Move heavy getUserDeviceKeys processing off the UI thread

lib/src/database/matrix_sdk_database.dart

@@ -19,6 +19,7 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:math';
+import 'dart:isolate';
 
 import 'package:sqflite_common/sqflite.dart';
 
@@ -798,52 +799,28 @@ class MatrixSdkDatabase extends DatabaseApi with DatabaseFileStorage {
         if (deviceKeysOutdated.isEmpty) {
           return {};
         }
-        final res = <String, DeviceKeysList>{};
+
         final userDeviceKeys = await _userDeviceKeysBox.getAllValues();
         final userCrossSigningKeys =
             await _userCrossSigningKeysBox.getAllValues();
-        for (final userId in deviceKeysOutdated.keys) {
-          final deviceKeysBoxKeys = userDeviceKeys.keys.where((tuple) {
-            final tupleKey = TupleKey.fromString(tuple);
-            return tupleKey.parts.first == userId;
-          });
-          final crossSigningKeysBoxKeys =
-              userCrossSigningKeys.keys.where((tuple) {
-            final tupleKey = TupleKey.fromString(tuple);
-            return tupleKey.parts.first == userId;
-          });
-          final childEntries = deviceKeysBoxKeys.map(
-            (key) {
-              final userDeviceKey = userDeviceKeys[key];
-              if (userDeviceKey == null) return null;
-              return copyMap(userDeviceKey);
-            },
-          );
-          final crossSigningEntries = crossSigningKeysBoxKeys.map(
-            (key) {
-              final crossSigningKey = userCrossSigningKeys[key];
-              if (crossSigningKey == null) return null;
-              return copyMap(crossSigningKey);
-            },
-          );
-          res[userId] = DeviceKeysList.fromDbJson(
-            {
-              'client_id': client.id,
-              'user_id': userId,
-              'outdated': deviceKeysOutdated[userId],
-            },
-            childEntries
-                .where((c) => c != null)
-                .toList()
-                .cast<Map<String, dynamic>>(),
-            crossSigningEntries
-                .where((c) => c != null)
-                .toList()
-                .cast<Map<String, dynamic>>(),
-            client,
-          );
-        }
-        return res;
+
+        final result = await _runParseUserDeviceKeys(
+          client.id,
+          deviceKeysOutdated,
+          userDeviceKeys,
+          userCrossSigningKeys,
+        );
+        return result.map(
+          (userId, json) => MapEntry(
+            userId,
+            DeviceKeysList.fromDbJson(
+              json['meta'] as Map<String, dynamic>,
+              (json['devices'] as List).cast<Map<String, dynamic>>(),
+              (json['crossSigning'] as List).cast<Map<String, dynamic>>(),
+              client,
+            ),
+          ),
+        );
       });
 
   @override
@@ -1913,3 +1890,83 @@ class TupleKey {
   @override
   int get hashCode => Object.hashAll(parts);
 }
+
+Future<Map<String, Map<String, dynamic>>> _runParseUserDeviceKeys(
+  dynamic clientId,
+  Map<String, dynamic> deviceKeysOutdated,
+  Map<String, dynamic> userDeviceKeys,
+  Map<String, dynamic> userCrossSigningKeys,
+) async {
+  final payload = <String, dynamic>{
+    'clientId': clientId,
+    'deviceKeysOutdated': Map<String, dynamic>.from(deviceKeysOutdated),
+    'userDeviceKeys': Map<String, dynamic>.from(userDeviceKeys),
+    'userCrossSigningKeys': Map<String, dynamic>.from(userCrossSigningKeys),
+  };
+  return Isolate.run(() => _parseUserDeviceKeys(payload));
+}
+
+Map<String, Map<String, dynamic>> _parseUserDeviceKeys(
+  Map<String, dynamic> payload,
+) {
+  final deviceKeysOutdated =
+      payload['deviceKeysOutdated'] as Map<String, dynamic>;
+  final userDeviceKeys = payload['userDeviceKeys'] as Map<String, dynamic>;
+  final userCrossSigningKeys =
+      payload['userCrossSigningKeys'] as Map<String, dynamic>;
+  final clientId = payload['clientId'];
+
+  Map<String, dynamic> inlineCopyMap(Map<String, dynamic> map) {
+    return map.map((k, v) {
+      if (v is Map<String, dynamic>) return MapEntry(k, inlineCopyMap(v));
+      if (v is List) return MapEntry(k, List.from(v));
+      return MapEntry(k, v);
+    });
+  }
+
+  final res = <String, Map<String, dynamic>>{};
+
+  for (final userId in deviceKeysOutdated.keys) {
+    final deviceKeysBoxKeys = userDeviceKeys.keys.where((tuple) {
+      final parts = tuple.split('\u0000');
+      return parts.isNotEmpty && parts.first == userId;
+    });
+
+    final crossSigningKeysBoxKeys = userCrossSigningKeys.keys.where((tuple) {
+      final parts = tuple.split('\u0000');
+      return parts.isNotEmpty && parts.first == userId;
+    });
+
+    final childEntries = deviceKeysBoxKeys
+        .map((key) {
+          final userDeviceKey = userDeviceKeys[key];
+          if (userDeviceKey == null) return null;
+          return inlineCopyMap(userDeviceKey as Map<String, dynamic>);
+        })
+        .where((c) => c != null)
+        .toList()
+        .cast<Map<String, dynamic>>();
+
+    final crossSigningEntries = crossSigningKeysBoxKeys
+        .map((key) {
+          final crossSigningKey = userCrossSigningKeys[key];
+          if (crossSigningKey == null) return null;
+          return inlineCopyMap(crossSigningKey as Map<String, dynamic>);
+        })
+        .where((c) => c != null)
+        .toList()
+        .cast<Map<String, dynamic>>();
+
+    res[userId] = {
+      'meta': {
+        'client_id': clientId,
+        'user_id': userId,
+        'outdated': deviceKeysOutdated[userId],
+      },
+      'devices': childEntries,
+      'crossSigning': crossSigningEntries,
+    };
+  }
+
+  return res;
+}