Add account switcher

Fixes #146

lib/widgets/account_scope.dart

@@ -0,0 +1,41 @@
+import "package:flutter_hooks/flutter_hooks.dart";
+import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:material_ui/material_ui.dart";
+import "package:nexus/controllers/active_account.dart";
+import "package:nexus/controllers/notification_request.dart";
+
+/// Runs [child] as one account, in a [ProviderScope] of its own that's
+/// replaced when switching accounts, so no state leaks between them.
+class const AccountScope({
+  required final String initialAccountId,
+  required final Widget child,
+  final List<ProviderObserver>? observers,
+  final Duration? Function(int retryCount, Object error)? retry,
+  super.key,
+}) extends HookWidget {
+  @override
+  Widget build(BuildContext context) {
+    final active = useState<AccountSwitch>((
+      accountId: initialAccountId,
+      notificationRowId: null,
+    ));
+
+    return ProviderScope(
+      key: ValueKey(active.value.accountId),
+      retry: retry,
+      observers: observers,
+      overrides: [
+        ActiveAccountController.provider.overrideWith(
+          () => ActiveAccountController(
+            active.value.accountId,
+            (next) => active.value = next,
+          ),
+        ),
+        NotificationRequestController.provider.overrideWithBuild(
+          (_, _) => active.value.notificationRowId,
+        ),
+      ],
+      child: child,
+    );
+  }
+}

lib/widgets/account_switcher.dart

@@ -0,0 +1,125 @@
+import "package:collection/collection.dart";
+import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:material_ui/material_ui.dart";
+import "package:nexus/controllers/accounts.dart";
+import "package:nexus/controllers/active_account.dart";
+import "package:nexus/helpers/extensions/log_out.dart";
+import "package:nexus/main.dart";
+import "package:nexus/models/account.dart";
+import "package:nexus/widgets/adaptive_menu_button.dart";
+import "package:nexus/widgets/avatar_or_hash.dart";
+
+/// Switches between, adds and logs out of accounts. With [onlyWithOthers], it's
+/// hidden when there's only one account.
+class const AccountSwitcher({final bool onlyWithOthers = false, super.key})
+    extends ConsumerWidget {
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final danger = Theme.of(context).colorScheme.error;
+    final accounts = ref.watch(AccountsController.provider).value;
+    final activeId = ref.watch(ActiveAccountController.provider);
+    if (accounts == null || (onlyWithOthers && accounts.length < 2)) {
+      return const SizedBox.shrink();
+    }
+
+    String nameOf(Account account) =>
+        account.displayName ?? account.userId ?? "New account";
+
+    Widget avatarOf(Account account, double dimension) => AvatarOrHash(
+      account.avatar,
+      nameOf(account),
+      dimension: dimension,
+      fallback: account.userId == null
+          ? Icon(Icons.account_circle, size: dimension)
+          : null,
+    );
+
+    final active = accounts.firstWhereOrNull(
+      (account) => account.id == activeId,
+    );
+
+    void switchTo(String accountId) => ref
+        .read(ActiveAccountController.provider.notifier)
+        .switchTo(accountId)
+        .onError(showError);
+
+    return AdaptiveMenuButton(
+      tooltip: "Switch account",
+      icon: active == null
+          ? const Icon(Icons.account_circle)
+          : avatarOf(active, 28),
+      itemBuilder: (_) => [
+        for (final account in accounts)
+          PopupMenuItem(
+            onTap: () => switchTo(account.id),
+            child: ListTile(
+              selected: account.id == activeId,
+              leading: avatarOf(account, 32),
+              title: Text(nameOf(account)),
+              subtitle: switch (account) {
+                Account(displayName: _?, :final userId?) => Text(userId),
+                _ => null,
+              },
+              trailing: account.userId == null
+                  ? null
+                  // Inside the menu, so it can close it
+                  : Builder(
+                      builder: (menuContext) => IconButton(
+                        tooltip: "Log out",
+                        icon: Icon(Icons.logout, color: danger),
+                        onPressed: () async {
+                          Navigator.of(menuContext).pop();
+
+                          final confirmed = await showDialog<bool>(
+                            context: context,
+                            builder: (dialogContext) => AlertDialog(
+                              title: Text("Log out of ${nameOf(account)}?"),
+                              content: Text(
+                                account.id == activeId
+                                    ? "You'll be switched to another account, or returned to the login page if this is your only one."
+                                    : "You'll stop receiving notifications for this account.",
+                              ),
+                              actions: [
+                                TextButton(
+                                  onPressed: () =>
+                                      Navigator.of(dialogContext).pop(false),
+                                  child: const Text("Cancel"),
+                                ),
+                                TextButton(
+                                  onPressed: () =>
+                                      Navigator.of(dialogContext).pop(true),
+                                  style: TextButton.styleFrom(
+                                    foregroundColor: danger,
+                                  ),
+                                  child: const Text("Log out"),
+                                ),
+                              ],
+                            ),
+                          );
+                          if (confirmed != true) return;
+
+                          await ref.logOut(account.id).onError(showError);
+                        },
+                      ),
+                    ),
+            ),
+          ),
+        const PopupMenuDivider(),
+        PopupMenuItem(
+          onTap: () {
+            final id = DateTime.now().millisecondsSinceEpoch.toString();
+            ref
+                .read(AccountsController.provider.notifier)
+                .save(.new(id: id))
+                .then((_) => switchTo(id))
+                .onError(showError);
+          },
+          child: const ListTile(
+            leading: Icon(Icons.person_add),
+            title: Text("Add account"),
+          ),
+        ),
+      ],
+    );
+  }
+}

lib/widgets/pages/select_server.dart

@@ -13,6 +13,7 @@ import "package:nexus/models/gomuks_exception.dart";
 import "package:nexus/models/homeserver.dart";
 import "package:nexus/models/oauth_auth_code_response.dart";
 import "package:nexus/widgets/pages/settings.dart";
+import "package:nexus/widgets/account_switcher.dart";
 import "package:nexus/widgets/appbar.dart";
 import "package:nexus/widgets/divider_text.dart";
 
@@ -122,6 +123,7 @@ class const SelectServerPage({super.key}) extends HookConsumerWidget {
     return Scaffold(
       appBar: Appbar(
         actions: .new([
+          const AccountSwitcher(onlyWithOthers: true),
           IconButton(
             onPressed: () =>
                 showDialog(context: context, builder: (_) => SettingsPage()),

lib/widgets/pages/verify.dart

@@ -7,6 +7,7 @@ import "package:nexus/models/client_state.dart";
 import "package:nexus/helpers/extensions/show_adaptive_sheet.dart";
 import "package:nexus/widgets/loading.dart";
 import "package:nexus/widgets/pages/settings.dart";
+import "package:nexus/widgets/account_switcher.dart";
 import "package:nexus/widgets/appbar.dart";
 import "package:nexus/helpers/required_validator_helper.dart";
 import "package:nexus/widgets/reset_encryption_sheet.dart";
@@ -50,6 +51,7 @@ class const VerifyPage({super.key}) extends HookConsumerWidget {
     return Scaffold(
       appBar: Appbar(
         actions: .new([
+          const AccountSwitcher(onlyWithOthers: true),
           IconButton(
             onPressed: () =>
                 showDialog(context: context, builder: (_) => SettingsPage()),

lib/widgets/room_list.dart

@@ -8,6 +8,7 @@ import "package:navigation_rail_m3e/navigation_rail_m3e.dart";
 import "package:nexus/helpers/extensions/get_all_child_rooms.dart";
 import "package:nexus/helpers/extensions/room_destinations.dart";
 import "package:nexus/helpers/extensions/show_adaptive_sheet.dart";
+import "package:nexus/widgets/account_switcher.dart";
 import "package:nexus/widgets/adaptive_menu_button.dart";
 import "package:nexus/models/nav_page.dart";
 import "package:nexus/widgets/appbar.dart";
@@ -192,6 +193,7 @@ class const SpacesRail({super.key}) extends ConsumerWidget {
                       ],
                       icon: const Icon(Icons.add),
                     ),
+                    const AccountSwitcher(),
                     const IconButton(
                       tooltip: "Explore other rooms (Not yet implemented)",
                       onPressed: null,