fn encode_hex(bytes: &Vec<u8>) -> Result<String, &str> {
    let x = bytes
        .iter()
        .map(|digit| {
            match (
                std::char::from_digit((digit / 16) as u32, 16),
                std::char::from_digit((digit % 16) as u32, 16),
            ) {
                (Some(x), Some(y)) => Ok(vec![x, y]),
                _ => Err("Could not convert digit"),
            }
        })
        .collect::<Result<Vec<Vec<char>>, &str>>()?
        .iter()
        .flatten()
        .collect::<String>();
    Ok(x.clone())
}

fn main() {
    let mut cyphertext: Vec<u8> = unimplemented!();

    cyphertext.truncate(cyphertext.len() - 16);
    cyphertext.reverse();

    println!("reduce {:?}", cyphertext);
    let plaintext: Vec<u8> = vec![];

    let s = encode_hex(&cyphertext).unwrap();
}