import aocd

from enum import Enum

class Direction(complex, Enum):
    NORTH = -1j
    SOUTH = 1j
    EAST = -1
    WEST = 1
    NORTHWEST = NORTH+WEST
    NORTHEAST = NORTH+EAST
    SOUTHWEST = SOUTH+WEST
    SOUTHEAST = SOUTH+EAST

class Paper:
    def __init__(self, x, y, floor):
        self.coords = complex(real=x, imag=y)
        self.floor = floor
    
    @property
    def x(self):
        return int(self.coords.real)
    
    @property
    def y(self):
        return int(self.coords.imag)
    
    @property
    def neighbours(self):
        yield from filter(None, (self.floor.get(self.coords + dir) for dir in Direction))

def parse(data):
    floor = {}

    for y, line in enumerate(data.split('\n')):
        for x, char in enumerate(line):
            if char == '@':
                floor[complex(real=x, imag=y)] = Paper(x, y, floor)
    
    return floor

def is_accessible(paper):
    return sum(1 for _ in paper.neighbours) < 4

def main(data):
    floor = parse(data.strip())
    total = 0
    while (removable := set(paper for paper in floor.values() if is_accessible(paper))):
        total += len(removable)
        for paper in removable:
            del floor[paper.coords]
    return total

if __name__ == '__main__':
    solution = main(aocd.get_data(day=4, year=2025))
    print(solution)
    aocd.submit(solution, part='b', day=4, year=2025)