/**
 * Copyright 2013-2014, 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
 * @providesModule ReactCSSTransitionGroupChild
 */

"use strict";

var React = require('React');

var CSSCore = require('CSSCore');
var ReactTransitionEvents = require('ReactTransitionEvents');

var onlyChild = require('onlyChild');

// We don't remove the element from the DOM until we receive an animationend or
// transitionend event. If the user screws up and forgets to add an animation
// their node will be stuck in the DOM forever, so we detect if an animation
// does not start and if it doesn't, we just call the end listener immediately.
var TICK = 17;
var NO_EVENT_TIMEOUT = 5000;

var noEventListener = null;


if (__DEV__) {
  noEventListener = function() {
    console.warn(
      'transition(): tried to perform an animation without ' +
      'an animationend or transitionend event after timeout (' +
      NO_EVENT_TIMEOUT + 'ms). You should either disable this ' +
      'transition in JS or add a CSS animation/transition.'
    );
  };
}

var ReactCSSTransitionGroupChild = React.createClass({
  displayName: 'ReactCSSTransitionGroupChild',

  transition: function(animationType, finishCallback) {
    var node = this.getDOMNode();
    var className = this.props.name + '-' + animationType;
    var activeClassName = className + '-active';
    var noEventTimeout = null;

    var endListener = function(e) {
      if (e && e.target !== node) {
        return;
      }
      if (__DEV__) {
        clearTimeout(noEventTimeout);
      }

      CSSCore.removeClass(node, className);
      CSSCore.removeClass(node, activeClassName);

      ReactTransitionEvents.removeEndEventListener(node, endListener);

      // Usually this optional callback is used for informing an owner of
      // a leave animation and telling it to remove the child.
      finishCallback && finishCallback();
    };

    ReactTransitionEvents.addEndEventListener(node, endListener);

    CSSCore.addClass(node, className);

    // Need to do this to actually trigger a transition.
    this.queueClass(activeClassName);

    if (__DEV__) {
      noEventTimeout = setTimeout(noEventListener, NO_EVENT_TIMEOUT);
    }
  },

  queueClass: function(className) {
    this.classNameQueue.push(className);

    if (!this.timeout) {
      this.timeout = setTimeout(this.flushClassNameQueue, TICK);
    }
  },

  flushClassNameQueue: function() {
    if (this.isMounted()) {
      this.classNameQueue.forEach(
        CSSCore.addClass.bind(CSSCore, this.getDOMNode())
      );
    }
    this.classNameQueue.length = 0;
    this.timeout = null;
  },

  componentWillMount: function() {
    this.classNameQueue = [];
  },

  componentWillUnmount: function() {
    if (this.timeout) {
      clearTimeout(this.timeout);
    }
  },

  componentWillEnter: function(done) {
    if (this.props.enter) {
      this.transition('enter', done);
    } else {
      done();
    }
  },

  componentWillLeave: function(done) {
    if (this.props.leave) {
      this.transition('leave', done);
    } else {
      done();
    }
  },

  render: function() {
    return onlyChild(this.props.children);
  }
});

module.exports = ReactCSSTransitionGroupChild;
