index.js

var baseGet = __webpack_require__(1514);

/**
 * A specialized version of `baseProperty` which supports deep paths.
 *
 * @private
 * @param {Array|string} path The path of the property to get.
 * @returns {Function} Returns the new accessor function.
 */
function basePropertyDeep(path) {
  return function(object) {
    return baseGet(object, path);
  };
}

module.exports = basePropertyDeep;


/***/ }),
/* 1567 */
/***/ (function(module, exports) {

/** Error message constants. */
var FUNC_ERROR_TEXT = 'Expected a function';

/**
 * Creates a function that negates the result of the predicate `func`. The
 * `func` predicate is invoked with the `this` binding and arguments of the
 * created function.
 *
 * @static
 * @memberOf _
 * @since 3.0.0
 * @category Function
 * @param {Function} predicate The predicate to negate.
 * @returns {Function} Returns the new negated function.
 * @example
 *
 * function isEven(n) {
 *   return n % 2 == 0;
 * }
 *
 * _.filter([1, 2, 3, 4, 5, 6], _.negate(isEven));
 * // => [1, 3, 5]
 */
function negate(predicate) {
  if (typeof predicate != 'function') {
    throw new TypeError(FUNC_ERROR_TEXT);
  }
  return function() {
    var args = arguments;
    switch (args.length) {
      case 0: return !predicate.call(this);
      case 1: return !predicate.call(this, args[0]);
      case 2: return !predicate.call(this, args[0], args[1]);
      case 3: return !predicate.call(this, args[0], args[1], args[2]);
    }
    return !predicate.apply(this, args);
  };
}

module.exports = negate;


/***/ }),
/* 1568 */
/***/ (function(module, exports, __webpack_require__) {

var arrayMap = __webpack_require__(1395),
    baseIteratee = __webpack_require__(1545),
    basePickBy = __webpack_require__(1532),
    getAllKeysIn = __webpack_require__(1483);

/**
 * Creates an object composed of the `object` properties `predicate` returns
 * truthy for. The predicate is invoked with two arguments: (value, key).
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Object
 * @param {Object} object The source object.
 * @param {Function} [predicate=_.identity] The function invoked per property.
 * @returns {Object} Returns the new object.
 * @example
 *
 * var object = { 'a': 1, 'b': '2', 'c': 3 };
 *
 * _.pickBy(object, _.isNumber);
 * // => { 'a': 1, 'c': 3 }
 */
function pickBy(object, predicate) {
  if (object == null) {
    return {};
  }
  var props = arrayMap(getAllKeysIn(object), function(prop) {
    return [prop];
  });
  predicate = baseIteratee(predicate);
  return basePickBy(object, props, function(value, path) {
    return predicate(value, path[0]);
  });
}

module.exports = pickBy;


/***/ }),
/* 1569 */
/***/ (function(module, exports) {

/**
 * Checks if `value` is `undefined`.
 *
 * @static
 * @since 0.1.0
 * @memberOf _
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is `undefined`, else `false`.
 * @example
 *
 * _.isUndefined(void 0);
 * // => true
 *
 * _.isUndefined(null);
 * // => false
 */
function isUndefined(value) {
  return value === undefined;
}

module.exports = isUndefined;


/***/ }),
/* 1570 */
/***/ (function(module, exports) {

/**
 * The inverse of `_.toPairs`; this method returns an object composed
 * from key-value `pairs`.
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Array
 * @param {Array} pairs The key-value pairs.
 * @returns {Object} Returns the new object.
 * @example
 *
 * _.fromPairs([['a', 1], ['b', 2]]);
 * // => { 'a': 1, 'b': 2 }
 */
function fromPairs(pairs) {
  var index = -1,
      length = pairs == null ? 0 : pairs.length,
      result = {};

  while (++index < length) {
    var pair = pairs[index];
    result[pair[0]] = pair[1];
  }
  return result;
}

module.exports = fromPairs;


/***/ }),
/* 1571 */
/***/ (function(module, exports, __webpack_require__) {

var baseFlatten = __webpack_require__(1521),
    map = __webpack_require__(1572);

/**
 * Creates a flattened array of values by running each element in `collection`
 * thru `iteratee` and flattening the mapped results. The iteratee is invoked
 * with three arguments: (value, index|key, collection).
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Collection
 * @param {Array|Object} collection The collection to iterate over.
 * @param {Function} [iteratee=_.identity] The function invoked per iteration.
 * @returns {Array} Returns the new flattened array.
 * @example
 *
 * function duplicate(n) {
 *   return [n, n];
 * }
 *
 * _.flatMap([1, 2], duplicate);
 * // => [1, 1, 2, 2]
 */
function flatMap(collection, iteratee) {
  return baseFlatten(map(collection, iteratee), 1);
}

module.exports = flatMap;


/***/ }),
/* 1572 */
/***/ (function(module, exports, __webpack_require__) {

var arrayMap = __webpack_require__(1395),
    baseIteratee = __webpack_require__(1545),
    baseMap = __webpack_require__(1573),
    isArray = __webpack_require__(1453);

/**
 * Creates an array of values by running each element in `collection` thru
 * `iteratee`. The iteratee is invoked with three arguments:
 * (value, index|key, collection).
 *
 * Many lodash methods are guarded to work as iteratees for methods like
 * `_.every`, `_.filter`, `_.map`, `_.mapValues`, `_.reject`, and `_.some`.
 *
 * The guarded methods are:
 * `ary`, `chunk`, `curry`, `curryRight`, `drop`, `dropRight`, `every`,
 * `fill`, `invert`, `parseInt`, `random`, `range`, `rangeRight`, `repeat`,
 * `sampleSize`, `slice`, `some`, `sortBy`, `split`, `take`, `takeRight`,
 * `template`, `trim`, `trimEnd`, `trimStart`, and `words`
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Collection
 * @param {Array|Object} collection The collection to iterate over.
 * @param {Function} [iteratee=_.identity] The function invoked per iteration.
 * @returns {Array} Returns the new mapped array.
 * @example
 *
 * function square(n) {
 *   return n * n;
 * }
 *
 * _.map([4, 8], square);
 * // => [16, 64]
 *
 * _.map({ 'a': 4, 'b': 8 }, square);
 * // => [16, 64] (iteration order is not guaranteed)
 *
 * var users = [
 *   { 'user': 'barney' },
 *   { 'user': 'fred' }
 * ];
 *
 * // The `_.property` iteratee shorthand.
 * _.map(users, 'user');
 * // => ['barney', 'fred']
 */
function map(collection, iteratee) {
  var func = isArray(collection) ? arrayMap : baseMap;
  return func(collection, baseIteratee(iteratee, 3));
}

module.exports = map;


/***/ }),
/* 1573 */
/***/ (function(module, exports, __webpack_require__) {

var baseEach = __webpack_require__(1574),
    isArrayLike = __webpack_require__(1466);

/**
 * The base implementation of `_.map` without support for iteratee shorthands.
 *
 * @private
 * @param {Array|Object} collection The collection to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @returns {Array} Returns the new mapped array.
 */
function baseMap(collection, iteratee) {
  var index = -1,
      result = isArrayLike(collection) ? Array(collection.length) : [];

  baseEach(collection, function(value, key, collection) {
    result[++index] = iteratee(value, key, collection);
  });
  return result;
}

module.exports = baseMap;


/***/ }),
/* 1574 */
/***/ (function(module, exports, __webpack_require__) {

var baseForOwn = __webpack_require__(1575),
    createBaseEach = __webpack_require__(1578);

/**
 * The base implementation of `_.forEach` without support for iteratee shorthands.
 *
 * @private
 * @param {Array|Object} collection The collection to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @returns {Array|Object} Returns `collection`.
 */
var baseEach = createBaseEach(baseForOwn);

module.exports = baseEach;


/***/ }),
/* 1575 */
/***/ (function(module, exports, __webpack_require__) {

var baseFor = __webpack_require__(1576),
    keys = __webpack_require__(1447);

/**
 * The base implementation of `_.forOwn` without support for iteratee shorthands.
 *
 * @private
 * @param {Object} object The object to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @returns {Object} Returns `object`.
 */
function baseForOwn(object, iteratee) {
  return object && baseFor(object, iteratee, keys);
}

module.exports = baseForOwn;


/***/ }),
/* 1576 */
/***/ (function(module, exports, __webpack_require__) {

var createBaseFor = __webpack_require__(1577);

/**
 * The base implementation of `baseForOwn` which iterates over `object`
 * properties returned by `keysFunc` and invokes `iteratee` for each property.
 * Iteratee functions may exit iteration early by explicitly returning `false`.
 *
 * @private
 * @param {Object} object The object to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @param {Function} keysFunc The function to get the keys of `object`.
 * @returns {Object} Returns `object`.
 */
var baseFor = createBaseFor();

module.exports = baseFor;


/***/ }),
/* 1577 */
/***/ (function(module, exports) {

/**
 * Creates a base function for methods like `_.forIn` and `_.forOwn`.
 *
 * @private
 * @param {boolean} [fromRight] Specify iterating from right to left.
 * @returns {Function} Returns the new base function.
 */
function createBaseFor(fromRight) {
  return function(object, iteratee, keysFunc) {
    var index = -1,
        iterable = Object(object),
        props = keysFunc(object),
        length = props.length;

    while (length--) {
      var key = props[fromRight ? length : ++index];
      if (iteratee(iterable[key], key, iterable) === false) {
        break;
      }
    }
    return object;
  };
}

module.exports = createBaseFor;


/***/ }),
/* 1578 */
/***/ (function(module, exports, __webpack_require__) {

var isArrayLike = __webpack_require__(1466);

/**
 * Creates a `baseEach` or `baseEachRight` function.
 *
 * @private
 * @param {Function} eachFunc The function to iterate over a collection.
 * @param {boolean} [fromRight] Specify iterating from right to left.
 * @returns {Function} Returns the new base function.
 */
function createBaseEach(eachFunc, fromRight) {
  return function(collection, iteratee) {
    if (collection == null) {
      return collection;
    }
    if (!isArrayLike(collection)) {
      return eachFunc(collection, iteratee);
    }
    var length = collection.length,
        index = fromRight ? length : -1,
        iterable = Object(collection);

    while ((fromRight ? index-- : ++index < length)) {
      if (iteratee(iterable[index], index, iterable) === false) {
        break;
      }
    }
    return collection;
  };
}

module.exports = createBaseEach;


/***/ }),
/* 1579 */
/***/ (function(module, exports, __webpack_require__) {

var baseAssignValue = __webpack_require__(1443),
    createAggregator = __webpack_require__(1580);

/** Used for built-in method references. */
var objectProto = Object.prototype;

/** Used to check objects for own properties. */
var hasOwnProperty = objectProto.hasOwnProperty;

/**
 * Creates an object composed of keys generated from the results of running
 * each element of `collection` thru `iteratee`. The order of grouped values
 * is determined by the order they occur in `collection`. The corresponding
 * value of each key is an array of elements responsible for generating the
 * key. The iteratee is invoked with one argument: (value).
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Collection
 * @param {Array|Object} collection The collection to iterate over.
 * @param {Function} [iteratee=_.identity] The iteratee to transform keys.
 * @returns {Object} Returns the composed aggregate object.
 * @example
 *
 * _.groupBy([6.1, 4.2, 6.3], Math.floor);
 * // => { '4': [4.2], '6': [6.1, 6.3] }
 *
 * // The `_.property` iteratee shorthand.
 * _.groupBy(['one', 'two', 'three'], 'length');
 * // => { '3': ['one', 'two'], '5': ['three'] }
 */
var groupBy = createAggregator(function(result, value, key) {
  if (hasOwnProperty.call(result, key)) {
    result[key].push(value);
  } else {
    baseAssignValue(result, key, [value]);
  }
});

module.exports = groupBy;


/***/ }),
/* 1580 */
/***/ (function(module, exports, __webpack_require__) {

var arrayAggregator = __webpack_require__(1581),
    baseAggregator = __webpack_require__(1582),
    baseIteratee = __webpack_require__(1545),
    isArray = __webpack_require__(1453);

/**
 * Creates a function like `_.groupBy`.
 *
 * @private
 * @param {Function} setter The function to set accumulator values.
 * @param {Function} [initializer] The accumulator object initializer.
 * @returns {Function} Returns the new aggregator function.
 */
function createAggregator(setter, initializer) {
  return function(collection, iteratee) {
    var func = isArray(collection) ? arrayAggregator : baseAggregator,
        accumulator = initializer ? initializer() : {};

    return func(collection, setter, baseIteratee(iteratee, 2), accumulator);
  };
}

module.exports = createAggregator;


/***/ }),
/* 1581 */
/***/ (function(module, exports) {

/**
 * A specialized version of `baseAggregator` for arrays.
 *
 * @private
 * @param {Array} [array] The array to iterate over.
 * @param {Function} setter The function to set `accumulator` values.
 * @param {Function} iteratee The iteratee to transform keys.
 * @param {Object} accumulator The initial aggregated object.
 * @returns {Function} Returns `accumulator`.
 */
function arrayAggregator(array, setter, iteratee, accumulator) {
  var index = -1,
      length = array == null ? 0 : array.length;

  while (++index < length) {
    var value = array[index];
    setter(accumulator, value, iteratee(value), array);
  }
  return accumulator;
}

module.exports = arrayAggregator;


/***/ }),
/* 1582 */
/***/ (function(module, exports, __webpack_require__) {

var baseEach = __webpack_require__(1574);

/**
 * Aggregates elements of `collection` on `accumulator` with keys transformed
 * by `iteratee` and values set by `setter`.
 *
 * @private
 * @param {Array|Object} collection The collection to iterate over.
 * @param {Function} setter The function to set `accumulator` values.
 * @param {Function} iteratee The iteratee to transform keys.
 * @param {Object} accumulator The initial aggregated object.
 * @returns {Function} Returns `accumulator`.
 */
function baseAggregator(collection, setter, iteratee, accumulator) {
  baseEach(collection, function(value, key, collection) {
    setter(accumulator, value, iteratee(value), collection);
  });
  return accumulator;
}

module.exports = baseAggregator;


/***/ }),
/* 1583 */
/***/ (function(module, exports, __webpack_require__) {

var baseFlatten = __webpack_require__(1521),
    baseOrderBy = __webpack_require__(1584),
    baseRest = __webpack_require__(1588),
    isIterateeCall = __webpack_require__(1589);

/**
 * Creates an array of elements, sorted in ascending order by the results of
 * running each element in a collection thru each iteratee. This method
 * performs a stable sort, that is, it preserves the original sort order of
 * equal elements. The iteratees are invoked with one argument: (value).
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Collection
 * @param {Array|Object} collection The collection to iterate over.
 * @param {...(Function|Function[])} [iteratees=[_.identity]]
 *  The iteratees to sort by.
 * @returns {Array} Returns the new sorted array.
 * @example
 *
 * var users = [
 *   { 'user': 'fred',   'age': 48 },
 *   { 'user': 'barney', 'age': 36 },
 *   { 'user': 'fred',   'age': 40 },
 *   { 'user': 'barney', 'age': 34 }
 * ];
 *
 * _.sortBy(users, [function(o) { return o.user; }]);
 * // => objects for [['barney', 36], ['barney', 34], ['fred', 48], ['fred', 40]]
 *
 * _.sortBy(users, ['user', 'age']);
 * // => objects for [['barney', 34], ['barney', 36], ['fred', 40], ['fred', 48]]
 */
var sortBy = baseRest(function(collection, iteratees) {
  if (collection == null) {
    return [];
  }
  var length = iteratees.length;
  if (length > 1 && isIterateeCall(collection, iteratees[0], iteratees[1])) {
    iteratees = [];
  } else if (length > 2 && isIterateeCall(iteratees[0], iteratees[1], iteratees[2])) {
    iteratees = [iteratees[0]];
  }
  return baseOrderBy(collection, baseFlatten(iteratees, 1), []);
});

module.exports = sortBy;


/***/ }),
/* 1584 */
/***/ (function(module, exports, __webpack_require__) {

var arrayMap = __webpack_require__(1395),
    baseIteratee = __webpack_require__(1545),
    baseMap = __webpack_require__(1573),
    baseSortBy = __webpack_require__(1585),
    baseUnary = __webpack_require__(1460),
    compareMultiple = __webpack_require__(1586),
    identity = __webpack_require__(1528);

/**
 * The base implementation of `_.orderBy` without param guards.
 *
 * @private
 * @param {Array|Object} collection The collection to iterate over.
 * @param {Function[]|Object[]|string[]} iteratees The iteratees to sort by.
 * @param {string[]} orders The sort orders of `iteratees`.
 * @returns {Array} Returns the new sorted array.
 */
function baseOrderBy(collection, iteratees, orders) {
  var index = -1;
  iteratees = arrayMap(iteratees.length ? iteratees : [identity], baseUnary(baseIteratee));

  var result = baseMap(collection, function(value, key, collection) {
    var criteria = arrayMap(iteratees, function(iteratee) {
      return iteratee(value);
    });
    return { 'criteria': criteria, 'index': ++index, 'value': value };
  });

  return baseSortBy(result, function(object, other) {
    return compareMultiple(object, other, orders);
  });
}

module.exports = baseOrderBy;


/***/ }),
/* 1585 */
/***/ (function(module, exports) {

/**
 * The base implementation of `_.sortBy` which uses `comparer` to define the
 * sort order of `array` and replaces criteria objects with their corresponding
 * values.
 *
 * @private
 * @param {Array} array The array to sort.
 * @param {Function} comparer The function to define sort order.
 * @returns {Array} Returns `array`.
 */
function baseSortBy(array, comparer) {
  var length = array.length;

  array.sort(comparer);
  while (length--) {
    array[length] = array[length].value;
  }
  return array;
}

module.exports = baseSortBy;


/***/ }),
/* 1586 */
/***/ (function(module, exports, __webpack_require__) {

var compareAscending = __webpack_require__(1587);

/**
 * Used by `_.orderBy` to compare multiple properties of a value to another
 * and stable sort them.
 *
 * If `orders` is unspecified, all values are sorted in ascending order. Otherwise,
 * specify an order of "desc" for descending or "asc" for ascending sort order
 * of corresponding values.
 *
 * @private
 * @param {Object} object The object to compare.
 * @param {Object} other The other object to compare.
 * @param {boolean[]|string[]} orders The order to sort by for each property.
 * @returns {number} Returns the sort order indicator for `object`.
 */
function compareMultiple(object, other, orders) {
  var index = -1,
      objCriteria = object.criteria,
      othCriteria = other.criteria,
      length = objCriteria.length,
      ordersLength = orders.length;

  while (++index < length) {
    var result = compareAscending(objCriteria[index], othCriteria[index]);
    if (result) {
      if (index >= ordersLength) {
        return result;
      }
      var order = orders[index];
      return result * (order == 'desc' ? -1 : 1);
    }
  }
  // Fixes an `Array#sort` bug in the JS engine embedded in Adobe applications
  // that causes it, under certain circumstances, to provide the same value for
  // `object` and `other`. See https://github.com/jashkenas/underscore/pull/1247
  // for more details.
  //
  // This also ensures a stable sort in V8 and other engines.
  // See https://bugs.chromium.org/p/v8/issues/detail?id=90 for more details.
  return object.index - other.index;
}

module.exports = compareMultiple;


/***/ }),
/* 1587 */
/***/ (function(module, exports, __webpack_require__) {

var isSymbol = __webpack_require__(1506);

/**
 * Compares values to sort them in ascending order.
 *
 * @private
 * @param {*} value The value to compare.
 * @param {*} other The other value to compare.
 * @returns {number} Returns the sort order indicator for `value`.
 */
function compareAscending(value, other) {
  if (value !== other) {
    var valIsDefined = value !== undefined,
        valIsNull = value === null,
        valIsReflexive = value === value,
        valIsSymbol = isSymbol(value);

    var othIsDefined = other !== undefined,
        othIsNull = other === null,
        othIsReflexive = other === other,
        othIsSymbol = isSymbol(other);

    if ((!othIsNull && !othIsSymbol && !valIsSymbol && value > other) ||
        (valIsSymbol && othIsDefined && othIsReflexive && !othIsNull && !othIsSymbol) ||
        (valIsNull && othIsDefined && othIsReflexive) ||
        (!valIsDefined && othIsReflexive) ||
        !valIsReflexive) {
      return 1;
    }
    if ((!valIsNull && !valIsSymbol && !othIsSymbol && value < other) ||
        (othIsSymbol && valIsDefined && valIsReflexive && !valIsNull && !valIsSymbol) ||
        (othIsNull && valIsDefined && valIsReflexive) ||
        (!othIsDefined && valIsReflexive) ||
        !othIsReflexive) {
      return -1;
    }
  }
  return 0;
}

module.exports = compareAscending;


/***/ }),
/* 1588 */
/***/ (function(module, exports, __webpack_require__) {

var identity = __webpack_require__(1528),
    overRest = __webpack_require__(1523),
    setToString = __webpack_require__(1525);

/**
 * The base implementation of `_.rest` which doesn't validate or coerce arguments.
 *
 * @private
 * @param {Function} func The function to apply a rest parameter to.
 * @param {number} [start=func.length-1] The start position of the rest parameter.
 * @returns {Function} Returns the new function.
 */
function baseRest(func, start) {
  return setToString(overRest(func, start, identity), func + '');
}

module.exports = baseRest;


/***/ }),
/* 1589 */
/***/ (function(module, exports, __webpack_require__) {

var eq = __webpack_require__(1402),
    isArrayLike = __webpack_require__(1466),
    isIndex = __webpack_require__(1456),
    isObject = __webpack_require__(1421);

/**
 * Checks if the given arguments are from an iteratee call.
 *
 * @private
 * @param {*} value The potential iteratee value argument.
 * @param {*} index The potential iteratee index or key argument.
 * @param {*} object The potential iteratee object argument.
 * @returns {boolean} Returns `true` if the arguments are from an iteratee call,
 *  else `false`.
 */
function isIterateeCall(value, index, object) {
  if (!isObject(object)) {
    return false;
  }
  var type = typeof index;
  if (type == 'number'
        ? (isArrayLike(object) && isIndex(index, object.length))
        : (type == 'string' && index in object)
      ) {
    return eq(object[index], value);
  }
  return false;
}

module.exports = isIterateeCall;


/***/ }),
/* 1590 */
/***/ (function(module, exports, __webpack_require__) {

const PromisePool = __webpack_require__(1591)

/**
 * Like a map, executed in parallel via a promise pool
 *
 * @param  {Array}    arr          Items to process
 * @param  {Function} fn           Promise creator (will be passed each item)
 * @param  {Number}   concurrency  How many promise can be in flight at the same time
 * @return {Promise}               Resolved with the results of the promise, not necessary in order
 */
const parallelMap = (iterable, fn, concurrencyArg) => {
  const concurrency = concurrencyArg || 30
  const res = []
  const pool = new PromisePool(function*() {
    for (let item of iterable) {
      yield fn(item).then(x => res.push(x))
    }
  }, concurrency)
  return pool.start().then(() => res)
}

module.exports = {
  parallelMap
}


/***/ }),
/* 1591 */
/***/ (function(module, exports, __webpack_require__) {

var __WEBPACK_AMD_DEFINE_FACTORY__, __WEBPACK_AMD_DEFINE_ARRAY__, __WEBPACK_AMD_DEFINE_RESULT__;(function (root, factory) {
  /* istanbul ignore next */
  if (true) {
    !(__WEBPACK_AMD_DEFINE_ARRAY__ = [], __WEBPACK_AMD_DEFINE_FACTORY__ = (factory),
				__WEBPACK_AMD_DEFINE_RESULT__ = (typeof __WEBPACK_AMD_DEFINE_FACTORY__ === 'function' ?
				(__WEBPACK_AMD_DEFINE_FACTORY__.apply(exports, __WEBPACK_AMD_DEFINE_ARRAY__)) : __WEBPACK_AMD_DEFINE_FACTORY__),
				__WEBPACK_AMD_DEFINE_RESULT__ !== undefined && (module.exports = __WEBPACK_AMD_DEFINE_RESULT__))
  } else {}
})(this, function () {
  'use strict'

  var EventTarget = function () {
    this._listeners = {}
  }

  EventTarget.prototype.addEventListener = function (type, listener) {
    this._listeners[type] = this._listeners[type] || []
    if (this._listeners[type].indexOf(listener) < 0) {
      this._listeners[type].push(listener)
    }
  }

  EventTarget.prototype.removeEventListener = function (type, listener) {
    if (this._listeners[type]) {
      var p = this._listeners[type].indexOf(listener)
      if (p >= 0) {
        this._listeners[type].splice(p, 1)
      }
    }
  }

  EventTarget.prototype.dispatchEvent = function (evt) {
    if (this._listeners[evt.type] && this._listeners[evt.type].length) {
      var listeners = this._listeners[evt.type].slice()
      for (var i = 0, l = listeners.length; i < l; ++i) {
        listeners[i].call(this, evt)
      }
    }
  }

  var isGenerator = function (func) {
    return (typeof func.constructor === 'function' &&
      func.constructor.name === 'GeneratorFunction')
  }

  var functionToIterator = function (func) {
    return {
      next: function () {
        var promise = func()
        return promise ? {value: promise} : {done: true}
      }
    }
  }

  var promiseToIterator = function (promise) {
    var called = false
    return {
      next: function () {
        if (called) {
          return {done: true}
        }
        called = true
        return {value: promise}
      }
    }
  }

  var toIterator = function (obj, Promise) {
    var type = typeof obj
    if (type === 'object') {
      if (typeof obj.next === 'function') {
        return obj
      }
      /* istanbul ignore else */
      if (typeof obj.then === 'function') {
        return promiseToIterator(obj)
      }
    }
    if (type === 'function') {
      return isGenerator(obj) ? obj() : functionToIterator(obj)
    }
    return promiseToIterator(Promise.resolve(obj))
  }

  var PromisePoolEvent = function (target, type, data) {
    this.target = target
    this.type = type
    this.data = data
  }

  var PromisePool = function (source, concurrency, options) {
    EventTarget.call(this)
    if (typeof concurrency !== 'number' ||
        Math.floor(concurrency) !== concurrency ||
        concurrency < 1) {
      throw new Error('Invalid concurrency')
    }
    this._concurrency = concurrency
    this._options = options || {}
    this._options.promise = this._options.promise || Promise
    this._iterator = toIterator(source, this._options.promise)
    this._done = false
    this._size = 0
    this._promise = null
    this._callbacks = null
  }
  PromisePool.prototype = new EventTarget()
  PromisePool.prototype.constructor = PromisePool

  PromisePool.prototype.concurrency = function (value) {
    if (typeof value !== 'undefined') {
      this._concurrency = value
      if (this.active()) {
        this._proceed()
      }
    }
    return this._concurrency
  }

  PromisePool.prototype.size = function () {
    return this._size
  }

  PromisePool.prototype.active = function () {
    return !!this._promise
  }

  PromisePool.prototype.promise = function () {
    return this._promise
  }

  PromisePool.prototype.start = function () {
    var that = this
    var Promise = this._options.promise