/**
 * Copyright 2013-2014 Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * @typechecks
 * @providesModule cloneWithProps
 */

"use strict";

var ReactPropTransferer = require('ReactPropTransferer');

var keyOf = require('keyOf');
var warning = require('warning');

var CHILDREN_PROP = keyOf({children: null});

/**
 * Sometimes you want to change the props of a child passed to you. Usually
 * this is to add a CSS class.
 *
 * @param {object} child child component you'd like to clone
 * @param {object} props props you'd like to modify. They will be merged
 * as if you used `transferPropsTo()`.
 * @return {object} a clone of child with props merged in.
 */
function cloneWithProps(child, props) {
  if (__DEV__) {
    warning(
      !child.props.ref,
      'You are calling cloneWithProps() on a child with a ref. This is ' +
      'dangerous because you\'re creating a new child which will not be ' +
      'added as a ref to its parent.'
    );
  }

  var newProps = ReactPropTransferer.mergeProps(props, child.props);

  // Use `child.props.children` if it is provided.
  if (!newProps.hasOwnProperty(CHILDREN_PROP) &&
      child.props.hasOwnProperty(CHILDREN_PROP)) {
    newProps.children = child.props.children;
  }

  // The current API doesn't retain _owner and _context, which is why this
  // doesn't use ReactDescriptor.cloneAndReplaceProps.
  return child.constructor(newProps);
}

module.exports = cloneWithProps;
