use std::time::Instant;
use utils;

pub fn task1() {
    let mut input = utils::read_file("input/day05.txt");
    let start = Instant::now();
    input = reduce(input.as_str());

    println!("Duration: {:?}", Instant::now() - start);
    println!("RESULT: {}", input.len());
}

pub fn task2() {
    let input = utils::read_file("input/day05.txt");
    let start = Instant::now();
    let input = reduce(&input);
    let best = "abcdefghijklmnopqrstuvwxyz"
        .chars()
        .map(|c| {
            (
                c,
                reduce(
                    &input
                        .chars()
                        .filter(|ch| ch.to_lowercase().next().unwrap() != c)
                        .collect::<String>(),
                ).len(),
            )
        }).min_by_key(|it| it.1)
        .unwrap();

    println!("Duration: {:?}", Instant::now() - start);
    println!("Best: {} (length {})", best.0, best.1);
}

fn reduce(input: &str) -> String {
    input
        .chars()
        .fold(Vec::<char>::new(), |mut stack, c| {
            let last: Option<char>;
            {
                if let Some(c) = stack.last() {
                    last = Some(*c)
                } else {
                    last = None
                }
            }

            if let Some(last) = last {
                if c.eq_ignore_ascii_case(&last) && c != last {
                    stack.pop();
                } else {
                    stack.push(c);
                }
            } else {
                stack.push(c);
            }
            stack
        }).iter()
        .collect()
}