esnext.math.seeded-prng.js

var $ = require('../internals/export');
var anObject = require('../internals/an-object');
var numberIsFinite = require('../internals/number-is-finite');
var createIteratorConstructor = require('../internals/create-iterator-constructor');
var InternalStateModule = require('../internals/internal-state');

var SEEDED_RANDOM = 'Seeded Random';
var SEEDED_RANDOM_GENERATOR = SEEDED_RANDOM + ' Generator';
var setInternalState = InternalStateModule.set;
var getInternalState = InternalStateModule.getterFor(SEEDED_RANDOM_GENERATOR);
var SEED_TYPE_ERROR = 'Math.seededPRNG() argument should have a "seed" field with a finite value.';

var $SeededRandomGenerator = createIteratorConstructor(function SeededRandomGenerator(seed) {
  setInternalState(this, {
    type: SEEDED_RANDOM_GENERATOR,
    seed: seed % 2147483647
  });
}, SEEDED_RANDOM, function next() {
  var state = getInternalState(this);
  var seed = state.seed = (state.seed * 1103515245 + 12345) % 2147483647;
  return { value: (seed & 1073741823) / 1073741823, done: false };
});

// `Math.seededPRNG` method
// https://github.com/tc39/proposal-seeded-random
// based on https://github.com/tc39/proposal-seeded-random/blob/78b8258835b57fc2100d076151ab506bc3202ae6/demo.html
$({ target: 'Math', stat: true, forced: true }, {
  seededPRNG: function seededPRNG(it) {
    var seed = anObject(it).seed;
    if (!numberIsFinite(seed)) throw TypeError(SEED_TYPE_ERROR);
    return new $SeededRandomGenerator(seed);
  }
});