pub const BASE: u8 = 62;
pub const ALPHABET: &[u8; BASE as usize] = 
    b"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

pub fn number_to_digits(mut x: u128, base: u8) -> Vec<u8> {
    let mut out = Vec::new();
    let base = base as u128;
    while x > base {
        out.push((x % base) as u8);
        x /= base;
    }
    out.push(x as u8);
    out.reverse();
    out
}

#[allow(dead_code)]
pub fn digits_to_number<I>(x: I, base: u8) -> u128
where I: Iterator<Item=u8> {
    let base = base as u128;
    x.fold(0, |out, digit| out * base + digit as u128)
}

pub fn digits_to_string<I>(x: I, alphabet: &[u8]) -> String
where I: Iterator<Item=u8> {
    x.map(|d| alphabet[d as usize] as char).collect()
}

#[cfg(test)]
mod test {
    use crate::base62::*;

    #[test]
    fn test_number_to_digits() {
        assert_eq!(vec![0], number_to_digits(0, 10));
        assert_eq!(vec![8], number_to_digits(8, BASE));
        assert_eq!(vec![1, 2], number_to_digits(64, BASE));
        assert_eq!(vec![6, 4], number_to_digits(64, 10));
    }

    #[test]
    fn test_digits_to_number() {
        assert_eq!(digits_to_number(vec![1u8, 2].into_iter(), BASE), 64);
        assert_eq!(digits_to_number(vec![6u8, 4].into_iter(), 10), 64);
    }

    #[test]
    fn test_digits_to_string() {
        assert_eq!(digits_to_string(vec![1u8, 2].into_iter(), ALPHABET), "12");
    }
}