use num::integer::lcm;
use std::collections::HashMap;
use std::fs::File;
use std::io::Read;

fn main() {
    // let filename = "in/day08.ref";
    let filename = "in/day08.pzl";

    let mut f = File::open(filename).expect("cannot open file");
    let mut content = String::new();
    f.read_to_string(&mut content).expect("cannot read file");
    let mut lines = content.trim_end().split("\n\n");

    let ops: Vec<char> = lines.next().unwrap().chars().collect();

    let mut tree: HashMap<&str, (&str, &str)> = HashMap::new();
    for line in lines.next().unwrap().split('\n') {
        let (first, rest) = line.split_once(" = ").unwrap();
        let (left, right) = rest.split_once(", ").unwrap();
        let left = &left[1..];
        let right = &right[..3];
        tree.insert(first, (left, right));
    }

    let traverse_tree_until = |start: &str, f: fn(&str) -> bool| {
        let mut loc = start;
        let mut steps: usize = 0;
        loop {
            let (left, right) = tree.get(loc).unwrap();
            let op = ops[steps % ops.len()];

            if op == 'L' {
                loc = left;
            } else {
                loc = right;
            }
            if f(&loc) {
                break;
            }
            steps += 1;
        }
        (steps + 1) as u64
    };

    let res1 = traverse_tree_until("AAA", |x| x == "ZZZ");

    let locs = tree.keys().filter(|x| &x[2..3] == "A").collect::<Vec<_>>();
    let mut stps: Vec<u64> = Vec::new();
    for i in 0..locs.len() {
        stps.push(traverse_tree_until(locs[i], |x| x.ends_with("Z")));
    }
    let res2 = stps.iter().fold(1, |x, y| lcm(x, *y));

    println!("res1: {}", res1);
    println!("res2: {}", res2);
    assert_eq!(res1, 14257);
    assert_eq!(res2, 16187743689077);
}