update OpenWeatherMap ambient temp in background

apps/OpenWeatherMapAmbientTemperature/openWeatherMapAmbientTemperatureComponent/owmAmbientTemperature.c

@@ -16,11 +16,14 @@ static char ApiKey[32 + 1];
 
 static struct
 {
+    // Must hold this lock to read/write the other values
+    le_mutex_Ref_t lock;
     int64_t timestampNs;
     double temperature;
 } LastResult;
 static le_data_RequestObjRef_t DataRequest = NULL;
-static bool AmbientTemperatureServiceAdvertised = false;
+static le_thread_Ref_t HttpThread = NULL;
+static le_timer_Ref_t UpdateTimer;
 
 static int64_t GetTimestampNs(void)
 {
@@ -31,35 +34,63 @@ static int64_t GetTimestampNs(void)
 
 le_result_t mangOH_ambientTemperature_Read(double *temperature)
 {
-    // Use a cached value if the temperature was requested recently
-    const int64_t now = GetTimestampNs();
-    const int64_t minDelay = 60LL * 1000LL * 1000LL * 1000LL;
-    if (LastResult.timestampNs && ((now - LastResult.timestampNs) < minDelay))
-    {
-        *temperature = LastResult.temperature;
-        return LE_OK;
-    }
+    le_mutex_Lock(LastResult.lock);
+    *temperature = LastResult.temperature;
+    le_mutex_Unlock(LastResult.lock);
+    return LE_OK;
+}
 
+static le_result_t UpdateAmbientTemperature(void)
+{
     json_t *response = OpenWeatherMapGet(Location.latitude, Location.longitude, ApiKey);
     if (!response)
     {
         return LE_FAULT;
     }
 
-    const int unpackRes = json_unpack(response, "{s:{s:f}}", "main", "temp", temperature);
+    double temperature;
+    const int unpackRes = json_unpack(response, "{s:{s:f}}", "main", "temp", &temperature);
     json_decref(response);
     if (unpackRes != 0)
     {
         return LE_FAULT;
     }
 
-    LE_DEBUG("Received ambient temperature reading: %f", *temperature);
+    LE_DEBUG("Received OpenWeatherMap temperature: %f", temperature);
+
+    le_mutex_Lock(LastResult.lock);
+    LastResult.timestampNs = GetTimestampNs();
+    LastResult.temperature = temperature;
+    le_mutex_Unlock(LastResult.lock);
 
-    LastResult.timestampNs = now;
-    LastResult.temperature = *temperature;
     return LE_OK;
 }
 
+void UpdateTimerHandler(le_timer_Ref_t timer)
+{
+    UpdateAmbientTemperature();
+}
+
+void *HttpThreadFunc(void *context)
+{
+    while (UpdateAmbientTemperature() != LE_OK)
+    {
+        sleep(20);
+    }
+
+    // A temperature is available, so advertise the service
+    mangOH_ambientTemperature_AdvertiseService();
+
+    UpdateTimer = le_timer_Create("owm ambient");
+    LE_ASSERT_OK(le_timer_SetHandler(UpdateTimer, UpdateTimerHandler));
+    LE_ASSERT_OK(le_timer_SetMsInterval(UpdateTimer, 1000 * 60 * 1));
+    LE_ASSERT_OK(le_timer_SetRepeat(UpdateTimer, 0));
+    LE_ASSERT_OK(le_timer_Start(UpdateTimer));
+
+    le_event_RunLoop();
+    return NULL;
+}
+
 static void DcsStateHandler
 (
     const char *intfName,
@@ -70,11 +101,11 @@ static void DcsStateHandler
     if (isConnected)
     {
         LE_INFO("Data connection established using interface %s", intfName);
-        // Now that we have a connection, advertise the ambient temperature service
-        if (!AmbientTemperatureServiceAdvertised)
+        // Now that we have a connection, start the thread which updates the temperature
+        if (!HttpThread)
         {
-            AmbientTemperatureServiceAdvertised = true;
-            mangOH_ambientTemperature_AdvertiseService();
+            HttpThread = le_thread_Create("owm http", HttpThreadFunc, NULL);
+            le_thread_Start(HttpThread);
         }
     }
     else
@@ -91,6 +122,8 @@ COMPONENT_INIT
         cfgRes != LE_OK || ApiKey[0] == '\0',
         "Failed to read OpenWeatherMap API Key from config tree");
 
+    LastResult.lock = le_mutex_CreateNonRecursive("owm LastResult");
+
     le_data_AddConnectionStateHandler(DcsStateHandler, NULL);
     LE_DEBUG("Requesting data connection");
     DataRequest = le_data_Request();