use md5;

fn solve_part1(seed: &str) -> String {
    let mut passw = String::new();

    let mut i = 0;
    loop {
        let data = format!("{}{}", seed, i.to_string());
        let hash = format!("{:x}", md5::compute(data));

        // We've mined a block, so-- wait wrong software
        if hash.starts_with("00000") {
            passw.push(hash.chars().nth(5).unwrap());
            if passw.len() >= 8 {
                break;
            }
        }

        i += 1;
    }

    passw
}

fn solve_part2(seed: &str) -> String {
    // We'll replace each `x' with the true character
    let mut passw = String::from("xxxxxxxx");

    let mut i = 0;
    loop {
        let data = format!("{}{}", seed, i.to_string());
        let hash = format!("{:x}", md5::compute(data));

        // I wonder how this loop affects global power consumption...
        if hash.starts_with("00000") {
            let c = hash.chars().nth(5).unwrap();
            if c.is_ascii_digit() {
                // Get index of character to replace
                let k = String::from(c).parse().unwrap();

                // Is `k' in bounds, and haven't we replaced `passw[k]' already?
                if k < 8 && passw.chars().nth(k).unwrap() == 'x' {
                    let s = String::from(hash.chars().nth(6).unwrap());
                    passw.replace_range(k..k + 1, &s);

                    // Have we replaced all characters in `passw'?
                    if !passw.contains('x') {
                        break;
                    }
                }
            }
        }

        i += 1;
    }

    passw
}

fn main() {
    // My personal input ID
    let id = "ugkcyxxp";

    // Part 1 gives "d4cd2ee1" for me
    println!("Part 1 solution: {}", solve_part1(id));

    // Part 2 gives "f2c730e5" for me
    println!("Part 2 solution: {}", solve_part2(id));
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn part1_example1() {
        let id = "abc";
        assert_eq!(solve_part1(id), "18f47a30");
    }

    #[test]
    fn part2_example1() {
        let id = "abc";
        assert_eq!(solve_part2(id), "05ace8e3");
    }
}