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

'use strict';

var SyntheticUIEvent = require("./SyntheticUIEvent");
var ViewportMetrics = require("./ViewportMetrics");

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

/**
 * @interface MouseEvent
 * @see http://www.w3.org/TR/DOM-Level-3-Events/
 */
var MouseEventInterface = {
  screenX: null,
  screenY: null,
  clientX: null,
  clientY: null,
  ctrlKey: null,
  shiftKey: null,
  altKey: null,
  metaKey: null,
  getModifierState: getEventModifierState,
  button: function(event) {
    // Webkit, Firefox, IE9+
    // which:  1 2 3
    // button: 0 1 2 (standard)
    var button = event.button;
    if ('which' in event) {
      return button;
    }
    // IE<9
    // which:  undefined
    // button: 0 0 0
    // button: 1 4 2 (onmouseup)
    return button === 2 ? 2 : button === 4 ? 1 : 0;
  },
  buttons: null,
  relatedTarget: function(event) {
    return event.relatedTarget || (
      ((event.fromElement === event.srcElement ? event.toElement : event.fromElement))
    );
  },
  // "Proprietary" Interface.
  pageX: function(event) {
    return 'pageX' in event ?
      event.pageX :
      event.clientX + ViewportMetrics.currentScrollLeft;
  },
  pageY: function(event) {
    return 'pageY' in event ?
      event.pageY :
      event.clientY + ViewportMetrics.currentScrollTop;
  }
};

/**
 * @param {object} dispatchConfig Configuration used to dispatch this event.
 * @param {string} dispatchMarker Marker identifying the event target.
 * @param {object} nativeEvent Native browser event.
 * @extends {SyntheticUIEvent}
 */
function SyntheticMouseEvent(dispatchConfig, dispatchMarker, nativeEvent) {
  SyntheticUIEvent.call(this, dispatchConfig, dispatchMarker, nativeEvent);
}

SyntheticUIEvent.augmentClass(SyntheticMouseEvent, MouseEventInterface);

module.exports = SyntheticMouseEvent;