notif: Ensure back navigation preserves target account context after opening notification

Fixes: #1210

Author: lakshya1goel

lib/notifications/display.dart

@@ -17,6 +17,7 @@ import '../model/narrow.dart';
 import '../widgets/app.dart';
 import '../widgets/color.dart';
 import '../widgets/dialog.dart';
+import '../widgets/home.dart';
 import '../widgets/message_list.dart';
 import '../widgets/page.dart';
 import '../widgets/store.dart';
@@ -214,8 +215,34 @@ class NotificationChannelManager {
   }
 }
 
+/// Tracks the currently active account in the navigation stack
+class AccountNavigationObserver extends NavigatorObserver {
+  int? _activeAccountId;
+  int? get activeAccountId => _activeAccountId;
+
+  @override
+  void didPush(Route<dynamic> route, Route<void>? previousRoute) {
+    _updateActiveAccount(route);
+  }
+
+  @override
+  void didReplace({Route<dynamic>? newRoute, Route<void>? oldRoute}) {
+    if (newRoute != null) {
+      _updateActiveAccount(newRoute);
+    }
+  }
+
+  void _updateActiveAccount(Route<void> route) {
+    if (route is AccountRoute) {
+      _activeAccountId = route.accountId;
+    }
+  }
+}
+
 /// Service for managing the notifications shown to the user.
 class NotificationDisplayManager {
+  static final accountObserver = AccountNavigationObserver();
+
   static Future<void> init() async {
     await NotificationChannelManager.ensureChannel();
   }
@@ -502,7 +529,14 @@ class NotificationDisplayManager {
     final route = routeForNotification(context: context, url: url);
     if (route == null) return; // TODO(log)
 
-    // TODO(nav): Better interact with existing nav stack on notif open
+    final currentAccountId = accountObserver.activeAccountId;
+
+    if (currentAccountId != route.accountId) {
+      navigator.popUntil((r) => r.isFirst);
+      HomePage.navigate(context, accountId: route.accountId);
+      navigator = await ZulipApp.navigator;
+    }
+
     unawaited(navigator.push(route));
   }
 

lib/widgets/app.dart

@@ -231,6 +231,7 @@ class _ZulipAppState extends State<ZulipApp> with WidgetsBindingObserver {
 
           navigatorKey: ZulipApp.navigatorKey,
           navigatorObservers: [
+            NotificationDisplayManager.accountObserver,
             if (widget.navigatorObservers != null)
               ...widget.navigatorObservers!,
             _PreventEmptyStack(),

test/notifications/display_test.dart

@@ -959,6 +959,8 @@ void main() {
 
   group('NotificationDisplayManager open', () {
     late List<Route<void>> pushedRoutes;
+    late List<Route<void>> poppedRoutes;
+    late TestNavigatorObserver testNavObserver;
 
     void takeStartingRoutes({Account? account, bool withAccount = true}) {
       account ??= eg.selfAccount;
@@ -978,8 +980,14 @@ void main() {
         {bool early = false, bool withAccount = true}) async {
       await init();
       pushedRoutes = [];
-      final testNavObserver = TestNavigatorObserver()
-        ..onPushed = (route, prevRoute) => pushedRoutes.add(route);
+      poppedRoutes = [];
+      testNavObserver = TestNavigatorObserver();
+      testNavObserver.onPushed = (route, prevRoute) => pushedRoutes.add(route);
+      testNavObserver.onPopped = (route, prevRoute) => poppedRoutes.add(route);
+      testNavObserver.onReplaced = (route, prevRoute) {
+        poppedRoutes.add(prevRoute!);
+        pushedRoutes.add(route!);
+      };
       // This uses [ZulipApp] instead of [TestZulipApp] because notification
       // logic uses `await ZulipApp.navigator`.
       await tester.pumpWidget(ZulipApp(navigatorObservers: [testNavObserver]));
@@ -1018,7 +1026,7 @@ void main() {
 
     Future<void> checkOpenNotification(WidgetTester tester, Account account, Message message) async {
       await openNotification(tester, account, message);
-      matchesNavigation(check(pushedRoutes).single, account, message);
+      check(pushedRoutes).any((it) => matchesNavigation(it, account, message));
       pushedRoutes.clear();
     }
 
@@ -1176,6 +1184,80 @@ void main() {
       takeStartingRoutes(account: accountB);
       matchesNavigation(check(pushedRoutes).single, accountB, message);
     });
+
+    testWidgets('notification switches account only when from different account', (tester) async {
+      addTearDown(testBinding.reset);
+
+      final accountA = eg.selfAccount;
+      final accountB = eg.otherAccount;
+      final message = eg.streamMessage();
+
+      await testBinding.globalStore.add(accountA, eg.initialSnapshot());
+      await testBinding.globalStore.add(accountB, eg.initialSnapshot());
+
+      await prepare(tester, early: true);
+      await tester.pump();
+      takeStartingRoutes(account: accountA);
+
+      await openNotification(tester, accountB, message);
+      check(poppedRoutes).any((it) => it.isA<MaterialAccountWidgetRoute>()
+        .accountId.equals(accountA.id));
+      check(pushedRoutes.last).isA<MaterialAccountWidgetRoute>()
+        ..accountId.equals(accountB.id)
+        ..page.isA<MessageListPage>();
+    });
+
+    testWidgets('notification preserves navigation stack when in same account', (tester) async {
+      addTearDown(testBinding.reset);
+
+      final account = eg.selfAccount;
+      final message = eg.streamMessage();
+
+      await testBinding.globalStore.add(account, eg.initialSnapshot());
+
+      await prepare(tester, early: true);
+      await tester.pump();
+      takeStartingRoutes(account: account);
+
+      await openNotification(tester, account, message);
+      check(pushedRoutes.last).isA<MaterialAccountWidgetRoute>()
+        ..accountId.equals(account.id)
+        ..page.isA<MessageListPage>();
+
+      check(poppedRoutes).isEmpty();
+    });
+
+    testWidgets('notification keeps AccountRoute in stack when opened from non-AccountRoute', (tester) async {
+      addTearDown(testBinding.reset);
+
+      final accountA = eg.selfAccount;
+      final accountB = eg.otherAccount;
+      final message = eg.streamMessage();
+
+      await testBinding.globalStore.add(accountA, eg.initialSnapshot());
+      await testBinding.globalStore.add(accountB, eg.initialSnapshot());
+
+      await prepare(tester, early: true);
+      await tester.pump();
+      takeStartingRoutes(account: accountA);
+
+      final navigator = await ZulipApp.navigator;
+      unawaited(navigator.push(MaterialWidgetRoute(page: const ChooseAccountPage())));
+      await tester.pumpAndSettle();
+
+      await openNotification(tester, accountA, message);
+      check(poppedRoutes).isEmpty();
+      check(pushedRoutes.last).isA<MaterialAccountWidgetRoute>()
+        ..accountId.equals(accountA.id)
+        ..page.isA<MessageListPage>();
+
+      await openNotification(tester, accountB, message);
+      check(poppedRoutes).any((it) => it.isA<MaterialAccountWidgetRoute>()
+        .accountId.equals(accountA.id));
+      check(pushedRoutes.last).isA<MaterialAccountWidgetRoute>()
+        ..accountId.equals(accountB.id)
+        ..page.isA<MessageListPage>();
+    });
   });
 
   group('NotificationOpenPayload', () {