add global/scan topic revealing status of --scanconfig option initiated scan (fixes #304)

src/ebusd/datahandler.h

@@ -160,6 +160,12 @@ class DataSink : virtual public DataHandler {
    */
   virtual void notifyUpdateCheckResult(const string& checkResult) {}
 
+  /**
+   * Notify the sink of the latest scan status.
+   * @param scanStatus a string describing the scan status.
+   */
+  virtual void notifyScanStatus(const string& scanStatus) {}
+
  protected:
   /** the allowed access levels. */
   string m_levels;

src/ebusd/mainloop.cpp

@@ -217,6 +217,7 @@ void MainLoop::run() {
   time_t lastTaskRun, now, start, lastSignal = 0, since, sinkSince = 1, nextCheckRun;
   int taskDelay = 5;
   symbol_t lastScanAddress = 0;  // 0 is known to be a master
+  string lastScanStatus = ".";
   time(&now);
   start = now;
   lastTaskRun = now;
@@ -252,12 +253,16 @@ void MainLoop::run() {
       }
       if (m_scanConfig) {
         bool loadDelay = false;
+        string scanStatus = lastScanStatus;
         if (m_initialScan != ESC && reload && m_busHandler->hasSignal()) {
           loadDelay = true;
           result_t result;
           if (m_initialScan == SYN) {
             logNotice(lf_main, "starting initial full scan");
             result = m_busHandler->startScan(true, "*");
+            if (result == RESULT_OK) {
+              scanStatus = "running";
+            }
           } else if (m_initialScan == BROADCAST) {
             logNotice(lf_main, "starting initial broadcast scan");
             Message* message = m_messages->getScanMessage(BROADCAST);
@@ -280,6 +285,7 @@ void MainLoop::run() {
               if (m_busHandler->formatScanResult(m_initialScan, false, &ret)) {
                 logNotice(lf_main, "initial scan result: %s", ret.str().c_str());
               }
+              scanStatus = "running";
             }
           }
           if (result != RESULT_OK) {
@@ -294,7 +300,11 @@ void MainLoop::run() {
           if (lastScanAddress == SYN) {
             taskDelay = 5;
             lastScanAddress = 0;
+            scanStatus = "finished";
           } else {
+            if (scanStatus!="running") {
+              scanStatus = "running";
+            }
             nextCheckRun = now + CHECK_INITIAL_DELAY;
             result_t result = m_busHandler->scanAndWait(lastScanAddress, true);
             taskDelay = (result == RESULT_ERR_NO_SIGNAL) ? 10 : 1;
@@ -305,6 +315,12 @@ void MainLoop::run() {
             }
           }
         }
+        if (scanStatus != lastScanStatus && !dataSinks.empty()) {
+          lastScanStatus = scanStatus;
+          for (const auto dataSink : dataSinks) {
+            dataSink->notifyScanStatus(scanStatus);
+          }
+        }
       } else if (reload && m_busHandler->hasSignal()) {
         reload = false;
         // execute initial instructions

src/ebusd/mqtthandler.cpp

@@ -435,7 +435,7 @@ void on_message(
 
 MqttHandler::MqttHandler(UserInfo* userInfo, BusHandler* busHandler, MessageMap* messages)
   : DataSink(userInfo, "mqtt"), DataSource(busHandler), WaitThread(), m_messages(messages), m_connected(false),
-    m_initialConnectFailed(false), m_lastUpdateCheckResult("."), m_lastErrorLogTime(0) {
+    m_initialConnectFailed(false), m_lastUpdateCheckResult("."), m_lastScanStatus("."), m_lastErrorLogTime(0) {
   m_publishByField = false;
   m_mosquitto = nullptr;
   if (g_topicFields.empty()) {
@@ -711,6 +711,14 @@ void MqttHandler::notifyUpdateCheckResult(const string& checkResult) {
   }
 }
 
+void MqttHandler::notifyScanStatus(const string& scanStatus) {
+  if (scanStatus != m_lastScanStatus) {
+    m_lastScanStatus = scanStatus;
+    const string sep = (g_publishFormat & OF_JSON) ? "\"" : "";
+    publishTopic(m_globalTopic+"scan", sep + (scanStatus.empty() ? "OK" : scanStatus) + sep, true);
+  }
+}
+
 void MqttHandler::run() {
   time_t lastTaskRun, now, start, lastSignal = 0, lastUpdates = 0;
   bool signal = false;
@@ -787,6 +795,7 @@ void MqttHandler::run() {
     }
   }
   publishTopic(signalTopic, "false", true);
+  publishTopic(m_globalTopic+"scan", "", true); // clear retain of scan status
 }
 
 bool MqttHandler::handleTraffic(bool allowReconnect) {

src/ebusd/mqtthandler.h

@@ -91,7 +91,10 @@ class MqttHandler : public DataSink, public DataSource, public WaitThread {
   // @copydoc
   void notifyUpdateCheckResult(const string& checkResult) override;
 
- protected:
+  // @copydoc
+  void notifyScanStatus(const string& scanStatus) override;
+
+protected:
   // @copydoc
   void run() override;
 
@@ -159,6 +162,9 @@ class MqttHandler : public DataSink, public DataSource, public WaitThread {
   /** the last update check result. */
   string m_lastUpdateCheckResult;
 
+  /** the last scan status. */
+  string m_lastScanStatus;
+
   /** the last system time when a communication error was logged. */
   time_t m_lastErrorLogTime;
 };