feat(learn): a Viewer opens a shared studyset's material read-only

Every route of a studyset says what the person may do there
(StudysetAccess, set in _inStudyset): whether it is shared with people,
and whether they only view and study it (Halkyon's ADR 0044, D35, D36).

A Viewer opens cards and notes on the same screens, read-only: the rich
fields show their content (LearnContentEditor shows LearnContentView),
the composer's plain fields are read-only and its changes go nowhere,
the note screen reads as a conflict leaves it, each with the line that
the studyset is theirs to view and study. The lists, the card browser
and a study session offer them nothing that writes: no new card, import,
edit, move, rename, reading deadline, reorder or delete. Their tags,
progress and reading stay theirs to change, being their own rows.

Burying and reporting a card are written on its row, which every member
shares, so they are hidden in shared studysets for everyone until they
become each person's own rows (D36).

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/test/feature/sharing/view_only_test.dart

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+import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_editor/halkyon_editor.dart';
+import 'package:halkyon_learn_flutter/src/core/router/route_paths.dart';
+import 'package:halkyon_learn_flutter/src/feature/card/data/card_repository.dart';
+import 'package:halkyon_learn_flutter/src/feature/card/model/card_content.dart';
+import 'package:halkyon_learn_flutter/src/feature/card/widget/card_tile.dart';
+import 'package:halkyon_learn_flutter/src/feature/note/data/note_repository.dart';
+import 'package:halkyon_learn_flutter/src/feature/note/model/note_content.dart';
+import 'package:halkyon_learn_flutter/src/feature/studyset/data/studyset_payload.dart';
+import 'package:halkyon_learn_flutter/src/feature/studyset/model/studyset_content.dart';
+import 'package:material_ui/material_ui.dart';
+
+import '../../support/fake_card_gateway.dart';
+import '../../support/fake_note_gateway.dart';
+import '../../support/fake_studyset_gateway.dart';
+import '../../support/pump_app.dart';
+import '../../support/test_dependencies.dart';
+
+/// What a member of a shared studyset may do in it (Halkyon's ADR 0044,
+/// D35, D36): a Viewer opens cards and notes read-only and is offered
+/// nothing that writes; nobody buries or reports a card every member
+/// shares; in the person's own studyset, all of it as before.
+void main() {
+  late FakeStudysetGateway studysets;
+  late FakeCardGateway cardGateway;
+  late FakeNoteGateway noteGateway;
+  late String cardId;
+  late String noteId;
+
+  setUp(() async {
+    studysets = FakeStudysetGateway()
+      ..receiveRemoteChange(
+        'japanese',
+        encodeStudysetPayload(StudysetContent.titled('Japanese')),
+      );
+    cardGateway = FakeCardGateway();
+    noteGateway = FakeNoteGateway();
+    final cards = CardRepository(cardGateway);
+    addTearDown(cards.dispose);
+    cardId = await cards.create(
+      'japanese',
+      CardContent(
+        front: RichContent.plain('Capital of Japan?'),
+        back: RichContent.plain('Tokyo'),
+      ),
+    );
+    final notes = NoteRepository(noteGateway);
+    addTearDown(notes.dispose);
+    noteId = (await notes.create(
+      'japanese',
+      NoteContent(title: 'Particles', body: RichContent.plain('は')),
+    )).noteId;
+  });
+
+  Future<void> showApp(WidgetTester tester, String location) async {
+    tester.view.physicalSize = const Size(1200, 1000);
+    tester.view.devicePixelRatio = 1;
+    addTearDown(tester.view.reset);
+    await pumpApp(
+      tester,
+      testDependencies(
+        studysetGateway: studysets,
+        cardGateway: cardGateway,
+        noteGateway: noteGateway,
+      ),
+      location: location,
+    );
+    await tester.pump(const Duration(seconds: 1));
+    await tester.pumpAndSettle();
+  }
+
+  /// The options of the card's row in the Flashcards tab, opened.
+  Future<void> openCardOptions(WidgetTester tester) async {
+    await showApp(tester, RoutePaths.studyset('japanese'));
+    await tester.tap(find.text('Flashcards'));
+    await tester.pumpAndSettle();
+    await tester.tap(
+      find.descendant(
+        of: find.byType(CardTile),
+        matching: find.byTooltip('Options'),
+      ),
+    );
+    await tester.pumpAndSettle();
+  }
+
+  void shared({required bool viewOnly}) =>
+      studysets.shared['japanese'] = (space: 'space-1', viewOnly: viewOnly);
+
+  testWidgets("a Viewer's card offers its info alone", (tester) async {
+    shared(viewOnly: true);
+    await openCardOptions(tester);
+
+    expect(find.text('More info'), findsOneWidget);
+    expect(find.text('Edit'), findsNothing);
+    expect(find.text('Delete'), findsNothing);
+    expect(find.text('Bury until tomorrow'), findsNothing);
+    expect(find.text('Report an error'), findsNothing);
+  });
+
+  testWidgets("an Editor's card is edited and deleted, never buried or "
+      'reported for everyone', (tester) async {
+    shared(viewOnly: false);
+    await openCardOptions(tester);
+
+    expect(find.text('Edit'), findsOneWidget);
+    expect(find.text('Delete'), findsOneWidget);
+    expect(find.text('Bury until tomorrow'), findsNothing);
+    expect(find.text('Report an error'), findsNothing);
+  });
+
+  testWidgets("the person's own card offers all of it", (tester) async {
+    await openCardOptions(tester);
+
+    expect(find.text('Edit'), findsOneWidget);
+    expect(find.text('Bury until tomorrow'), findsOneWidget);
+    expect(find.text('Report an error'), findsOneWidget);
+  });
+
+  testWidgets('a Viewer opens a card read-only, adding none', (tester) async {
+    shared(viewOnly: true);
+    await showApp(tester, RoutePaths.card('japanese', cardId));
+
+    expect(
+      find.text('You can view and study this, not change it.'),
+      findsOneWidget,
+    );
+    expect(find.text('New flashcard'), findsNothing);
+    expect(find.byTooltip('More actions'), findsNothing);
+    expect(find.byType(RichContentEditor), findsNothing);
+    expect(
+      find.textContaining('Capital of Japan?', findRichText: true),
+      findsWidgets,
+    );
+  });
+
+  testWidgets('a Viewer opens a note read-only', (tester) async {
+    shared(viewOnly: true);
+    await showApp(tester, RoutePaths.note('japanese', noteId));
+
+    expect(
+      find.text('You can view and study this, not change it.'),
+      findsOneWidget,
+    );
+    expect(find.byType(RichContentEditor), findsNothing);
+    expect(
+      tester.widget<TextField>(find.byType(TextField).first).readOnly,
+      isTrue,
+    );
+  });
+}