// Artalk 的 email_encrypted 字段 = MD5(email 小写)，前端拿它当 Gravatar / Cravatar 的 hash。
// Workers 的 crypto.subtle 不提供 MD5，所以这里自带一份。

const K_HEX = [
  'd76aa478', 'e8c7b756', '242070db', 'c1bdceee', 'f57c0faf', '4787c62a', 'a8304613', 'fd469501',
  '698098d8', '8b44f7af', 'ffff5bb1', '895cd7be', '6b901122', 'fd987193', 'a679438e', '49b40821',
  'f61e2562', 'c040b340', '265e5a51', 'e9b6c7aa', 'd62f105d', '02441453', 'd8a1e681', 'e7d3fbc8',
  '21e1cde6', 'c33707d6', 'f4d50d87', '455a14ed', 'a9e3e905', 'fcefa3f8', '676f02d9', '8d2a4c8a',
  'fffa3942', '8771f681', '6d9d6122', 'fde5380c', 'a4beea44', '4bdecfa9', 'f6bb4b60', 'bebfbc70',
  '289b7ec6', 'eaa127fa', 'd4ef3085', '04881d05', 'd9d4d039', 'e6db99e5', '1fa27cf8', 'c4ac5665',
  'f4292244', '432aff97', 'ab9423a7', 'fc93a039', '655b59c3', '8f0ccc92', 'ffeff47d', '85845dd1',
  '6fa87e4f', 'fe2ce6e0', 'a3014314', '4e0811a1', 'f7537e82', 'bd3af235', '2ad7d2bb', 'eb86d391',
].map((h) => parseInt(h, 16) >>> 0);

const S = [
  7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22,
  5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20,
  4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23,
  6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21,
];

function wordToHexLE(n: number): string {
  let out = '';
  for (let i = 0; i < 4; i++) out += ((n >>> (i * 8)) & 0xff).toString(16).padStart(2, '0');
  return out;
}

export function md5(input: string): string {
  const bytes = new TextEncoder().encode(input);
  const len = bytes.length;
  const padded = new Uint8Array((((len + 8) >> 6) + 1) * 64);
  padded.set(bytes);
  padded[len] = 0x80;

  const dv = new DataView(padded.buffer);
  const bitLen = len * 8;
  dv.setUint32(padded.length - 8, bitLen >>> 0, true);
  dv.setUint32(padded.length - 4, Math.floor(bitLen / 0x100000000), true);

  let a0 = 0x67452301;
  let b0 = 0xefcdab89;
  let c0 = 0x98badcfe;
  let d0 = 0x10325476;

  for (let chunk = 0; chunk < padded.length; chunk += 64) {
    const M = new Uint32Array(16);
    for (let i = 0; i < 16; i++) M[i] = dv.getUint32(chunk + i * 4, true);

    let A = a0;
    let B = b0;
    let C = c0;
    let D = d0;

    for (let i = 0; i < 64; i++) {
      let F: number;
      let g: number;
      if (i < 16) {
        F = (B & C) | (~B & D);
        g = i;
      } else if (i < 32) {
        F = (D & B) | (~D & C);
        g = (5 * i + 1) % 16;
      } else if (i < 48) {
        F = B ^ C ^ D;
        g = (3 * i + 5) % 16;
      } else {
        F = C ^ (B | ~D);
        g = (7 * i) % 16;
      }

      const sum = (F + A + K_HEX[i] + M[g]) >>> 0;
      A = D;
      D = C;
      C = B;
      B = (B + (((sum << S[i]) | (sum >>> (32 - S[i]))) >>> 0)) >>> 0;
    }

    a0 = (a0 + A) >>> 0;
    b0 = (b0 + B) >>> 0;
    c0 = (c0 + C) >>> 0;
    d0 = (d0 + D) >>> 0;
  }

  return wordToHexLE(a0) + wordToHexLE(b0) + wordToHexLE(c0) + wordToHexLE(d0);
}

export function md5Lower(input: string): string {
  return md5(input.trim().toLowerCase());
}