from part1 import *


verbose = False
sssst = True

thoughts = \
"""
So, we can place an obstacle on each of the 130*130 - #obstacles = 16900
- obstacles positions, but the initial path only covers 1512 positions
(thus 1512 - 1 = 1511 steps). By instead placing an obstacle on each of
those steps, we can find a loop.

The other thing we need to do, is detect loops. For that, It would be
nice to store both positions and directions to establish uniqueness,
or just check whether it is the fifth time in a position (as we have
then travelled to that position at least twice from at least one
position; see Pigeonhole principle).
"""

#map_to_load = "testinput"
map_to_load = "input"

if __name__ == "__main__":
	m = Map()
	m.load_map(map_to_load)

	# Prepare forked map for speed
	forked_map = m.copy()
	#forked_map = Map()
	#forked_map.load_map(map_to_load)
	begin_pos = m.pos
	begin_direction = m.direction

	trace = [m.pos]
	while m.step():
		trace.append(m.pos)
	#print(trace)

	loop_obstacles = []

	for i in range(1, len(trace)):
		pos, next_pos = trace[i - 1], trace[i]

		if not forked_map.pos_in_map(next_pos):
			continue

		if verbose:
			print(m.pos, m.direction)

		# Setup the fork
		forked_map.map[next_pos] = Map.Tiles.OBSTACLE.value
		forked_map.map[pos] = m.map[pos]
		forked_map.pos = begin_pos
		forked_map.direction = begin_direction
		forked_map.trace = [begin_pos]
		forked_map.pos_counter *= 0
		#print(forked_map.trace)
		#forked_map.show()
		if not sssst:
			print(f"Forking at {next_pos}... ", end="")
		try:
			while forked_map.step():
				continue
		except Map.LoopException:
			if not sssst:
				print("loop.")
			loop_obstacles.append(next_pos)
			#print(forked_map.trace)
			#forked_map.show()
		else:
			if not sssst:
				print("no loop.")
			#print(forked_map.trace)
			#forked_map.show()
	print(len(set(loop_obstacles)))