use crate::{bytes::Bytes, mt19937};

pub fn decrypt(key: u16, data: &Bytes) -> Bytes {
    encrypt(key, data)
}

pub fn encrypt(key: u16, Bytes(data): &Bytes) -> Bytes {
    // You can create a trivial stream cipher out of any PRNG; use it to
    // generate a sequence of 8 bit outputs and call those outputs a keystream.
    // XOR each byte of plaintext with each successive byte of keystream.
    // Write the function that does this for MT19937 using a 16-bit seed.

    let mut mt = mt19937::MT19937::new();
    mt.seed(key as u32);
    let mut result: Vec<u8> = vec![];

    for chunk in data.chunks(4) {
        let key = mt.extract_bytes();
        for i in 0..chunk.len() {
            let cipher_char = chunk[i] ^ key[i];
            result.push(cipher_char);
        }
    }

    Bytes(result)
}