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

@@ -453,36 +453,57 @@ 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 and shows an error dialog if the associated account is not
+  /// found in the global store.
+  static AccountRoute<void>? routeForNotification({
+    required BuildContext context,
+    required Uri url,
+  }) {
+    final globalStore = GlobalStoreWidget.of(context);
+    final zulipLocalizations = ZulipLocalizations.of(context);
+
+    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.origin == payload.realmUrl.origin
+                && account.userId == payload.userId);
+    if (account == null) { // TODO(log)
+      showErrorDialog(context: context,
+        title: zulipLocalizations.errorNotificationOpenTitle,
+        message: zulipLocalizations.errorNotificationOpenAccountMissing);
+      return null;
+    }
+
+    return MessageListPage.buildRoute(
+      accountId: account.id,
+      // TODO(#82): Open at specific message, not just conversation
+      narrow: payload.narrow);
+  }
+
   /// 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)
-      showErrorDialog(context: context,
-        title: zulipLocalizations.errorNotificationOpenTitle,
-        message: zulipLocalizations.errorNotificationOpenAccountMissing);
-      return;
-    }
+    final route = routeForNotification(context: context, url: url);
+    if (route == null) return; // TODO(log)
 
     // 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(route));
   }
 
   static Future<Uint8List?> _fetchBitmap(Uri url) async {

lib/widgets/app.dart

@@ -143,7 +143,6 @@ class _ZulipAppState extends State<ZulipApp> with WidgetsBindingObserver {
   void initState() {
     super.initState();
     WidgetsBinding.instance.addObserver(this);
-    _handleInitialRoute();
   }
 
   @override
@@ -157,8 +156,25 @@ class _ZulipAppState extends State<ZulipApp> with WidgetsBindingObserver {
     // we use the Navigator which should be available when this callback is
     // called and it's context should have the required dependencies.
     final context = ZulipApp.navigatorKey.currentContext!;
-    final globalStore = GlobalStoreWidget.of(context);
 
+    final initialRouteUrl = Uri.tryParse(initialRoute);
+    if (initialRouteUrl case Uri(scheme: 'zulip', host: 'notification')) {
+      final route = NotificationDisplayManager.routeForNotification(
+        context: context,
+        url: initialRouteUrl);
+
+      if (route != null) {
+        return [
+          HomePage.buildRoute(accountId: route.accountId),
+          route,
+        ];
+      } else {
+        // The account didn't match any existing accounts,
+        // fall through to show the default route below.
+      }
+    }
+
+    final globalStore = GlobalStoreWidget.of(context);
     // TODO(#524) choose initial account as last one used
     final initialAccountId = globalStore.accounts.firstOrNull?.id;
     return [
@@ -169,13 +185,6 @@ 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
   Future<bool> didPushRouteInformation(routeInformation) async {
     switch (routeInformation.uri) {

test/notifications/display_test.dart

@@ -960,11 +960,12 @@ void main() {
   group('NotificationDisplayManager open', () {
     late List<Route<void>> pushedRoutes;
 
-    void takeStartingRoutes({bool withAccount = true}) {
+    void takeStartingRoutes({Account? account, bool withAccount = true}) {
+      account ??= eg.selfAccount;
       final expected = <Condition<Object?>>[
         if (withAccount)
           (it) => it.isA<MaterialAccountWidgetRoute>()
-            ..accountId.equals(eg.selfAccount.id)
+            ..accountId.equals(account!.id)
             ..page.isA<HomePage>()
         else
           (it) => it.isA<WidgetRoute>().page.isA<ChooseAccountPage>(),
@@ -1130,6 +1131,36 @@ void main() {
       takeStartingRoutes();
       matchesNavigation(check(pushedRoutes).single, account, message);
     });
+
+    testWidgets('uses associated account as initial account; if initial route', (tester) async {
+      addTearDown(testBinding.reset);
+
+      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();
+      addTearDown(tester.binding.platformDispatcher.clearDefaultRouteNameTestValue);
+      tester.binding.platformDispatcher.defaultRouteNameTestValue = intentDataUrl.toString();
+
+      await prepare(tester, early: true);
+      check(pushedRoutes).isEmpty(); // GlobalStore hasn't loaded yet
+
+      await tester.pump();
+      takeStartingRoutes(account: accountB);
+      matchesNavigation(check(pushedRoutes).single, accountB, message);
+    });
   });
 
   group('NotificationOpenPayload', () {