perf(learn): a conversation deleted goes at once, with an Undo

Deleting a kept conversation asked first and then waited while its
turns were blanked and deleted. It now goes as a card or a note does:
ConversationDeletions, a DelayedDeletions opened with the person's
data, takes it off the history at once (the list leaves out what is
pending), offers Undo for a moment on the sheet (hasSnackBars), and
blanks and deletes it once that is over; a deletion that fails shows
the conversation again, as every DelayedDeletions does. The question
before deleting goes, as Undo replaces it.

Whats-New: A conversation with an assistant is deleted at once, and Undo brings it back.
Whats-New-De: Eine Unterhaltung mit einem Assistenten wird sofort gelöscht, und „Rückgängig“ holt sie zurück.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/learn/halkyon_learn_flutter/lib/l10n/app_de.arb

@@ -1778,8 +1778,7 @@
   "assistantHistoryExplained": "Karte erklärt",
   "assistantHistoryChecked": "Auf Fehler geprüft",
   "assistantHistoryDelete": "Unterhaltung löschen",
-  "assistantHistoryDeleteMessage": "„{title}“ verschwindet von allen deinen Geräten.",
+  "assistantHistoryDeleted": "Unterhaltung gelöscht",
-  "assistantHistoryDeleteConfirm": "Löschen",
   "assistantGone": "Ein nicht mehr angebotener Assistent",
   "assistantGoneNote": "Dieser Assistent wird dir hier nicht mehr angeboten, also lässt sich die Unterhaltung nicht fortsetzen.",
   "assistantNotKept": "Nicht gespeichert: Dieses Gerät kann Unterhaltungen nicht verschlüsseln, also ist diese weg, sobald du sie schließt.",

apps/learn/halkyon_learn_flutter/lib/l10n/app_en.arb

@@ -2117,9 +2117,7 @@
   "assistantHistoryChecked": "Checked for mistakes",
   "@assistantHistoryChecked": {"description": "A conversation that checked what was written (D54)."},
   "assistantHistoryDelete": "Delete conversation",
-  "assistantHistoryDeleteMessage": "“{title}” goes from all your devices.",
+  "assistantHistoryDeleted": "Conversation deleted",
-  "@assistantHistoryDeleteMessage": {"placeholders": {"title": {"type": "String"}}},
-  "assistantHistoryDeleteConfirm": "Delete",
   "assistantGone": "An assistant no longer offered",
   "assistantGoneNote": "This assistant is no longer offered to you here, so the conversation can't go on.",
   "assistantNotKept": "Not kept: this device can't encrypt conversations, so this one is gone once you close it.",

apps/learn/halkyon_learn_flutter/lib/l10n/app_localizations.dart

@@ -10497,17 +10497,11 @@ abstract class AppLocalizations {
   /// **'Delete conversation'**
   String get assistantHistoryDelete;
 
-  /// No description provided for @assistantHistoryDeleteMessage.
+  /// No description provided for @assistantHistoryDeleted.
   ///
   /// In en, this message translates to:
-  /// **'“{title}” goes from all your devices.'**
+  /// **'Conversation deleted'**
-  String assistantHistoryDeleteMessage(String title);
+  String get assistantHistoryDeleted;
-
-  /// No description provided for @assistantHistoryDeleteConfirm.
-  ///
-  /// In en, this message translates to:
-  /// **'Delete'**
-  String get assistantHistoryDeleteConfirm;
 
   /// No description provided for @assistantGone.
   ///

apps/learn/halkyon_learn_flutter/lib/l10n/app_localizations_de.dart

@@ -6634,12 +6634,7 @@ class AppLocalizationsDe extends AppLocalizations {
   String get assistantHistoryDelete => 'Unterhaltung löschen';
 
   @override
-  String assistantHistoryDeleteMessage(String title) {
+  String get assistantHistoryDeleted => 'Unterhaltung gelöscht';
-    return '„$title“ verschwindet von allen deinen Geräten.';
-  }
-
-  @override
-  String get assistantHistoryDeleteConfirm => 'Löschen';
 
   @override
   String get assistantGone => 'Ein nicht mehr angebotener Assistent';

apps/learn/halkyon_learn_flutter/lib/l10n/app_localizations_en.dart

@@ -6574,12 +6574,7 @@ class AppLocalizationsEn extends AppLocalizations {
   String get assistantHistoryDelete => 'Delete conversation';
 
   @override
-  String assistantHistoryDeleteMessage(String title) {
+  String get assistantHistoryDeleted => 'Conversation deleted';
-    return '“$title” goes from all your devices.';
-  }
-
-  @override
-  String get assistantHistoryDeleteConfirm => 'Delete';
 
   @override
   String get assistantGone => 'An assistant no longer offered';

apps/learn/halkyon_learn_flutter/lib/src/core/dependencies/dependencies.dart

@@ -26,6 +26,7 @@ import 'package:halkyon_learn_flutter/src/feature/anki/data/anki_package_reader.
 import 'package:halkyon_learn_flutter/src/feature/archive/data/archive_reader.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/assistant_files.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/assistant_lookups.dart';
+import 'package:halkyon_learn_flutter/src/feature/assistant/data/conversation_deletions.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/conversation_repository.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/photo_picker.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/sync_conversation_gateway.dart';
@@ -567,6 +568,7 @@ Future<PersonDependencies> _openPersonData(
   final pathDeletions = LearningPathDeletions(paths);
   final stepDeletions = StepDeletions(paths);
   final pdfDeletions = PdfDeletions(pdfSources);
+  final conversationDeletions = ConversationDeletions(conversations);
   final publishing = PublishRepository(
     ServerpodPublishGateway(client),
     FilePublishedStore(File(p.join(folder.path, 'published.json'))),
@@ -628,6 +630,7 @@ Future<PersonDependencies> _openPersonData(
     pathDeletions: pathDeletions,
     stepDeletions: stepDeletions,
     pdfDeletions: pdfDeletions,
+    conversationDeletions: conversationDeletions,
     pomodoroRuns: FilePomodoroRunStore(
       File(p.join(folder.path, 'pomodoro.json')),
     ),
@@ -666,6 +669,7 @@ Future<PersonDependencies> _openPersonData(
         await pathDeletions.dispose();
         await stepDeletions.dispose();
         await pdfDeletions.dispose();
+        await conversationDeletions.dispose();
         await discussions.dispose();
         await counting.dispose();
         await studysetProgress.dispose();

apps/learn/halkyon_learn_flutter/lib/src/core/dependencies/person_dependencies.dart

@@ -3,6 +3,7 @@ import 'package:halkyon_app/halkyon_app.dart';
 import 'package:halkyon_learn_flutter/src/core/asset/data/asset_repository.dart';
 import 'package:halkyon_learn_flutter/src/core/grammar/grammar_checks.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/assistant_lookups.dart';
+import 'package:halkyon_learn_flutter/src/feature/assistant/data/conversation_deletions.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/conversation_repository.dart';
 import 'package:halkyon_learn_flutter/src/feature/card/data/card_deletions.dart';
 import 'package:halkyon_learn_flutter/src/feature/card/data/card_repository.dart';
@@ -96,6 +97,9 @@ class PersonDependencies({
   /// The PDF deletions that can still be undone.
   required final PdfDeletions pdfDeletions,
 
+  /// The deletions of kept conversations that can still be undone.
+  required final ConversationDeletions conversationDeletions,
+
   /// Where this device keeps the person's Pomodoro timer.
   required final PomodoroRunStore pomodoroRuns,
 

apps/learn/halkyon_learn_flutter/lib/src/feature/assistant/data/conversation_deletions.dart

@@ -0,0 +1,13 @@
+import 'package:halkyon_app/halkyon_app.dart';
+import 'package:halkyon_learn_flutter/src/feature/assistant/data/conversation_repository.dart';
+
+/// The person's deletions of kept conversations (ADR 0021, D48), which can
+/// be undone for a moment (see [DelayedDeletions]), as a card's or a note's:
+/// the conversation leaves the history at once, and is blanked and deleted
+/// with its turns once the time to undo is over.
+class ConversationDeletions(
+  ConversationRepository conversations, {
+  super.undoWindow,
+}) extends DelayedDeletions {
+  this : super(conversations.delete, logName: 'Conversations');
+}

apps/learn/halkyon_learn_flutter/lib/src/feature/assistant/widget/conversation_history.dart

@@ -16,8 +16,8 @@ import 'package:material_ui/material_ui.dart';
 
 /// The person's kept conversations (ADR 0021, D48), the newest first, those
 /// asked on [studysetId] before the rest, each with who answers and how far
-/// it looks: opening one continues it in its sheet; deleting one asks
+/// it looks: opening one continues it in its sheet; deleting one takes it
-/// first.
+/// off at once, with an Undo for a moment.
 Future<void> showConversationHistory(
   BuildContext context, {
   String? studysetId,
@@ -42,6 +42,11 @@ class _HistoryState() extends State<_History> {
     context,
   ).conversations.watch();
 
+  /// The conversations being deleted, which the list leaves out at once.
+  late final _deleting = PersonDependencies.of(
+    context,
+  ).conversationDeletions.watchPending();
+
   /// Every studyset's title, for the conversations asked on one.
   late final Future<Map<String, String>> _titles =
       PersonDependencies.of(
@@ -70,37 +75,49 @@ class _HistoryState() extends State<_History> {
     final l10n = AppLocalizations.of(context);
     return SheetScaffold(
       title: l10n.assistantHistory,
-      body: StreamBuilder<List<AssistantConversation>>(
+      // A deletion's Undo shows on it, not behind its barrier.
-        stream: _conversations,
+      hasSnackBars: true,
-        builder: (context, snapshot) => switch (snapshot.data) {
+      body: StreamBuilder<Set<String>>(
-          null => const Padding(
+        stream: _deleting,
-            padding: EdgeInsets.all(24),
+        builder: (context, deleting) =>
-            child: Center(child: AppLoadingIndicator()),
+            StreamBuilder<List<AssistantConversation>>(
-          ),
+              stream: _conversations,
-          [] => Padding(
+              builder: (context, snapshot) => switch (snapshot.data
-            padding: const EdgeInsets.symmetric(vertical: 24),
+                  ?.where(
-            child: EmptyListMessage(
+                    (conversation) =>
-              icon: LucideIcons.messagesSquare,
+                        !(deleting.data?.contains(conversation.id) ?? false),
-              title: l10n.assistantHistoryEmpty,
+                  )
-              hint: l10n.assistantHistoryEmptyHint,
+                  .toList()) {
-            ),
+                null => const Padding(
-          ),
+                  padding: EdgeInsets.all(24),
-          final all => FutureBuilder<Map<String, String>>(
+                  child: Center(child: AppLoadingIndicator()),
-            future: _titles,
+                ),
-            builder: (context, titles) => Column(
+                [] => Padding(
-              children: [
+                  padding: const EdgeInsets.symmetric(vertical: 24),
-                for (final conversation in _ordered(all))
+                  child: EmptyListMessage(
-                  _ConversationTile(
+                    icon: LucideIcons.messagesSquare,
-                    conversation: conversation,
+                    title: l10n.assistantHistoryEmpty,
-                    studysetTitle: switch (conversation.scope.studysetId) {
+                    hint: l10n.assistantHistoryEmptyHint,
-                      final id? => titles.data?[id],
-                      null => null,
-                    },
                   ),
-              ],
+                ),
+                final all => FutureBuilder<Map<String, String>>(
+                  future: _titles,
+                  builder: (context, titles) => Column(
+                    children: [
+                      for (final conversation in _ordered(all))
+                        _ConversationTile(
+                          conversation: conversation,
+                          studysetTitle:
+                              switch (conversation.scope.studysetId) {
+                                final id? => titles.data?[id],
+                                null => null,
+                              },
+                        ),
+                    ],
+                  ),
+                ),
+              },
             ),
-          ),
-        },
       ),
     );
   }
@@ -152,7 +169,7 @@ class const _ConversationTile({
       trailing: IconButton(
         tooltip: l10n.assistantHistoryDelete,
         icon: const Icon(LucideIcons.trash2),
-        onPressed: () => unawaited(_delete(context)),
+        onPressed: () => _delete(context),
       ),
       onTap: () {
         // The conversation's sheet over the screen, not over this list,
@@ -176,16 +193,17 @@ class const _ConversationTile({
     );
   }
 
-  Future<void> _delete(BuildContext context) async {
+  /// Takes the conversation off at once and offers to undo that for a
+  /// moment, as a card or a note; it is blanked and deleted once that is
+  /// over, the deletion outliving this list.
+  void _delete(BuildContext context) {
     final l10n = AppLocalizations.of(context);
-    final conversations = PersonDependencies.of(context).conversations;
+    final deletions = PersonDependencies.of(context).conversationDeletions
-    if (await confirmDestructiveAction(
+      ..delete(conversation.id);
+    showUndoSnackBar(
       context,
-      title: l10n.assistantHistoryDelete,
+      message: l10n.assistantHistoryDeleted,
-      message: l10n.assistantHistoryDeleteMessage(conversation.title),
+      onUndo: () => deletions.undo(conversation.id),
-      confirmLabel: l10n.assistantHistoryDeleteConfirm,
+    );
-    )) {
-      await conversations.delete(conversation.id);
-    }
   }
 }

apps/learn/halkyon_learn_flutter/test/feature/assistant/conversation_test.dart

@@ -764,8 +764,8 @@ void main() {
   });
 
   testWidgets('kept conversations are listed in the field, those about '
-      'where the person is first; one opens in its sheet, and goes after '
+      'where the person is first; one opens in its sheet, and goes at once, '
-      'asking (D48)', (tester) async {
+      'with an Undo (D48)', (tester) async {
     final conversations = ConversationRepository(kept);
     addTearDown(conversations.dispose);
     final id = await conversations.start(
@@ -799,13 +799,24 @@ void main() {
 
     await tester.tap(find.byTooltip('Conversations'));
     await tester.pumpAndSettle();
+    // Gone at once, with an Undo for a moment, as a card or a note.
     await tester.tap(find.byTooltip('Delete conversation'));
+    await tester.pump();
+    expect(find.text('Why て-form?'), findsNothing);
     await tester.pumpAndSettle();
-    await tester.tap(find.text('Delete'));
+    expect(find.text('Conversation deleted'), findsOneWidget);
+    await tester.tap(find.text('Undo'));
     await tester.pumpAndSettle();
+    expect(find.text('Why て-form?'), findsOneWidget);
 
+    await tester.tap(find.byTooltip('Delete conversation'));
+    await tester.pump();
     expect(find.text('No conversations yet'), findsOneWidget);
+    expect(kept.blanked, isEmpty, reason: 'Undo is still offered');
+    await tester.pump(const Duration(seconds: 5));
+    await tester.pumpAndSettle();
     expect(kept.blanked, [id]);
+    expect(find.text('No conversations yet'), findsOneWidget);
   });
 
   testWidgets("a device that can't seal answers, and says it keeps nothing "

apps/learn/halkyon_learn_flutter/test/support/test_dependencies.dart

@@ -23,6 +23,7 @@ import 'package:halkyon_learn_flutter/src/feature/archive/data/archive_reader.da
 import 'package:halkyon_learn_flutter/src/feature/archive/model/import_archive.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/assistant_files.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/assistant_lookups.dart';
+import 'package:halkyon_learn_flutter/src/feature/assistant/data/conversation_deletions.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/conversation_repository.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/photo_picker.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/web_search.dart';
@@ -345,6 +346,7 @@ Dependencies testDependencies({
           final pathDeletions = LearningPathDeletions(paths);
           final stepDeletions = StepDeletions(paths);
           final pdfDeletions = PdfDeletions(pdfSources);
+          final conversationDeletions = ConversationDeletions(conversations);
           final studysetTabs = StudysetTabs(
             studysetTabStore ?? MemoryStudysetTabStore(),
           );
@@ -376,6 +378,7 @@ Dependencies testDependencies({
             pathDeletions: pathDeletions,
             stepDeletions: stepDeletions,
             pdfDeletions: pdfDeletions,
+            conversationDeletions: conversationDeletions,
             pomodoroRuns: pomodoroRuns ?? MemoryPomodoroRunStore(),
             studysetTabs: studysetTabs,
             privateOffer: privateOffer ?? MemoryPrivateOfferStore(),
@@ -427,6 +430,7 @@ Dependencies testDependencies({
               await pathDeletions.dispose();
               await stepDeletions.dispose();
               await pdfDeletions.dispose();
+              await conversationDeletions.dispose();
               await studysetProgress.dispose();
               await studysets.dispose();
               await tags.dispose();