Add account switcher

Fixes #146

lib/controllers/accounts.dart

@@ -0,0 +1,60 @@
+import "dart:convert";
+
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:nexus/controllers/key.dart";
+import "package:nexus/models/account.dart";
+
+class AccountsController extends AsyncNotifier<IList<Account>> {
+  @override
+  Future<IList<Account>> build() async {
+    final stored = await ref.watch(
+      KeyController.provider(KeyController.accountsKey).future,
+    );
+    final accounts = IList<Account>(
+      (json.decode(stored ?? "[]") as List).map(
+        (account) => .fromJson(account),
+      ),
+    );
+
+    // Installs from before account switching are logged into the legacy slot
+    return accounts.isEmpty
+        ? .new([const .new(id: Account.legacyId)])
+        : accounts;
+  }
+
+  Future<void> _set(IList<Account> accounts) async {
+    state = .data(accounts);
+    await ref
+        .read(KeyController.provider(KeyController.accountsKey).notifier)
+        .set(json.encode(accounts.map((account) => account.toJson()).toList()));
+  }
+
+  Future<IList<Account>> get _current async {
+    await future;
+    return state.requireValue;
+  }
+
+  Future<void> save(Account account) async {
+    final accounts = await _current;
+    final index = accounts.indexWhere((existing) => existing.id == account.id);
+
+    await _set(
+      index == -1 ? accounts.add(account) : accounts.replace(index, account),
+    );
+  }
+
+  Future<void> reset(String id) async {
+    final accounts = await _current;
+    final index = accounts.indexWhere((account) => account.id == id);
+    if (index != -1) await _set(accounts.replace(index, .new(id: id)));
+  }
+
+  Future<void> remove(String id) async =>
+      _set((await _current).removeWhere((account) => account.id == id));
+
+  static final provider =
+      AsyncNotifierProvider<AccountsController, IList<Account>>(
+        AccountsController.new,
+      );
+}

lib/controllers/active_account.dart

@@ -0,0 +1,53 @@
+import "package:collection/collection.dart";
+import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:nexus/controllers/accounts.dart";
+import "package:nexus/controllers/key.dart";
+import "package:nexus/controllers/notification_request.dart";
+import "package:nexus/models/account.dart";
+import "package:shared_preferences/shared_preferences.dart";
+
+typedef AccountSwitch = ({String accountId, int? notificationRowId});
+
+class ActiveAccountController(
+  final String accountId,
+  final void Function(AccountSwitch next) restart,
+) extends Notifier<String> {
+  @override
+  String build() => accountId;
+
+  static Future<String> stored() async =>
+      await SharedPreferencesAsync().getString(
+        KeyController.activeAccountKey,
+      ) ??
+      Account.legacyId;
+
+  /// Restarts the app as [accountId], then opens [notificationRowId] if given.
+  Future<void> switchTo(String accountId, {int? notificationRowId}) async {
+    if (accountId == state) {
+      if (notificationRowId != null) {
+        ref
+            .read(NotificationRequestController.provider.notifier)
+            .request(notificationRowId);
+      }
+      return;
+    }
+
+    final accounts = await ref.read(AccountsController.provider.future);
+    if (!accounts.any((account) => account.id == accountId)) return;
+
+    if (accounts.firstWhereOrNull((account) => account.id == state)
+        case Account(userId: null)) {
+      await ref.read(AccountsController.provider.notifier).remove(state);
+    }
+
+    await ref
+        .read(KeyController.provider(KeyController.activeAccountKey).notifier)
+        .set(accountId);
+
+    restart((accountId: accountId, notificationRowId: notificationRowId));
+  }
+
+  static final provider = NotifierProvider<ActiveAccountController, String>(
+    () => throw UnimplementedError("Provided by AccountScope"),
+  );
+}

lib/controllers/client.dart

@@ -1,15 +1,18 @@
 import "dart:async";
 import "dart:ffi";
 import "dart:io";
-import "dart:isolate";
 import "dart:math";
 
 import "package:fast_immutable_collections/fast_immutable_collections.dart";
 import "package:ffi/ffi.dart";
 import "package:flutter/cupertino.dart";
 import "package:intl/intl.dart";
+import "package:nexus/controllers/accounts.dart";
+import "package:nexus/controllers/active_account.dart";
 import "package:nexus/controllers/settings.dart";
 import "package:nexus/helpers/extensions/gomuks_buffer.dart";
+import "package:nexus/main.dart";
+import "package:nexus/models/account.dart";
 import "package:nexus/models/capabilities.dart";
 import "package:nexus/models/content/message.dart";
 import "package:nexus/models/event.dart";
@@ -57,47 +60,47 @@ import "package:nexus/models/space_hierarchy.dart";
 import "package:nexus/models/spec_versions_response.dart";
 import "package:nexus/src/third_party/gomuks.g.dart";
 import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:path/path.dart";
 import "package:path_provider/path_provider.dart";
 
-class ClientController extends AsyncNotifier<int> {
+class ClientController(final String? accountId) extends AsyncNotifier<int> {
   @override
   Future<int> build() async {
-    debugPrint("Setting Gomuks env...");
-    if (Platform.isAndroid || Platform.isIOS) {
-      final env = {
-        "GOMUKS_ROOT": (await getApplicationSupportDirectory()).path,
-        "GOMUKS_CACHE_HOME": (await getApplicationCacheDirectory()).path,
-      };
-      for (final MapEntry(:key, :value) in env.entries) {
-        final keyPtr = key.toNativeUtf8().cast<Char>();
-        final valuePtr = value.toNativeUtf8().cast<Char>();
-        try {
-          GomuksSetEnv(keyPtr, valuePtr);
-        } finally {
-          calloc
-            ..free(keyPtr)
-            ..free(valuePtr);
-        }
+    final String account =
+        accountId ?? ref.watch(ActiveAccountController.provider);
+    if (accountId == null && !isInBackground) await _deleteRemovedAccounts();
+
+    final environment = await _environment(account);
+
+    debugPrint("Setting Gomuks env for $account...");
+    for (final MapEntry(:key, :value) in environment.entries) {
+      final keyPtr = key.toNativeUtf8().cast<Char>();
+      final valuePtr = value.toNativeUtf8().cast<Char>();
+      try {
+        GomuksSetEnv(keyPtr, valuePtr);
+      } finally {
+        calloc
+          ..free(keyPtr)
+          ..free(valuePtr);
       }
     }
 
     debugPrint("Initializing Gomuks...");
-    final handle = await Isolate.run(() {
-      final bufferPointer = GomuksConfig(
-        matrix: .new(
-          initialDeviceDisplayName:
-              "Nexus on ${toBeginningOfSentenceCase(Platform.operatingSystem)}",
-        ),
-      ).toJson().toGomuksBufferPtr();
+    final bufferPointer = GomuksConfig(
+      matrix: .new(
+        initialDeviceDisplayName:
+            "Nexus on ${toBeginningOfSentenceCase(Platform.operatingSystem)}",
+      ),
+    ).toJson().toGomuksBufferPtr();
 
-      try {
-        return GomuksInit(bufferPointer.ref);
-      } finally {
-        calloc
-          ..free(bufferPointer.ref.base)
-          ..free(bufferPointer);
-      }
-    });
+    final int handle;
+    try {
+      handle = GomuksInit(bufferPointer.ref);
+    } finally {
+      calloc
+        ..free(bufferPointer.ref.base)
+        ..free(bufferPointer);
+    }
 
     if (!ref.mounted) {
       GomuksDestroy(handle);
@@ -106,9 +109,60 @@ class ClientController extends AsyncNotifier<int> {
 
     ref.onDispose(() => GomuksDestroy(handle));
 
+    if (accountId != null) {
+      await _callGomuksMethod(handle, {}, GomuksHandlePushAsync);
+    }
+
     return handle;
   }
 
+  static Future<({Directory data, Directory cache})>
+  _accountsDirectories() async => (
+    data: Directory(
+      join((await getApplicationSupportDirectory()).path, "accounts"),
+    ),
+    cache: Directory(
+      join((await getApplicationCacheDirectory()).path, "accounts"),
+    ),
+  );
+
+  static Future<IMap<String, String>> _environment(String accountId) async {
+    if (accountId == Account.legacyId) {
+      // Keep the directories gomuks used before account switching existed
+      final isMobile = Platform.isAndroid || Platform.isIOS;
+      return .new({
+        "GOMUKS_ROOT": isMobile
+            ? (await getApplicationSupportDirectory()).path
+            : Platform.environment["GOMUKS_ROOT"] ?? "",
+        "GOMUKS_CACHE_HOME": isMobile
+            ? (await getApplicationCacheDirectory()).path
+            : Platform.environment["GOMUKS_CACHE_HOME"] ?? "",
+      });
+    }
+
+    final (:data, :cache) = await _accountsDirectories();
+    return .new({
+      "GOMUKS_ROOT": join(data.path, accountId),
+      "GOMUKS_CACHE_HOME": join(cache.path, accountId),
+    });
+  }
+
+  // Can't be done on removal, since the old container still has them open
+  Future<void> _deleteRemovedAccounts() async {
+    final ids = (await ref.read(AccountsController.provider.future))
+        .map((account) => account.id)
+        .toISet();
+
+    final (:data, :cache) = await _accountsDirectories();
+    final removed = await Stream.fromIterable([data, cache])
+        .where((directory) => directory.existsSync())
+        .asyncExpand((directory) => directory.list())
+        .where((entry) => !ids.contains(basename(entry.path)))
+        .toList();
+
+    await Future.wait(removed.map((entry) => entry.delete(recursive: true)));
+  }
+
   /// Calls gomuks with [data] as JSON, returning its decoded response.
   Future<dynamic> callGomuksMethod(
     Map<String, dynamic> data,
@@ -118,8 +172,18 @@ class ClientController extends AsyncNotifier<int> {
       Pointer<NativeFunction<Void Function(GomuksResponse)>> callback,
     )
     call,
-  ) async {
-    final handle = await future;
+  ) async => _callGomuksMethod(await future, data, call);
+
+  static Future<dynamic> _callGomuksMethod(
+    int handle,
+    Map<String, dynamic> data,
+    void Function(
+      int handle,
+      GomuksOwnedBuffer data,
+      Pointer<NativeFunction<Void Function(GomuksResponse)>> callback,
+    )
+    call,
+  ) {
     final buffer = data.toGomuksOwnedBuffer();
 
     final completer = Completer<dynamic>();
@@ -421,6 +485,12 @@ class ClientController extends AsyncNotifier<int> {
   }
 
   static final provider = AsyncNotifierProvider<ClientController, int>(
-    ClientController.new,
+    () => ClientController(null),
   );
+
+  /// The instance for an account other than the active one.
+  static final forAccount =
+      AsyncNotifierProvider.family<ClientController, int, String>(
+        ClientController.new,
+      );
 }

lib/controllers/gomuks_listener.dart

@@ -3,9 +3,12 @@ import "dart:ffi";
 import "dart:io";
 import "dart:isolate";
 
+import "package:collection/collection.dart";
 import "package:fast_immutable_collections/fast_immutable_collections.dart";
 import "package:flutter/foundation.dart";
 import "package:nexus/controllers/account_data.dart";
+import "package:nexus/controllers/accounts.dart";
+import "package:nexus/controllers/active_account.dart";
 import "package:nexus/controllers/app_paused.dart";
 import "package:nexus/controllers/client.dart";
 import "package:nexus/controllers/client_state.dart";
@@ -152,6 +155,45 @@ class GomuksListenerController extends AsyncNotifier<void> {
 
     if (!ref.mounted) return;
 
+    // Cached so the account switcher and push routing have them while the
+    // account isn't active
+    ref.listen(
+      ClientStateController.provider.select(
+        (state) => (state?.isInitialized, state?.userId, state?.deviceId),
+      ),
+      (_, ids) => Future(() async {
+        final id = ref.read(ActiveAccountController.provider);
+        final accounts = ref.read(AccountsController.provider.notifier);
+
+        switch (ids) {
+          // Logged out, so it shouldn't show as an account anymore
+          case (true, null, _):
+            await accounts.reset(id);
+          case (_, final userId?, final deviceId):
+            final previous = (await ref.read(
+              AccountsController.provider.future,
+            )).firstWhereOrNull((account) => account.id == id);
+            final profile =
+                (await ref
+                        .read(ClientController.provider.notifier)
+                        .getProfile(userId))
+                    .profile;
+
+            // Fetching the profile fails while offline, so keep what was cached
+            await accounts.save(
+              .new(
+                id: id,
+                userId: userId,
+                deviceId: deviceId,
+                displayName: profile.displayName ?? previous?.displayName,
+                avatar: profile.avatarUrl ?? previous?.avatar,
+              ),
+            );
+        }
+      }).catchError(showError),
+      fireImmediately: true,
+    );
+
     if (Platform.isAndroid || Platform.isIOS) {
       // Mobile OSes block network access for backgrounded apps, so pause
       // syncing instead of letting it fail.

lib/controllers/key.dart

@@ -1,23 +1,38 @@
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
 import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:nexus/controllers/active_account.dart";
 import "package:nexus/controllers/shared_prefs.dart";
+import "package:nexus/models/account.dart";
 
 class KeyController(final String key) extends AsyncNotifier<String?> {
   static const String spaceKey = "space";
   static const String roomKey = "room";
   static const String pushKeyKey = "pushKey";
+  static const String accountsKey = "accounts";
+  static const String activeAccountKey = "activeAccount";
+
+  static const ISet<String> _perAccountKeys = ISetConst({spaceKey, roomKey});
+
+  String get _prefsKey {
+    final account = ref.read(ActiveAccountController.provider);
+
+    return _perAccountKeys.contains(key) && account != Account.legacyId
+        ? "$account/$key"
+        : key;
+  }
 
   @override
   Future<String?> build() =>
-      ref.watch(SharedPrefsController.provider).getString(key);
+      ref.watch(SharedPrefsController.provider).getString(_prefsKey);
 
   Future<void> set(String? value) async {
     final prefs = ref.read(SharedPrefsController.provider);
     state = .data(value);
 
     if (value == null) {
-      await prefs.remove(key);
+      await prefs.remove(_prefsKey);
     } else {
-      await prefs.setString(key, value);
+      await prefs.setString(_prefsKey, value);
     }
   }
 

lib/controllers/notification.dart

@@ -4,12 +4,12 @@ import "dart:io";
 
 import "package:flutter/services.dart";
 import "package:material_ui/material_ui.dart";
+import "package:nexus/controllers/active_account.dart";
 import "package:nexus/controllers/portal.dart";
 import "package:nexus/controllers/sidebar_page.dart";
 import "package:nexus/main.dart";
 import "package:flutter_local_notifications/flutter_local_notifications.dart";
 import "package:flutter_riverpod/flutter_riverpod.dart";
-import "package:nexus/controllers/notification_request.dart";
 import "package:nexus/models/push_notification.dart";
 import "package:xdg_desktop_portal/xdg_desktop_portal.dart";
 
@@ -41,17 +41,7 @@ class NotificationController
           macOS: darwin,
         ),
         onDidReceiveNotificationResponse: (details) {
-          if (details.payload == null) return;
-
-          if (int.tryParse(details.payload!) case final rowId?) {
-            navigatorKey.currentState?.popUntil((route) => route.isFirst);
-            ref
-                .read(SidebarPageController.provider.notifier)
-                .set(.notifications);
-            ref
-                .read(NotificationRequestController.provider.notifier)
-                .request(rowId);
-          }
+          if (details.payload case final payload?) _open(payload);
         },
       );
     }
@@ -64,21 +54,36 @@ class NotificationController
           return;
         }
 
-        if (int.tryParse(call.arguments) case int rowId) {
-          navigatorKey.currentState?.popUntil((route) => route.isFirst);
-          ref.read(SidebarPageController.provider.notifier).set(.notifications);
-          ref
-              .read(NotificationRequestController.provider.notifier)
-              .request(rowId);
-        }
+        if (call.arguments case final String payload) _open(payload);
       });
-
-      ref.onDispose(() => notificationChannel.setMethodCallHandler(null));
     }
 
     return notifications;
   }
 
+  static String payloadFor(String accountId, int rowId) => "$accountId:$rowId";
+
+  void _open(String payload) {
+    final (accountId, rowId) = switch (payload.split(":")) {
+      [final accountId, final rowId] => (accountId, int.tryParse(rowId)),
+      // From before notifications were per account
+      [final rowId] => (null, int.tryParse(rowId)),
+      _ => (null, null),
+    };
+    if (rowId == null) return;
+
+    navigatorKey.currentState?.popUntil((route) => route.isFirst);
+    ref.read(SidebarPageController.provider.notifier).set(.notifications);
+
+    ref
+        .read(ActiveAccountController.provider.notifier)
+        .switchTo(
+          accountId ?? ref.read(ActiveAccountController.provider),
+          notificationRowId: rowId,
+        )
+        .onError(showError);
+  }
+
   Future<bool> requestPermissions() async {
     if (Platform.isLinux) {
       return true;
@@ -149,10 +154,12 @@ class NotificationController
   }
 
   /// Passing [message] shows it as a chat message in the conversation for
-  /// [threadId], naming the sender in group chats.
+  /// [threadId], naming the sender in group chats. [subtitle] is shown on
+  /// platforms that support it.
   Future<void> send({
     required int id,
     required String title,
+    String? subtitle,
     required String body,
     String? payload,
     String? threadId,
@@ -208,6 +215,7 @@ class NotificationController
         : null;
 
     final darwin = DarwinNotificationDetails(
+      subtitle: subtitle,
       presentSound: sound,
       threadIdentifier: threadId,
     );
@@ -222,6 +230,7 @@ class NotificationController
             ? .new(
                 "general",
                 "General",
+                subText: subtitle,
                 silent: !sound,
                 when: timestamp?.millisecondsSinceEpoch,
                 largeIcon: icon == null
@@ -232,6 +241,7 @@ class NotificationController
             : .new(
                 "messages",
                 "Messages",
+                subText: subtitle,
                 silent: !sound,
                 when: timestamp?.millisecondsSinceEpoch,
                 category: .message,

lib/controllers/settings_sections.dart

@@ -11,7 +11,6 @@ import "package:nexus/controllers/account_data.dart";
 import "package:nexus/controllers/client.dart";
 import "package:nexus/controllers/client_state.dart";
 import "package:nexus/controllers/enabled_image_packs.dart";
-import "package:nexus/controllers/init_complete.dart";
 import "package:nexus/controllers/notification.dart";
 import "package:nexus/controllers/profile.dart";
 import "package:nexus/controllers/rooms.dart";
@@ -809,43 +808,6 @@ class SettingsSectionsController
                 ),
                 icon: Icons.key_off,
               ),
-              .new(
-                title: "Log Out",
-                description:
-                    "Log out of your account, returning you to the login page.",
-                builder: (title, description, icon) => Builder(
-                  builder: (context) {
-                    final colorScheme = Theme.of(context).colorScheme;
-                    return M3EButton.icon(
-                      onPressed: () async {
-                        final container = ProviderScope.containerOf(context);
-
-                        final route = ModalRoute.of(context)!;
-                        Navigator.of(context).popUntil((r) => r.isFirst);
-                        await route.completed;
-
-                        await container
-                            .read(UnifiedPushController.provider.notifier)
-                            .deregister()
-                            .onError(showError);
-                        container.invalidate(InitCompleteController.provider);
-                        await container
-                            .read(ClientController.provider.notifier)
-                            .logout()
-                            .onError(showError);
-                      },
-                      label: Text(title),
-                      icon: Icon(icon),
-                      tooltip: description,
-                      decoration: .styleFrom(
-                        backgroundColor: colorScheme.errorContainer,
-                        foregroundColor: colorScheme.onErrorContainer,
-                      ),
-                    );
-                  },
-                ),
-                icon: Icons.logout,
-              ),
             ]),
           ),
         ]),

lib/controllers/sidebar_page.dart

@@ -1,9 +1,14 @@
 import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:nexus/controllers/notification_request.dart";
 import "package:nexus/models/sidebar_page.dart";
 
 class SidebarPageController extends Notifier<SidebarPage> {
+  // Show the notification that switched accounts, if one did
   @override
-  SidebarPage build() => .rooms;
+  SidebarPage build() =>
+      ref.read(NotificationRequestController.provider) == null
+      ? .rooms
+      : .notifications;
 
   void set(SidebarPage page) => state = page;
 

lib/controllers/unified_push.dart

@@ -2,11 +2,15 @@ import "dart:async";
 import "dart:convert";
 import "dart:io";
 
+import "package:collection/collection.dart";
 import "package:flutter/foundation.dart";
 import "package:flutter_riverpod/flutter_riverpod.dart";
 import "package:intl/intl.dart";
+import "package:nexus/controllers/accounts.dart";
+import "package:nexus/controllers/active_account.dart";
 import "package:nexus/controllers/selected_room.dart";
 import "package:nexus/controllers/notification.dart";
+import "package:nexus/controllers/client_state.dart";
 import "package:nexus/controllers/push_key.dart";
 import "package:nexus/main.dart";
 import "package:nexus/controllers/client.dart";
@@ -18,6 +22,19 @@ import "package:window_manager/window_manager.dart";
 class UnifiedPushController extends AsyncNotifier<String?> {
   Completer<void>? _endpoint;
 
+  /// The account [instance] (its device ID) belongs to, or the active one for
+  /// devices registered before account switching.
+  Future<String> _accountFor(String instance) async =>
+      (await ref.read(AccountsController.provider.future))
+          .firstWhereOrNull((account) => account.deviceId == instance)
+          ?.id ??
+      ref.read(ActiveAccountController.provider);
+
+  ClientController _clientFor(String accountId) =>
+      accountId == ref.read(ActiveAccountController.provider)
+      ? ref.read(ClientController.provider.notifier)
+      : ref.read(ClientController.forAccount(accountId).notifier);
+
   @override
   Future<String?> build() async {
     if (!Platform.isLinux && !Platform.isAndroid) return null;
@@ -36,23 +53,21 @@ class UnifiedPushController extends AsyncNotifier<String?> {
               .read(PushKeyController.provider(instance).notifier)
               .set(pushKey);
 
-          await ref
-              .read(ClientController.provider.notifier)
-              .registerPusher(
-                .new(
-                  appDisplayName: "Nexus",
-                  appId: "nexus.federated.nexus",
-                  data: .webPush(
-                    url: .parse(endpoint.url),
-                    auth: endpoint.pubKeySet!.auth,
-                  ),
-                  deviceDisplayName:
-                      "Nexus on ${toBeginningOfSentenceCase(Platform.operatingSystem)}",
-                  kind: .webPush,
-                  lang: "en",
-                  pushKey: pushKey,
-                ),
-              );
+          await _clientFor(await _accountFor(instance)).registerPusher(
+            .new(
+              appDisplayName: "Nexus",
+              appId: "nexus.federated.nexus",
+              data: .webPush(
+                url: .parse(endpoint.url),
+                auth: endpoint.pubKeySet!.auth,
+              ),
+              deviceDisplayName:
+                  "Nexus on ${toBeginningOfSentenceCase(Platform.operatingSystem)}",
+              kind: .webPush,
+              lang: "en",
+              pushKey: pushKey,
+            ),
+          );
 
           state = .data(await UnifiedPush.getDistributor());
         });
@@ -82,12 +97,17 @@ class UnifiedPushController extends AsyncNotifier<String?> {
             "Failed to decrypt notification. Try toggling off and on UnifiedPush in settings.",
           );
         }
-        final notification = await ref
-            .read(ClientController.provider.notifier)
-            .handlePush(json.decode(String.fromCharCodes(message.content)));
+        final accountId = await _accountFor(instance);
+        final client = _clientFor(accountId);
+        final isActive =
+            accountId == ref.read(ActiveAccountController.provider);
+        final notification = await client.handlePush(
+          json.decode(String.fromCharCodes(message.content)),
+        );
 
         if (notification == null ||
             (!isInBackground &&
+                isActive &&
                 (!Platform.isAndroid &&
                     (WindowManager.instance.getCurrent()?.isFocused ?? true)) &&
                 ref.read(SelectedRoomController.provider) ==
@@ -96,7 +116,8 @@ class UnifiedPushController extends AsyncNotifier<String?> {
           return;
         }
 
-        final client = ref.read(ClientController.provider.notifier);
+        final hasOtherAccounts =
+            (await ref.read(AccountsController.provider.future)).length > 1;
 
         final icon = notification.roomAvatar == null
             ? null
@@ -116,17 +137,20 @@ class UnifiedPushController extends AsyncNotifier<String?> {
         await ref
             .read(NotificationController.provider.notifier)
             .send(
-              // Android stacks messages into one conversation per room
+              // Android stacks messages into one conversation per room (and
+              // account, since two accounts can share a room)
               id:
-                  (Platform.isAndroid
-                          ? notification.roomId
-                          : notification.eventId)
+                  "$accountId/${Platform.isAndroid ? notification.roomId : notification.eventId}"
                       .hashCode &
                   0x7fffffff,
-              threadId: notification.roomId,
+              threadId: "$accountId/${notification.roomId}",
               title: notification.roomName,
+              subtitle: hasOtherAccounts ? notification.self.id : null,
               body: notification.text,
-              payload: notification.eventRowId.toString(),
+              payload: NotificationController.payloadFor(
+                accountId,
+                notification.eventRowId,
+              ),
               timestamp: notification.timestamp,
               icon: icon,
               sound: notification.sound,
@@ -147,14 +171,32 @@ class UnifiedPushController extends AsyncNotifier<String?> {
 
     if (!registered || isInBackground) return null;
 
-    try {
-      if (await deregisterIfDisabled()) return null;
+    ref.listen(
+      ClientStateController.provider.select((state) => state?.isLoggedIn),
+      (previous, isLoggedIn) => Future(() async {
+        if (isLoggedIn != true) return;
+        if (await deregisterIfDisabled()) return;
 
-      return await register();
-    } catch (error, stackTrace) {
-      showError(error, stackTrace);
-      return null;
-    }
+        // On startup, only accounts with push on (which have a push key).
+        // After logging in, push is on by default.
+        final deviceId = ref.read(ClientStateController.provider)?.deviceId;
+        if (previous != false &&
+            (deviceId == null ||
+                await ref.read(PushKeyController.provider(deviceId).future) ==
+                    null)) {
+          return;
+        }
+
+        try {
+          await register();
+        } on UnsupportedError {
+          // The settings tile explains that the homeserver can't send Web Push
+        }
+      }).catchError(showError),
+      fireImmediately: true,
+    );
+
+    return null;
   }
 
   /// Registers with [distributor], or the current/default distributor if none
@@ -166,12 +208,13 @@ class UnifiedPushController extends AsyncNotifier<String?> {
       await deregister();
     }
 
+    // Not loading until logged in, since the app waits for this
+    final deviceId = await ref
+        .read(GomuksListenerController.provider.notifier)
+        .deviceId();
+
     state = .loading();
     try {
-      final deviceId = await ref
-          .read(GomuksListenerController.provider.notifier)
-          .deviceId();
-
       await Future(() async {
         final capabilities = await ref
             .read(ClientController.provider.notifier)
@@ -238,10 +281,10 @@ class UnifiedPushController extends AsyncNotifier<String?> {
 
     final keyProvider = PushKeyController.provider(instance);
     final key = await ref.read(keyProvider.future);
+    final accountId = await _accountFor(instance);
 
     if (key != null) {
-      await ref
-          .read(ClientController.provider.notifier)
+      await _clientFor(accountId)
           .deregisterPusher(.new(appId: "nexus.federated.nexus", pushKey: key));
       await ref.read(keyProvider.notifier).set(null);
     } else {
@@ -251,7 +294,9 @@ class UnifiedPushController extends AsyncNotifier<String?> {
     }
 
     await UnifiedPush.unregister(instance);
-    state = .data(null);
+    if (accountId == ref.read(ActiveAccountController.provider)) {
+      state = .data(null);
+    }
   }
 
   static final provider = AsyncNotifierProvider<UnifiedPushController, String?>(

lib/helpers/extensions/log_out.dart

@@ -0,0 +1,53 @@
+import "package:collection/collection.dart";
+import "package:flutter_riverpod/experimental/mutation.dart";
+import "package:nexus/controllers/accounts.dart";
+import "package:nexus/controllers/active_account.dart";
+import "package:nexus/controllers/client.dart";
+import "package:nexus/controllers/init_complete.dart";
+import "package:nexus/controllers/unified_push.dart";
+import "package:nexus/main.dart";
+
+extension LogOut on MutationTarget {
+  Future<void> logOut(String accountId) async {
+    final accounts = await container.read(AccountsController.provider.future);
+    final account = accounts.firstWhereOrNull(
+      (account) => account.id == accountId,
+    );
+    if (account == null) return;
+
+    final isActive =
+        accountId == container.read(ActiveAccountController.provider);
+    final client = isActive
+        ? container.read(ClientController.provider.notifier)
+        : container.read(ClientController.forAccount(accountId).notifier);
+
+    if (account.deviceId case final deviceId?) {
+      await container
+          .read(UnifiedPushController.provider.notifier)
+          .deregister(deviceId)
+          .onError(showError);
+    }
+    if (isActive) container.invalidate(InitCompleteController.provider);
+    await client.logout().onError(showError);
+
+    if (!isActive) {
+      container.invalidate(ClientController.forAccount(accountId));
+      await container
+          .read(AccountsController.provider.notifier)
+          .remove(accountId);
+      return;
+    }
+
+    final other = accounts.firstWhereOrNull(
+      (account) => account.id != accountId,
+    );
+    if (other == null) return;
+
+    await container
+        .read(AccountsController.provider.notifier)
+        .remove(accountId);
+    await container
+        .read(ActiveAccountController.provider.notifier)
+        .switchTo(other.id);
+  }
+}

lib/main.dart

@@ -5,6 +5,7 @@ import "package:flutter/foundation.dart";
 import "package:flutter_riverpod/flutter_riverpod.dart";
 import "package:material_emoji_picker/material_emoji_picker.dart";
 import "package:media_kit/media_kit.dart";
+import "package:nexus/controllers/active_account.dart";
 import "package:nexus/controllers/client.dart";
 import "package:nexus/controllers/client_state.dart";
 import "package:nexus/controllers/gomuks_listener.dart";
@@ -20,6 +21,7 @@ import "package:nexus/widgets/pages/chat.dart";
 import "package:nexus/widgets/pages/select_server.dart";
 import "package:nexus/widgets/pages/settings.dart";
 import "package:nexus/widgets/pages/verify.dart";
+import "package:nexus/widgets/account_scope.dart";
 import "package:nexus/widgets/appbar.dart";
 import "package:nexus/widgets/error_dialog.dart";
 import "package:nexus/widgets/loading.dart";
@@ -74,10 +76,17 @@ void main(List<String> args) async {
       Platform.environment["FLUTTER_HEADLESS"] != null ||
       args.contains("--unifiedpush-bg");
 
+  final accountId = await ActiveAccountController.stored();
+
   if (isInBackground) {
-    await ProviderContainer()
-        .read(UnifiedPushController.provider.future)
-        .timeout(Duration(seconds: 5));
+    await ProviderContainer(
+      overrides: [
+        // Nothing to switch to in the background
+        ActiveAccountController.provider.overrideWith(
+          () => ActiveAccountController(accountId, (_) {}),
+        ),
+      ],
+    ).read(UnifiedPushController.provider.future).timeout(Duration(seconds: 5));
 
     await Future.delayed(Duration(seconds: 10));
     exit(0);
@@ -90,7 +99,8 @@ void main(List<String> args) async {
     }
 
     runApp(
-      ProviderScope(
+      AccountScope(
+        initialAccountId: accountId,
         retry: (_, _) => null,
         observers: [
           // Change false to true if you want debug information on provider reloads

lib/models/account.dart

@@ -0,0 +1,26 @@
+import "package:freezed_annotation/freezed_annotation.dart";
+
+part "account.freezed.dart";
+part "account.g.dart";
+
+/// An account slot, each with its own gomuks directories.
+///
+/// Everything but [id] is cached from the last time the account was active, so
+/// the account switcher and push routing work while it isn't.
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable()
+class const Account({
+  required final String id,
+  final String? userId,
+  final String? deviceId,
+  final String? displayName,
+  final Uri? avatar,
+}) with _$Account {
+  /// The slot accounts from before account switching existed
+  static const String legacyId = "default";
+
+  Map<String, Object?> toJson() => _$AccountToJson(this);
+
+  factory Account.fromJson(Map<String, Object?> json) =>
+      _$AccountFromJson(json);
+}

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,