Move remote album files to a subdir

lib/entity/album.dart

@@ -24,10 +24,10 @@ import 'package:quiver/iterables.dart';
 import 'package:tuple/tuple.dart';
 
 String getAlbumFileRoot(Account account) =>
-    "${api_util.getWebdavRootUrlRelative(account)}/.com.nkming.nc_photos";
+    "${api_util.getWebdavRootUrlRelative(account)}/.com.nkming.nc_photos/albums";
 
 bool isAlbumFile(File file) =>
-    path.basename(path.dirname(file.path)) == ".com.nkming.nc_photos";
+    path.dirname(file.path).endsWith(".com.nkming.nc_photos/albums");
 
 List<AlbumItem> makeDistinctAlbumItems(List<AlbumItem> items) =>
     items.distinctIf(

lib/use_case/compat/v15.dart

@@ -0,0 +1,81 @@
+import 'package:logging/logging.dart';
+import 'package:nc_photos/account.dart';
+import 'package:nc_photos/api/api_util.dart' as api_util;
+import 'package:nc_photos/entity/album.dart';
+import 'package:nc_photos/entity/file.dart';
+import 'package:nc_photos/exception.dart';
+import 'package:nc_photos/use_case/create_dir.dart';
+import 'package:nc_photos/use_case/ls.dart';
+import 'package:path/path.dart' as path;
+
+/// Compatibility helper for v15
+class CompatV15 {
+  /// Migrate album files from old location pre v15 to the new location in v15+
+  ///
+  /// Return true if album files are migrated successfully, false otherwise.
+  /// Note that false does not necessarily mean that the migration has failed,
+  /// it could simply mean that no migration is needed
+  static Future<bool> migrateAlbumFiles(Account account, FileRepo fileRepo) {
+    return _MigrateAlbumFiles(fileRepo)(account);
+  }
+}
+
+class _MigrateAlbumFiles {
+  _MigrateAlbumFiles(this.fileRepo);
+
+  Future<bool> call(Account account) async {
+    try {
+      // get files from the old location
+      final ls = await Ls(fileRepo)(
+          account,
+          File(
+            path: _getAlbumFileRootCompat14(account),
+          ));
+      final albumFiles =
+          ls.where((element) => element.isCollection != true).toList();
+      if (albumFiles.isEmpty) {
+        return false;
+      }
+      // copy to an intermediate location
+      final intermediateDir = "${getAlbumFileRoot(account)}.tmp";
+      _log.info("[call] Copy album files to '$intermediateDir'");
+      if (!ls.any((element) =>
+          element.isCollection == true && element.path == intermediateDir)) {
+        await CreateDir(fileRepo)(account, intermediateDir);
+      }
+      for (final f in albumFiles) {
+        final fileName = path.basename(f.path);
+        await fileRepo.copy(account, f, "$intermediateDir/$fileName",
+            shouldOverwrite: true);
+      }
+      // rename intermediate
+      await fileRepo.move(
+          account, File(path: intermediateDir), getAlbumFileRoot(account));
+      _log.info(
+          "[call] Album files moved to '${getAlbumFileRoot(account)}' successfully");
+      // remove old files
+      for (final f in albumFiles) {
+        try {
+          await fileRepo.remove(account, f);
+        } catch (_) {}
+      }
+      return true;
+    } catch (e, stacktrace) {
+      if (e is ApiException && e.response.statusCode == 404) {
+        // no albums
+        return false;
+      }
+      _log.shout("[call] Failed while migrating album files to new location", e,
+          stacktrace);
+      rethrow;
+    }
+  }
+
+  // old album root location on v14-
+  static String _getAlbumFileRootCompat14(Account account) =>
+      "${api_util.getWebdavRootUrlRelative(account)}/.com.nkming.nc_photos";
+
+  final FileRepo fileRepo;
+
+  static final _log = Logger("use_case.compat.v15._MigrateAlbumFiles");
+}

lib/use_case/list_album.dart

@@ -3,6 +3,7 @@ import 'package:nc_photos/account.dart';
 import 'package:nc_photos/entity/album.dart';
 import 'package:nc_photos/entity/file.dart';
 import 'package:nc_photos/exception.dart';
+import 'package:nc_photos/use_case/compat/v15.dart';
 import 'package:nc_photos/use_case/ls.dart';
 
 class ListAlbum {
@@ -10,6 +11,21 @@ class ListAlbum {
 
   /// List all albums associated with [account]
   Future<List<Album>> call(Account account) async {
+    final results = await _call(account);
+    if (results.isEmpty) {
+      if (await CompatV15.migrateAlbumFiles(account, fileRepo)) {
+        // migrated
+        return await _call(account);
+      } else {
+        // no need to migrate
+        return [];
+      }
+    } else {
+      return results;
+    }
+  }
+
+  Future<List<Album>> _call(Account account) async {
     try {
       final ls = await Ls(fileRepo)(
           account,
@@ -27,7 +43,7 @@ class ListAlbum {
         albumRepo.cleanUp(account, albumFiles);
       } catch (e, stacktrace) {
         // not important, log and ignore
-        _log.shout("[call] Failed while cleanUp", e, stacktrace);
+        _log.shout("[_call] Failed while cleanUp", e, stacktrace);
       }
       return albums;
     } catch (e) {