import copy
from pprint import pprint


class PuzzleSolver:
	def __init__(self, filename):
		self.load(filename)

	def load(self, filename):
		with open(filename, "r", encoding="utf-8") as f:
			self.data = [list(x.rstrip()) for x in f.readlines()]
		self.width = len(self.data[0])
		self.height = len(self.data)

	def occupied_adjacent(self, x, y):
		n = 0
		for j in range(y-1, y+2):
			for i in range(x-1, x+2):
				if (i, j) == (x, y):
					continue
				if not (0 <= i < self.width):
					continue
				if not (0 <= j < self.height):
					continue

				s = self.get(i, j)
				if s == "#":
					n += 1

		return n

	def get(self, x, y):
		return self.data[y][x]

	def mutate(self):
		ret = copy.deepcopy(self.data)
		for y in range(self.height):
			for x in range(self.width):
				s = self.get(x, y)
				if s == ".":
					continue

				n = self.occupied_adjacent(x, y)
				if s == "L":
					if n == 0:
						ret[y][x] = "#"
				elif s == "#":
					if n >= 4:
						ret[y][x] = "L"

		return ret

	def print(self):
		for y in range(self.height):
			print("".join(self.data[y]))
		print()

	def solve(self):
		stable = False
		rounds = 0
		self.print()
		while not stable:
			x = self.mutate()
			stable = x == self.data
			self.data = x
			rounds += 1

			self.print()

		return rounds

	def count_occupied(self):
		return sum([x.count("#") for x in self.data])


ps = PuzzleSolver("test.txt")
rounds = ps.solve()
cs = PuzzleSolver("test-1.txt")
assert ps.data == cs.data

ps = PuzzleSolver("data.txt")
rounds = ps.solve()
n = ps.count_occupied()
print(f"There are {n} occupied seats.")