fix(resolve): release cancelled previews and preserve task ownership

ui/flutter/lib/api/api.dart

@@ -81,6 +81,9 @@ Future<ResolveResult> resolve(ResolveTask resolveTask) {
   );
 }
 
+Future<void> releaseResolve(String id) =>
+    _parse<void>(() => _request('api/v1/resolve/${Uri.encodeComponent(id)}', method: 'DELETE'), null);
+
 Future<String> createTask(CreateTask createTask) {
   return _parse<String>(() => _request('api/v1/tasks', method: 'POST', data: createTask), (data) => data as String);
 }

ui/flutter/lib/api/model/resolve_task.dart

@@ -8,7 +8,10 @@ part 'resolve_task.g.dart';
 class ResolveTask {
   Request? req;
 
-  ResolveTask({this.req});
+  @JsonKey(includeIfNull: false)
+  String? id;
+
+  ResolveTask({this.req, this.id});
 
   factory ResolveTask.fromJson(Map<String, dynamic> json) => _$ResolveTaskFromJson(json);
   Map<String, dynamic> toJson() => _$ResolveTaskToJson(this);

ui/flutter/lib/api/model/resolve_task.g.dart

@@ -10,7 +10,8 @@ ResolveTask _$ResolveTaskFromJson(Map<String, dynamic> json) => ResolveTask(
   req: json['req'] == null
       ? null
       : Request.fromJson(json['req'] as Map<String, dynamic>),
+  id: json['id'] as String?,
 );
 
 Map<String, dynamic> _$ResolveTaskToJson(ResolveTask instance) =>
-    <String, dynamic>{'req': ?instance.req};
+    <String, dynamic>{'req': ?instance.req, 'id': ?instance.id};

ui/flutter/lib/core/capabilities/app_capabilities.dart

@@ -93,6 +93,10 @@ void _bindGopeed(CapabilityRegistry registry, _ConfigStore configStore) {
       (p) => api.getMirrorCandidates(p['provider'] as String, p['url'] as String),
     )
     ..bind(GopeedMethods.resolve, api.resolve)
+    ..bind(GopeedMethods.releaseResolve, (id) async {
+      await api.releaseResolve(id);
+      return const RpcUnit();
+    })
     ..bind(GopeedMethods.createTask, api.createTask)
     ..bind(GopeedMethods.createTaskBatch, api.createTaskBatch)
     ..bind(GopeedMethods.patchTask, (params) async {

ui/flutter/lib/core/capabilities/gopeed_capability.dart

@@ -16,6 +16,7 @@ abstract final class GopeedMethods {
   static const triggerProtocolJob = RpcMethod<Map<String, dynamic>, RpcUnit>('gopeed.protocol.job.trigger');
   static const getMirrorCandidates = RpcMethod<Map<String, dynamic>, List<String>>('gopeed.mirrors.candidates');
   static const resolve = RpcMethod<ResolveTask, ResolveResult>('gopeed.resolve');
+  static const releaseResolve = RpcMethod<String, RpcUnit>('gopeed.releaseResolve');
   static const createTask = RpcMethod<CreateTask, String>('gopeed.task.create');
   static const createTaskBatch = RpcMethod<CreateTaskBatch, CreateTaskBatchResult>('gopeed.task.createBatch');
   static const patchTask = RpcMethod<Map<String, dynamic>, RpcUnit>('gopeed.task.patch');
@@ -50,6 +51,7 @@ class GopeedService {
   Future<List<String>> getMirrorCandidates(String provider, String url) =>
       _invoker.invoke(GopeedMethods.getMirrorCandidates, {'provider': provider, 'url': url});
   Future<ResolveResult> resolve(ResolveTask request) => _invoker.invoke(GopeedMethods.resolve, request);
+  Future<void> releaseResolve(String id) async => _invoker.invoke(GopeedMethods.releaseResolve, id);
 
   Future<String> createTask(CreateTask request) => _invoker.invoke(GopeedMethods.createTask, request);
 

ui/flutter/lib/features/tasks/application/pending_download.dart

@@ -1,3 +1,5 @@
+import 'dart:developer' as developer;
+import 'package:uuid/uuid.dart';
 import 'package:path/path.dart' as path;
 
 import '../../../api/model/create_task_batch.dart';
@@ -16,6 +18,8 @@ class PendingDownload {
   final Request request;
   final Options options;
   ResolveResult? result;
+  String? _resolveID;
+  bool _cancelled = false;
   String? resolveError;
   String? createError;
   final Set<int> selected = {};
@@ -50,11 +54,16 @@ class PendingDownload {
   bool get hasSelection => !created && result != null && selected.isNotEmpty;
 
   Future<void> resolve(GopeedService service) async {
-    if (result != null || resolving) return;
+    if (_cancelled || result != null || resolving) return;
     resolving = true;
     resolveError = null;
     try {
-      result = await service.resolve(ResolveTask(req: request));
+      _resolveID = const Uuid().v4();
+      result = await service.resolve(ResolveTask(req: request, id: _resolveID));
+      if (_cancelled) {
+        await _release(service, result!.id);
+        return;
+      }
       selected.addAll(List.generate(files.isEmpty ? 1 : files.length, (index) => index));
     } catch (error) {
       resolveError = error.toString();
@@ -63,6 +72,23 @@ class PendingDownload {
     }
   }
 
+  /// Stop an outstanding preview and release any resource it already owns.
+  /// A response arriving after cancellation is released by resolve() as well.
+  Future<void> cancel(GopeedService service) async {
+    if (_cancelled || created) return;
+    _cancelled = true;
+    await _release(service, result?.id.isNotEmpty == true ? result!.id : _resolveID);
+  }
+
+  Future<void> _release(GopeedService service, String? id) async {
+    if (id == null || id.isEmpty) return;
+    try {
+      await service.releaseResolve(id);
+    } catch (error, stack) {
+      developer.log('Failed to release resolved resource', name: 'gopeed.resolve', error: error, stackTrace: stack);
+    }
+  }
+
   List<CreateTaskBatchItem> creationItems() {
     final indexes = selected.toList()..sort();
     if (result!.id.isNotEmpty || files.isEmpty) {

ui/flutter/lib/features/tasks/presentation/widgets/resolve_download_dialog.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:shadcn_flutter/shadcn_flutter.dart';
 import 'package:flutter/widgets.dart' as flutter show Flexible;
 
@@ -49,6 +51,7 @@ class _ResolveDownloadsDialogState extends State<_ResolveDownloadsDialog> {
   @override
   void dispose() {
     _cancelled = true;
+    _releasePreviews();
     super.dispose();
   }
 
@@ -64,8 +67,15 @@ class _ResolveDownloadsDialogState extends State<_ResolveDownloadsDialog> {
     }
   }
 
+  void _releasePreviews() {
+    for (final source in widget.sources) {
+      unawaited(source.cancel(widget.service));
+    }
+  }
+
   void _cancel() {
     _cancelled = true;
+    _releasePreviews();
     closeOverlay(context, false);
   }
 

ui/flutter/test/features/tasks/presentation/resolve_download_dialog_test.dart

@@ -96,6 +96,49 @@ void main() {
     expect(released, contains('late-rid'));
   });
 
+  testWidgets('cancel sends the request ID before a preview completes', (tester) async {
+    final response = Completer<ResolveResult>();
+    final released = <String>[];
+    String? requestedID;
+    final registry = CapabilityRegistry(createAppCapabilityCodecs())
+      ..bind(GopeedMethods.resolve, (request) {
+        requestedID = request.id;
+        return response.future;
+      })
+      ..bind(GopeedMethods.releaseResolve, (id) {
+        released.add(id);
+        return const RpcUnit();
+      });
+    await open(tester, [pending('torrent')], registry);
+    await tester.tap(find.byKey(const ValueKey('resolve-close-button')));
+    await tester.pumpAndSettle();
+    expect(requestedID, isNotEmpty);
+    expect(released, contains(requestedID));
+    response.complete(
+      ResolveResult(
+        id: requestedID!,
+        res: Resource(files: [FileInfo(name: 'late.txt')]),
+      ),
+    );
+    await tester.pumpAndSettle();
+    expect(released.where((id) => id == requestedID), hasLength(2));
+  });
+
+  testWidgets('successful creation keeps task-owned resources', (tester) async {
+    final released = <String>[];
+    final registry = CapabilityRegistry(createAppCapabilityCodecs())
+      ..bind(GopeedMethods.resolve, (_) => resolved('task-owned'))
+      ..bind(GopeedMethods.createTaskBatch, (_) => CreateTaskBatchResult(taskIds: ['task']))
+      ..bind(GopeedMethods.releaseResolve, (id) {
+        released.add(id);
+        return const RpcUnit();
+      });
+    await open(tester, [pending('torrent')], registry);
+    await tester.pumpAndSettle();
+    await tester.tap(find.byKey(const ValueKey('resolve-create-button')));
+    await tester.pumpAndSettle();
+    expect(released, isEmpty);
+  });
   for (final width in [390.0, 700.0, 1024.0]) {
     testWidgets('file list fits and exposes ready selections at width $width', (tester) async {
       final registry = CapabilityRegistry(createAppCapabilityCodecs())