HORIZON PROJECT

var baseRest = require('./_baseRest'),

    eq = require('./eq'),

    isIterateeCall = require('./_isIterateeCall'),

    keysIn = require('./keysIn');

/** Used for built-in method references. */

var objectProto = Object.prototype;

/** Used to check objects for own properties. */

var hasOwnProperty = objectProto.hasOwnProperty;

/**

 * Assigns own and inherited enumerable string keyed properties of source

 * objects to the destination object for all destination properties that

 * resolve to `undefined`. Source objects are applied from left to right.

 * Once a property is set, additional values of the same property are ignored.

 *

 * **Note:** This method mutates `object`.

 *

 * @static

 * @since 0.1.0

 * @memberOf _

 * @category Object

 * @param {Object} object The destination object.

 * @param {...Object} [sources] The source objects.

 * @returns {Object} Returns `object`.

 * @see _.defaultsDeep

 * @example

 *

 * _.defaults({ 'a': 1 }, { 'b': 2 }, { 'a': 3 });

 * // => { 'a': 1, 'b': 2 }

 */

var defaults = baseRest(function(object, sources) {

  object = Object(object);

  var index = -1;

  var length = sources.length;

  var guard = length > 2 ? sources[2] : undefined;

  if (guard && isIterateeCall(sources[0], sources[1], guard)) {

    length = 1;

  }

  while (++index < length) {

    var source = sources[index];

    var props = keysIn(source);

    var propsIndex = -1;

    var propsLength = props.length;

    while (++propsIndex < propsLength) {

      var key = props[propsIndex];

      var value = object[key];

      if (value === undefined ||

          (eq(value, objectProto[key]) && !hasOwnProperty.call(object, key))) {

        object[key] = source[key];

      }

    }

  }

  return object;

});

module.exports = defaults;