var randHex = require('./randHex');
var choice = require('./choice');

  /**
   * Returns pseudo-random guid (UUID v4)
   * IMPORTANT: it's not totally "safe" since randHex/choice uses Math.random
   * by default and sequences can be predicted in some cases. See the
   * "random/random" documentation for more info about it and how to replace
   * the default PRNG.
   */
  function guid() {
    return (
        randHex(8)+'-'+
        randHex(4)+'-'+
        // v4 UUID always contain "4" at this position to specify it was
        // randomly generated
        '4' + randHex(3) +'-'+
        // v4 UUID always contain chars [a,b,8,9] at this position
        choice(8, 9, 'a', 'b') + randHex(3)+'-'+
        randHex(12)
    );
  }
  module.exports = guid;