Add automatic Google calendar sync

lib/google_calendar_page.dart

@@ -28,21 +28,30 @@ class AccountsPage extends StatefulWidget {
 
 class _AccountsPageState extends State<AccountsPage>
     with WidgetsBindingObserver {
+  static const googleAutoSyncInterval = Duration(minutes: 5);
+  static const googleResumeSyncInterval = Duration(minutes: 2);
+
   List<GoogleCalendarInfo> googleCalendars = [];
   bool loadingCalendars = false;
   bool syncing = false;
   bool waitingForGoogleAuthReturn = false;
+  Timer? googleAutoSyncTimer;
   String? statusMessage;
 
   @override
   void initState() {
     super.initState();
     WidgetsBinding.instance.addObserver(this);
+    googleAutoSyncTimer = Timer.periodic(
+      googleAutoSyncInterval,
+      (_) => _autoSyncSelectedCalendars(),
+    );
     _loadGoogleConnectionStatus();
   }
 
   @override
   void dispose() {
+    googleAutoSyncTimer?.cancel();
     WidgetsBinding.instance.removeObserver(this);
     super.dispose();
   }
@@ -66,6 +75,10 @@ class _AccountsPageState extends State<AccountsPage>
     if (state == AppLifecycleState.resumed && waitingForGoogleAuthReturn) {
       waitingForGoogleAuthReturn = false;
       _loadGoogleConnectionStatus();
+      return;
+    }
+    if (state == AppLifecycleState.resumed) {
+      _autoSyncSelectedCalendars(minAge: googleResumeSyncInterval);
     }
   }
 
@@ -106,6 +119,30 @@ class _AccountsPageState extends State<AccountsPage>
     return null;
   }
 
+  bool _canAutoSync() {
+    final current = connection;
+    return current != null &&
+        current.accountEmail.isNotEmpty &&
+        current.enabledCalendarIds.isNotEmpty &&
+        !syncing &&
+        !loadingCalendars &&
+        _jarvisConfigError() == null;
+  }
+
+  Future<void> _autoSyncSelectedCalendars({
+    Duration minAge = googleAutoSyncInterval,
+  }) async {
+    final current = connection;
+    if (!_canAutoSync() || current == null) return;
+
+    final lastSync = current.lastSync;
+    if (lastSync != null && DateTime.now().difference(lastSync) < minAge) {
+      return;
+    }
+
+    await _syncSelectedCalendars(automatic: true);
+  }
+
   Future<void> _loadGoogleConnectionStatus() async {
     setState(() {
       loadingCalendars = true;
@@ -287,9 +324,10 @@ class _AccountsPageState extends State<AccountsPage>
     }
   }
 
-  Future<void> _syncSelectedCalendars() async {
+  Future<void> _syncSelectedCalendars({bool automatic = false}) async {
     final current = connection;
     if (current == null || current.enabledCalendarIds.isEmpty) {
+      if (automatic) return;
       setState(
         () => statusMessage =
             'V\u00e1lassz ki legal\u00e1bb egy Google napt\u00e1rat.',
@@ -299,7 +337,9 @@ class _AccountsPageState extends State<AccountsPage>
 
     setState(() {
       syncing = true;
-      statusMessage = 'Google esem\u00e9nyek beolvas\u00e1sa...';
+      statusMessage = automatic
+          ? 'Automatikus Google szinkron fut...'
+          : 'Google esem\u00e9nyek beolvas\u00e1sa...';
     });
 
     try {
@@ -377,14 +417,17 @@ class _AccountsPageState extends State<AccountsPage>
       ]);
       setState(() {
         syncing = false;
-        statusMessage =
-            '${synced.length} Google esem\u00e9ny szinkroniz\u00e1lva \u00e9s JSON cache-be mentve.'
-            '${syncDetails.isEmpty ? '' : ' R\u00e9szletek: ${syncDetails.join('; ')}.'}';
+        statusMessage = automatic
+            ? '${synced.length} Google esem\u00e9ny automatikusan friss\u00edtve.'
+            : '${synced.length} Google esem\u00e9ny szinkroniz\u00e1lva \u00e9s JSON cache-be mentve.'
+                  '${syncDetails.isEmpty ? '' : ' R\u00e9szletek: ${syncDetails.join('; ')}.'}';
       });
     } catch (error) {
       setState(() {
         syncing = false;
-        statusMessage = 'A Google szinkron nem siker\u00fclt: $error';
+        statusMessage = automatic
+            ? 'Az automatikus Google szinkron most nem siker\u00fclt, a kor\u00e1bbi cache marad: $error'
+            : 'A Google szinkron nem siker\u00fclt: $error';
       });
     }
   }