use cipher::{
    BlockDecryptMut as _, BlockEncryptMut as _, BlockSizeUser as _, KeyIvInit as _,
    block_padding::Pkcs7, generic_array::GenericArray,
};
use nyquest::{
    AsyncClient,
    r#async::{Body, Request},
    header::USER_AGENT,
};

use crate::error::ApiError;

const AES_KEY: &[u8; 16] = br#"/?jo+"L&\Cr9(=kG"#;
const AES_IV: &[u8; 16] = b"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";

pub async fn delivery_raw(
    client: &AsyncClient,
    title_ver: impl AsRef<str>,
) -> Result<Vec<u8>, ApiError> {
    let title_ver = title_ver.as_ref();
    let params = format!("title_id=SDGB&title_ver={title_ver}&client_id=A63E01C2805");
    let enc_data = encrypt(params, AES_KEY, AES_IV)?;

    let req = Request::post("http://at.sys-allnet.cn/net/delivery/instruction")
        .with_body(Body::bytes(enc_data, "application/xxx-form-urlencoded"))
        .with_header(USER_AGENT, "SDGB;Windows/Lite")
        .with_header("Pragma", "DFI");

    let mut resp = client.request(req).await?.bytes().await?;
    let dec_len = decrypt(&mut resp, AES_KEY, AES_IV)?.len();
    resp.truncate(dec_len);
    Ok(resp)
}

type Aes128CbcEnc = cbc::Encryptor<aes::Aes128>;
type Aes128CbcDec = cbc::Decryptor<aes::Aes128>;

fn encrypt(data: impl AsRef<[u8]>, key: &[u8; 16], iv: &[u8; 16]) -> Result<Vec<u8>, ApiError> {
    let key = GenericArray::from_slice(key);
    let iv = GenericArray::from_slice(iv);
    let encryptor = Aes128CbcEnc::new(key, iv);
    let data = data.as_ref();
    let bs = aes::Aes256::block_size();
    let pad_len = bs - data.len() % bs;

    let mut buf = vec![0; pad_len + data.len()];
    buf[..data.len()].copy_from_slice(&data);
    encryptor.encrypt_padded_mut::<Pkcs7>(&mut buf, data.len())?;
    Ok(buf)
}

fn decrypt<'ct>(
    data: &'ct mut impl AsMut<[u8]>,
    key: &[u8; 16],
    iv: &[u8; 16],
) -> Result<&'ct [u8], ApiError> {
    let key = GenericArray::from_slice(key);
    let iv = GenericArray::from_slice(iv);
    let decryptor = Aes128CbcDec::new(key, iv);
    let result = decryptor.decrypt_padded_mut::<Pkcs7>(data.as_mut())?;
    Ok(result)
}