Offline tab as Files view, automatic background sync, sync notifications

- Offline tab is now FilesView(offline: true) over a FolderBrowser interface
  (FilesController / OfflineController) sharing controls, tiles, thumbnails
- Synced files follow the Files Cache rule (default: refresh every 15 min):
  per-account WorkManager jobs, in-app timer, resume and pull triggers;
  root-etag shortcut skips full walks when nothing changed
- Single sync at a time (shared lock); logging out stops that account's sync
- Sync safety: PROPFIND failures skip the path instead of deleting local files
- Mirror empty folders and remove deleted ones; drop synced paths deleted on
  the server; missing local files are re-downloaded
- Notifications: silent per-account sync notifications, "Background sync
  notifications" setting, audible upload/download completion
- Files refresh in place (no spinner flash); retry after network returns
- Fix sync badges not updating (shared native status stream), "Sync off" on
  launch (eager providers), Files Cache section moved under Device Sync

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lib/services/sync_service.dart

@@ -1,9 +1,13 @@
 import 'dart:convert';
 import 'dart:io';
+import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:path/path.dart' as p;
+import 'package:shared_preferences/shared_preferences.dart';
 import 'package:path_provider/path_provider.dart';
 import '../models/sync_status.dart';
+import '../models/saved_account.dart';
+import '../providers/files_controller.dart';
 import '../providers/session_controller.dart';
 import '../providers/sync_status_controller.dart';
 
@@ -16,12 +20,17 @@ class SyncStatusSnapshot {
   final Set<String> syncedFileIds;
   final List<SyncConflictInfo> conflicts;
 
+  /// Configured sync paths the server says no longer exist (deleted on the
+  /// web) - the app drops them from its synced list.
+  final Set<String> missingRoots;
+
   const SyncStatusSnapshot({
     required this.accountId,
     required this.syncing,
     required this.syncingFileIds,
     required this.syncedFileIds,
     required this.conflicts,
+    this.missingRoots = const {},
   });
 
   factory SyncStatusSnapshot.fromMap(Map<dynamic, dynamic> map) {
@@ -38,6 +47,9 @@ class SyncStatusSnapshot {
           .cast<Map<dynamic, dynamic>>()
           .map(SyncConflictInfo.fromMap)
           .toList(),
+      missingRoots: ((map['missingRoots'] as List?) ?? const [])
+          .cast<String>()
+          .toSet(),
     );
   }
 }
@@ -56,42 +68,89 @@ class SyncService {
     'dev.ayushya.noo/sync_service/status',
   );
 
-  /// Cancels (if [SyncStatusController.syncedPaths] is now empty) or
-  /// re-enqueues the periodic sync job with fresh account/credentials/
-  /// path-list/network-constraint data - call this any time one of those
-  /// changes, since a periodic `WorkRequest`'s input is fixed at enqueue
-  /// time and can only be updated by re-enqueueing.
+  /// Brings the background periodic sync jobs in line with every saved
+  /// account's current settings - one job per account with sync enabled
+  /// (paths or "sync everything", and the Files Cache policy set to refresh
+  /// periodically), cancelled for accounts without and for accounts the
+  /// user logged out of. Background sync is deliberately not limited to the
+  /// active account: each account's job carries that account's own
+  /// credentials, paths and interval, so switching accounts doesn't stop the
+  /// others.
+  ///
+  /// Call whenever any of that changes - a periodic `WorkRequest`'s input is
+  /// fixed at enqueue time and can only be updated by re-enqueueing. The
+  /// active account's settings come from [sync]/its live state (they may not
+  /// have been persisted yet); every other account's are read from storage.
   static Future<void> reschedule(
     SessionController session,
     SyncStatusController sync,
   ) async {
-    final accountId = session.activeAccountId;
-    final authHeader = session.service?.authHeaders['Authorization'];
-    if (accountId == null || authHeader == null) {
-      return cancel();
+    final prefs = await session.prefsFuture;
+    final store = session.accountStore;
+    final wifiOnly = !sync.syncOnCellular;
+    final signedOut = store.loadSignedOut(prefs);
+
+    for (final account in session.accounts) {
+      try {
+        if (signedOut.contains(account.id)) {
+          await cancelAccount(account.id);
+          continue;
+        }
+        final isActive = account.id == session.activeAccountId;
+        final config = isActive
+            ? _SyncConfig(
+                paths: sync.syncEverything ? ['/'] : sync.syncedPaths,
+                intervalMinutes: sync.backgroundSyncIntervalMinutes,
+              )
+            : _SyncConfig.fromPrefs(prefs, store.accountPrefKey, account.id);
+        final password = await store.readPassword(account.id);
+        if (password == null ||
+            config.paths.isEmpty ||
+            config.intervalMinutes == null) {
+          await cancelAccount(account.id);
+          continue;
+        }
+        await _channel.invokeMethod('reschedule', {
+          'accountId': account.id,
+          'serverUrl': account.serverUrl,
+          'username': account.username,
+          'authHeader': _basicAuth(account, password),
+          'folders': jsonEncode(config.paths),
+          'wifiOnly': wifiOnly,
+          'intervalMinutes': config.intervalMinutes,
+          'notify': sync.syncNotifications,
+        });
+      } catch (e) {
+        debugPrint('[SyncService] Could not schedule ${account.id}: $e');
+      }
     }
-
-    final paths = sync.syncEverything ? ['/'] : sync.syncedPaths;
-    await _channel.invokeMethod('reschedule', {
-      'accountId': accountId,
-      'serverUrl': session.serverUrl,
-      'username': session.username,
-      'authHeader': authHeader,
-      'folders': jsonEncode(paths),
-      'wifiOnly': !sync.syncOnCellular,
-    });
   }
 
-  static Future<void> cancel() async {
-    await _channel.invokeMethod('cancel');
+  static String _basicAuth(SavedAccount account, String password) =>
+      'Basic ${base64Encode(utf8.encode('${account.username}:$password'))}';
+
+  /// Stops [accountId]'s periodic job (the account was removed, or has
+  /// nothing left to sync).
+  static Future<void> cancelAccount(String accountId) async {
+    await _channel.invokeMethod('cancel', {'accountId': accountId});
   }
 
-  /// Runs a one-off sync pass immediately (Settings' "Sync now"),
-  /// independent of the periodic schedule.
+  /// Runs a one-off sync pass immediately, independent of the periodic
+  /// schedule.
+  ///
+  /// [force] (Settings' "Sync now", a newly-added path): full walk of every
+  /// synced root, visible progress notification, supersedes any run already
+  /// in flight. Without it (pull-to-refresh, foreground timer, app resume)
+  /// the pass is a quiet check that uses the cheap root-etag shortcut and
+  /// never interrupts a run already in progress. [respectNetworkSetting]
+  /// makes such a pass wait for Wi-Fi when "Sync on cellular" is off (the
+  /// automatic triggers do; a deliberate pull doesn't).
   static Future<void> syncNow(
     SessionController session,
-    SyncStatusController sync,
-  ) async {
+    SyncStatusController sync, {
+    bool force = true,
+    bool respectNetworkSetting = false,
+  }) async {
     final accountId = session.activeAccountId;
     final authHeader = session.service?.authHeaders['Authorization'];
     if (accountId == null || authHeader == null) {
@@ -105,26 +164,43 @@ class SyncService {
       'username': session.username,
       'authHeader': authHeader,
       'folders': jsonEncode(paths),
+      'force': force,
+      'notify': sync.syncNotifications,
+      if (respectNetworkSetting) 'wifiOnly': !sync.syncOnCellular,
     });
   }
 
   /// One-shot status snapshot - used to seed [SyncStatusController]'s state
   /// right after login/account-switch, before the first [statusStream]
   /// event arrives.
-  static Future<SyncStatusSnapshot> getStatus() async {
+  ///
+  /// [accountId] is required for `syncedFileIds` to be populated on a fresh
+  /// app start - the native bus only knows an account once a sync pass has
+  /// run in this process.
+  static Future<SyncStatusSnapshot> getStatus(String? accountId) async {
     final result = await _channel.invokeMethod<Map<dynamic, dynamic>>(
       'getSyncStatus',
+      {'accountId': accountId},
     );
     return SyncStatusSnapshot.fromMap(result ?? const {});
   }
 
   /// Live status updates pushed from `SyncStatusBus` (Kotlin) - syncing
   /// started/stopped, per-file progress, new/resolved conflicts.
-  static Stream<SyncStatusSnapshot> get statusStream {
-    return _statusChannel.receiveBroadcastStream().map(
-      (event) => SyncStatusSnapshot.fromMap(event as Map<dynamic, dynamic>),
-    );
-  }
+  ///
+  /// One shared stream, deliberately: every call to
+  /// `EventChannel.receiveBroadcastStream()` opens its *own* native
+  /// subscription, and the native side only keeps one listener - a second
+  /// subscriber (the Offline tab's controller, once it became eagerly
+  /// created) silently took the events away from the first
+  /// (`SyncStatusController`), so sync badges stopped updating until the app
+  /// was restarted. This is a broadcast stream, so any number of Dart
+  /// listeners share the one native subscription.
+  static final Stream<SyncStatusSnapshot> statusStream = _statusChannel
+      .receiveBroadcastStream()
+      .map(
+        (event) => SyncStatusSnapshot.fromMap(event as Map<dynamic, dynamic>),
+      );
 
   /// In-app conflict resolution (the header's "Keep local"/"Use server"
   /// buttons) - shares the exact same native `ConflictResolveWorker`
@@ -184,3 +260,66 @@ class SyncService {
     return file.existsSync() ? file.path : null;
   }
 }
+
+/// One account's background-sync settings, as far as scheduling is
+/// concerned.
+class _SyncConfig {
+  final List<String> paths;
+
+  /// Null = background sync off for this account.
+  final int? intervalMinutes;
+
+  const _SyncConfig({required this.paths, required this.intervalMinutes});
+
+  /// Reads a *non-active* account's persisted settings - the same per-account
+  /// keys `SyncStatusController`/`FilesController` write. Malformed values
+  /// fall back to "nothing to sync" rather than throwing.
+  factory _SyncConfig.fromPrefs(
+    SharedPreferences prefs,
+    String Function(String accountId, String baseKey) key,
+    String accountId,
+  ) {
+    var paths = <String>[];
+    try {
+      final everything =
+          prefs.getBool(
+            key(accountId, SyncStatusController.prefSyncEverything),
+          ) ??
+          false;
+      final json = prefs.getString(
+        key(accountId, SyncStatusController.prefSyncedPaths),
+      );
+      if (everything) {
+        paths = ['/'];
+      } else if (json != null) {
+        paths = (jsonDecode(json) as List).cast<String>();
+      }
+    } catch (e) {
+      debugPrint('[SyncService] Unreadable sync paths for $accountId: $e');
+    }
+
+    var policy = defaultCachePolicy;
+    var minutes = defaultCacheIntervalMinutes;
+    try {
+      final policyName = prefs.getString(
+        key(accountId, FilesController.prefCachePolicy),
+      );
+      policy = CachePolicy.values.firstWhere(
+        (c) => c.name == policyName,
+        orElse: () => defaultCachePolicy,
+      );
+      minutes =
+          prefs.getInt(
+            key(accountId, FilesController.prefCacheIntervalMinutes),
+          ) ??
+          defaultCacheIntervalMinutes;
+    } catch (e) {
+      debugPrint('[SyncService] Unreadable cache rule for $accountId: $e');
+    }
+
+    return _SyncConfig(
+      paths: paths,
+      intervalMinutes: policy == CachePolicy.interval ? minutes : null,
+    );
+  }
+}