var baseIteratee = require('./_baseIteratee'),
      createInverter = require('./_createInverter');
  
  /** Used for built-in method references. */
  var objectProto = Object.prototype;
  
  /** Used to check objects for own properties. */
  var hasOwnProperty = objectProto.hasOwnProperty;
  
  /**
   * This method is like `_.invert` except that the inverted object is generated
   * from the results of running each element of `object` thru `iteratee`. The
   * corresponding inverted value of each inverted key is an array of keys
   * responsible for generating the inverted value. The iteratee is invoked
   * with one argument: (value).
   *
   * @static
   * @memberOf _
   * @since 4.1.0
   * @category Object
   * @param {Object} object The object to invert.
   * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
   * @returns {Object} Returns the new inverted object.
   * @example
   *
   * var object = { 'a': 1, 'b': 2, 'c': 1 };
   *
   * _.invertBy(object);
   * // => { '1': ['a', 'c'], '2': ['b'] }
   *
   * _.invertBy(object, function(value) {
   *   return 'group' + value;
   * });
   * // => { 'group1': ['a', 'c'], 'group2': ['b'] }
   */
  var invertBy = createInverter(function(result, value, key) {
    if (hasOwnProperty.call(result, value)) {
      result[value].push(key);
    } else {
      result[value] = [key];
    }
  }, baseIteratee);
  
  module.exports = invertBy;