var lines = File.ReadAllLines("input.txt");
var charArray = new char[lines.Length, lines[0].Length];
Dictionary<Direction, (int dx, int dy)> moves = new()
{
    { Direction.Up, (-1, 0) },
    { Direction.Right, (0, 1) },
    { Direction.Down, (1, 0) },
    { Direction.Left, (0, -1) }
};

var guardCurrentPosition = (0, 0);
var guardDirection = Direction.Up;
var visitedPositions = new List<int[]>();

for (var i = 0; i < charArray.GetLength(0); i++)
for (var j = 0; j < charArray.GetLength(1); j++)
{
    if (lines[i][j] == '^')
    {
        guardCurrentPosition.Item1 = i;
        guardCurrentPosition.Item2 = j;
        visitedPositions.Add([guardCurrentPosition.Item1, guardCurrentPosition.Item2]);
    }

    charArray[i, j] = lines[i][j];
}

var part1 = Part1(guardCurrentPosition, guardDirection, charArray, visitedPositions);
var part2 = Part2(guardCurrentPosition, charArray);
Console.WriteLine($"Part1: {part1}\nPart2: {part2}");

int Part2((int,int) currentPosition, char[,] input)
{
    var potentialLoopPositions = new List<(int row, int col)>();

    for (var i = 0; i < input.GetLength(0); i++)
    for (var j = 0; j < input.GetLength(1); j++)
    {
        if ((i, j) == currentPosition || input[i, j] == '#') continue;
        
        var modifiedGrid = (char[,])input.Clone();
        modifiedGrid[i, j] = '#';
        
        if (CausesLoop(currentPosition, modifiedGrid))
        {
            potentialLoopPositions.Add((i, j));
        }
    }
    
    return potentialLoopPositions.Count;
}

bool CausesLoop((int row, int col) startPosition, char[,] input)
{
    var currentPosition = startPosition;
    var currentDirection = Direction.Up;

    var visited = new HashSet<((int row, int col), Direction)>();
    visited.Add((currentPosition, currentDirection));

    while (true)
    {
        var nextPosition = CalculateNextPosition(currentPosition.row, currentPosition.col, currentDirection);

        if (!IsValid(nextPosition.Item1, nextPosition.Item2, input))
            return false;

        if (input[nextPosition.Item1, nextPosition.Item2] == '#')
        {
            currentDirection = (Direction)(((int)currentDirection + 1) % 4);
        }
        else
        {
            currentPosition = nextPosition;
        }
        
        if (!visited.Add((currentPosition, currentDirection)))
        {
            return true;
        }
    }
}

int Part1((int,int) currentPosition, Direction direction, char[,] input, List<int[]> traveledPositions)
{
    var nextPosition = CalculateNextPosition(currentPosition.Item1, currentPosition.Item2, direction);

    while (IsValid(nextPosition.Item1, nextPosition.Item2, input))
    {
        if (IsBlocked(nextPosition.Item1, nextPosition.Item2, input))
        {
            direction = (Direction)(((int)direction + 1) % 4);
        }
        else
        {
            currentPosition = (nextPosition.Item1, nextPosition.Item2);
            traveledPositions.Add([currentPosition.Item1, currentPosition.Item2]);
        }

        nextPosition = CalculateNextPosition(currentPosition.Item1, currentPosition.Item2, direction);
    }

    return traveledPositions.Select(x => $"r{x[0]},c{x[1]}").Distinct().Count();
}

(int, int) CalculateNextPosition(int row, int col, Direction direction)
{
    var (dx, dy) = moves[direction];
    return (row + dx, col + dy);
}

bool IsValid(int row, int column, char[,] grid) => row >= 0 && row < grid.GetLength(0) && column >= 0 && column < grid.GetLength(1);

bool IsBlocked(int row, int col, char[,] grid) => grid[row, col] == '#';

enum Direction
{
    Up,
    Right,
    Down,
    Left
}