'use strict';
  
  Object.defineProperty(exports, "__esModule", {
      value: true
  });
  exports.default = transform;
  
  var _isArray = require('lodash/isArray');
  
  var _isArray2 = _interopRequireDefault(_isArray);
  
  var _noop = require('lodash/noop');
  
  var _noop2 = _interopRequireDefault(_noop);
  
  var _eachOf = require('./eachOf');
  
  var _eachOf2 = _interopRequireDefault(_eachOf);
  
  var _once = require('./internal/once');
  
  var _once2 = _interopRequireDefault(_once);
  
  var _wrapAsync = require('./internal/wrapAsync');
  
  var _wrapAsync2 = _interopRequireDefault(_wrapAsync);
  
  function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
  
  /**
   * A relative of `reduce`.  Takes an Object or Array, and iterates over each
   * element in series, each step potentially mutating an `accumulator` value.
   * The type of the accumulator defaults to the type of collection passed in.
   *
   * @name transform
   * @static
   * @memberOf module:Collections
   * @method
   * @category Collection
   * @param {Array|Iterable|Object} coll - A collection to iterate over.
   * @param {*} [accumulator] - The initial state of the transform.  If omitted,
   * it will default to an empty Object or Array, depending on the type of `coll`
   * @param {AsyncFunction} iteratee - A function applied to each item in the
   * collection that potentially modifies the accumulator.
   * Invoked with (accumulator, item, key, callback).
   * @param {Function} [callback] - A callback which is called after all the
   * `iteratee` functions have finished. Result is the transformed accumulator.
   * Invoked with (err, result).
   * @example
   *
   * async.transform([1,2,3], function(acc, item, index, callback) {
   *     // pointless async:
   *     process.nextTick(function() {
   *         acc.push(item * 2)
   *         callback(null)
   *     });
   * }, function(err, result) {
   *     // result is now equal to [2, 4, 6]
   * });
   *
   * @example
   *
   * async.transform({a: 1, b: 2, c: 3}, function (obj, val, key, callback) {
   *     setImmediate(function () {
   *         obj[key] = val * 2;
   *         callback();
   *     })
   * }, function (err, result) {
   *     // result is equal to {a: 2, b: 4, c: 6}
   * })
   */
  function transform(coll, accumulator, iteratee, callback) {
      if (arguments.length <= 3) {
          callback = iteratee;
          iteratee = accumulator;
          accumulator = (0, _isArray2.default)(coll) ? [] : {};
      }
      callback = (0, _once2.default)(callback || _noop2.default);
      var _iteratee = (0, _wrapAsync2.default)(iteratee);
  
      (0, _eachOf2.default)(coll, function (v, k, cb) {
          _iteratee(accumulator, v, k, cb);
      }, function (err) {
          callback(err, accumulator);
      });
  }
  module.exports = exports['default'];