'use strict'
var inherits = require('inherits')
var HashBase = require('hash-base')
var Buffer = require('safe-buffer').Buffer

var ARRAY16 = new Array(16)

function MD5 () {
  HashBase.call(this, 64)

  // state
  this._a = 0x67452301
  this._b = 0xefcdab89
  this._c = 0x98badcfe
  this._d = 0x10325476
}

inherits(MD5, HashBase)

MD5.prototype._update = function () {
  var M = ARRAY16
  for (var i = 0; i < 16; ++i) M[i] = this._block.readInt32LE(i * 4)

  var a = this._a
  var b = this._b
  var c = this._c
  var d = this._d

  a = fnF(a, b, c, d, M[0], 0xd76aa478, 7)
  d = fnF(d, a, b, c, M[1], 0xe8c7b756, 12)
  c = fnF(c, d, a, b, M[2], 0x242070db, 17)
  b = fnF(b, c, d, a, M[3], 0xc1bdceee, 22)
  a = fnF(a, b, c, d, M[4], 0xf57c0faf, 7)
  d = fnF(d, a, b, c, M[5], 0x4787c62a, 12)
  c = fnF(c, d, a, b, M[6], 0xa8304613, 17)
  b = fnF(b, c, d, a, M[7], 0xfd469501, 22)
  a = fnF(a, b, c, d, M[8], 0x698098d8, 7)
  d = fnF(d, a, b, c, M[9], 0x8b44f7af, 12)
  c = fnF(c, d, a, b, M[10], 0xffff5bb1, 17)
  b = fnF(b, c, d, a, M[11], 0x895cd7be, 22)
  a = fnF(a, b, c, d, M[12], 0x6b901122, 7)
  d = fnF(d, a, b, c, M[13], 0xfd987193, 12)
  c = fnF(c, d, a, b, M[14], 0xa679438e, 17)
  b = fnF(b, c, d, a, M[15], 0x49b40821, 22)

  a = fnG(a, b, c, d, M[1], 0xf61e2562, 5)
  d = fnG(d, a, b, c, M[6], 0xc040b340, 9)
  c = fnG(c, d, a, b, M[11], 0x265e5a51, 14)
  b = fnG(b, c, d, a, M[0], 0xe9b6c7aa, 20)
  a = fnG(a, b, c, d, M[5], 0xd62f105d, 5)
  d = fnG(d, a, b, c, M[10], 0x02441453, 9)
  c = fnG(c, d, a, b, M[15], 0xd8a1e681, 14)
  b = fnG(b, c, d, a, M[4], 0xe7d3fbc8, 20)
  a = fnG(a, b, c, d, M[9], 0x21e1cde6, 5)
  d = fnG(d, a, b, c, M[14], 0xc33707d6, 9)
  c = fnG(c, d, a, b, M[3], 0xf4d50d87, 14)
  b = fnG(b, c, d, a, M[8], 0x455a14ed, 20)
  a = fnG(a, b, c, d, M[13], 0xa9e3e905, 5)
  d = fnG(d, a, b, c, M[2], 0xfcefa3f8, 9)
  c = fnG(c, d, a, b, M[7], 0x676f02d9, 14)
  b = fnG(b, c, d, a, M[12], 0x8d2a4c8a, 20)

  a = fnH(a, b, c, d, M[5], 0xfffa3942, 4)
  d = fnH(d, a, b, c, M[8], 0x8771f681, 11)
  c = fnH(c, d, a, b, M[11], 0x6d9d6122, 16)
  b = fnH(b, c, d, a, M[14], 0xfde5380c, 23)
  a = fnH(a, b, c, d, M[1], 0xa4beea44, 4)
  d = fnH(d, a, b, c, M[4], 0x4bdecfa9, 11)
  c = fnH(c, d, a, b, M[7], 0xf6bb4b60, 16)
  b = fnH(b, c, d, a, M[10], 0xbebfbc70, 23)
  a = fnH(a, b, c, d, M[13], 0x289b7ec6, 4)
  d = fnH(d, a, b, c, M[0], 0xeaa127fa, 11)
  c = fnH(c, d, a, b, M[3], 0xd4ef3085, 16)
  b = fnH(b, c, d, a, M[6], 0x04881d05, 23)
  a = fnH(a, b, c, d, M[9], 0xd9d4d039, 4)
  d = fnH(d, a, b, c, M[12], 0xe6db99e5, 11)
  c = fnH(c, d, a, b, M[15], 0x1fa27cf8, 16)
  b = fnH(b, c, d, a, M[2], 0xc4ac5665, 23)

  a = fnI(a, b, c, d, M[0], 0xf4292244, 6)
  d = fnI(d, a, b, c, M[7], 0x432aff97, 10)
  c = fnI(c, d, a, b, M[14], 0xab9423a7, 15)
  b = fnI(b, c, d, a, M[5], 0xfc93a039, 21)
  a = fnI(a, b, c, d, M[12], 0x655b59c3, 6)
  d = fnI(d, a, b, c, M[3], 0x8f0ccc92, 10)
  c = fnI(c, d, a, b, M[10], 0xffeff47d, 15)
  b = fnI(b, c, d, a, M[1], 0x85845dd1, 21)
  a = fnI(a, b, c, d, M[8], 0x6fa87e4f, 6)
  d = fnI(d, a, b, c, M[15], 0xfe2ce6e0, 10)
  c = fnI(c, d, a, b, M[6], 0xa3014314, 15)
  b = fnI(b, c, d, a, M[13], 0x4e0811a1, 21)
  a = fnI(a, b, c, d, M[4], 0xf7537e82, 6)
  d = fnI(d, a, b, c, M[11], 0xbd3af235, 10)
  c = fnI(c, d, a, b, M[2], 0x2ad7d2bb, 15)
  b = fnI(b, c, d, a, M[9], 0xeb86d391, 21)

  this._a = (this._a + a) | 0
  this._b = (this._b + b) | 0
  this._c = (this._c + c) | 0
  this._d = (this._d + d) | 0
}

MD5.prototype._digest = function () {
  // create padding and handle blocks
  this._block[this._blockOffset++] = 0x80
  if (this._blockOffset > 56) {
    this._block.fill(0, this._blockOffset, 64)
    this._update()
    this._blockOffset = 0
  }

  this._block.fill(0, this._blockOffset, 56)
  this._block.writeUInt32LE(this._length[0], 56)
  this._block.writeUInt32LE(this._length[1], 60)
  this._update()

  // produce result
  var buffer = Buffer.allocUnsafe(16)
  buffer.writeInt32LE(this._a, 0)
  buffer.writeInt32LE(this._b, 4)
  buffer.writeInt32LE(this._c, 8)
  buffer.writeInt32LE(this._d, 12)
  return buffer
}

function rotl (x, n) {
  return (x << n) | (x >>> (32 - n))
}

function fnF (a, b, c, d, m, k, s) {
  return (rotl((a + ((b & c) | ((~b) & d)) + m + k) | 0, s) + b) | 0
}

function fnG (a, b, c, d, m, k, s) {
  return (rotl((a + ((b & d) | (c & (~d))) + m + k) | 0, s) + b) | 0
}

function fnH (a, b, c, d, m, k, s) {
  return (rotl((a + (b ^ c ^ d) + m + k) | 0, s) + b) | 0
}

function fnI (a, b, c, d, m, k, s) {
  return (rotl((a + ((c ^ (b | (~d)))) + m + k) | 0, s) + b) | 0
}

module.exports = MD5