power meter refactoring: split loop task init from init()

when performing a test request using the web UI, we need to init() the
respective power meter, but we do not want to start the polling task.
hence we move initialization of the polling task to the poll() function.
it will return if the task is setup already, otherwise setup the task.

include/PowerMeterHttpJson.h

@@ -23,7 +23,7 @@ public:
     ~PowerMeterHttpJson();
 
     bool init() final;
-    void loop() final { } // polling is performed asynchronously
+    void loop() final;
     float getPowerTotal() const final;
     bool isDataValid() const final;
     void doMqttPublish() const final;

include/PowerMeterHttpSml.h

@@ -20,7 +20,7 @@ public:
     ~PowerMeterHttpSml();
 
     bool init() final;
-    void loop() final { } // polling is performed asynchronously
+    void loop() final;
     bool isDataValid() const final;
 
     // returns an empty string on success,

include/PowerMeterSerialSdm.h

@@ -23,7 +23,7 @@ public:
     ~PowerMeterSerialSdm();
 
     bool init() final;
-    void loop() final { } // polling is performed asynchronously
+    void loop() final;
     float getPowerTotal() const final;
     bool isDataValid() const final;
     void doMqttPublish() const final;

include/PowerMeterSerialSml.h

@@ -12,7 +12,7 @@ public:
     ~PowerMeterSerialSml();
 
     bool init() final;
-    void loop() final { } // polling is performed asynchronously
+    void loop() final;
 
 private:
     // we assume that an SML datagram is complete after no additional

src/PowerMeterHttpJson.cpp

@@ -48,6 +48,13 @@ bool PowerMeterHttpJson::init()
         return false;
     }
 
+    return true;
+}
+
+void PowerMeterHttpJson::loop()
+{
+    if (_taskHandle != nullptr) { return; }
+
     std::unique_lock<std::mutex> lock(_pollingMutex);
     _stopPolling = false;
     lock.unlock();
@@ -55,8 +62,6 @@ bool PowerMeterHttpJson::init()
     uint32_t constexpr stackSize = 3072;
     xTaskCreate(PowerMeterHttpJson::pollingLoopHelper, "PM:HTTP+JSON",
             stackSize, this, 1/*prio*/, &_taskHandle);
-
-    return true;
 }
 
 void PowerMeterHttpJson::pollingLoopHelper(void* context)

src/PowerMeterHttpSml.cpp

@@ -25,16 +25,7 @@ bool PowerMeterHttpSml::init()
 {
     _upHttpGetter = std::make_unique<HttpGetter>(_cfg.HttpRequest);
 
-    if (_upHttpGetter->init()) {
+    if (_upHttpGetter->init()) { return true; }
-        std::unique_lock<std::mutex> lock(_pollingMutex);
-        _stopPolling = false;
-        lock.unlock();
-
-        uint32_t constexpr stackSize = 3072;
-        xTaskCreate(PowerMeterHttpSml::pollingLoopHelper, "PM:HTTP+SML",
-                stackSize, this, 1/*prio*/, &_taskHandle);
-        return true;
-    }
 
     MessageOutput.printf("[PowerMeterHttpSml] Initializing HTTP getter failed:\r\n");
     MessageOutput.printf("[PowerMeterHttpSml] %s\r\n", _upHttpGetter->getErrorText());
@@ -44,6 +35,19 @@ bool PowerMeterHttpSml::init()
     return false;
 }
 
+void PowerMeterHttpSml::loop()
+{
+    if (_taskHandle != nullptr) { return; }
+
+    std::unique_lock<std::mutex> lock(_pollingMutex);
+    _stopPolling = false;
+    lock.unlock();
+
+    uint32_t constexpr stackSize = 3072;
+    xTaskCreate(PowerMeterHttpSml::pollingLoopHelper, "PM:HTTP+SML",
+            stackSize, this, 1/*prio*/, &_taskHandle);
+}
+
 void PowerMeterHttpSml::pollingLoopHelper(void* context)
 {
     auto pInstance = static_cast<PowerMeterHttpSml*>(context);

src/PowerMeterSerialSdm.cpp

@@ -43,6 +43,13 @@ bool PowerMeterSerialSdm::init()
             SWSERIAL_8N1, pin.powermeter_rx, pin.powermeter_tx);
     _upSdm->begin();
 
+    return true;
+}
+
+void PowerMeterSerialSdm::loop()
+{
+    if (_taskHandle != nullptr) { return; }
+
     std::unique_lock<std::mutex> lock(_pollingMutex);
     _stopPolling = false;
     lock.unlock();
@@ -50,8 +57,6 @@ bool PowerMeterSerialSdm::init()
     uint32_t constexpr stackSize = 3072;
     xTaskCreate(PowerMeterSerialSdm::pollingLoopHelper, "PM:SDM",
             stackSize, this, 1/*prio*/, &_taskHandle);
-
-    return true;
 }
 
 float PowerMeterSerialSdm::getPowerTotal() const

src/PowerMeterSerialSml.cpp

@@ -23,6 +23,13 @@ bool PowerMeterSerialSml::init()
     _upSmlSerial->enableTx(false);
     _upSmlSerial->flush();
 
+    return true;
+}
+
+void PowerMeterSerialSml::loop()
+{
+    if (_taskHandle != nullptr) { return; }
+
     std::unique_lock<std::mutex> lock(_pollingMutex);
     _stopPolling = false;
     lock.unlock();
@@ -30,8 +37,6 @@ bool PowerMeterSerialSml::init()
     uint32_t constexpr stackSize = 3072;
     xTaskCreate(PowerMeterSerialSml::pollingLoopHelper, "PM:SML",
             stackSize, this, 1/*prio*/, &_taskHandle);
-
-    return true;
 }
 
 PowerMeterSerialSml::~PowerMeterSerialSml()