INPUT_FILE = "input.txt"

# True for roll of paper
floor: list[list[bool]] = [ [ c == '@' for c in line.strip() ] for line in open(INPUT_FILE, 'r').readlines() ]
buffer_floor = floor.copy()

class iVec2d:
    x: int
    y: int

    def __init__(self, x: int, y: int):
        self.x = x
        self.y = y

max_y = len(floor)
max_x = len(floor[0])

min_y = 0
min_x = 0

def count_neighbors(floor: list[list[bool]], pos: iVec2d) -> int:
    DIRECTIONS = [
        iVec2d(-1, -1),
        iVec2d(0, -1),
        iVec2d(1, -1),
        iVec2d(-1, 0),
        iVec2d(1, 0),
        iVec2d(-1, 1),
        iVec2d(0, 1),
        iVec2d(1, 1)
    ]

    neighbors = 0
    for direction in DIRECTIONS:
        dx, dy = direction.x, direction.y

        new_x = pos.x + dx
        new_y = pos.y + dy

        if new_x >= max_x or new_x < min_x:
            continue

        if new_y >= max_y or new_y < min_y:
            continue

        if floor[new_y][new_x]:
            neighbors += 1

    return neighbors

total_moveable_rolls = 0
while True:
    moveable_rolls = 0

    # Count Moveable Rolls
    for y in range(len(floor)):
        for x in range(len(floor[0])):

            pos = iVec2d(x, y)

            if floor[pos.y][pos.x]:
                if count_neighbors(floor, pos) < 4:
                    moveable_rolls += 1
                    print('x', end='')
                    buffer_floor[pos.y][pos.x] = False
                else:
                    print('@', end='')
            else:
                print('.', end='')

        print()

    if moveable_rolls == 0:
        break

    total_moveable_rolls += moveable_rolls

    # Swap buffers
    floor = buffer_floor.copy()


print(f'Moveable Rolls: {total_moveable_rolls}')