use std::collections::VecDeque;

use openssl::bn::BigNum;

use crate::PK_LENGTH;

/// The allowed character set in a product key.
pub const P_KEY_CHARSET: [char; 24] = [
    'B', 'C', 'D', 'F', 'G', 'H', 'J', 'K', 'M', 'P', 'Q', 'R', 'T', 'V', 'W', 'X', 'Y', '2', '3',
    '4', '6', '7', '8', '9',
];

pub fn base24_decode(cd_key: &str) -> Vec<u8> {
    let p_decoded_key: Vec<u8> = cd_key
        .chars()
        .filter_map(|c| P_KEY_CHARSET.iter().position(|&x| x == c).map(|i| i as u8))
        .collect();

    let mut y = BigNum::from_u32(0).unwrap();

    for i in p_decoded_key {
        y.mul_word((PK_LENGTH - 1) as u32).unwrap();
        y.add_word(i.into()).unwrap();
    }

    y.to_vec()
}

pub fn base24_encode(byte_seq: &[u8]) -> String {
    let mut z = BigNum::from_slice(byte_seq).unwrap();
    let mut out: VecDeque<char> = VecDeque::new();
    (0..=24).for_each(|_| out.push_front(P_KEY_CHARSET[z.div_word(24).unwrap() as usize]));
    out.iter().collect()
}

#[cfg(test)]
mod tests {
    #[test]
    fn test_base24() {
        let input = "JTW3TJ7PFJ7V9CCMX84V9PFT8";
        let unbase24 = super::base24_decode(input);
        println!("{:?}", unbase24);
        let base24 = super::base24_encode(&unbase24);
        println!("{}", base24);
        assert_eq!(input, base24);
    }
}