/**
 * 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.
 *
 * @providesModule ReactLink
 * @typechecks static-only
 */

"use strict";

/**
 * ReactLink encapsulates a common pattern in which a component wants to modify
 * a prop received from its parent. ReactLink allows the parent to pass down a
 * value coupled with a callback that, when invoked, expresses an intent to
 * modify that value. For example:
 *
 * React.createClass({
 *   getInitialState: function() {
 *     return {value: ''};
 *   },
 *   render: function() {
 *     var valueLink = new ReactLink(this.state.value, this._handleValueChange);
 *     return <input valueLink={valueLink} />;
 *   },
 *   this._handleValueChange: function(newValue) {
 *     this.setState({value: newValue});
 *   }
 * });
 *
 * We have provided some sugary mixins to make the creation and
 * consumption of ReactLink easier; see LinkedValueUtils and LinkedStateMixin.
 */

var React = require("./React");

/**
 * @param {*} value current value of the link
 * @param {function} requestChange callback to request a change
 */
function ReactLink(value, requestChange) {
  this.value = value;
  this.requestChange = requestChange;
}

/**
 * Creates a PropType that enforces the ReactLink API and optionally checks the
 * type of the value being passed inside the link. Example:
 *
 * MyComponent.propTypes = {
 *   tabIndexLink: ReactLink.PropTypes.link(React.PropTypes.number)
 * }
 */
function createLinkTypeChecker(linkType) {
  var shapes = {
    value: typeof linkType === 'undefined' ?
      React.PropTypes.any.isRequired :
      linkType.isRequired,
    requestChange: React.PropTypes.func.isRequired
  };
  return React.PropTypes.shape(shapes);
}

ReactLink.PropTypes = {
  link: createLinkTypeChecker
};

module.exports = ReactLink;
