from dataclasses import dataclass

@dataclass
class Beam:
    i : int
    j : int
    direction : str


def move(beam):
    if beam.direction == "N": beam.i -= 1
    if beam.direction == "W": beam.j -= 1
    if beam.direction == "S": beam.i += 1
    if beam.direction == "E": beam.j += 1

def beam_advance(beam):
    global beams_todo
    global beams_done
    global exits

    # beam being explored, remove from todo
    beams_todo.pop(0)

    # move beam in its direction
    move(beam)

    i = beam.i
    j = beam.j
    direction = beam.direction

    if i < 0 or j < 0 or i >= len(lines) or j >= len(lines[0]):
        # OOB/out of grid
        # print("oob")
        # exit reached, reverse the direction to remember to remove this start later
        if   direction == "N": rev_dir = "S"
        elif direction == "W": rev_dir = "E"
        elif direction == "S": rev_dir = "N"
        elif direction == "E": rev_dir = "W"
        exits.append(Beam(i, j, rev_dir))
        return

    if beam in beams_done:
        # already explored this beam on this tile and direction, skip
        # print(beam, "done")
        return

    # add to explored beams
    beams_done.append(beam)

    # explore
    char = lines[i][j]

    if char == ".":
        beams_todo.append(Beam(i, j, direction))

    elif char == "/":
        if   direction == "N": beams_todo.append(Beam(i, j, "E"))
        elif direction == "W": beams_todo.append(Beam(i, j, "S"))
        elif direction == "S": beams_todo.append(Beam(i, j, "W"))
        elif direction == "E": beams_todo.append(Beam(i, j, "N"))

    elif char == "\\":
        if   direction == "N": beams_todo.append(Beam(i, j, "W"))
        elif direction == "W": beams_todo.append(Beam(i, j, "N"))
        elif direction == "S": beams_todo.append(Beam(i, j, "E"))
        elif direction == "E": beams_todo.append(Beam(i, j, "S"))

    elif char == "|":
        if   direction in "NS":
            beams_todo.append(Beam(i, j, direction))
        elif direction in "WE":
            beams_todo.append(Beam(i, j, "N"))
            beams_todo.append(Beam(i, j, "S"))

    elif char == "-":
        if   direction in "WE":
            beams_todo.append(Beam(i, j, direction))
        elif direction in "NS":
            beams_todo.append(Beam(i, j, "W"))
            beams_todo.append(Beam(i, j, "E"))

# script start
with open("input.txt", "r") as f:
    lines = f.readlines()

lines = [l.replace("\n", "") for l in lines]
best_energized = 0

# starts to explore
starts_todo = []
for i in range(len(lines)):
    starts_todo.append(Beam(i, -1, "E"))
    starts_todo.append(Beam(i, len(lines[0]), "W"))
for j in range(len(lines[0])):
    starts_todo.append(Beam(-1, j, "S"))
    starts_todo.append(Beam(len(lines), j, "N"))

while starts_todo:
    beams_todo = [] # list of beams to explore with the current start
    beams_done = [] # list of beams explored with the current start
    energized = []
    exits = [] # exits reached with the current start

    beams_todo.append(starts_todo[0])

    while beams_todo:
        beam_advance(beams_todo[0])

    print(starts_todo[0], "done, remaining:", len(starts_todo), "/ 440")
    starts_todo.pop(0)

    # all exits reached by the start are at best equal, so they can be safely not explored
    for exit in exits:
        # remove 1 by 1 because of potential issues with pop indexes
        for x, start in enumerate(starts_todo):
            if exit == start:
                print(starts_todo[x], "pop, remaining:", len(starts_todo), "/ 440")
                starts_todo.pop(x)

    print(len(beams_done))

    for e in beams_done:
        if (e.i, e.j) not in energized:
            energized.append((e.i, e.j))

    print(len(energized))
    if len(energized) > best_energized:
        best_energized = len(energized)

print(f"{best_energized=}")