function _drainOperationQueue()

in device/index.js [688:750]

• 36 lines of code
• 9 McCabe index (conditional complexity)

   function _drainOperationQueue() {

      //
      // Handle our active subscriptions first, using a cloned
      // copy of the array.  We shift them out one-by-one until
      // all have been processed, leaving the official record
      // of active subscriptions untouched.
      //
      var subscription = clonedSubscriptions.shift();

      if (!isUndefined(subscription)) {
         //
         // If the 3rd argument (namely callback) is not present, we will
         // use two-argument form to call mqtt.Client#subscribe(), which
         // supports both subscribe(topics, options) and subscribe(topics, callback).
         //
         if (!isUndefined(subscription.callback)) {
            device.subscribe(subscription.topic, subscription.options, subscription.callback);
         } else {
            device.subscribe(subscription.topic, subscription.options);
         }
      } else {
         //
         // If no remaining active subscriptions to process,
         // then handle subscription requests queued while offline.
         //
         var req = offlineSubscriptionQueue.shift();

         if (!isUndefined(req)) {
            _updateSubscriptionCache(req.type, req.topics, req.options);
            if (req.type === 'subscribe') {
               if (!isUndefined(req.callback)) {
                  device.subscribe(req.topics, req.options, req.callback);
               } else {
                  device.subscribe(req.topics, req.options);
               }
            } else if (req.type === 'unsubscribe') {
               device.unsubscribe(req.topics, req.callback);
            }
         } else {
            //
            // If no active or queued subscriptions remaining to process,
            // then handle queued publish operations.
            //
            var offlinePublishMessage = offlinePublishQueue.shift();

            if (!isUndefined(offlinePublishMessage)) {
               device.publish(offlinePublishMessage.topic,
                  offlinePublishMessage.message,
                  offlinePublishMessage.options,
                  offlinePublishMessage.callback);
            }
            if (offlinePublishQueue.length === 0) {
               //
               // The subscription and offlinePublishQueue queues are fully drained,
               // cancel the draining timer.
               //
               clearInterval(drainingTimer);
               drainingTimer = null;
            }
         }
      }
   }