add to legacy control bottom bar

mobile/lib/widgets/asset_grid/control_bottom_app_bar.dart

@@ -33,6 +33,7 @@ class ControlBottomAppBar extends HookConsumerWidget {
   final void Function([bool force])? onDelete;
   final void Function([bool force])? onDeleteServer;
   final void Function(bool onlyBackedUp)? onDeleteLocal;
+  final void Function()? onSetAlbumCover;
   final Function(Album album) onAddToAlbum;
   final void Function() onCreateNewAlbum;
   final void Function() onUpload;
@@ -57,6 +58,7 @@ class ControlBottomAppBar extends HookConsumerWidget {
     this.onDelete,
     this.onDeleteServer,
     this.onDeleteLocal,
+    this.onSetAlbumCover,
     required this.onAddToAlbum,
     required this.onCreateNewAlbum,
     required this.onUpload,
@@ -267,6 +269,15 @@ class ControlBottomAppBar extends HookConsumerWidget {
               onPressed: enabled ? onRemoveFromAlbum : null,
             ),
           ),
+        if (onSetAlbumCover != null)
+          ConstrainedBox(
+            constraints: const BoxConstraints(maxWidth: 90),
+            child: ControlBoxButton(
+              iconData: Icons.image_outlined,
+              label: 'set_as_album_cover'.tr(),
+              onPressed: enabled ? onSetAlbumCover : null,
+            ),
+          ),
         if (selectionAssetState.hasLocal)
           ControlBoxButton(
             iconData: Icons.backup_outlined,

mobile/lib/widgets/asset_grid/multiselect_grid.dart

@@ -17,11 +17,13 @@ import 'package:immich_mobile/providers/album/album.provider.dart';
 import 'package:immich_mobile/providers/asset.provider.dart';
 import 'package:immich_mobile/providers/asset_viewer/download.provider.dart';
 import 'package:immich_mobile/providers/backup/manual_upload.provider.dart';
+import 'package:immich_mobile/providers/infrastructure/current_album.provider.dart';
 import 'package:immich_mobile/providers/multiselect.provider.dart';
 import 'package:immich_mobile/providers/routes.provider.dart';
 import 'package:immich_mobile/providers/user.provider.dart';
 import 'package:immich_mobile/routing/router.dart';
 import 'package:immich_mobile/services/album.service.dart';
+import 'package:immich_mobile/services/action.service.dart';
 import 'package:immich_mobile/services/stack.service.dart';
 import 'package:immich_mobile/utils/immich_loading_overlay.dart';
 import 'package:immich_mobile/utils/selection_handlers.dart';
@@ -77,6 +79,7 @@ class MultiselectGrid extends HookConsumerWidget {
 
     final selection = useState(<Asset>{});
     final currentUser = ref.watch(currentUserProvider);
+    final currentAlbum = ref.watch(currentRemoteAlbumProvider);
     final processing = useProcessingOverlay();
 
     useEffect(() {
@@ -400,6 +403,37 @@ class MultiselectGrid extends HookConsumerWidget {
       }
     };
 
+    Future<bool> setAsAlbumCover() async {
+      final album = currentAlbum;
+      if (album == null) {
+        return false;
+      }
+
+      if (currentUser?.id != album.ownerId) {
+        return false;
+      }
+
+      if (selection.value.length != 1) {
+        return false;
+      }
+
+      final asset = selection.value.first;
+      final assetId = asset.remoteId;
+      if (assetId == null) {
+        ImmichToast.show(context: context, msg: 'errors.unable_to_update_album_cover'.tr(), toastType: ToastType.error);
+        return false;
+      }
+
+      try {
+        await ref.read(actionServiceProvider).setAlbumCover(album.id, assetId);
+        ImmichToast.show(context: context, msg: 'album_cover_updated'.tr(), toastType: ToastType.success);
+        return true;
+      } catch (_) {
+        ImmichToast.show(context: context, msg: 'errors.unable_to_update_album_cover'.tr(), toastType: ToastType.error);
+        return false;
+      }
+    }
+
     return SafeArea(
       top: true,
       bottom: false,
@@ -447,6 +481,9 @@ class MultiselectGrid extends HookConsumerWidget {
               unfavorite: unfavorite,
               unarchive: unarchive,
               onToggleLocked: onToggleLockedVisibility,
+              onSetAlbumCover: (currentAlbum != null && currentUser?.id == currentAlbum.ownerId)
+                  ? wrapLongRunningFun(setAsAlbumCover)
+                  : null,
               onRemoveFromAlbum: onRemoveFromAlbum != null
                   ? wrapLongRunningFun(() => onRemoveFromAlbum!(selection.value))
                   : null,