notif: Use associated account as initial account; if opened from background

Previously, when two accounts (Account-1 and Account-2) were
logged in, the app always defaulted to showing the home page
of Account-1 on launch. If the app was closed and the user
opened a notification from Account-2, the navigation stack
would be:
  HomePage(Account-1) -> MessageListPage(Account-2)

This commit fixes that behaviour, now when a notification is
opened while the app is closed, the home page will correspond
to the account associated with the notification's conversation.

This addresses zulip#1210 for background notifications.

Author: rajveermalviya

lib/notifications/display.dart

@@ -14,11 +14,11 @@ import '../log.dart';
 import '../model/binding.dart';
 import '../model/localizations.dart';
 import '../model/narrow.dart';
+import '../model/store.dart';
 import '../widgets/app.dart';
 import '../widgets/color.dart';
 import '../widgets/dialog.dart';
 import '../widgets/message_list.dart';
-import '../widgets/page.dart';
 import '../widgets/store.dart';
 import '../widgets/theme.dart';
 
@@ -452,36 +452,58 @@ class NotificationDisplayManager {
 
   static String _personKey(Uri realmUrl, int userId) => "$realmUrl|$userId";
 
+  /// Provides the route and the account ID by parsing the notification URL.
+  ///
+  /// The URL must have been generated using [NotificationOpenPayload.buildUrl]
+  /// while creating the notification.
+  ///
+  /// Returns null if the associated account is not found in the global
+  /// store.
+  static ({Route<void> route, int accountId})? routeForNotification({
+    required GlobalStore globalStore,
+    required Uri url,
+  }) {
+    assert(debugLog('got notif: url: $url'));
+    assert(url.scheme == 'zulip' && url.host == 'notification');
+    final payload = NotificationOpenPayload.parseUrl(url);
+
+    final account = globalStore.accounts.firstWhereOrNull((account) =>
+      account.realmUrl == payload.realmUrl && account.userId == payload.userId);
+    if (account == null) return null;
+
+    final route = MessageListPage.buildRoute(
+      accountId: account.id,
+      // TODO(#82): Open at specific message, not just conversation
+      narrow: payload.narrow);
+    return (route: route, accountId: account.id);
+  }
+
   /// Navigates to the [MessageListPage] of the specific conversation
   /// given the `zulip://notification/…` Android intent data URL,
   /// generated with [NotificationOpenPayload.buildUrl] while creating
   /// the notification.
   static Future<void> navigateForNotification(Uri url) async {
     assert(debugLog('opened notif: url: $url'));
 
-    assert(url.scheme == 'zulip' && url.host == 'notification');
-    final payload = NotificationOpenPayload.parseUrl(url);
-
     NavigatorState navigator = await ZulipApp.navigator;
     final context = navigator.context;
     assert(context.mounted);
     if (!context.mounted) return; // TODO(linter): this is impossible as there's no actual async gap, but the use_build_context_synchronously lint doesn't see that
 
     final zulipLocalizations = ZulipLocalizations.of(context);
     final globalStore = GlobalStoreWidget.of(context);
-    final account = globalStore.accounts.firstWhereOrNull((account) =>
-      account.realmUrl == payload.realmUrl && account.userId == payload.userId);
-    if (account == null) { // TODO(log)
+
+    final notificationResult =
+      routeForNotification(globalStore: globalStore, url: url);
+    if (notificationResult == null) { // TODO(log)
       showErrorDialog(context: context,
         title: zulipLocalizations.errorNotificationOpenTitle,
         message: zulipLocalizations.errorNotificationOpenAccountMissing);
       return;
     }
 
     // TODO(nav): Better interact with existing nav stack on notif open
-    unawaited(navigator.push(MaterialAccountWidgetRoute<void>(accountId: account.id,
-      // TODO(#82): Open at specific message, not just conversation
-      page: MessageListPage(initNarrow: payload.narrow))));
+    unawaited(navigator.push(notificationResult.route));
   }
 
   static Future<Uint8List?> _fetchBitmap(Uri url) async {

lib/widgets/app.dart

@@ -155,7 +155,38 @@ class _ZulipAppState extends State<ZulipApp> with WidgetsBindingObserver {
   InitialRouteListFactory _handleGenerateInitialRoutes(BuildContext context) {
     final globalStore = GlobalStoreWidget.of(context);
 
+    void showNotificationErrorDialog() async {
+      final navigator = await ZulipApp.navigator;
+      final navigatorContext = navigator.context;
+      assert(navigatorContext.mounted);
+      // TODO(linter): this is impossible as there's no actual async gap, but
+      //   the use_build_context_synchronously lint doesn't see that.
+      if (!navigatorContext.mounted) return;
+
+      final zulipLocalizations = ZulipLocalizations.of(navigatorContext);
+      showErrorDialog(context: navigatorContext,
+        title: zulipLocalizations.errorNotificationOpenTitle,
+        message: zulipLocalizations.errorNotificationOpenAccountMissing);
+    }
+
     return (String initialRoute) {
+      final initialRouteUrl = Uri.parse(initialRoute);
+      if (initialRouteUrl case Uri(scheme: 'zulip', host: 'notification')) {
+        final notificationResult = NotificationDisplayManager.routeForNotification(
+          globalStore: globalStore,
+          url: initialRouteUrl);
+
+        if (notificationResult != null) {
+          return [
+            HomePage.buildRoute(accountId: notificationResult.accountId),
+            notificationResult.route,
+          ];
+        } else {
+          showNotificationErrorDialog();
+          // Fallthrough to show default route below.
+        }
+      }
+
       // TODO(#524) choose initial account as last one used
       final initialAccountId = globalStore.accounts.firstOrNull?.id;
       return [
@@ -167,18 +198,10 @@ class _ZulipAppState extends State<ZulipApp> with WidgetsBindingObserver {
     };
   }
 
-  Future<void> _handleInitialRoute() async {
-    final initialRouteUrl = Uri.parse(WidgetsBinding.instance.platformDispatcher.defaultRouteName);
-    if (initialRouteUrl case Uri(scheme: 'zulip', host: 'notification')) {
-      await NotificationDisplayManager.navigateForNotification(initialRouteUrl);
-    }
-  }
-
   @override
   void initState() {
     super.initState();
     WidgetsBinding.instance.addObserver(this);
-    _handleInitialRoute();
   }
 
   @override

test/notifications/display_test.dart

@@ -1130,6 +1130,45 @@ void main() {
       takeStartingRoutes();
       matchesNavigation(check(pushedRoutes).single, account, message);
     });
+
+    testWidgets('uses associated account as initial account; if initial route', (tester) async {
+      addTearDown(testBinding.reset);
+      addTearDown(tester.binding.platformDispatcher.clearDefaultRouteNameTestValue);
+
+      final accountA = eg.selfAccount;
+      final accountB = eg.otherAccount;
+      final message = eg.streamMessage();
+      final data = messageFcmMessage(message, account: accountB);
+      await testBinding.globalStore.add(accountA, eg.initialSnapshot());
+      await testBinding.globalStore.add(accountB, eg.initialSnapshot());
+
+      final intentDataUrl = NotificationOpenPayload(
+        realmUrl: data.realmUrl,
+        userId: data.userId,
+        narrow: switch (data.recipient) {
+          FcmMessageChannelRecipient(:var streamId, :var topic) =>
+            TopicNarrow(streamId, topic),
+          FcmMessageDmRecipient(:var allRecipientIds) =>
+            DmNarrow(allRecipientIds: allRecipientIds, selfUserId: data.userId),
+        }).buildUrl();
+      tester.binding.platformDispatcher.defaultRouteNameTestValue = intentDataUrl.toString();
+
+      await prepare(tester, early: true);
+      check(pushedRoutes).isEmpty(); // GlobalStore hasn't loaded yet
+
+      await tester.pump();
+      check(pushedRoutes).deepEquals(<Condition<Object?>>[
+        (it) => it.isA<MaterialAccountWidgetRoute>()
+          ..accountId.equals(accountB.id)
+          ..page.isA<HomePage>(),
+        (it) => it.isA<MaterialAccountWidgetRoute>()
+          ..accountId.equals(accountB.id)
+          ..page.isA<MessageListPage>()
+            .initNarrow.equals(SendableNarrow.ofMessage(message,
+              selfUserId: accountB.userId))
+      ]);
+      pushedRoutes.clear();
+    });
   });
 
   group('NotificationOpenPayload', () {