import lib

EXAMPLE = """
..F7.
.FJ|.
SJ.L7
|F--J
LJ...
"""

EXAMPLE2 = """
...........
.S-------7.
.|F-----7|.
.||.....||.
.||.....||.
.|L-7.F-J|.
.|..|.|..|.
.L--J.L--J.
...........
"""

EXAMPLE3 = """
..........
.S------7.
.|F----7|.
.||OOOO||.
.||OOOO||.
.|L-7F-J|.
.|II||II|.
.L--JL--J.
..........
"""

EXAMPLE4 = """
FF7FSF7F7F7F7F7F---7
L|LJ||||||||||||F--J
FL-7LJLJ||||||LJL-77
F--JF--7||LJLJIF7FJ-
L---JF-JLJIIIIFJLJJ7
|F|F-JF---7IIIL7L|7|
|FFJF7L7F-JF7IIL---7
7-L-JL7||F7|L7F-7F7|
L.L7LFJ|||||FJL7||LJ
L7JLJL-JLJLJL--JLJ.L
"""


# | is a vertical pipe connecting north and south.
# - is a horizontal pipe connecting east and west.
# L is a 90-degree bend connecting north and east.
# J is a 90-degree bend connecting north and west.
# 7 is a 90-degree bend connecting south and west.
# F is a 90-degree bend connecting south and east.
# . is ground; there is no pipe in this tile.
# S is the starting position of the animal; there is a pipe on this tile, but your sketch doesn't show what shape the pipe has.

# Mapping of in-direction to out-direction for each piece.
DIRS = {
        '|': {
            (1, 0): (1, 0),
            (-1, 0): (-1, 0),
        },
        '-': {
            (0, -1): (0, -1),
            (0, 1): (0, 1),
        },
        'L': {
            (1, 0): (0, 1),
            (0, -1): (-1, 0),
        },
        'J': {
            (0, 1): (-1, 0),
            (1, 0): (0, -1),
        },
        '7': {
            (0, 1): (1, 0),
            (-1, 0): (0, -1),
        },
        'F': {
            (-1, 0): (0, 1),
            (0, -1): (1, 0),
        }
}

RIGHTS = {
        '|': {
            (1, 0): [(0, -1)],
            (-1, 0): [(0, 1)],
        },
        '-': {
            (0, -1): [(-1, 0)],
            (0, 1): [(1, 0)],
        },
        'L': {
            (1, 0): [(0, -1), (1, 0)],
            (0, -1): [(-1, 1)],
        },
        'J': {
            (0, 1): [(1, 0), (0, 1)],
            (1, 0): [(-1, -1)],
        },
        '7': {
            (0, 1): [(1, -1)],
            (-1, 0): [(0, 1), (-1, 0)],
        },
        'F': {
            (-1, 0): [(1, 1)],
            (0, -1): [(-1, 0), (0, -1)],
        }
}

def solve(lines: list[str], return_path=False):
    res = 0
    maze = []
    start = ()
    max_path, max_right = [], []
    maze = list(map(list, lines))
    for i, row in enumerate(maze):
        for j, col in enumerate(row):
            if col == "S":
                start = (i , j)
    row_max, col_max = len(maze), len(maze[0])

    for current_dir in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
        current_field = start
        steps = 0
        path = []
        right = []
        # print(f"START: {start} {current_dir=}")
        while True:
            path.append(current_field)
            next_field = (current_field[0] + current_dir[0], current_field[1] + current_dir[1])
            if next_field == start:
                break

            if next_field[0] < 0 or next_field[1] < 0 or next_field[0] >= row_max or next_field[1] >= col_max:
                # print(f"BREAK: Cannot go to {next_field=}!")
                break

            prev_dir = current_dir
            next_char = maze[next_field[0]][next_field[1]]
            try:
                current_dir = DIRS[next_char][current_dir]
            except KeyError:
                # print(f"BREAK: Cannot go from {current_field=} with {current_dir=} to {next_field=} ({next_char})!")
                break

            for rights in RIGHTS[next_char][prev_dir]:
                rf = (next_field[0] + rights[0], next_field[1] + rights[1])
                right.append(rf)

            current_field = next_field
            steps += 1
        res = max(res, (steps + 1) // 2)
        if len(path) > len(max_path):
            max_path = path
            max_right = right

    if return_path:
        return res, max_path, max_right
    else:
        return res

def solve2(lines: list[str]):
    row_max = len(lines)
    col_max = len(lines[0])
    length, path, right = solve(lines, True)

    def clean(fields):
        fields = list(set(fields))
        cleaned = []
        for f in fields:
            if f in path:
                continue
            if f[0] < 0 or f[1] < 0 or f[0] >= row_max or f[1] >= col_max:
                continue
            cleaned.append(f)
        return cleaned

    right = clean(right)
    visited = set()
    to_visit = list(right)
    while to_visit:
        current = to_visit.pop()
        for nb in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
            f = (current[0] + nb[0], current[1] + nb[1])
            if f[0] < 0 or f[1] < 0 or f[0] >= row_max or f[1] >= col_max:
                continue

            if f not in visited and f not in path:
                right.append(f)
                to_visit.append(f)
                visited.add(f)

    right = clean(right)

    n_all = row_max * col_max
    n_right = len(right)
    n_left = n_all - n_right - len(path)

    return min(n_left, n_right)

def main():
    lines = lib.str_to_lines_no_empty(EXAMPLE)
    print("Example  1:", solve(lines))

    lines = lib.str_to_lines_no_empty(open("i10.txt").read())
    print("Solution 1:", solve(lines))

    lines = lib.str_to_lines_no_empty(EXAMPLE4)
    print("Example  2:", solve2(lines))

    lines = lib.str_to_lines_no_empty(open("i10.txt").read())
    print("Solution 2:", solve2(lines))

if __name__ == "__main__":
    main()