Attempt to fix DST changes

app/src/main/AndroidManifest.xml

@@ -33,6 +33,9 @@
     <uses-permission android:name="android.permission.SEND_SMS" />
     <uses-permission android:name="android.permission.READ_CONTACTS" />
 
+    <!-- Schedule exact alarms (eg. for DST changes) -->
+    <uses-permission android:name="android.permission.SCHEDULE_EXACT_ALARM" />
+
     <!-- Read loyalty cards from Catima -->
     <uses-permission android:name="me.hackerchick.catima.READ_CARDS"/>
     <uses-permission android:name="me.hackerchick.catima.debug.READ_CARDS"/>

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/GBApplication.java

@@ -68,6 +68,7 @@ import nodomain.freeyourgadget.gadgetbridge.entities.DaoMaster;
 import nodomain.freeyourgadget.gadgetbridge.entities.DaoSession;
 import nodomain.freeyourgadget.gadgetbridge.entities.Device;
 import nodomain.freeyourgadget.gadgetbridge.externalevents.BluetoothStateChangeReceiver;
+import nodomain.freeyourgadget.gadgetbridge.externalevents.TimeChangeReceiver;
 import nodomain.freeyourgadget.gadgetbridge.externalevents.opentracks.OpenTracksContentObserver;
 import nodomain.freeyourgadget.gadgetbridge.impl.GBDevice;
 import nodomain.freeyourgadget.gadgetbridge.impl.GBDeviceService;
@@ -224,6 +225,7 @@ public class GBApplication extends Application {
         loadAppsPebbleBlackList();
 
         PeriodicExporter.enablePeriodicExport(context);
+        TimeChangeReceiver.scheduleNextDstChange(context);
 
         if (isRunningMarshmallowOrLater()) {
             notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/externalevents/TimeChangeReceiver.java

@@ -16,34 +16,122 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>. */
 package nodomain.freeyourgadget.gadgetbridge.externalevents;
 
+import android.app.AlarmManager;
+import android.app.PendingIntent;
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
+import android.os.Build;
+import android.os.SystemClock;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.threeten.bp.Instant;
+import org.threeten.bp.ZoneId;
+import org.threeten.bp.zone.ZoneOffsetTransition;
+import org.threeten.bp.zone.ZoneRules;
 
 import java.util.Date;
 import java.util.GregorianCalendar;
 
 import nodomain.freeyourgadget.gadgetbridge.GBApplication;
 import nodomain.freeyourgadget.gadgetbridge.util.DateTimeUtils;
+import nodomain.freeyourgadget.gadgetbridge.util.GB;
+import nodomain.freeyourgadget.gadgetbridge.util.PendingIntentUtils;
 import nodomain.freeyourgadget.gadgetbridge.util.Prefs;
 
 
 public class TimeChangeReceiver extends BroadcastReceiver {
-
     private static final Logger LOG = LoggerFactory.getLogger(TimeChangeReceiver.class);
 
+    public static final String ACTION_DST_CHANGED = "nodomain.freeyourgadget.gadgetbridge.DST_CHANGED";
+
     @Override
     public void onReceive(Context context, Intent intent) {
-        Prefs prefs = GBApplication.getPrefs();
+        final Prefs prefs = GBApplication.getPrefs();
         final String action = intent.getAction();
+        if (action == null) {
+            LOG.warn("Null action");
+            return;
+        }
 
-        if (prefs.getBoolean("datetime_synconconnect", true) && (action.equals(Intent.ACTION_TIME_CHANGED) || action.equals(Intent.ACTION_TIMEZONE_CHANGED))) {
+        if (!prefs.getBoolean("datetime_synconconnect", true)) {
-            Date newTime = GregorianCalendar.getInstance().getTime();
+            LOG.warn("Ignoring time change for {}, time sync is disabled", action);
-            LOG.info("Time or Timezone changed, syncing with device: " + DateTimeUtils.formatDate(newTime) + " (" + newTime.toGMTString() + "), " + intent.getAction());
+            return;
-            GBApplication.deviceService().onSetTime();
+        }
+
+        switch (action) {
+            case Intent.ACTION_TIME_CHANGED:
+            case Intent.ACTION_TIMEZONE_CHANGED:
+            case ACTION_DST_CHANGED:
+                // Continue after the switch
+                break;
+            default:
+                LOG.warn("Unknown action {}", action);
+                return;
+        }
+
+        final Date newTime = GregorianCalendar.getInstance().getTime();
+        LOG.info("Time or Timezone changed, syncing with device: {} ({}), {}", DateTimeUtils.formatDate(newTime), newTime.toGMTString(), intent.getAction());
+        GBApplication.deviceService().onSetTime();
+
+        // Reschedule the next DST change, since the timezone may have changed
+        scheduleNextDstChange(context);
+    }
+
+    /**
+     * Schedule an alarm to trigger on the next DST change, since ACTION_TIMEZONE_CHANGED is not broadcast otherwise.
+     *
+     * @param context the context
+     */
+    public static void scheduleNextDstChange(final Context context) {
+        final ZoneId zoneId = ZoneId.systemDefault();
+        final ZoneRules zoneRules = zoneId.getRules();
+        final Instant now = Instant.now();
+        final ZoneOffsetTransition transition = zoneRules.nextTransition(now);
+        final long nextDstMillis = transition.getInstant().toEpochMilli();
+        final long delayMillis = nextDstMillis - now.toEpochMilli() + 5000L;
+
+        final Intent i = new Intent(context, TimeChangeReceiver.class);
+        i.setAction(ACTION_DST_CHANGED);
+        final PendingIntent pi = PendingIntentUtils.getBroadcast(context, 0, i, 0, false);
+
+        final AlarmManager am = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
+        final boolean exactAlarm = canScheduleExactAlarms(context, am);
+
+        LOG.info("Scheduling next DST change: {} (in {} millis) (exact = {})", nextDstMillis, delayMillis, exactAlarm);
+
+        am.cancel(pi);
+
+        boolean scheduledExact = false;
+        if (exactAlarm) {
+            try {
+                am.setExact(AlarmManager.ELAPSED_REALTIME, SystemClock.elapsedRealtime() + delayMillis, pi);
+                scheduledExact = true;
+            } catch (final Exception e) {
+                LOG.error("Failed to schedule exact alarm for next DST change", e);
+            }
+        }
+
+        // Fallback to inexact alarm if the exact one failed
+        if (!scheduledExact) {
+            try {
+                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+                    am.setAndAllowWhileIdle(AlarmManager.ELAPSED_REALTIME, SystemClock.elapsedRealtime() + delayMillis, pi);
+                } else {
+                    am.set(AlarmManager.ELAPSED_REALTIME, SystemClock.elapsedRealtime() + delayMillis, pi);
+                }
+            } catch (final Exception e) {
+                LOG.error("Failed to schedule inexact alarm next DST change", e);
+            }
         }
     }
-}
+
+    private static boolean canScheduleExactAlarms(final Context context, final AlarmManager am) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
+            return am.canScheduleExactAlarms();
+        } else {
+            return GB.checkPermission(context, "android.permission.SCHEDULE_EXACT_ALARM");
+        }
+    }
+}

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/DeviceCommunicationService.java

@@ -1247,6 +1247,7 @@ public class DeviceCommunicationService extends Service implements SharedPrefere
                 IntentFilter filter = new IntentFilter();
                 filter.addAction("android.intent.action.TIME_SET");
                 filter.addAction("android.intent.action.TIMEZONE_CHANGED");
+                filter.addAction(TimeChangeReceiver.ACTION_DST_CHANGED);
                 registerReceiver(mTimeChangeReceiver, filter);
             }
             if (mBlueToothPairingRequestReceiver == null) {