'use strict'
/*
 * A JavaScript implementation of the RSA Data Security, Inc. MD5 Message
 * Digest Algorithm, as defined in RFC 1321.
 * Version 2.1 Copyright (C) Paul Johnston 1999 - 2002.
 * Other contributors: Greg Holt, Andrew Kepert, Ydnar, Lostinet
 * Distributed under the BSD License
 * See http://pajhome.org.uk/crypt/md5 for more info.
 */

var makeHash = require('./make-hash')

/*
 * Calculate the MD5 of an array of little-endian words, and a bit length
 */
function core_md5 (x, len) {
  /* append padding */
  x[len >> 5] |= 0x80 << ((len) % 32)
  x[(((len + 64) >>> 9) << 4) + 14] = len

  var a = 1732584193
  var b = -271733879
  var c = -1732584194
  var d = 271733878

  for (var i = 0; i < x.length; i += 16) {
    var olda = a
    var oldb = b
    var oldc = c
    var oldd = d

    a = md5_ff(a, b, c, d, x[i + 0], 7, -680876936)
    d = md5_ff(d, a, b, c, x[i + 1], 12, -389564586)
    c = md5_ff(c, d, a, b, x[i + 2], 17, 606105819)
    b = md5_ff(b, c, d, a, x[i + 3], 22, -1044525330)
    a = md5_ff(a, b, c, d, x[i + 4], 7, -176418897)
    d = md5_ff(d, a, b, c, x[i + 5], 12, 1200080426)
    c = md5_ff(c, d, a, b, x[i + 6], 17, -1473231341)
    b = md5_ff(b, c, d, a, x[i + 7], 22, -45705983)
    a = md5_ff(a, b, c, d, x[i + 8], 7, 1770035416)
    d = md5_ff(d, a, b, c, x[i + 9], 12, -1958414417)
    c = md5_ff(c, d, a, b, x[i + 10], 17, -42063)
    b = md5_ff(b, c, d, a, x[i + 11], 22, -1990404162)
    a = md5_ff(a, b, c, d, x[i + 12], 7, 1804603682)
    d = md5_ff(d, a, b, c, x[i + 13], 12, -40341101)
    c = md5_ff(c, d, a, b, x[i + 14], 17, -1502002290)
    b = md5_ff(b, c, d, a, x[i + 15], 22, 1236535329)

    a = md5_gg(a, b, c, d, x[i + 1], 5, -165796510)
    d = md5_gg(d, a, b, c, x[i + 6], 9, -1069501632)
    c = md5_gg(c, d, a, b, x[i + 11], 14, 643717713)
    b = md5_gg(b, c, d, a, x[i + 0], 20, -373897302)
    a = md5_gg(a, b, c, d, x[i + 5], 5, -701558691)
    d = md5_gg(d, a, b, c, x[i + 10], 9, 38016083)
    c = md5_gg(c, d, a, b, x[i + 15], 14, -660478335)
    b = md5_gg(b, c, d, a, x[i + 4], 20, -405537848)
    a = md5_gg(a, b, c, d, x[i + 9], 5, 568446438)
    d = md5_gg(d, a, b, c, x[i + 14], 9, -1019803690)
    c = md5_gg(c, d, a, b, x[i + 3], 14, -187363961)
    b = md5_gg(b, c, d, a, x[i + 8], 20, 1163531501)
    a = md5_gg(a, b, c, d, x[i + 13], 5, -1444681467)
    d = md5_gg(d, a, b, c, x[i + 2], 9, -51403784)
    c = md5_gg(c, d, a, b, x[i + 7], 14, 1735328473)
    b = md5_gg(b, c, d, a, x[i + 12], 20, -1926607734)

    a = md5_hh(a, b, c, d, x[i + 5], 4, -378558)
    d = md5_hh(d, a, b, c, x[i + 8], 11, -2022574463)
    c = md5_hh(c, d, a, b, x[i + 11], 16, 1839030562)
    b = md5_hh(b, c, d, a, x[i + 14], 23, -35309556)
    a = md5_hh(a, b, c, d, x[i + 1], 4, -1530992060)
    d = md5_hh(d, a, b, c, x[i + 4], 11, 1272893353)
    c = md5_hh(c, d, a, b, x[i + 7], 16, -155497632)
    b = md5_hh(b, c, d, a, x[i + 10], 23, -1094730640)
    a = md5_hh(a, b, c, d, x[i + 13], 4, 681279174)
    d = md5_hh(d, a, b, c, x[i + 0], 11, -358537222)
    c = md5_hh(c, d, a, b, x[i + 3], 16, -722521979)
    b = md5_hh(b, c, d, a, x[i + 6], 23, 76029189)
    a = md5_hh(a, b, c, d, x[i + 9], 4, -640364487)
    d = md5_hh(d, a, b, c, x[i + 12], 11, -421815835)
    c = md5_hh(c, d, a, b, x[i + 15], 16, 530742520)
    b = md5_hh(b, c, d, a, x[i + 2], 23, -995338651)

    a = md5_ii(a, b, c, d, x[i + 0], 6, -198630844)
    d = md5_ii(d, a, b, c, x[i + 7], 10, 1126891415)
    c = md5_ii(c, d, a, b, x[i + 14], 15, -1416354905)
    b = md5_ii(b, c, d, a, x[i + 5], 21, -57434055)
    a = md5_ii(a, b, c, d, x[i + 12], 6, 1700485571)
    d = md5_ii(d, a, b, c, x[i + 3], 10, -1894986606)
    c = md5_ii(c, d, a, b, x[i + 10], 15, -1051523)
    b = md5_ii(b, c, d, a, x[i + 1], 21, -2054922799)
    a = md5_ii(a, b, c, d, x[i + 8], 6, 1873313359)
    d = md5_ii(d, a, b, c, x[i + 15], 10, -30611744)
    c = md5_ii(c, d, a, b, x[i + 6], 15, -1560198380)
    b = md5_ii(b, c, d, a, x[i + 13], 21, 1309151649)
    a = md5_ii(a, b, c, d, x[i + 4], 6, -145523070)
    d = md5_ii(d, a, b, c, x[i + 11], 10, -1120210379)
    c = md5_ii(c, d, a, b, x[i + 2], 15, 718787259)
    b = md5_ii(b, c, d, a, x[i + 9], 21, -343485551)

    a = safe_add(a, olda)
    b = safe_add(b, oldb)
    c = safe_add(c, oldc)
    d = safe_add(d, oldd)
  }

  return [a, b, c, d]
}

/*
 * These functions implement the four basic operations the algorithm uses.
 */
function md5_cmn (q, a, b, x, s, t) {
  return safe_add(bit_rol(safe_add(safe_add(a, q), safe_add(x, t)), s), b)
}

function md5_ff (a, b, c, d, x, s, t) {
  return md5_cmn((b & c) | ((~b) & d), a, b, x, s, t)
}

function md5_gg (a, b, c, d, x, s, t) {
  return md5_cmn((b & d) | (c & (~d)), a, b, x, s, t)
}

function md5_hh (a, b, c, d, x, s, t) {
  return md5_cmn(b ^ c ^ d, a, b, x, s, t)
}

function md5_ii (a, b, c, d, x, s, t) {
  return md5_cmn(c ^ (b | (~d)), a, b, x, s, t)
}

/*
 * Add integers, wrapping at 2^32. This uses 16-bit operations internally
 * to work around bugs in some JS interpreters.
 */
function safe_add (x, y) {
  var lsw = (x & 0xFFFF) + (y & 0xFFFF)
  var msw = (x >> 16) + (y >> 16) + (lsw >> 16)
  return (msw << 16) | (lsw & 0xFFFF)
}

/*
 * Bitwise rotate a 32-bit number to the left.
 */
function bit_rol (num, cnt) {
  return (num << cnt) | (num >>> (32 - cnt))
}

module.exports = function md5 (buf) {
  return makeHash(buf, core_md5)
}