namespace AdventOfCodeLibrary._2022.Day_09
{
    internal class VirtualPoint
    {
        internal int X { get; set; } = 0;

        internal int Y { get; set; } = 0;

        internal void Translate(int x, int y)
        {
            X += x;
            Y += y;
        }
    }

    internal class RopeWalker
    {
        private readonly VirtualPoint HeadLocation = new();
        private VirtualPoint LastHeadLocation = new();

        private VirtualPoint TailLocation = new();

        private List<string> TailVistedLocations = new();

        internal int ProcessMovement(string[] movements)
        {
            // add the start position
            TailVistedLocations.Add($"0,0");

            for (int movementIndex = 0; movementIndex < movements.Length; movementIndex++)
            {
                char direction = movements[movementIndex][0];
                int amountToMove = Convert.ToInt32(movements[movementIndex].Substring(2));

                for (int movement = 0; movement < amountToMove; movement++)
                {
                    // set the last pos before moving
                    LastHeadLocation.X = HeadLocation.X;
                    LastHeadLocation.Y = HeadLocation.Y;

                    // do the actual move
                    switch (direction)
                    {
                        case 'U': HeadLocation.Translate(0, 1); break;
                        case 'D': HeadLocation.Translate(0, -1); break;
                        case 'R': HeadLocation.Translate(1, 0); break;
                        case 'L': HeadLocation.Translate(-1, 0); break;
                    }

                    // check if the tail is touching
                    if (!IsTailTouchingHead(HeadLocation, TailLocation))
                    {
                        TailLocation.Translate(Math.Sign(HeadLocation.X - TailLocation.X), Math.Sign(HeadLocation.Y - TailLocation.Y));

                        // add the new position to the list of visited positions
                        TailVistedLocations.Add($"{TailLocation.X},{TailLocation.Y}");
                    }
                }
            }

            return TailVistedLocations.Distinct().Count();
        }

        private bool IsTailTouchingHead(VirtualPoint point1, VirtualPoint point2)
        {
            return !(Math.Abs(point1.X - point2.X) > 1) && !(Math.Abs(point1.Y - point2.Y) > 1);
        }
    }
}