fn sedol(input: &str) -> Option<String> {
    let weights = vec![1, 3, 1, 7, 3, 9, 1];
    let valid_chars = "0123456789BCDFGHJKLMNPQRSTVWXYZ";

    if input.len() != 6 {
        return None;
    }

    // could be done by regex if needed
    for c in input.chars() {
        if !valid_chars.contains(c) {
            return None;
        }
    }

    let mut result: u32 = input
        .chars()
        .map(|c| {
            if c.is_digit(10) {
                c as u32 - 48
            } else {
                c as u32 - 55
            }
        })
        .zip(weights)
        .map(|(cnum, w)| w * cnum)
        .collect::<Vec<u32>>()
        .iter()
        .sum();

    result = (10 - result % 10) % 10;

    Some(input.to_owned() + &result.to_string())
}

fn main() {
    let inputs = vec![
        "710889", "B0YBKJ", "406566", "B0YBLH", "228276", "B0YBKL", "557910", "B0YBKR", "585284",
        "B0YBKT", "B00030",
    ];

    for input in inputs {
        println!("{} SEDOL: {:?}", &input, sedol(&input).unwrap());
    }
}