HORIZON PROJECT

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;

/**

 * Used to resolve the

 * [`toStringTag`](http://ecma-international.org/ecma-262/7.0/#sec-object.prototype.tostring)

 * of values.

 */

var nativeObjectToString = objectProto.toString;

/**

 * 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 (value != null &&

      typeof value.toString != 'function') {

    value = nativeObjectToString.call(value);

  }

  if (hasOwnProperty.call(result, value)) {

    result[value].push(key);

  } else {

    result[value] = [key];

  }

}, baseIteratee);

module.exports = invertBy;