login: Support logging out of an account

Fixes: zulip#463

assets/l10n/app_en.arb

@@ -19,6 +19,22 @@
   "@chooseAccountPageTitle": {
     "description": "Title for ChooseAccountPage"
   },
+  "chooseAccountPageLogOutButton": "Log out",
+  "@chooseAccountPageLogOutButton": {
+    "description": "Label for the 'Log out' button for an account on the choose-account page"
+  },
+  "logOutConfirmationDialogTitle": "Log out?",
+  "@logOutConfirmationDialogTitle": {
+    "description": "Title for a confirmation dialog for logging out."
+  },
+  "logOutConfirmationDialogMessage": "To use this account in the future, you will have to re-enter the URL for your organization and your account information.",
+  "@logOutConfirmationDialogMessage": {
+    "description": "Message for a confirmation dialog for logging out."
+  },
+  "logOutConfirmationDialogConfirmButton": "Log out",
+  "@logOutConfirmationDialogConfirmButton": {
+    "description": "Label for the 'Log out' button on a confirmation dialog for logging out."
+  },
   "chooseAccountButtonAddAnAccount": "Add an account",
   "@chooseAccountButtonAddAnAccount": {
     "description": "Label for ChooseAccountPage button to add an account"

lib/widgets/actions.dart

@@ -6,16 +6,53 @@
 /// in order to present success or error feedback to the user through the UI.
 library;
 
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 import 'package:flutter_gen/gen_l10n/zulip_localizations.dart';
 
 import '../api/model/model.dart';
 import '../api/model/narrow.dart';
 import '../api/route/messages.dart';
 import '../model/narrow.dart';
+import '../model/store.dart';
+import '../notifications/receive.dart';
 import 'dialog.dart';
 import 'store.dart';
 
+Future<void> logOutAccount(BuildContext context, int accountId) async {
+  final globalStore = GlobalStoreWidget.of(context);
+
+  final account = globalStore.getAccount(accountId);
+  if (account == null) return; // TODO(log)
+
+  // Unawaited, to not block removing the account on this request.
+  unawaited(unregisterToken(globalStore, accountId));
+
+  await globalStore.removeAccount(accountId);
+}
+
+Future<void> unregisterToken(GlobalStore globalStore, int accountId) async {
+  final account = globalStore.getAccount(accountId);
+  if (account == null) return; // TODO(log)
+
+  // TODO(#322) use actual acked push token; until #322, this is just null.
+  final token = account.ackedPushToken
+    // Try the current token as a fallback; maybe the server has registered
+    // it and we just haven't recorded that fact in the client.
+    ?? NotificationService.instance.token.value;
+  if (token == null) return;
+
+  final connection = globalStore.apiConnectionFromAccount(account);
+  try {
+    await NotificationService.unregisterToken(connection, token: token);
+  } catch (e) {
+    // TODO retry? handle failures?
+  } finally {
+    connection.close();
+  }
+}
+
 Future<void> markNarrowAsRead(BuildContext context, Narrow narrow) async {
   final store = PerAccountStoreWidget.of(context);
   final connection = store.connection;

lib/widgets/app.dart

@@ -8,8 +8,10 @@ import 'package:flutter_gen/gen_l10n/zulip_localizations.dart';
 import '../log.dart';
 import '../model/localizations.dart';
 import '../model/narrow.dart';
+import '../model/store.dart';
 import '../notifications/display.dart';
 import 'about_zulip.dart';
+import 'actions.dart';
 import 'app_bar.dart';
 import 'dialog.dart';
 import 'inbox.dart';
@@ -232,11 +234,45 @@ class ChooseAccountPage extends StatelessWidget {
     required Widget title,
     Widget? subtitle,
   }) {
+    final designVariables = DesignVariables.of(context);
+    final zulipLocalizations = ZulipLocalizations.of(context);
+    final materialLocalizations = MaterialLocalizations.of(context);
     return Card(
       clipBehavior: Clip.hardEdge,
       child: ListTile(
         title: title,
         subtitle: subtitle,
+        trailing: MenuAnchor(
+          menuChildren: [
+            MenuItemButton(
+              onPressed: () {
+                showSuggestedActionDialog(context: context,
+                  title: zulipLocalizations.logOutConfirmationDialogTitle,
+                  message: zulipLocalizations.logOutConfirmationDialogMessage,
+                  // TODO(#1032) "destructive" style for action button
+                  actionButtonText: zulipLocalizations.logOutConfirmationDialogConfirmButton,
+                  onActionButtonPress: () {
+                    // TODO error handling if db write fails?
+                    logOutAccount(context, accountId);
+                  });
+              },
+              child: Text(zulipLocalizations.chooseAccountPageLogOutButton)),
+          ],
+        builder: (BuildContext context, MenuController controller, Widget? child) {
+          return IconButton(
+            tooltip: materialLocalizations.showMenuTooltip, // "Show menu"
+            onPressed: () {
+              if (controller.isOpen) {
+                controller.close();
+              } else {
+                controller.open();
+              }
+            },
+            icon: Icon(Icons.adaptive.more, color: designVariables.icon));
+        }),
+        // The default trailing padding with M3 is 24px. Decrease by 12 because
+        // IconButton (the "…" button) comes with 12px padding on all sides.
+        contentPadding: const EdgeInsetsDirectional.only(start: 16, end: 12),
         onTap: () => Navigator.push(context,
           HomePage.buildRoute(accountId: accountId))));
   }

lib/widgets/page.dart

@@ -40,6 +40,7 @@ mixin AccountPageRouteMixin<T extends Object?> on PageRoute<T> {
     return PerAccountStoreWidget(
       accountId: accountId,
       placeholder: const LoadingPlaceholderPage(),
+      routeToRemoveOnLogout: this,
       child: super.buildPage(context, animation, secondaryAnimation));
   }
 }

lib/widgets/store.dart

@@ -1,7 +1,9 @@
 import 'package:flutter/material.dart';
+import 'package:flutter/scheduler.dart';
 
 import '../model/binding.dart';
 import '../model/store.dart';
+import 'page.dart';
 
 /// Provides access to the app's data.
 ///
@@ -112,11 +114,19 @@ class PerAccountStoreWidget extends StatefulWidget {
     super.key,
     required this.accountId,
     this.placeholder = const LoadingPlaceholder(),
+    this.routeToRemoveOnLogout,
     required this.child,
   });
 
   final int accountId;
   final Widget placeholder;
+
+  /// A per-account [Route] that should be removed on logout.
+  ///
+  /// Use this when the widget is a page on a route that should go away
+  /// when the account is logged out, instead of lingering with [placeholder].
+  final AccountPageRouteMixin? routeToRemoveOnLogout;
+
   final Widget child;
 
   /// The user's data for the relevant Zulip account for this widget.
@@ -195,6 +205,16 @@ class _PerAccountStoreWidgetState extends State<PerAccountStoreWidget> {
   void didChangeDependencies() {
     super.didChangeDependencies();
     final globalStore = GlobalStoreWidget.of(context);
+    final accountExists = globalStore.getAccount(widget.accountId) != null;
+    if (!accountExists) {
+      // logged out
+      _setStore(null);
+      if (widget.routeToRemoveOnLogout != null) {
+        SchedulerBinding.instance.addPostFrameCallback(
+          (_) => Navigator.of(context).removeRoute(widget.routeToRemoveOnLogout!));
+      }
+      return;
+    }
     // If we already have data, get it immediately. This avoids showing one
     // frame of loading indicator each time we have a new PerAccountStoreWidget.
     final store = globalStore.perAccountSync(widget.accountId);
@@ -212,13 +232,13 @@ class _PerAccountStoreWidgetState extends State<PerAccountStoreWidget> {
           // The account was logged out while its store was loading.
           // This widget will be showing [placeholder] perpetually,
           // but that's OK as long as other code will be removing it from the UI
-          // (for example by removing a per-account route from the nav).
+          // (usually by using [routeToRemoveOnLogout]).
         }
       }();
     }
   }
 
-  void _setStore(PerAccountStore store) {
+  void _setStore(PerAccountStore? store) {
     if (store != this.store) {
       setState(() {
         this.store = store;

test/model/test_store.dart

@@ -47,6 +47,10 @@ class TestGlobalStore extends GlobalStore {
   /// but that breach is sometimes convenient for tests.
   bool useCachedApiConnections = false;
 
+  void clearCachedApiConnections() {
+    _apiConnections.clear();
+  }
+
   /// Get or construct a [FakeApiConnection] with the given arguments.
   ///
   /// To access the same [FakeApiConnection] that the code under test will get,
@@ -120,9 +124,21 @@ class TestGlobalStore extends GlobalStore {
     // Nothing to do.
   }
 
+  static const Duration removeAccountDuration = Duration(milliseconds: 1);
+
+  /// Consume the log of calls made to [doRemoveAccount].
+  List<int> takeDoRemoveAccountCalls() {
+    final result = _doRemoveAccountCalls;
+    _doRemoveAccountCalls = null;
+    return result ?? [];
+  }
+  List<int>? _doRemoveAccountCalls;
+
   @override
   Future<void> doRemoveAccount(int accountId) async {
-    // Nothing to do.
+    (_doRemoveAccountCalls ??= []).add(accountId);
+    await Future<void>.delayed(removeAccountDuration);
+    // Nothing else to do.
   }
 
   @override