Compute sunrise and sunset only if necessary.

Sunrise and -set must recomputed if one of the following conditions is met:
* The date changed (based on the selected timezone)
* Location (Lat/Lon) changed
* Sunset type changed

So instead of calculating that every minute just do it on update via web interface or date change.

If a new config is uploaded, the DTU gets restarted. There is no need to initiate a recalculation in this case.

include/SunPosition.h

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 #pragma once
 
+#include <mutex>
 #include <sunset.h>
 
 #define SUNPOS_UPDATE_INTERVAL 60000l
@@ -15,9 +16,12 @@ public:
     bool isSunsetAvailable();
     bool sunsetTime(struct tm* info);
     bool sunriseTime(struct tm* info);
+    void setDoRecalc(bool doRecalc);
 
 private:
     void updateSunData();
+    bool checkRecalcDayChanged();
+    bool getDoRecalc();
 
     SunSet _sun;
     bool _isDayPeriod = true;
@@ -25,8 +29,10 @@ private:
     uint32_t _sunriseMinutes = 0;
     uint32_t _sunsetMinutes = 0;
 
-    uint32_t _lastUpdate = 0;
     bool _isValidInfo = false;
+    bool _doRecalc = true;
+    std::mutex _recalcLock;
+    uint32_t _lastSunPositionCalculatedYMD = 0;
 };
 
-extern SunPositionClass SunPosition;
+extern SunPositionClass SunPosition;