public class ConnectivityReceiver extends BroadcastReceiver {
  @Override
  public void onReceive(Context ctx, Intent intent) {
    final ClockSync cs = ClockSync.getInstance();

    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(ctx);
    final boolean bootSync = prefs.getBoolean(BOOT_SYNC, false) && !cs.isBootSynced();
    final boolean autoSync = prefs.getBoolean(AUTO_SYNC, false);

    // no automatic or boot synchronization enabled, abort
    if (!bootSync && !autoSync) return;

    final NetworkStatus state = getNetworkState(ctx);
    final boolean canUseNetwork = state == NetworkStatus.CAN_USE_NETWORK;
    final int intState = canUseNetwork ? 1 : 0;

    // connection state didn't change, nothing to do
    if (cs.getCachedConnectionState() == intState) {
      return;
    }
    cs.setCachedConnectionState(intState);

    if (!canUseNetwork) {
      // if we can't use network, disable all alarm timers
      Log.d(ClockSync.TAG, "Network disabled, cancel timer");
      scheduleSynchronization(ctx, 0, true);
    } else {
      // when network is available again, schedule synchronization or sync instantly if missed last sync
      final long interval = Integer.parseInt(prefs.getString(SYNC_INTERVAL, DEFAULT_SYNC_INTERVAL)) * 1000L;
      final long now = System.currentTimeMillis();
      long lastSuccess = prefs.getLong(LAST_SUCCESS, 0L);
      // incorrect timestamp was saved
      if (lastSuccess > now) {
        lastSuccess = 0L;
      }
      // missed sync, or after hard reset now = 0, or on boot
      final boolean missedSync = now - lastSuccess > interval;
      final boolean clockReset = now < interval;
      if (missedSync || clockReset || bootSync) {
        if (missedSync) {
          Log.d(ClockSync.TAG, "Last synchronization missed (no network), sync now and set timer!");
        } else if (bootSync) {
          Log.d(ClockSync.TAG, "Sync on boot");
        }
        scheduleSynchronization(ctx, 0, false);
        WakefulIntentService.acquireStaticLock(ctx);
        ctx.startService(new Intent(ctx, SyncTaskService.class));
      } else {
        // should sync earlier than now + interval
        // now = 12:00 lastSuccess = 11:00 interval = 2h => sync @ 13:00, NOT at 12:00 + 2h = 14:00
        long firstSyncDelta = lastSuccess - now + interval;
        Log.d(ClockSync.TAG, "Network enabled, timer will fire in: " + firstSyncDelta / 1000);
        scheduleSynchronization(ctx, firstSyncDelta, false);
      }
    }
  }
}