feat(app): About Halkyon Learn, with the licences and the source

The account dialog opens Flutter's about dialog: the licences (AGPL-3.0-or-later for the app, SSPL-1.0 for the server), the address of the source the instance names, as selectable text, and "View licenses" with every package's notice, which the BSD and MIT packages require in a distributed app. The address comes through a small about feature (gateway, repository, bloc) that says so when the instance can't be reached. Tests cover the bloc both ways and the way from the account dialog; AGENTS.md records the obligation.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

AGENTS.md

@@ -122,6 +122,7 @@ A spaced-repetition learning app: studysets of flashcards, reviewed on an FSRS s
   - **Every synced table indexes `spaceId`** (`indexes: <table>_space_idx: fields: spaceId`, e.g. `studyset.spy.yaml`): deleting a space cascades into every synced table, and Postgres doesn't index foreign keys by itself, so account deletion and pruning would otherwise read whole tables.
   - **The client's local migration** (in `halkyon_learn_client/lib/migrations/`, written by the same `create-migration`) creates the device's SQLite schema from the whole definition, so it also contains the server's own tables. Only the synced tables and the bookkeeping ever hold data on a device.
 - **Serverpod's version moves together with `serverpod_offline_sync`**, which pins Serverpod exactly: the root `pubspec.yaml` overrides the four core packages to the project's version. Upgrade Serverpod only together with those overrides, after reading the sync package's changelog.
+- **The source-code link**: both licences require offering the source of what an instance runs to the people who use it. `instance.info().sourceCodeUrl` names it (the operator's `SOURCE_URL`, else this project's repository) and the app's About dialog shows it next to the licences and every package's notice. Keep it working when changing the dialog or the endpoint.
 - **Session logs are not persisted** (`persistentEnabled: false` in every run mode) for privacy. Don't re-enable them.
 - **Secrets** live in `halkyon_learn_server/config/passwords.yaml` (git-ignored). Never change `serverSideSessionKeyHashPepper`: it would sign everyone out, and anonymous accounts can't sign back in.
 - **Linux builds need** `libwebkit2gtk-4.1-dev` and `libsecret-1-dev`. If a Linux build tries to install to `/usr/local`, the CMake cache is stale: delete `build/linux`.

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

@@ -4,6 +4,8 @@ import 'package:halkyon_learn_client/halkyon_learn_client.dart'
     show Client, UuidValue;
 import 'package:halkyon_learn_flutter/src/core/dependencies/person_dependencies.dart';
 import 'package:halkyon_learn_flutter/src/core/sync/sync_service.dart';
+import 'package:halkyon_learn_flutter/src/feature/about/data/about_repository.dart';
+import 'package:halkyon_learn_flutter/src/feature/about/data/serverpod_about_gateway.dart';
 import 'package:halkyon_learn_flutter/src/feature/auth/data/auth_repository.dart';
 import 'package:halkyon_learn_flutter/src/feature/auth/data/serverpod_auth_gateway.dart';
 import 'package:halkyon_learn_flutter/src/feature/auth/model/auth_status.dart';
@@ -29,6 +31,9 @@ class Dependencies({
   /// Who is signed in, and signing in and out.
   required final AuthRepository auth,
 
+  /// What the instance says about itself, such as where its source is.
+  required final AboutRepository about,
+
   /// Opens a signed-in person's local data (see `PersonScope`).
   required final OpenPerson openPerson,
   final Future<void> Function()? _onDispose,
@@ -48,6 +53,7 @@ class Dependencies({
     final authGateway = ServerpodAuthGateway(client);
     return Dependencies(
       auth: AuthRepository(authGateway),
+      about: AboutRepository(ServerpodAboutGateway(client)),
       openPerson: (person) => _openPerson(client, person),
       onDispose: () async {
         await authGateway.dispose();

halkyon_learn_flutter/lib/src/feature/about/bloc/about_bloc.dart

@@ -0,0 +1,53 @@
+import 'package:equatable/equatable.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:halkyon_learn_flutter/src/feature/about/data/about_repository.dart';
+
+/// Finds where the source of what the instance runs is, for the About dialog.
+class AboutBloc(final AboutRepository _about)
+    extends Bloc<AboutEvent, AboutState> {
+  this : super(const AboutStateLoading()) {
+    on<AboutEventStarted>(_onStarted);
+  }
+
+  Future<void> _onStarted(
+    AboutEventStarted event,
+    Emitter<AboutState> emit,
+  ) async {
+    try {
+      emit(AboutStateLoaded(await _about.sourceCodeUrl()));
+    } on Exception catch (error, st) {
+      addError(error, st);
+      emit(const AboutStateUnreachable());
+    }
+  }
+}
+
+/// What happens to the About dialog.
+sealed class const AboutEvent() with Equatable {
+  @override
+  List<Object?> get props => const [];
+}
+
+/// The About dialog opens.
+final class const AboutEventStarted() extends AboutEvent;
+
+/// What the About dialog knows about the instance.
+sealed class const AboutState() with Equatable {
+  @override
+  List<Object?> get props => const [];
+}
+
+/// Asking the instance.
+final class const AboutStateLoading() extends AboutState;
+
+/// Where the source of what the instance runs is.
+final class const AboutStateLoaded(
+  /// Its address.
+  final String sourceCodeUrl,
+) extends AboutState {
+  @override
+  List<Object?> get props => [sourceCodeUrl];
+}
+
+/// The instance couldn't be reached.
+final class const AboutStateUnreachable() extends AboutState;

halkyon_learn_flutter/lib/src/feature/about/data/about_gateway.dart

@@ -0,0 +1,6 @@
+/// The boundary to what the instance says about itself. Tests replace it with
+/// a fake.
+abstract interface class AboutGateway() {
+  /// Where the source of what the instance runs is.
+  Future<String> sourceCode();
+}

halkyon_learn_flutter/lib/src/feature/about/data/about_repository.dart

@@ -0,0 +1,8 @@
+import 'package:halkyon_learn_flutter/src/feature/about/data/about_gateway.dart';
+
+/// What the instance says about itself, as the About dialog shows it.
+class AboutRepository(final AboutGateway _gateway) {
+  /// Where the source of what the instance runs is: both licences require
+  /// offering it to the people who use the instance.
+  Future<String> sourceCodeUrl() => _gateway.sourceCode();
+}

halkyon_learn_flutter/lib/src/feature/about/data/serverpod_about_gateway.dart

@@ -0,0 +1,9 @@
+import 'package:halkyon_learn_client/halkyon_learn_client.dart' show Client;
+import 'package:halkyon_learn_flutter/src/feature/about/data/about_gateway.dart';
+
+/// [AboutGateway] asking the instance through the Serverpod client.
+class ServerpodAboutGateway(final Client _client) implements AboutGateway {
+  @override
+  Future<String> sourceCode() async =>
+      (await _client.instance.info()).sourceCodeUrl;
+}

halkyon_learn_flutter/lib/src/feature/about/widget/about.dart

@@ -0,0 +1,45 @@
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:halkyon_learn_flutter/src/feature/about/bloc/about_bloc.dart';
+import 'package:halkyon_learn_flutter/src/feature/about/data/about_repository.dart';
+import 'package:material_ui/material_ui.dart';
+
+/// Shows what Halkyon Learn is under which licences, and where the source of
+/// what this instance runs is; its "View licenses" lists every package's
+/// notice, which the BSD and MIT packages require in a distributed app.
+void showAbout(BuildContext context, AboutRepository about) => showAboutDialog(
+  context: context,
+  applicationName: 'Halkyon Learn',
+  applicationLegalese:
+      'Free software: the app is under the GNU Affero General Public License, '
+      'version 3 or any later version, the server under the Server Side '
+      'Public License, version 1.',
+  children: [
+    BlocProvider(
+      create: (context) => AboutBloc(about)..add(const AboutEventStarted()),
+      child: const _SourceCode(),
+    ),
+  ],
+);
+
+class const _SourceCode() extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) => Padding(
+    padding: const EdgeInsets.only(top: 16),
+    child: BlocBuilder<AboutBloc, AboutState>(
+      builder: (context, state) => switch (state) {
+        AboutStateLoading() => const SizedBox.shrink(),
+        AboutStateLoaded(:final sourceCodeUrl) => Column(
+          mainAxisSize: MainAxisSize.min,
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            const Text('The source of what this instance runs:'),
+            SelectableText(sourceCodeUrl),
+          ],
+        ),
+        AboutStateUnreachable() => const Text(
+          "Couldn't reach this instance to ask where its source is.",
+        ),
+      },
+    ),
+  );
+}

halkyon_learn_flutter/lib/src/feature/auth/widget/account_button.dart

@@ -1,6 +1,7 @@
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:halkyon_learn_flutter/src/core/dependencies/dependencies_scope.dart';
 import 'package:halkyon_learn_flutter/src/core/dependencies/person_scope.dart';
+import 'package:halkyon_learn_flutter/src/feature/about/widget/about.dart';
 import 'package:halkyon_learn_flutter/src/feature/auth/bloc/github_sign_in_bloc.dart';
 import 'package:halkyon_learn_flutter/src/feature/auth/bloc/session_bloc.dart';
 import 'package:material_ui/material_ui.dart';
@@ -68,6 +69,12 @@ class const _AccountDialog() extends StatelessWidget {
                   : 'Progress is saved on this device. Sign in to keep it.',
             ),
             if (!isIdentified) const _GitHubSignIn(),
+            const SizedBox(height: 8),
+            TextButton(
+              onPressed: () =>
+                  showAbout(context, DependenciesScope.of(context).about),
+              child: const Text('About Halkyon Learn'),
+            ),
           ],
         ),
         actions: [

halkyon_learn_flutter/test/feature/about/about_test.dart

@@ -0,0 +1,66 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_learn_flutter/src/core/dependencies/dependencies_scope.dart';
+import 'package:halkyon_learn_flutter/src/feature/about/bloc/about_bloc.dart';
+import 'package:halkyon_learn_flutter/src/feature/about/data/about_repository.dart';
+import 'package:halkyon_learn_flutter/src/feature/auth/widget/account_button.dart';
+import 'package:halkyon_learn_flutter/src/feature/auth/widget/session_gate.dart';
+import 'package:material_ui/material_ui.dart';
+
+import '../../support/fake_about_gateway.dart';
+import '../../support/test_dependencies.dart';
+
+void main() {
+  group('AboutBloc', () {
+    test('finds where the instance says its source is', () async {
+      final bloc = AboutBloc(AboutRepository(FakeAboutGateway()))
+        ..add(const AboutEventStarted());
+      addTearDown(bloc.close);
+
+      await expectLater(
+        bloc.stream,
+        emits(const AboutStateLoaded('https://example.org/halkyon-learn')),
+      );
+    });
+
+    test('says so when the instance cannot be reached', () async {
+      final gateway = FakeAboutGateway()
+        ..unreachable = Exception('No connection');
+      final bloc = AboutBloc(AboutRepository(gateway))
+        ..add(const AboutEventStarted());
+      addTearDown(bloc.close);
+
+      await expectLater(bloc.stream, emits(const AboutStateUnreachable()));
+    });
+  });
+
+  testWidgets('the account dialog leads to the licences and the source', (
+    tester,
+  ) async {
+    await tester.pumpWidget(
+      DependenciesScope(
+        dependencies: testDependencies(),
+        child: MaterialApp(
+          home: SessionGate(
+            child: Scaffold(
+              appBar: AppBar(actions: const [AccountButton()]),
+              body: const Text('Home'),
+            ),
+          ),
+        ),
+      ),
+    );
+    await tester.pumpAndSettle();
+    await tester.tap(find.byTooltip('Account'));
+    await tester.pumpAndSettle();
+
+    await tester.tap(find.text('About Halkyon Learn'));
+    await tester.pumpAndSettle();
+
+    expect(
+      find.textContaining('GNU Affero General Public License'),
+      findsOneWidget,
+    );
+    expect(find.text('https://example.org/halkyon-learn'), findsOneWidget);
+    expect(find.text('View licenses'), findsOneWidget);
+  });
+}

halkyon_learn_flutter/test/support/fake_about_gateway.dart

@@ -0,0 +1,19 @@
+import 'package:halkyon_learn_flutter/src/feature/about/data/about_gateway.dart';
+
+/// An [AboutGateway] without a server, naming [sourceCodeUrl]; [unreachable]
+/// makes it fail as when the instance can't be reached.
+class FakeAboutGateway({
+  /// Where the instance says its source is.
+  final String sourceCodeUrl = 'https://example.org/halkyon-learn',
+}) implements AboutGateway {
+  /// Thrown by the next calls while set.
+  Exception? unreachable;
+
+  @override
+  Future<String> sourceCode() async {
+    if (unreachable case final error?) {
+      throw error;
+    }
+    return sourceCodeUrl;
+  }
+}

halkyon_learn_flutter/test/support/test_dependencies.dart

@@ -1,5 +1,7 @@
 import 'package:halkyon_learn_flutter/src/core/dependencies/dependencies.dart';
 import 'package:halkyon_learn_flutter/src/core/dependencies/person_dependencies.dart';
+import 'package:halkyon_learn_flutter/src/feature/about/data/about_gateway.dart';
+import 'package:halkyon_learn_flutter/src/feature/about/data/about_repository.dart';
 import 'package:halkyon_learn_flutter/src/feature/auth/data/auth_gateway.dart';
 import 'package:halkyon_learn_flutter/src/feature/auth/data/auth_repository.dart';
 import 'package:halkyon_learn_flutter/src/feature/card/data/card_gateway.dart';
@@ -7,6 +9,7 @@ import 'package:halkyon_learn_flutter/src/feature/card/data/card_repository.dart
 import 'package:halkyon_learn_flutter/src/feature/studyset/data/studyset_gateway.dart';
 import 'package:halkyon_learn_flutter/src/feature/studyset/data/studyset_repository.dart';
 
+import 'fake_about_gateway.dart';
 import 'fake_auth_gateway.dart';
 import 'fake_card_gateway.dart';
 import 'fake_studyset_gateway.dart';
@@ -21,9 +24,11 @@ Dependencies testDependencies({
   AuthGateway? authGateway,
   StudysetGateway? studysetGateway,
   CardGateway? cardGateway,
+  AboutGateway? aboutGateway,
   OpenPerson? openPerson,
 }) => Dependencies(
   auth: AuthRepository(authGateway ?? FakeAuthGateway()),
+  about: AboutRepository(aboutGateway ?? FakeAboutGateway()),
   openPerson:
       openPerson ??
       (person) async {