridPos( 1, 0 ),
		Direction.Down => new GridPos( 0, -1 ),
		Direction.Left => new GridPos( -1, 0 ),
		_ => GridPos.Zero
	};

	public static Direction Opposite( this Direction direction ) => direction switch
	{
		Direction.Up => Direction.Down,
		Direction.Right => Direction.Left,
		Direction.Down => Direction.Up,
		Direction.Left => Direction.Right,
		_ => direction
	};

	/// <summary>True when travelling <paramref name="other"/> would be a reversal.</summary>
	public static bool IsOpposite( this Direction direction, Direction other ) =>
		direction.Opposite() == other;

}