feat: Make waiting on init db optional

This can improve the start-up time of apps.
The three big db reads on init are
loading account data, rooms and
device keys.
This makes it now possible to let
them run parallel
(while it may depend on platform
if this has any effect)
and the init() method can skip
awaiting them. They will
be at least awaited before handling
the first received sync.
So the app can already display the
room list before device keys are
loaded and request the first sync
from the server before anything
else is loaded from the DB.

lib/src/client.dart

@@ -893,6 +893,10 @@ class Client extends MatrixApi {
   /// If one of [newToken], [newUserID], [newDeviceID], [newDeviceName] is set then
   /// all of them must be set! If you don't set them, this method will try to
   /// get them from the database.
+  ///
+  /// Set [waitForFirstSync] and [waitUntilLoadCompletedLoaded] to false to speed this
+  /// up. You can then wait for `roomsLoading`, `accountDataLoading` and
+  /// `userDeviceKeysLoading` where it is necessary.
   Future<void> init({
     String? newToken,
     Uri? newHomeserver,
@@ -901,6 +905,7 @@ class Client extends MatrixApi {
     String? newDeviceID,
     String? newOlmAccount,
     bool waitForFirstSync = true,
+    bool waitUntilLoadCompletedLoaded = true,
   }) async {
     if ((newToken != null ||
             newUserID != null ||
@@ -1012,11 +1017,22 @@ class Client extends MatrixApi {
             encryption?.pickledOlmAccount,
           );
         }
-        _userDeviceKeys = await database.getUserDeviceKeys(this);
-        _rooms = await database.getRoomList(this);
+        userDeviceKeysLoading = database
+            .getUserDeviceKeys(this)
+            .then((keys) => _userDeviceKeys = keys);
+        roomsLoading = database.getRoomList(this).then((rooms) {
+          _rooms = rooms;
+          _sortRooms();
+        });
         _sortRooms();
-        accountData = await database.getAccountData();
+        accountDataLoading =
+            database.getAccountData().then((data) => accountData = data);
         presences.clear();
+        if (waitUntilLoadCompletedLoaded) {
+          await userDeviceKeysLoading;
+          await roomsLoading;
+          await accountDataLoading;
+        }
       }
       _initLock = false;
       _loginState = LoginState.loggedIn;
@@ -1154,6 +1170,9 @@ class Client extends MatrixApi {
 
       final database = this.database;
       if (database != null) {
+        await userDeviceKeysLoading;
+        await roomsLoading;
+        await accountDataLoading;
         _currentTransaction = database.transaction(() async {
           await _handleSync(syncResp);
           if (prevBatch != syncResp.nextBatch) {
@@ -1648,6 +1667,10 @@ class Client extends MatrixApi {
     _sortLock = false;
   }
 
+  Future? userDeviceKeysLoading;
+  Future? roomsLoading;
+  Future? accountDataLoading;
+
   /// A map of known device keys per user.
   Map<String, DeviceKeysList> get userDeviceKeys => _userDeviceKeys;
   Map<String, DeviceKeysList> _userDeviceKeys = {};

lib/src/room.dart

@@ -1882,6 +1882,7 @@ class Room {
 
   /// Returns all known device keys for all participants in this room.
   Future<List<DeviceKeys>> getUserDeviceKeys() async {
+    await client.userDeviceKeysLoading;
     final deviceKeys = <DeviceKeys>[];
     final users = await requestParticipants();
     for (final user in users) {