[mob][photos] Add iOS upload grace window and bg handoff

mobile/apps/photos/ios/Podfile.lock

@@ -116,6 +116,8 @@ PODS:
   - GoogleUtilities/UserDefaults (8.1.0):
     - GoogleUtilities/Logger
     - GoogleUtilities/Privacy
+  - grace_window_ios (1.0.0):
+    - Flutter
   - home_widget (0.0.1):
     - Flutter
   - in_app_purchase_storekit (0.0.1):
@@ -292,6 +294,7 @@ DEPENDENCIES:
   - flutter_sodium (from `.symlinks/plugins/flutter_sodium/ios`)
   - flutter_timezone (from `.symlinks/plugins/flutter_timezone/ios`)
   - fluttertoast (from `.symlinks/plugins/fluttertoast/ios`)
+  - grace_window_ios (from `.symlinks/plugins/grace_window_ios/ios`)
   - home_widget (from `.symlinks/plugins/home_widget/ios`)
   - in_app_purchase_storekit (from `.symlinks/plugins/in_app_purchase_storekit/darwin`)
   - integration_test (from `.symlinks/plugins/integration_test/ios`)
@@ -409,6 +412,8 @@ EXTERNAL SOURCES:
     :path: ".symlinks/plugins/flutter_timezone/ios"
   fluttertoast:
     :path: ".symlinks/plugins/fluttertoast/ios"
+  grace_window_ios:
+    :path: ".symlinks/plugins/grace_window_ios/ios"
   home_widget:
     :path: ".symlinks/plugins/home_widget/ios"
   in_app_purchase_storekit:
@@ -525,6 +530,7 @@ SPEC CHECKSUMS:
   fluttertoast: 2c67e14dce98bbdb200df9e1acf610d7a6264ea1
   GoogleDataTransport: aae35b7ea0c09004c3797d53c8c41f66f219d6a7
   GoogleUtilities: 00c88b9a86066ef77f0da2fab05f65d7768ed8e1
+  grace_window_ios: b98b82feaabeee818af7b7e0e3ff49b2acd7942a
   home_widget: f169fc41fd807b4d46ab6615dc44d62adbf9f64f
   in_app_purchase_storekit: d1a48cb0f8b29dbf5f85f782f5dd79b21b90a5e6
   integration_test: 4a889634ef21a45d28d50d622cf412dc6d9f586e

mobile/apps/photos/ios/Runner.xcodeproj/project.pbxproj

@@ -650,6 +650,7 @@
 				"${BUILT_PRODUCTS_DIR}/flutter_sodium/flutter_sodium.framework",
 				"${BUILT_PRODUCTS_DIR}/flutter_timezone/flutter_timezone.framework",
 				"${BUILT_PRODUCTS_DIR}/fluttertoast/fluttertoast.framework",
+				"${BUILT_PRODUCTS_DIR}/grace_window_ios/grace_window_ios.framework",
 				"${BUILT_PRODUCTS_DIR}/home_widget/home_widget.framework",
 				"${BUILT_PRODUCTS_DIR}/in_app_purchase_storekit/in_app_purchase_storekit.framework",
 				"${BUILT_PRODUCTS_DIR}/integration_test/integration_test.framework",
@@ -754,6 +755,7 @@
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/flutter_sodium.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/flutter_timezone.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/fluttertoast.framework",
+				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/grace_window_ios.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/home_widget.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/in_app_purchase_storekit.framework",
 				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/integration_test.framework",

mobile/apps/photos/lib/app.dart

@@ -21,6 +21,7 @@ import "package:photos/services/home_widget_service.dart";
 import "package:photos/services/memory_home_widget_service.dart";
 import "package:photos/services/people_home_widget_service.dart";
 import 'package:photos/services/sync/sync_service.dart';
+import 'package:photos/services/upload_background_coordinator.dart';
 import 'package:photos/ui/tabs/home_widget.dart';
 import "package:photos/ui/viewer/actions/file_viewer.dart";
 import "package:photos/utils/bg_task_utils.dart";
@@ -193,14 +194,21 @@ class _EnteAppState extends State<EnteApp> with WidgetsBindingObserver {
   @override
   void didChangeAppLifecycleState(AppLifecycleState state) {
     final String stateChangeReason = 'app -> $state';
+    final wasForeground = AppLifecycleService.instance.isForeground;
     if (state == AppLifecycleState.resumed) {
       final lastAppOpenTime = AppLifecycleService.instance.getLastAppOpenTime();
       AppLifecycleService.instance
           .onAppInForeground(stateChangeReason + ': sync now');
+      if (!wasForeground) {
+        unawaited(onUploadAppForeground());
+      }
       unawaited(_reloadCachesUpdatedInBackground(lastAppOpenTime));
       SyncService.instance.sync();
     } else {
       AppLifecycleService.instance.onAppInBackground(stateChangeReason);
+      if (wasForeground) {
+        unawaited(onUploadAppBackground());
+      }
     }
   }
 

mobile/apps/photos/lib/services/upload_background_coordinator.dart

@@ -0,0 +1,130 @@
+import "dart:async";
+import "dart:io";
+
+import "package:grace_window_ios/grace_window_ios.dart";
+import "package:logging/logging.dart";
+import "package:photos/db/upload_locks_db.dart";
+import "package:photos/service_locator.dart";
+import "package:photos/utils/bg_task_utils.dart";
+import "package:photos/utils/file_uploader.dart";
+import "package:shared_preferences/shared_preferences.dart";
+
+const _keyIOSUploadGraceActive = "ios_bg_upload_grace_active";
+
+final _logger = Logger("UploadBackgroundCoordinator");
+bool _isGraceWindowActiveInProcess = false;
+
+Future<void> onUploadAppBackground() async {
+  if (!Platform.isIOS || !flagService.enableIOSBackgroundHandoff) {
+    return;
+  }
+
+  if (FileUploader.instance.hasActiveUploads) {
+    if (!flagService.enableIOSBackgroundGraceWindow) {
+      return;
+    }
+
+    final prefs = await SharedPreferences.getInstance();
+    if (prefs.getBool(_keyIOSUploadGraceActive) ?? false) {
+      if (_isGraceWindowActiveInProcess) {
+        return;
+      }
+
+      _logger.info("Clearing stale iOS upload grace window marker");
+      await prefs.remove(_keyIOSUploadGraceActive);
+    }
+
+    _logger.info("Starting iOS upload grace window");
+    await GraceWindowIos.beginGraceWindow("ente-upload-grace-window");
+    await prefs.setBool(_keyIOSUploadGraceActive, true);
+    _isGraceWindowActiveInProcess = true;
+    await BgTaskUtils.scheduleIOSBackgroundProcessingTask(
+      source: "graceWindowStarted",
+      initialDelay: BgTaskUtils.continuationDelay(),
+      reason: BgTaskUtils.iOSBackgroundProcessingReasonContinuation,
+    );
+    unawaited(_waitForGraceWindowExpiration());
+    return;
+  }
+
+  if (await BgTaskUtils.isIOSBackupEligible()) {
+    await BgTaskUtils.scheduleIOSBackgroundProcessingTask(
+      source: "appBackground:maintenance",
+      initialDelay: BgTaskUtils.maintenanceDelay(),
+      reason: BgTaskUtils.iOSBackgroundProcessingReasonMaintenance,
+    );
+  }
+}
+
+Future<void> onUploadAppForeground() async {
+  if (!Platform.isIOS || !flagService.enableIOSBackgroundHandoff) {
+    return;
+  }
+
+  if (!flagService.enableIOSBackgroundGraceWindow) {
+    await BgTaskUtils.cancelIOSBackgroundProcessingTask(
+      source: "appForeground",
+    );
+    return;
+  }
+
+  final prefs = await SharedPreferences.getInstance();
+  final graceWasActive = prefs.getBool(_keyIOSUploadGraceActive) ?? false;
+
+  if (graceWasActive) {
+    final cutoffMicros = DateTime.now().microsecondsSinceEpoch;
+
+    _logger.info("Finishing iOS upload grace window and reconciling uploads");
+    await GraceWindowIos.endGraceWindow();
+    final didExpireGraceWindow = await GraceWindowIos.consumeExpiredState();
+    await prefs.remove(_keyIOSUploadGraceActive);
+    _isGraceWindowActiveInProcess = false;
+    if (didExpireGraceWindow) {
+      _logger.info(
+        "Grace window expiration was observed natively before foreground recovery",
+      );
+      await UploadLocksDB.instance.releaseLocksAcquiredByOwnerBefore(
+        ProcessType.foreground.toString(),
+        cutoffMicros,
+      );
+    }
+    await FileUploader.instance.reconcileAfterBackground();
+  }
+
+  await BgTaskUtils.cancelIOSBackgroundProcessingTask(
+    source: "appForeground",
+  );
+}
+
+/// Best-effort same-process expiration detection via a pending MethodChannel
+/// call. Swift holds the result and completes it when the native expiration
+/// handler fires. If this path misses (e.g. process suspended before
+/// delivery), [onUploadAppForeground] catches it via [consumeExpiredState].
+Future<void> _waitForGraceWindowExpiration() async {
+  final expired = await GraceWindowIos.awaitExpiration();
+  if (!expired) {
+    return;
+  }
+
+  final cutoffMicros = DateTime.now().microsecondsSinceEpoch;
+
+  _logger.info("iOS upload grace window expired (via pending call)");
+
+  // Consume the durable marker *before* releasing locks so that
+  // onUploadAppForeground (which can run between any two awaits here) won't
+  // see the marker and do a second lock release against freshly
+  // reacquired locks.
+  final didOwnExpiration = await GraceWindowIos.consumeExpiredState();
+  if (!didOwnExpiration) {
+    return;
+  }
+
+  await UploadLocksDB.instance.releaseLocksAcquiredByOwnerBefore(
+    ProcessType.foreground.toString(),
+    cutoffMicros,
+  );
+
+  final prefs = await SharedPreferences.getInstance();
+  await prefs.remove(_keyIOSUploadGraceActive);
+  _isGraceWindowActiveInProcess = false;
+}

mobile/apps/photos/lib/utils/file_uploader.dart

@@ -1617,6 +1617,129 @@ class FileUploader {
       await _pollBackgroundUploadStatus();
     });
   }
+
+  Future<void> reconcileAfterBackground({
+    Future<EnteFile?> Function(int generatedID)? lookupFile,
+  }) async {
+    bool changed = false;
+    bool queueChanged = false;
+    final resolveFile = lookupFile ?? FilesDB.instance.getFile;
+    final backupEntries = _allBackups.entries.toList(growable: false);
+    for (final entry in backupEntries) {
+      final backup = entry.value;
+      final generatedID = backup.file.generatedID;
+      if (generatedID == null) {
+        continue;
+      }
+
+      final dbFile = await resolveFile(generatedID);
+      if (dbFile?.uploadedFileID == null) {
+        final queueItem = _queue[entry.key];
+        if (queueItem == null) {
+          continue;
+        }
+
+        final localID = backup.file.localID!;
+        bool shouldReconcile = false;
+
+        if (queueItem.status == UploadStatus.inBackground) {
+          final isStillLockedInBackground = await _uploadLocks.isLocked(
+            localID,
+            ProcessType.background.toString(),
+          );
+          shouldReconcile = !isStillLockedInBackground;
+        } else if (queueItem.status == UploadStatus.inProgress) {
+          final isStillLockedInForeground = await _uploadLocks.isLocked(
+            localID,
+            ProcessType.foreground.toString(),
+          );
+          if (!isStillLockedInForeground) {
+            final isTakenOverByBackground = await _uploadLocks.isLocked(
+              localID,
+              ProcessType.background.toString(),
+            );
+            shouldReconcile = !isTakenOverByBackground;
+          }
+        }
+
+        if (!shouldReconcile) {
+          continue;
+        }
+
+        _logger.info(
+          "Foreground reconciliation detected incomplete upload "
+          "(status=${queueItem.status}) ${backup.file.tag}",
+        );
+
+        if (queueItem.status == UploadStatus.inProgress) {
+          // Leave the queue entry in place so the active worker can unwind and
+          // complete its normal queue/completer cleanup without null asserts.
+          _allBackups[entry.key] = backup.copyWith(
+            status: BackupItemStatus.retry,
+            error: SilentlyCancelUploadsError(),
+          );
+          changed = true;
+          continue;
+        }
+
+        await _uploadLocks.releaseLock(
+          localID,
+          ProcessType.foreground.toString(),
+        );
+        final removedQueueItem = _queue.remove(entry.key);
+        if (removedQueueItem != null) {
+          queueChanged = true;
+          if (!removedQueueItem.completer.isCompleted) {
+            removedQueueItem.completer.completeError(
+              SilentlyCancelUploadsError(),
+            );
+          }
+        }
+        _allBackups[entry.key] = backup.copyWith(
+          status: BackupItemStatus.retry,
+          error: SilentlyCancelUploadsError(),
+        );
+        changed = true;
+        continue;
+      }
+
+      final queueItem = _queue[entry.key];
+      if (queueItem?.status == UploadStatus.inProgress) {
+        // Let the active worker finish its normal success cleanup. Removing the
+        // queue entry here would trip the worker's `_queue.remove(localID)!`.
+        if (backup.status != BackupItemStatus.uploaded) {
+          _allBackups[entry.key] = backup.copyWith(
+            status: BackupItemStatus.uploaded,
+            file: dbFile,
+          );
+          changed = true;
+        }
+        continue;
+      }
+
+      final removedQueueItem = _queue.remove(entry.key);
+      if (removedQueueItem != null) {
+        queueChanged = true;
+        if (!removedQueueItem.completer.isCompleted) {
+          removedQueueItem.completer.complete(dbFile!);
+        }
+      }
+      if (backup.status != BackupItemStatus.uploaded) {
+        _allBackups[entry.key] = backup.copyWith(
+          status: BackupItemStatus.uploaded,
+          file: dbFile,
+        );
+        changed = true;
+      }
+    }
+
+    if (changed) {
+      Bus.instance.fire(BackupUpdatedEvent(_allBackups));
+    }
+    if (queueChanged) {
+      _pollQueue();
+    }
+  }
 }
 
 class FileUploadItem {

mobile/apps/photos/plugins/ente_feature_flag/lib/src/service.dart

@@ -127,6 +127,7 @@ class FlagService {
   bool get enableIOSBackgroundHandoff => internalUser;
   bool get enableBgLocalUploadPriority => internalUser;
   bool get syncRecoveryDiagnostics => internalUser;
+  bool get enableIOSBackgroundGraceWindow => internalUser;
 
   Future<void> tryRefreshFlags() async {
     try {