// love from https://github.com/LagrangeDev/lagrangejs/blob/main/src/core/tea.ts & https://github.com/takayama-lily/oicq/blob/main/lib/core/tea.ts

// @ts-nocheck
const BUF7 = Buffer.alloc(7);
const deltas = [
  0x9e3779b9, 0x3c6ef372, 0xdaa66d2b, 0x78dde6e4, 0x1715609d, 0xb54cda56, 0x5384540f, 0xf1bbcdc8, 0x8ff34781,
  0x2e2ac13a, 0xcc623af3, 0x6a99b4ac, 0x08d12e65, 0xa708a81e, 0x454021d7, 0xe3779b90,
];

function _toUInt32 (num: number) {
  return num >>> 0;
}

function _encrypt (x: number, y: number, k0: number, k1: number, k2: number, k3: number): [number, number] {
  for (let i = 0; i < 16; ++i) {
    let aa = ((_toUInt32(((y << 4) >>> 0) + k0) ^ _toUInt32(y + deltas[i])) >>> 0) ^ _toUInt32(~~(y / 32) + k1);
    aa >>>= 0;
    x = _toUInt32(x + aa);
    let bb = ((_toUInt32(((x << 4) >>> 0) + k2) ^ _toUInt32(x + deltas[i])) >>> 0) ^ _toUInt32(~~(x / 32) + k3);
    bb >>>= 0;
    y = _toUInt32(y + bb);
  }
  return [x, y];
}

export function encrypt (data: Buffer, key: Buffer) {
  let n = (6 - data.length) >>> 0;
  n = (n % 8) + 2;
  const v = Buffer.concat([Buffer.from([(n - 2) | 0xf8]), Buffer.allocUnsafe(n), data, BUF7]);
  const k0 = key.readUInt32BE(0);
  const k1 = key.readUInt32BE(4);
  const k2 = key.readUInt32BE(8);
  const k3 = key.readUInt32BE(12);
  let r1 = 0; let r2 = 0; let t1 = 0; let t2 = 0;
  for (let i = 0; i < v.length; i += 8) {
    const a1 = v.readUInt32BE(i);
    const a2 = v.readUInt32BE(i + 4);
    const b1 = a1 ^ r1;
    const b2 = a2 ^ r2;
    const [x, y] = _encrypt(b1 >>> 0, b2 >>> 0, k0, k1, k2, k3);
    r1 = x ^ t1;
    r2 = y ^ t2;
    t1 = b1;
    t2 = b2;
    v.writeInt32BE(r1, i);
    v.writeInt32BE(r2, i + 4);
  }
  return v;
}

function _decrypt (x: number, y: number, k0: number, k1: number, k2: number, k3: number) {
  for (let i = 15; i >= 0; --i) {
    const aa = ((_toUInt32(((x << 4) >>> 0) + k2) ^ _toUInt32(x + deltas[i])) >>> 0) ^ _toUInt32(~~(x / 32) + k3);
    y = (y - aa) >>> 0;
    const bb = ((_toUInt32(((y << 4) >>> 0) + k0) ^ _toUInt32(y + deltas[i])) >>> 0) ^ _toUInt32(~~(y / 32) + k1);
    x = (x - bb) >>> 0;
  }
  return [x, y];
}

export function decrypt (encrypted: Buffer, key: Buffer) {
  if (encrypted.length % 8) throw ERROR_ENCRYPTED_LENGTH;
  const k0 = key.readUInt32BE(0);
  const k1 = key.readUInt32BE(4);
  const k2 = key.readUInt32BE(8);
  const k3 = key.readUInt32BE(12);
  let r1 = 0; let r2 = 0; let t1 = 0; let t2 = 0; let x = 0; let y = 0;
  for (let i = 0; i < encrypted.length; i += 8) {
    const a1 = encrypted.readUInt32BE(i);
    const a2 = encrypted.readUInt32BE(i + 4);
    const b1 = a1 ^ x;
    const b2 = a2 ^ y;
    [x, y] = _decrypt(b1 >>> 0, b2 >>> 0, k0, k1, k2, k3);
    r1 = x ^ t1;
    r2 = y ^ t2;
    t1 = a1;
    t2 = a2;
    encrypted.writeInt32BE(r1, i);
    encrypted.writeInt32BE(r2, i + 4);
  }
  if (Buffer.compare(encrypted.subarray(encrypted.length - 7), BUF7) !== 0) throw ERROR_ENCRYPTED_ILLEGAL;
  // if (Buffer.compare(encrypted.slice(encrypted.length - 7), BUF7) !== 0) throw ERROR_ENCRYPTED_ILLEGAL;
  return encrypted.subarray((encrypted[0] & 0x07) + 3, encrypted.length - 7);
  // return encrypted.slice((encrypted[0] & 0x07) + 3, encrypted.length - 7);
}

const ERROR_ENCRYPTED_LENGTH = new Error('length of encrypted data must be a multiple of 8');
const ERROR_ENCRYPTED_ILLEGAL = new Error('encrypted data is illegal');
