use wasm_bindgen::prelude::*;

use aes::Aes128Enc;
use blowfish::Blowfish;
use md5::{Md5, Digest};
use cipher::{
    BlockEncrypt, BlockDecryptMut, KeyInit, KeyIvInit,
    block_padding::{NoPadding, ZeroPadding}
};

type BfCbcDec = cbc::Decryptor<Blowfish>;

const TRACK_CDN_KEY: [u8; 16] = [106, 111, 54, 97, 101, 121, 54, 104, 97, 105, 100, 50, 84, 101, 105, 104];
const BF_SECRET: [u8; 16] = [103, 52, 101, 108, 53, 56, 119, 99, 48, 122, 118, 102, 57, 110, 97, 49];

#[wasm_bindgen]
pub struct Cipher {
    cipher: BfCbcDec
}

#[wasm_bindgen]
impl Cipher {
    #[wasm_bindgen(constructor)]
    pub fn new(id: &str) -> Self {
        let id_md5 = format!("{:x}", Md5::digest(id.as_bytes()));
        let id_md5 = id_md5.as_bytes();
        let mut key = [0u8; 16];
        for i in 0..16 {
            key[i] = id_md5[i] ^ id_md5[i+16] ^ BF_SECRET[i]
        };
        Self { cipher: BfCbcDec::new_from_slices(&key, &[0, 1, 2, 3, 4, 5, 6, 7]).unwrap() }
    }

    pub fn decrypt_chunk(&self, chunk: &mut [u8]) {
        self.cipher.clone().decrypt_padded_mut::<NoPadding>(chunk).unwrap();
    }
}

#[wasm_bindgen]
pub fn legacy_stream_url(md5_origin: &str, format: &str, id: &str, media_version: u8) -> String {
    // md5 origin + format num + id + media version
    let metadata = [
        md5_origin.as_bytes(),
        &[b'\xa4'],
        format.as_bytes(),
        &[b'\xa4'],
        id.as_bytes(),
        &[b'\xa4'],
        media_version.to_string().as_bytes(),
    ].concat();

    let hash = format!("{:x}", Md5::digest(&metadata));

    // md5 hash + previous metadata
    let metadata_hash = [
        hash.as_bytes(),
        &[b'\xa4'],
        &metadata,
        &[b'\xa4'],
    ].concat();

    let cipher = Aes128Enc::new_from_slice(&TRACK_CDN_KEY).unwrap();
    let ciphertext = cipher.encrypt_padded_vec::<ZeroPadding>(&metadata_hash);

    format!("https://cdns-proxy-{}.dzcdn.net/mobile/1/{}", md5_origin.chars().next().unwrap(), hex::encode(ciphertext))
}