from itertools import cycle

path = "day_06.txt"
# path = "test.txt"

with open(path) as f:
    lines = [l.strip() for l in f.readlines()]

ROWS = len(lines)
COLS = len(lines[0])

directions = {">": (0,1), 'v': (1,0), '<': (0,-1), '^': (-1, 0)}

loop = cycle(directions)

def reset_loop(loop, char):
    while next(loop) != char:
        continue

initial_pos = ()
d = ()
for i in range(ROWS):
    for j in range(COLS):
        if lines[i][j] in directions:
            initial_pos = (i,j)
            d = directions[lines[i][j]]

            reset_loop(loop, lines[i][j])

def is_inside(lines, pos):
    return 0 <= pos[0] < ROWS and 0<= pos[1] < COLS

def walk(lines, pos, d, obstacle, d_loop):
    i,j = pos
    x,y = d

    new_pos = (x+i, y+j)
    if is_inside(lines, new_pos) and \
        (lines[new_pos[0]][new_pos[1]] == '#' or new_pos == obstacle):
        return pos, directions[next(d_loop)]

    return new_pos, d

def evaluate_path(lines, initial_pos, initial_d, obstacle, d_loop):
    inside = True
    in_loop = False
    pos = initial_pos
    d = initial_d
    walked = set()
    loop_detec = set()
    while inside and not in_loop:
        walked.add(pos)
        loop_detec.add((pos, d))
        pos, d = walk(lines, pos, d, obstacle, d_loop)

        in_loop = (pos,d) in loop_detec
        inside = is_inside(lines, pos)

    return len(walked), in_loop

print( "p1: ", evaluate_path(lines, initial_pos, d, None, loop)[0])

# P2 brute force?
p2 = 0
for row in range(ROWS):
    for col in range(COLS):
        reset_loop(loop, lines[initial_pos[0]][initial_pos[1]])

        size, in_loop = evaluate_path(lines, initial_pos, d, (row, col), loop)

        p2 += 1 if in_loop else 0
        percentage = int((row*ROWS + col)/(ROWS*COLS) * 100)
        print(f'{percentage}%', end='\r')

print('100%')

print('p2: ', p2)