// Copyright (C) 2010 by Johannes Baagøe <baagoe@baagoe.org>
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use, copy,
// modify, merge, publish, distribute, sublicense, and/or sell copies
// of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
// ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

function Alea() {
  function Mash() {
    var n = 0xefc8249d;

    var mash = function(data) {
      data = data.toString();
      for (var i = 0; i < data.length; i++) {
        n += data.charCodeAt(i);
        var h = 0.02519603282416938 * n;
        n = h >>> 0;
        h -= n;
        h *= n;
        n = h >>> 0;
        h -= n;
        n += h * 0x100000000; // 2^32
      }
      return (n >>> 0) * 2.3283064365386963e-10; // 2^-32
    };

    mash.version = 'Mash 0.9';
    return mash;
  }

  return (function (args) {
    var s0 = 0;
    var s1 = 0;
    var s2 = 0;
    var c = 1;

    if (args.length == 0) {
      args = [+new Date];
    }
    var mash = Mash();
    s0 = mash(' ');
    s1 = mash(' ');
    s2 = mash(' ');

    for (var i = 0; i < args.length; i++) {
      s0 -= mash(args[i]);
      if (s0 < 0) {
        s0 += 1;
      }
      s1 -= mash(args[i]);
      if (s1 < 0) {
        s1 += 1;
      }
      s2 -= mash(args[i]);
      if (s2 < 0) {
        s2 += 1;
      }
    }
    mash = null;

    var random = function() {
      var t = 2091639 * s0 + c * 2.3283064365386963e-10; // 2^-32
      s0 = s1;
      s1 = s2;
      return s2 = t - (c = t | 0);
    };
    random.uint32 = function() {
      return random() * 0x100000000; // 2^32
    };
    random.fract53 = function() {
      return random() +
        (random() * 0x200000 | 0) * 1.1102230246251565e-16; // 2^-53
    };
    random.version = 'Alea 0.9';
    random.args = args;
    return random;

  } (Array.prototype.slice.call(arguments)));
}

// instantiate RNG.  use the default seed, which is current time.
var random = new Alea();

// Modified RFC 4122 v4 UUID
exports.create = function (length) {
  length = length || 16;
  var s = [];
  var hexDigits = "0123456789abcdef";
  for (var i = 0; i < length; i++) {
    s[i] = hexDigits.substr(Math.floor(random() * 0x10), 1);
  }
  s[length - 3] = hexDigits.substr((s[length - 3] & 0x3) | 0x8, 1);

  // return the uuid
  return s.join('');
}