Add Day 6

src/2024/06/Guard.cs

@@ -0,0 +1,68 @@
+class Guard : IUpdate
+{
+	private readonly Map _map;
+	private readonly HashSet<(Vector2I, char)> _path = [];
+
+	public char Direction { get; set; }
+
+	public Vector2I Position { get; set; }
+
+	public Guard(Map map)
+	{
+		_map = map;
+		map.RegisterOnUpdate(this);
+	}
+
+	public bool? Step()
+	{
+		if (!_path.Add((Position, Direction)))
+		{
+			return null;
+		}
+		var test = NextPosition();
+		if (!_map.IsValid(test))
+		{
+			return false;
+		}
+		else if (_map.IsOccupied(test))
+		{
+			Direction = Turn();
+		}
+		else
+		{
+			Position = test;
+		}
+
+		return true;
+	}
+
+	public void Update()
+	{
+		var tmpPosition = Position;
+		if (Step() is not true)
+		{
+			_map.UnregisterOnUpdate(this);
+		}
+		else
+		{
+			_map.Move(tmpPosition, Position);
+		}
+	}
+
+	private Vector2I NextPosition()
+	{
+		return Position + Program.ToVector(Direction);
+	}
+
+	private char Turn()
+	{
+		return Direction switch
+		{
+			'^' => '>',
+			'>' => 'v',
+			'v' => '<',
+			'<' => '^',
+			_ => throw new InvalidOperationException()
+		};
+	}
+}