use rand::rngs::OsRng;
use rand::seq::IteratorRandom;
use rand::seq::SliceRandom;
use std::iter::FromIterator;

pub fn generate(spec: &str) {
    let (len, rest) = {
        let mut separated = spec.splitn(2, ',');
        let len = separated.next().unwrap();
        let rest = separated.next().unwrap();
        (len, rest)
    };
    let mut rnd = OsRng::new().unwrap();

    let mut password_vec: Vec<char> = rest
        .chars()
        .cycle()
        .map(|c| match c {
            'a' => "abcdefghijklmnopqrstuvwxyz"
                .chars()
                .choose(&mut rnd)
                .expect("Could not get random element"),
            'A' => "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                .chars()
                .choose(&mut rnd)
                .expect("Could not get random element"),
            '1' => "1234567890"
                .chars()
                .choose(&mut rnd)
                .expect("Could not get random element"),
            '.' => ".,/?-=#%^"
                .chars()
                .choose(&mut rnd)
                .expect("Could not get random element"),
            _ => panic!("Unknown character spec: {}", c),
        })
        .take(len.parse().unwrap())
        .collect();

    password_vec.shuffle(&mut rnd);
    let shuffled: String = String::from_iter(password_vec.into_iter());
    println!("{}", shuffled);
}