/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  SHA-1 implementation in JavaScript (c) Chris Veness 2002-2009                                 */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

function sha1Hash(msg){
  // constants [§4.2.1]
  var K = [0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6];


  // PREPROCESSING

  msg += String.fromCharCode(0x80); // add trailing '1' bit (+ 0's padding) to string [§5.1.1]

  // convert string msg into 512-bit/16-integer blocks arrays of ints [§5.2.1]
  var l = msg.length/4 + 2;  // length (in 32-bit integers) of msg + ‘1’ + appended length
  var N = Math.ceil(l/16);   // number of 16-integer-blocks required to hold 'l' ints
  var M = new Array(N);
  for (var i=0; i<N; i++) {
    M[i] = new Array(16);
    for (var j=0; j<16; j++) {  // encode 4 chars per integer, big-endian encoding
      M[i][j] = (msg.charCodeAt(i*64+j*4)<<24) | (msg.charCodeAt(i*64+j*4+1)<<16) |
      (msg.charCodeAt(i*64+j*4+2)<<8) | (msg.charCodeAt(i*64+j*4+3));
    }
  }
  // add length (in bits) into final pair of 32-bit integers (big-endian) [5.1.1]
  // note: most significant word would be (len-1)*8 >>> 32, but since JS converts
  // bitwise-op args to 32 bits, we need to simulate this by arithmetic operators
  M[N-1][14] = ((msg.length-1)*8) / Math.pow(2, 32);
  M[N-1][14] = Math.floor(M[N-1][14])
  M[N-1][15] = ((msg.length-1)*8) & 0xffffffff;

  // set initial hash value [§5.3.1]
  var H0 = 0x67452301;
  var H1 = 0xefcdab89;
  var H2 = 0x98badcfe;
  var H3 = 0x10325476;
  var H4 = 0xc3d2e1f0;

  // HASH COMPUTATION [§6.1.2]

  var W = new Array(80);
  var a, b, c, d, e;
  for (var i=0; i<N; i++) {

    // 1 - prepare message schedule 'W'
    for (var t=0;  t<16; t++) W[t] = M[i][t];
    for (var t=16; t<80; t++) W[t] = ROTL(W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16], 1);

    // 2 - initialise five working variables a, b, c, d, e with previous hash value
    a = H0;
    b = H1;
    c = H2;
    d = H3;
    e = H4;

    // 3 - main loop
    for (var t=0; t<80; t++) {
      var s = Math.floor(t/20); // seq for blocks of 'f' functions and 'K' constants
      var T = (ROTL(a,5) + f(s,b,c,d) + e + K[s] + W[t]) & 0xffffffff;
      e = d;
      d = c;
      c = ROTL(b, 30);
      b = a;
      a = T;
    }

    // 4 - compute the new intermediate hash value
    H0 = (H0+a) & 0xffffffff;  // note 'addition modulo 2^32'
    H1 = (H1+b) & 0xffffffff;
    H2 = (H2+c) & 0xffffffff;
    H3 = (H3+d) & 0xffffffff;
    H4 = (H4+e) & 0xffffffff;
  }

  return H0.toHexStr() + H1.toHexStr() + H2.toHexStr() + H3.toHexStr() + H4.toHexStr();
}

//
// function 'f' [§4.1.1]
//
function f(s, x, y, z) {
  switch (s) {
    case 0:
      return (x & y) ^ (~x & z);           // Ch()
    case 1:
      return x ^ y ^ z;                    // Parity()
    case 2:
      return (x & y) ^ (x & z) ^ (y & z);  // Maj()
    case 3:
      return x ^ y ^ z;                    // Parity()
  }
}

//
// rotate left (circular left shift) value x by n positions [§3.2.5]
//
function ROTL(x, n){
  return (x<<n) | (x>>>(32-n));
}

//
// extend Number class with a tailored hex-string method
//   (note toString(16) is implementation-dependant, and
//   in IE returns signed numbers when used on full words)
//
Number.prototype.toHexStr = function(){
  var s="", v;
  for (var i=7; i>=0; i--) {
    v = (this>>>(i*4)) & 0xf;
    s += v.toString(16);
  }
  return s;
}