Add API to fetch backed up files

lib/db/files_db.dart

@@ -213,6 +213,21 @@ class FilesDB {
     return ids;
   }
 
+  Future<Set<String>> getUploadedLocalIDs() async {
+    final db = await instance.database;
+    final results = await db.query(
+      table,
+      columns: [columnLocalID],
+      where:
+          '$columnLocalID IS NOT NULL AND ($columnUploadedFileID IS NOT NULL AND $columnUploadedFileID IS NOT -1)',
+    );
+    final ids = Set<String>();
+    for (final result in results) {
+      ids.add(result[columnLocalID]);
+    }
+    return ids;
+  }
+
   Future<List<File>> getAllFiles(int startTime, int endTime,
       {int limit, bool asc}) async {
     final db = await instance.database;

lib/models/backed_up_files.dart

@@ -0,0 +1,6 @@
+class BackedUpFiles {
+  final Set<String> localIDs;
+  final int space;
+
+  BackedUpFiles(this.localIDs, this.space);
+}

lib/services/local_sync_service.dart

@@ -7,6 +7,7 @@ import 'package:photos/core/event_bus.dart';
 import 'package:photos/db/files_db.dart';
 import 'package:photos/events/local_photos_updated_event.dart';
 import 'package:photos/events/sync_status_update_event.dart';
+import 'package:photos/models/backed_up_files.dart';
 import 'package:photos/models/file.dart';
 import 'package:photos/utils/file_sync_util.dart';
 import 'package:shared_preferences/shared_preferences.dart';
@@ -173,6 +174,16 @@ class LocalSyncService {
     return _prefs.getBool(kHasCompletedFirstImportKey) ?? false;
   }
 
+  Future<BackedUpFiles> getBackupStatus() async {
+    final localIDs = await FilesDB.instance.getUploadedLocalIDs();
+    int space = 0;
+    for (final id in localIDs) {
+      final asset = await AssetEntity.fromId(id);
+      space += (await asset.originFile).lengthSync();
+    }
+    return BackedUpFiles(localIDs, space);
+  }
+
   Future<void> _loadAndStorePhotos(
     int fromTime,
     int toTime,