// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

library crypto.md5;

import 'dart:typed_data';

import 'hash.dart';
import 'hash_base.dart';
import 'utils.dart';

/// An implementation of the [MD5][rfc] hash function.
///
/// [rfc]: https://tools.ietf.org/html/rfc1321
///
/// **Warning**: MD5 has known collisions and should only be used when required
/// for backwards compatibility.
abstract class MD5 implements Hash {
  factory MD5() = _MD5;

  MD5 newInstance();
}

/// The concrete implementation of [MD5].
///
/// This is separate so that it can extend [HashBase] without leaking additional
/// public memebers.
class _MD5 extends HashBase implements MD5 {
  _MD5() : super(16, 4, false) {
    h[0] = 0x67452301;
    h[1] = 0xefcdab89;
    h[2] = 0x98badcfe;
    h[3] = 0x10325476;
  }

  MD5 newInstance() {
    return new _MD5();
  }

  /// Data from a non-linear mathematical function that functions as
  /// reproducible noise.
  static const _k = const [
    0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee, 0xf57c0faf, 0x4787c62a,
    0xa8304613, 0xfd469501, 0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
    0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821, 0xf61e2562, 0xc040b340,
    0x265e5a51, 0xe9b6c7aa, 0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
    0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed, 0xa9e3e905, 0xfcefa3f8,
    0x676f02d9, 0x8d2a4c8a, 0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
    0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70, 0x289b7ec6, 0xeaa127fa,
    0xd4ef3085, 0x04881d05, 0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
    0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039, 0x655b59c3, 0x8f0ccc92,
    0xffeff47d, 0x85845dd1, 0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
    0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
  ];

  /// Per-round shift amounts.
  static const _r = const [
    07, 12, 17, 22, 07, 12, 17, 22, 07, 12, 17, 22, 07, 12, 17, 22, 05, 09, 14,
    20, 05, 09, 14, 20, 05, 09, 14, 20, 05, 09, 14, 20, 04, 11, 16, 23, 04, 11,
    16, 23, 04, 11, 16, 23, 04, 11, 16, 23, 06, 10, 15, 21, 06, 10, 15, 21, 06,
    10, 15, 21, 06, 10, 15, 21
  ];

  void updateHash(Uint32List m) {
    assert(m.length == 16);

    var a = h[0];
    var b = h[1];
    var c = h[2];
    var d = h[3];

    var t0;
    var t1;

    for (var i = 0; i < 64; i++) {
      if (i < 16) {
        t0 = (b & c) | ((~b & MASK_32) & d);
        t1 = i;
      } else if (i < 32) {
        t0 = (d & b) | ((~d & MASK_32) & c);
        t1 = ((5 * i) + 1) % 16;
      } else if (i < 48) {
        t0 = b ^ c ^ d;
        t1 = ((3 * i) + 5) % 16;
      } else {
        t0 = c ^ (b | (~d & MASK_32));
        t1 = (7 * i) % 16;
      }

      var temp = d;
      d = c;
      c = b;
      b = add32(
          b, rotl32(add32(add32(a, t0), add32(_k[i], m[t1])), _r[i]));
      a = temp;
    }

    h[0] = add32(a, h[0]);
    h[1] = add32(b, h[1]);
    h[2] = add32(c, h[2]);
    h[3] = add32(d, h[3]);
  }
}