this._handleMessages = function()

in thing/index.js [197:313]
52 lines of code
16 McCabe index (conditional complexity)

   this._handleMessages = function(thingName, operation, operationStatus, payload) {
      var stateObject = {};
      try {
         stateObject = JSON.parse(payload.toString());
      } catch (err) {
         if (deviceOptions.debug === true) {
            console.error('failed parsing JSON \'' + payload.toString() + '\', ' + err);
         }
         return;
      }
      var clientToken = stateObject.clientToken;
      var version = stateObject.version;
      //
      // Remove the properties 'clientToken' and 'version' from the stateObject;
      // these properties are internal to this class.
      //
      delete stateObject.clientToken;
      //Expose shadow version from raw object
      //delete stateObject.version;
      //
      // Update the thing version on every accepted or delta message which 
      // contains it.
      //
      if ((!isUndefined(version)) && (operationStatus !== 'rejected')) {
         //
         // The thing shadow version is incremented by AWS IoT and should always
         // increase.  Do not update our local version if the received version is
         // less than our version.  
         //
         if ((isUndefined(thingShadows[thingName].version)) ||
            (version >= thingShadows[thingName].version)) {
            thingShadows[thingName].version = version;
         } else {
            //
            // We've received a message from AWS IoT with a version number lower than
            // we would expect.  There are two things that can cause this:
            //
            //  1) The shadow has been deleted (version # reverts to 1 in this case.)
            //  2) The message has arrived out-of-order.
            //
            // For case 1) we can look at the operation to determine that this
            // is the case and notify the client if appropriate.  For case 2, 
            // we will not process it unless the client has specifically expressed
            // an interested in these messages by setting 'discardStale' to false.
            //
            if (operation !== 'delete' && thingShadows[thingName].discardStale === true) {
               if (deviceOptions.debug === true) {
                  console.warn('out-of-date version \'' + version + '\' on \'' +
                     thingName + '\' (local version \'' +
                     thingShadows[thingName].version + '\')');
               }
               return;
            }
         }
      }
      //
      // If this is a 'delta' message, emit an event for it and return.
      //
      if (operationStatus === 'delta') {
         this.emit('delta', thingName, stateObject);
         return;
      }
      //
      // only accepted/rejected messages past this point
      // ===============================================
      // If this is an unkown clientToken (e.g., it doesn't have a corresponding
      // client token property, the shadow has been modified by another client.
      // If it's an update/accepted or delete/accepted, update the shadow and
      // notify the client.
      //
      if (isUndefined(thingShadows[thingName].clientToken) ||
         thingShadows[thingName].clientToken !== clientToken) {
         if ((operationStatus === 'accepted') && (operation !== 'get')) {
            //
            // This is a foreign update or delete accepted, update our
            // shadow with the latest state and send a notification.
            //
            this.emit('foreignStateChange', thingName, operation, stateObject);
         }
         return;
      }
      //
      // A response has been received, so cancel any outstanding timeout on this
      // thingName/clientToken, delete the timeout handle, and unsubscribe from
      // all sub-topics.
      //
      clearTimeout(
         thingShadows[thingName].timeout);

      delete thingShadows[thingName].timeout;
      //
      // Delete the operation's client token.
      //
      delete thingShadows[thingName].clientToken;
      //
      // Mark this operation as complete.
      //
      thingShadows[thingName].pending = false;

      //
      // Unsubscribe from the 'accepted' and 'rejected' sub-topics unless we are
      // persistently subscribed to this thing shadow.
      //
      if (thingShadows[thingName].persistentSubscribe === false) {
         this._handleSubscriptions(thingName, [{
            operations: [operation],
            statii: ['accepted', 'rejected']
         }], 'unsubscribe');
      }

      //
      // Emit an event detailing the operation status; the clientToken is included
      // as an argument so that the application can correlate status events to
      // the operations they are associated with.
      //
      this.emit('status', thingName, operationStatus, clientToken, stateObject);
   };