var ShortPollingNotification = {
  datasInterval: null,
  subscribe: function() {
    this.datasInterval = setInterval(function() {
      Request.getDatas().then(function(res) {
        window.ChatroomDOM.renderData(res);
      });
    }, TIMEOUT);
    return this.unsubscribe;
  },
  unsubscribe: function() {
    this.datasInterval && clearInterval(this.datasInterval);
  }
}

// 客户端
var LongPollingNotification = {
    // ....
    subscribe: function() {
      var that = this;

      // 设置超时时间
      Request.getV2Datas(this.getKey(),{ timeout: 10000 }).then(function(res) {
        var data = res.data;
        window.ChatroomDOM.renderData(res);
        // 成功获取数据后会再次发送请求
        that.subscribe();
      }).catch(function (error) {
        // timeout 之后也会再次发送请求
        that.subscribe();
      });
      return this.unsubscribe;
    }

    // ....
}

// 服务器端

router.get('/v2/datas', function(req, res) {
  const key = _.get(req.query, 'key', '');
  let contentKey = chatRoom.getContentKey();

  while (key === contentKey) {
    sleep.sleep(5);
    contentKey = chatRoom.getContentKey();
  }

  const connectors = chatRoom.getConnectors();
  const messages = chatRoom.getMessages();
  res.json({
    code: 200,
    data: { connectors: connectors, messages: messages, key: contentKey },
  });
});

// mini-chatroom/public/javascripts/server/longPolling.js

function pushDataToClient(key, longpoll) {
  var contentKey = chatRoom.getContentKey();

  if (key !== contentKey) {
    var connectors = chatRoom.getConnectors();
    var messages = chatRoom.getMessages();

    longpoll.publish(
      '/v2/datas',
      {
        code: 200,
        data: {connectors: connectors, messages: messages, key: contentKey},
      }
    );
  }
}

longpoll.create("/v2/datas", function(req, res, next) {
  key = _.get(req.query, 'key', '');
  pushDataToClient(key, longpoll);
  next();
});

intervalId = setInterval(function() {
  pushDataToClient(key, longpoll);
}, LONG_POLLING_TIMEOUT);

// 客户端
var SSENotification = {
  source: null,
  subscribe: function() {
    if ('EventSource' in window) {
      this.source = new EventSource('/sse');

      this.source.addEventListener('message', function(res) {
        const d = res.data;
        window.ChatroomDOM.renderData(JSON.parse(d));
      });
    }
    return this.unsubscribe;
  },
  unsubscribe: function () {
    this.source && this.source.close();
  }
}

// 服务器端
router.get('/sse', function(req, res) {
  const connectors = chatRoom.getConnectors();
  const messages = chatRoom.getMessages();
  const response = { code: 200, data: { connectors: connectors, messages: messages } };

  res.writeHead(200, {
    "Content-Type":"text/event-stream",
    "Cache-Control":"no-cache",
    "Connection":"keep-alive",
    "Access-Control-Allow-Origin": '*',
  });

  res.write("retry: 10000\n");
  res.write("data: " + JSON.stringify(response) + "\n\n");

  var unsubscribe = Event.subscribe(function() {
    const connectors = chatRoom.getConnectors();
    const messages = chatRoom.getMessages();
    const response = { code: 200, data: { connectors: connectors, messages: messages } };
    res.write("data: " + JSON.stringify(response) + "\n\n");
  });

  req.connection.addListener("close", function () {
    unsubscribe();
  }, false);
});

// 客户端
var WebsocketNotification = {
  // ...
  subscribe: function(args) {
    var connector = args[1];
    this.socket = io();

    this.socket.emit('register', connector);

    this.socket.on('register done', function() {
      window.ChatroomDOM.renderAfterRegister();
    });

    this.socket.on('data', function(res) {
      window.ChatroomDOM.renderData(res);
    });

    this.socket.on('disconnect', function() {
      window.ChatroomDOM.renderAfterLogout();
    });
  }
  // ...
}

// 服务器端
var io = socketIo(httpServer);

io.on('connection', (socket) => {
  socket.on('register', function(connector) {
    chatRoom.onConnect(connector);

    io.emit('register done');

    var data = chatRoom.getDatas();
    io.emit('data', { data });
  });

  socket.on('chat', function(message) {
    chatRoom.receive(message);

    var data = chatRoom.getDatas();
    io.emit('data', { data });
  });
});