Replace checkCloudConnection and associated functions with an easier to read state machine

Author: aentinger

src/ArduinoIoTCloudTCP.cpp

@@ -74,7 +74,8 @@ extern "C" unsigned long getTime()
  ******************************************************************************/
 
 ArduinoIoTCloudTCP::ArduinoIoTCloudTCP()
-: _lastSyncRequestTickTime{0}
+: _state{State::ConnectMqttBroker}
+, _lastSyncRequestTickTime{0}
 , _mqtt_data_buf{0}
 , _mqtt_data_len{0}
 , _mqtt_data_request_retransmit{false}
@@ -186,7 +187,18 @@ void ArduinoIoTCloudTCP::update()
 #endif /* OTA_ENABLED */
 
   if(checkPhyConnection()   != NetworkConnectionState::CONNECTED)     return;
-  if(checkCloudConnection() != ArduinoIoTConnectionStatus::CONNECTED) return;
+
+  State next_state = _state;
+  switch (_state)
+  {
+  case State::ConnectMqttBroker:   next_state = handle_ConnectMqttBroker();   break;
+  case State::SubscribeMqttTopics: next_state = handle_SubscribeMqttTopics(); break;
+  case State::Connected:           next_state = handle_Connected();           break;
+  }
+  _state = next_state;
+
+  /* For now exit here if we are not connected. */
+  if (_state != State::Connected) return;
 
   /* Check if a primitive property wrapper is locally changed.
    * This function requires an existing time service which in
@@ -250,44 +262,71 @@ void ArduinoIoTCloudTCP::setOTAStorage(OTAStorage & ota_storage)
 }
 #endif /* OTA_ENABLED */
 
-int ArduinoIoTCloudTCP::reconnect()
-{
-  if (_mqttClient.connected()) {
-    _mqttClient.stop();
-  }
-  return connect();
-}
-
 /******************************************************************************
- * PROTECTED MEMBER FUNCTIONS
+ * PRIVATE MEMBER FUNCTIONS
  ******************************************************************************/
 
-int ArduinoIoTCloudTCP::connect()
+ArduinoIoTCloudTCP::State ArduinoIoTCloudTCP::handle_ConnectMqttBroker()
 {
-  if (!_mqttClient.connect(_brokerAddress.c_str(), _brokerPort)) return CONNECT_FAILURE;
-  if (_mqttClient.subscribe(_stdinTopic) == 0)                   return CONNECT_FAILURE_SUBSCRIBE;
-  if (_mqttClient.subscribe(_dataTopicIn) == 0)                  return CONNECT_FAILURE_SUBSCRIBE;
-  if (_mqttClient.subscribe(_ota_topic_in) == 0)                 return CONNECT_FAILURE_SUBSCRIBE;
+  if (_mqttClient.connect(_brokerAddress.c_str(), _brokerPort))
+    return State::SubscribeMqttTopics;
+
+  DBG_ERROR("ArduinoIoTCloudTCP::%s could not connect to %s:%d", __FUNCTION__, _brokerAddress.c_str(), _brokerPort);
+  return State::ConnectMqttBroker;
+}
+
+ArduinoIoTCloudTCP::State ArduinoIoTCloudTCP::handle_SubscribeMqttTopics()
+{
+  if (!_mqttClient.subscribe(_stdinTopic))
+  {
+    DBG_ERROR("ArduinoIoTCloudTCP::%s could not subscribe to %s", __FUNCTION__, _stdinTopic.c_str());
+    return State::SubscribeMqttTopics;
+  }
+
+  if (!_mqttClient.subscribe(_dataTopicIn))
+  {
+    DBG_ERROR("ArduinoIoTCloudTCP::%s could not subscribe to %s", __FUNCTION__, _dataTopicIn.c_str());
+    return State::SubscribeMqttTopics;
+  }
+
+  if (!_mqttClient.subscribe(_ota_topic_in))
+  {
+    DBG_ERROR("ArduinoIoTCloudTCP::%s could not subscribe to %s", __FUNCTION__, _ota_topic_in.c_str());
+    return State::SubscribeMqttTopics;
+  }
 
   if (_shadowTopicIn != "")
   {
-    if (_mqttClient.subscribe(_shadowTopicIn) == 0)              return CONNECT_FAILURE_SUBSCRIBE;
+    if (!_mqttClient.subscribe(_shadowTopicIn))
+    {
+      DBG_ERROR("ArduinoIoTCloudTCP::%s could not subscribe to %s", __FUNCTION__, _ota_topic_in.c_str());
+      return State::SubscribeMqttTopics;
+    }
     _syncStatus = ArduinoIoTSynchronizationStatus::SYNC_STATUS_WAIT_FOR_CLOUD_VALUES;
     _lastSyncRequestTickTime = 0;
   }
 
-  return CONNECT_SUCCESS;
+  DBG_VERBOSE("Connected to Arduino IoT Cloud");
+  execCloudEventCallback(ArduinoIoTCloudEvent::CONNECT);
+  return State::Connected;
 }
 
-void ArduinoIoTCloudTCP::disconnect()
+ArduinoIoTCloudTCP::State ArduinoIoTCloudTCP::handle_Connected()
 {
+  if (_mqttClient.connected())
+    return State::Connected;
+
+  /* The last message was definitely lost, trigger a retransmit. */
+  _mqtt_data_request_retransmit = true;
+
+  /* We are not connected anymore, trigger the callback for a disconnected event. */
+  execCloudEventCallback(ArduinoIoTCloudEvent::DISCONNECT);
+
+  /* Forcefully disconnect MQTT client and trigger a reconnection. */
   _mqttClient.stop();
+  return State::ConnectMqttBroker;
 }
 
-/******************************************************************************
- * PRIVATE MEMBER FUNCTIONS
- ******************************************************************************/
-
 void ArduinoIoTCloudTCP::onMessage(int length)
 {
   ArduinoCloud.handleMessage(length);
@@ -345,62 +384,6 @@ void ArduinoIoTCloudTCP::requestLastValue()
   write(_shadowTopicOut, CBOR_REQUEST_LAST_VALUE_MSG, sizeof(CBOR_REQUEST_LAST_VALUE_MSG));
 }
 
-ArduinoIoTConnectionStatus ArduinoIoTCloudTCP::checkCloudConnection()
-{
-  ArduinoIoTConnectionStatus next_iot_status = _iot_status;
-
-  switch (_iot_status)
-  {
-    case ArduinoIoTConnectionStatus::IDLE:         next_iot_status = ArduinoIoTConnectionStatus::CONNECTING;   break;
-    case ArduinoIoTConnectionStatus::ERROR:        next_iot_status = ArduinoIoTConnectionStatus::RECONNECTING; break;
-    case ArduinoIoTConnectionStatus::DISCONNECTED: next_iot_status = ArduinoIoTConnectionStatus::RECONNECTING; break;
-    case ArduinoIoTConnectionStatus::CONNECTING:
-    {
-      DBG_INFO("Arduino IoT Cloud connecting ...");
-      int const ret = connect();
-      if (ret == CONNECT_SUCCESS)
-      {
-        next_iot_status = ArduinoIoTConnectionStatus::CONNECTED;
-      }
-      else if (ret == CONNECT_FAILURE_SUBSCRIBE)
-      {
-        DBG_ERROR("ERROR - Please verify your THING ID");
-      }
-    }
-    break;
-
-    case ArduinoIoTConnectionStatus::RECONNECTING:
-    {
-      DBG_INFO("Arduino IoT Cloud reconnecting ...");
-      if (reconnect() == CONNECT_SUCCESS)
-      {
-        next_iot_status = ArduinoIoTConnectionStatus::CONNECTED;
-      }
-    }
-    break;
-
-    case ArduinoIoTConnectionStatus::CONNECTED:
-    {
-      if (!_mqttClient.connected())
-      {
-        next_iot_status = ArduinoIoTConnectionStatus::DISCONNECTED;
-        _mqtt_data_request_retransmit = true;
-      }
-    }
-    break;
-  }
-
-  if(next_iot_status != _iot_status)
-  {
-    printConnectionStatus(next_iot_status);
-    if     (next_iot_status == ArduinoIoTConnectionStatus::DISCONNECTED) execCloudEventCallback(ArduinoIoTCloudEvent::DISCONNECT);
-    else if(next_iot_status == ArduinoIoTConnectionStatus::CONNECTED)    execCloudEventCallback(ArduinoIoTCloudEvent::CONNECT);
-    _iot_status = next_iot_status;
-  }
-
-  return _iot_status;
-}
-
 int ArduinoIoTCloudTCP::write(String const topic, byte const data[], int const length)
 {
   if (_mqttClient.beginMessage(topic, length, false, 0)) {

src/ArduinoIoTCloudTCP.h

@@ -89,13 +89,22 @@ class ArduinoIoTCloudTCP: public ArduinoIoTCloudClass
 
   protected:
 
-    virtual int  connect       () override;
-    virtual void disconnect    () override;
+    virtual int  connect       () override { }
+    virtual void disconnect    () override { }
 
 
   private:
     static const int MQTT_TRANSMIT_BUFFER_SIZE = 256;
 
+    enum class State
+    {
+      ConnectMqttBroker,
+      SubscribeMqttTopics,
+      Connected,
+    };
+
+    State _state;
+
     int _lastSyncRequestTickTime;
     String _brokerAddress;
     uint16_t _brokerPort;
@@ -138,11 +147,14 @@ class ArduinoIoTCloudTCP: public ArduinoIoTCloudClass
     inline String getTopic_datain   () { return ( getThingId().length() == 0) ? String("/a/d/" + getDeviceId() + "/e/i") : String("/a/t/" + getThingId() + "/e/i"); }
     inline String getTopic_ota_in   () { return String("/a/d/" + getDeviceId() + "/ota/i"); }
 
+    State handle_ConnectMqttBroker();
+    State handle_SubscribeMqttTopics();
+    State handle_Connected();
+
     static void onMessage(int length);
     void handleMessage(int length);
     void sendPropertiesToCloud();
     void requestLastValue();
-    ArduinoIoTConnectionStatus checkCloudConnection();
     int write(String const topic, byte const data[], int const length);
 
 };