extern crate crypto;
extern crate iterslide;

use crypto::digest::Digest;
use crypto::md5::Md5;
use iterslide::SlideIterator;

const SALT: &'static str = "ahsbgdzn";

fn hash(salt: &str, n: u32, loops: usize) -> String {
    let mut md5 = Md5::new();
    md5.input_str(salt);
    md5.input_str(&n.to_string());
    let mut result = md5.result_str();
    for _ in 0..loops {
        md5.reset();
        md5.input_str(&result);
        result = md5.result_str();
    }
    result
}

fn threes(s: &str) -> Option<char> {
    s.chars().slide(3).find(|ss| ss[0] == ss[1] && ss[1] == ss[2]).map(|ss| ss[0])
}

fn has_five(s: &str, c: char) -> bool {
    s.chars().slide(5).any(|ss| ss.iter().all(|cc| c == *cc))
}

fn p14(salt: &str, mut index: u32, loops: usize) -> u32 {
    for v in (0..100000).map(|n| {
        let s = hash(salt, n, loops);
        (s, n)
    }).slide(1001).filter(|v| {
        if let Some(c) = threes(&v[0].0) {
            v.iter().skip(1).any(|&(ref k, _)| has_five(&k, c))
        } else {
            false
        }
    }) {
        if index == 0 {
            return v[0].1;
        } else {
            index -= 1;
        }
    }
    0
}

fn main() {
    println!("P1 = {}", p14(SALT, 63, 0));
    println!("P2 = {}", p14(SALT, 63, 2016));
}