added support for multiple accounts with an account switcher in settings

lib/view/login/login.dart

@@ -1,12 +1,13 @@
 import 'dart:async';
+import 'dart:developer';
 
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 
 import '../../background/widget_background_task.dart';
 import '../../session/session_lifecycle.dart';
+import '../../session/session_manager.dart';
 import '../../state/app/modules/account/bloc/account_bloc.dart';
-import '../../state/app/modules/account/bloc/account_state.dart';
 import '../../state/app/modules/settings/bloc/settings_cubit.dart';
 import '../../storage/dev_tools_settings.dart';
 import '../../storage/settings.dart' as model;
@@ -20,7 +21,10 @@ import 'widgets/login_branding.dart';
 import 'widgets/login_card.dart';
 
 class Login extends StatefulWidget {
-  const Login({super.key});
+  /// Signs in another account while one is active; offers to go back.
+  final bool addingAccount;
+
+  const Login({super.key, this.addingAccount = false});
 
   @override
   State<Login> createState() => _LoginState();
@@ -65,59 +69,100 @@ class _LoginState extends State<Login> with SingleTickerProviderStateMixin {
     super.dispose();
   }
 
-  void _onLoginSuccess() {
+  Future<void> _onLoginSuccess() async {
     Haptics.heavyAccent();
+    final accountBloc = context.read<AccountBloc>();
+    // Fade the login content out before handing over to the post-login splash.
+    // Both share the red backdrop, so this reads as one continuous transition
+    // instead of an abrupt swap.
+    final finished = SessionLifecycle.finishLogin();
+    await _fade.reverse().orCancel.onError<TickerCanceled>((_, _) {});
+    String? accountId;
+    try {
+      accountId = await finished;
+    } on Object catch (e) {
+      log('Login: finishing failed: $e');
+      accountId = SessionManager().activeAccount?.id;
+    }
     // Re-register the periodic refresh (cancelAll runs on logout) and kick
     // off an immediate one-off so the widget populates within seconds
     // instead of waiting up to 30 minutes for the next periodic slot.
     unawaited(WidgetBackgroundTask.initialize());
     unawaited(WidgetBackgroundTask.requestImmediateRefresh());
-    // Fade the login content out before handing over to the post-login splash.
-    // Both share the red backdrop, so this reads as one continuous transition
-    // instead of an abrupt swap.
-    _fade.reverse().whenComplete(() {
-      if (!mounted) return;
-      context.read<AccountBloc>().setStatus(AccountStatus.loggedIn);
-    });
+    accountBloc.activated(accountId, freshLogin: true);
+  }
+
+  Future<void> _cancelAddAccount() async {
+    final accountBloc = context.read<AccountBloc>();
+    await SessionLifecycle.cancelAddAccount();
+    accountBloc.activated(SessionManager().activeAccount?.id);
   }
 
   @override
-  Widget build(BuildContext context) => Scaffold(
-    backgroundColor: _marianumRed,
-    body: FadeTransition(
-      opacity: _fade,
-      child: SafeArea(
-        child: LayoutBuilder(
-          builder: (context, constraints) => SingleChildScrollView(
-            padding: const EdgeInsets.symmetric(horizontal: 24),
-            child: Center(
-              child: ConstrainedBox(
-                constraints: BoxConstraints(
-                  minHeight: constraints.maxHeight,
-                  maxWidth: 420,
+  Widget build(BuildContext context) => PopScope(
+    canPop: !widget.addingAccount,
+    onPopInvokedWithResult: (didPop, _) {
+      if (!didPop && !_busy) unawaited(_cancelAddAccount());
+    },
+    child: Scaffold(
+      backgroundColor: _marianumRed,
+      appBar: widget.addingAccount
+          ? AppBar(
+              backgroundColor: Colors.transparent,
+              foregroundColor: Colors.white,
+              elevation: 0,
+              leading: ListenableBuilder(
+                listenable: _controller,
+                builder: (context, _) => IconButton(
+                  icon: const Icon(Icons.close),
+                  tooltip: 'Abbrechen',
+                  onPressed: _busy ? null : _cancelAddAccount,
                 ),
-                // spaceBetween statt Spacer-in-IntrinsicHeight: Letzteres würde
-                // die Column bei Inhaltsänderungen im unteren Block auf die
-                // intrinsic-Höhe pinnen und ein paar Pixel Overflow erzeugen.
-                child: Column(
-                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
-                  children: [
-                    Column(
-                      children: [
-                        const LoginHeader(),
-                        const SizedBox(height: 28),
-                        LoginCard(
-                          controller: _controller,
-                          onSuccess: _onLoginSuccess,
-                        ),
-                        const SizedBox(height: 12),
-                      ],
-                    ),
-                    const Column(
-                      mainAxisSize: MainAxisSize.min,
-                      children: [_EndpointLink(), LoginFooter()],
-                    ),
-                  ],
+              ),
+              title: const Text('Konto hinzufügen'),
+            )
+          : null,
+      body: FadeTransition(
+        opacity: _fade,
+        child: SafeArea(
+          child: LayoutBuilder(
+            builder: (context, constraints) => SingleChildScrollView(
+              padding: const EdgeInsets.symmetric(horizontal: 24),
+              child: Center(
+                child: ConstrainedBox(
+                  constraints: BoxConstraints(
+                    minHeight: constraints.maxHeight,
+                    maxWidth: 420,
+                  ),
+                  // spaceBetween statt Spacer-in-IntrinsicHeight: Letzteres würde
+                  // die Column bei Inhaltsänderungen im unteren Block auf die
+                  // intrinsic-Höhe pinnen und ein paar Pixel Overflow erzeugen.
+                  child: Column(
+                    mainAxisAlignment: MainAxisAlignment.spaceBetween,
+                    children: [
+                      Column(
+                        children: [
+                          LoginHeader(addingAccount: widget.addingAccount),
+                          const SizedBox(height: 28),
+                          LoginCard(
+                            controller: _controller,
+                            onSuccess: _onLoginSuccess,
+                            addingAccount: widget.addingAccount,
+                          ),
+                          const SizedBox(height: 12),
+                        ],
+                      ),
+                      Column(
+                        mainAxisSize: MainAxisSize.min,
+                        children: [
+                          // The new account must live on the server the app
+                          // already talks to.
+                          if (!widget.addingAccount) const _EndpointLink(),
+                          const LoginFooter(),
+                        ],
+                      ),
+                    ],
+                  ),
                 ),
               ),
             ),
@@ -126,6 +171,8 @@ class _LoginState extends State<Login> with SingleTickerProviderStateMixin {
       ),
     ),
   );
+
+  bool get _busy => _controller.loading;
 }
 
 /// Subtle text link above the footer that surfaces the currently selected

lib/view/login/widgets/login_branding.dart

@@ -1,7 +1,10 @@
 import 'package:flutter/material.dart';
 
 class LoginHeader extends StatelessWidget {
-  const LoginHeader({super.key});
+  /// Signs in an additional account instead of the first one.
+  final bool addingAccount;
+
+  const LoginHeader({this.addingAccount = false, super.key});
 
   @override
   Widget build(BuildContext context) => Column(
@@ -29,7 +32,10 @@ class LoginHeader extends StatelessWidget {
       ),
       const SizedBox(height: 6),
       Text(
-        'Stundenplan, Talk, Dateien und mehr - alles an einem Ort für deinen Schulalltag am Marianum Fulda.',
+        addingAccount
+            ? 'Melde ein weiteres Konto an. In den Einstellungen kannst du '
+                  'danach jederzeit zwischen deinen Konten wechseln.'
+            : 'Stundenplan, Talk, Dateien und mehr - alles an einem Ort für deinen Schulalltag am Marianum Fulda.',
         textAlign: TextAlign.center,
         style: TextStyle(
           color: Colors.white.withValues(alpha: 0.85),

lib/view/login/widgets/login_card.dart

@@ -12,9 +12,13 @@ class LoginCard extends StatefulWidget {
   final LoginController controller;
   final VoidCallback onSuccess;
 
+  /// Signs in an additional account instead of the first one.
+  final bool addingAccount;
+
   const LoginCard({
     required this.controller,
     required this.onSuccess,
+    this.addingAccount = false,
     super.key,
   });
 
@@ -83,8 +87,11 @@ class _LoginCardState extends State<LoginCard> {
     return Form(
       key: _formKey,
       child: LoginCardFrame(
-        title: 'Anmelden',
-        hint: 'Melde dich mit deinen Marianum-Zugangsdaten an.',
+        title: widget.addingAccount ? 'Konto hinzufügen' : 'Anmelden',
+        hint: widget.addingAccount
+            ? 'Melde dich mit den Marianum-Zugangsdaten des Kontos an, das '
+                  'du hinzufügen möchtest.'
+            : 'Melde dich mit deinen Marianum-Zugangsdaten an.',
         children: [
           TextFormField(
             key: const Key('login-username-field'),
@@ -127,7 +134,7 @@ class _LoginCardState extends State<LoginCard> {
           const SizedBox(height: 20),
           LoginSubmitButton(
             key: const Key('login-submit-button'),
-            label: 'Anmelden',
+            label: widget.addingAccount ? 'Hinzufügen' : 'Anmelden',
             loading: loading,
             onPressed: _submit,
           ),