app: Keep IntGlobalSetting.lastVisitedAccountId up-to-date

Author: sm-sayedi

lib/model/actions.dart

@@ -4,6 +4,7 @@ import 'package:flutter/foundation.dart';
 
 import '../notifications/display.dart';
 import '../notifications/receive.dart';
+import 'settings.dart';
 import 'store.dart';
 
 // TODO: Make this a part of GlobalStore
@@ -21,6 +22,18 @@ Future<void> logOutAccount(GlobalStore globalStore, int accountId) async {
   await globalStore.removeAccount(accountId);
 }
 
+Future<void> removeLastVisitedAccountIfNecessary(GlobalStore store, int loggedOutAccountId) async {
+  // If account is not logged out yet, do nothing.
+  if (store.getAccount(loggedOutAccountId) != null) return;
+
+  // If the logged-out account is different than the last visited one, do nothing.
+  if (loggedOutAccountId != store.settings.getInt(IntGlobalSetting.lastVisitedAccountId)) {
+    return;
+  }
+
+  await store.settings.setInt(IntGlobalSetting.lastVisitedAccountId, null);
+}
+
 Future<void> unregisterToken(GlobalStore globalStore, int accountId) async {
   final account = globalStore.getAccount(accountId);
   if (account == null) return; // TODO(log)

lib/model/settings.dart

@@ -226,6 +226,12 @@ enum BoolGlobalSetting {
 enum IntGlobalSetting {
   /// A pseudo-setting recording the id of the account the user has visited most
   /// recently, from the list of all the available accounts on the device.
+  ///
+  /// In some very rare cases, this may point to an account that actually
+  /// doesn't exist on the device, for example, when the last visited account is
+  /// logged out, but this field didn't get updated (set to null) for whatever
+  /// reason. For cases like these, it's the responsibility of the callers to
+  /// check for the availability of the account that relates to this id.
   lastVisitedAccountId,
 
   // Former settings which might exist in the database,

lib/widgets/app.dart

@@ -8,6 +8,7 @@ import '../generated/l10n/zulip_localizations.dart';
 import '../log.dart';
 import '../model/actions.dart';
 import '../model/localizations.dart';
+import '../model/settings.dart';
 import '../model/store.dart';
 import '../notifications/open.dart';
 import 'about_zulip.dart';
@@ -254,6 +255,7 @@ class _ZulipAppState extends State<ZulipApp> with WidgetsBindingObserver {
             if (widget.navigatorObservers != null)
               ...widget.navigatorObservers!,
             _PreventEmptyStack(),
+            _UpdateLastVisitedAccount(GlobalStoreWidget.settingsOf(context)),
           ],
           builder: (BuildContext context, Widget? child) {
             if (!ZulipApp.ready.value) {
@@ -305,6 +307,20 @@ class _PreventEmptyStack extends NavigatorObserver {
   }
 }
 
+class _UpdateLastVisitedAccount extends NavigatorObserver {
+  _UpdateLastVisitedAccount(this.globalSettings);
+
+  final GlobalSettingsStore globalSettings;
+
+  @override
+  void didChangeTop(Route<void> topRoute, Route<void>? previousTopRoute) {
+    final old = globalSettings.getInt(IntGlobalSetting.lastVisitedAccountId);
+    if (topRoute case AccountPageRouteMixin(accountId: var new_) when new_ != old) {
+      globalSettings.setInt(IntGlobalSetting.lastVisitedAccountId, new_);
+    }
+  }
+}
+
 class ChooseAccountPage extends StatelessWidget {
   const ChooseAccountPage({super.key});
 
@@ -337,7 +353,13 @@ class ChooseAccountPage extends StatelessWidget {
                 if (await dialog.result == true) {
                   if (!context.mounted) return;
                   // TODO error handling if db write fails?
-                  unawaited(logOutAccount(GlobalStoreWidget.of(context), accountId));
+                  unawaited(Future(() async {
+                    if (!context.mounted) return;
+                    await logOutAccount(GlobalStoreWidget.of(context), accountId);
+                    if (!context.mounted) return;
+                    await removeLastVisitedAccountIfNecessary(
+                      GlobalStoreWidget.of(context), accountId);
+                  }));
                 }
               },
               child: Text(zulipLocalizations.chooseAccountPageLogOutButton)),