fn mogu_levo(c: char) -> bool {
    return c == 'S' || c == 'L' || c == 'F' || c == '-';
}

fn mogu_desno(c: char) -> bool {
    return c == 'S' || c == '7' || c == 'J' || c == '-';
}

fn mogu_gore(c: char) -> bool {
    return c == 'S' || c == '7' || c == 'F' || c == '|';
}

fn mogu_dole(c: char) -> bool {
    return c == 'S' || c == 'L' || c == 'J' || c == '|';
}

fn bfs(input: &Vec<String>, was: &mut Vec<Vec<bool>>, x: i32, y: i32, s: u32) -> u32 {
    if s > 2 && input[y as usize].chars().nth(x as usize).unwrap() == 'S' {
        return s;
    }

    if was[y as usize][x as usize] {
        return 0;
    }

    was[y as usize][x as usize] = true;

    for (dx, dy) in [(-1, 0), (1, 0), (0, -1), (0, 1)] {
        let nx = x + dx;
        let ny = y + dy;
        if nx >= 0 && nx < input[y as usize].len() as i32 && ny >= 0 && ny < input.len() as i32 {
            let t = input[y as usize].chars().nth(x as usize).unwrap();
            let n = input[ny as usize].chars().nth(nx as usize).unwrap();

            let ind: bool;
            if dx == 1 {
                ind = mogu_levo(t) && mogu_desno(n);
            } else if dx == -1 {
                ind = mogu_desno(t) && mogu_levo(n);
            } else if dy == 1 {
                ind = mogu_gore(t) && mogu_dole(n);
            } else {
                ind = mogu_dole(t) && mogu_gore(n);
            }

            if !ind {
                continue;
            }

            let ret = bfs(input, was, nx, ny, s + 1);
            //            was[ny as usize][nx as usize] = false;

            if ret != 0 {
                return ret;
            }
        }
    }
    return 0;
}

fn set_s(input: &mut Vec<String>, xs: i32, ys: i32) {
    let levi = mogu_levo(input[ys as usize].chars().nth(xs as usize - 1).unwrap());
    let gornji = mogu_gore(input[ys as usize - 1].chars().nth(xs as usize).unwrap());
    let donji = mogu_dole(input[ys as usize + 1].chars().nth(xs as usize).unwrap());
    let desni = mogu_desno(input[ys as usize].chars().nth(xs as usize + 1).unwrap());

    if donji && gornji {
        input[ys as usize] = input[ys as usize].replace("S", "|");
    } else if donji && levi {
        input[ys as usize] = input[ys as usize].replace("S", "7");
    } else if donji && desni {
        input[ys as usize] = input[ys as usize].replace("S", "F");
    } else if gornji && levi {
        input[ys as usize] = input[ys as usize].replace("S", "J");
    } else if gornji && desni {
        input[ys as usize] = input[ys as usize].replace("S", "L");
    } else if levi && desni {
        input[ys as usize] = input[ys as usize].replace("S", "-");
    } else {
        panic!();
    }
}

fn part2(input: &Vec<String>, was: Vec<Vec<bool>>) -> u32 {
    let mut s: u32 = 0;
    let mut en: bool;
    let mut lc: char;

    for i in 0..input.len() {
        en = false;
        lc = 'S';

        for j in 0..input[i].len() {
            let c = input[i].chars().nth(j).unwrap();

            if !was[i][j] {
                s += en as u32;
                continue;
            }

            if c == '-' {
                continue;
            } else if c == '|' {
                en = !en;
                continue;
            }

            if lc == 'S' {
                lc = c;
                if lc == 'J' || lc == '7' {
                    panic!();
                }
            } else {
                if (lc == 'F' && c == 'J') || (lc == 'L' && c == '7') {
                    en = !en;
                }
                lc = 'S';
            }
        }
    }

    return s;
}

pub fn main() {
    let txt = std::fs::read_to_string("./input/day10.txt").unwrap();
    let mut input: Vec<_> = vec![];
    for line in txt.lines() {
        input.push(line.to_string());
    }

    let mut xs = 0;
    let mut ys = 0;

    for i in 0..input.len() {
        for j in 0..input[i].len() {
            if input[i].chars().nth(j).unwrap() == 'S' {
                xs = j as i32;
                ys = i as i32;
            }
        }
    }

    let mut was = vec![vec![false; input[0].len()]; input.len()];
    bfs(&input, &mut was, xs, ys, 0);
    set_s(&mut input, xs, ys);

    println!("{}", part2(&input, was));
}