const INPUT: &str = include_str!("../inputs/02");

fn get_instructions() -> impl Iterator<Item = (&'static str, isize)> {
    INPUT
        .lines()
        .filter_map(|s| s.split_once(' '))
        .filter_map(|(op, n)| n.parse::<isize>().ok().map(|n| (op, n)))
}

fn part_1() -> isize {
    let x: isize = get_instructions()
        .filter(|(op, _)| *op == "forward")
        .map(|(_, n)| n)
        .sum();

    let y: isize = get_instructions()
        .filter_map(|(op, n)| match op {
            "up" => Some(-n),
            "down" => Some(n),
            _ => None,
        })
        .sum();

    x * y
}

fn part_2() -> isize {
    let mut x = 0isize;
    let mut depth = 0isize;
    let mut aim = 0isize;

    for (op, n) in get_instructions() {
        match op {
            "forward" => {
                x += n;
                depth += n * aim;
            }
            "down" => aim += n,
            "up" => aim -= n,
            _ => unreachable!(),
        }
    }

    x * depth
}

pub fn main() {
    println!("Day 2:");
    println!("  Part 1: {}", part_1());
    println!("  Part 2: {}", part_2());
}