/**
 * Copyright 2013-2015, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @typechecks static-only
 * @providesModule cloneWithProps
 */

'use strict';

var ReactElement = require("./ReactElement");
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 {ReactElement} child child element you'd like to clone
 * @param {object} props props you'd like to modify. className and style will be
 * merged automatically.
 * @return {ReactElement} a clone of child with props merged in.
 */
function cloneWithProps(child, props) {
  if ("production" !== process.env.NODE_ENV) {
    ("production" !== process.env.NODE_ENV ? warning(
      !child.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.'
    ) : null);
  }

  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 ReactElement.cloneAndReplaceProps.
  return ReactElement.createElement(child.type, newProps);
}

module.exports = cloneWithProps;
