Fix default download directory and persist built-in aria2 sessions

lib/app.dart

@@ -948,9 +948,7 @@ class _MainWindowState extends State<MainWindow> with WindowListener, Loggable {
               mainAxisAlignment: MainAxisAlignment.spaceBetween,
               children: [
                 Chip(
-                  label: Text(
-                    l10n.totalSpeed(formatSpeed(totalDownloadSpeed)),
-                  ),
+                  label: Text(l10n.totalSpeed(formatSpeed(totalDownloadSpeed))),
                   avatar: const Icon(Icons.speed, size: 16),
                   backgroundColor: colorScheme.surfaceContainerHighest,
                   padding: const EdgeInsets.symmetric(

lib/models/settings.dart

@@ -1,9 +1,13 @@
+import 'dart:convert' show jsonDecode, jsonEncode;
 import 'dart:io';
+
 import 'package:flutter/material.dart';
 import 'package:flutter/scheduler.dart';
-import '../utils/logging.dart';
+import 'package:path/path.dart' as p;
+
 import '../utils/app_data_dir.dart';
-import 'dart:convert' show jsonDecode, jsonEncode;
+import '../utils/default_download_directory.dart';
+import '../utils/logging.dart';
 
 enum AppRunMode { standard, tray, hideTray }
 
@@ -90,7 +94,11 @@ class Settings extends ChangeNotifier with Loggable {
     return getAppDataDirectory();
   }
 
-  void _assignDefaultSettings() {
+  Future<String> _defaultDownloadDirectory() async {
+    return getDefaultDownloadDirectory();
+  }
+
+  void _assignDefaultSettings({required String defaultDownloadDir}) {
     _autoStart = false;
     _minimizeToTray = true;
     _runMode = AppRunMode.tray;
@@ -119,7 +127,7 @@ class Settings extends ChangeNotifier with Loggable {
     _maxConnectionPerServer = 16;
     _split = 16;
     _continueDownloads = true;
-    _downloadDir = '';
+    _downloadDir = defaultDownloadDir;
 
     // Speed settings
     _maxOverallDownloadLimit = 0;
@@ -158,11 +166,11 @@ class Settings extends ChangeNotifier with Loggable {
   /// Get settings file path
   String _getSettingsFilePath() {
     final dataDir = _getDataDirectory();
-    final configDir = Directory('${dataDir.path}/config');
+    final configDir = Directory(p.join(dataDir.path, 'config'));
     if (!configDir.existsSync()) {
       configDir.createSync(recursive: true);
     }
-    return '${configDir.path}/$_settingsFileName';
+    return p.join(configDir.path, _settingsFileName);
   }
 
   String _normalizeBtTracker(String trackers) {
@@ -244,6 +252,7 @@ class Settings extends ChangeNotifier with Loggable {
       if (file.existsSync()) {
         final jsonString = await file.readAsString();
         final settingsMap = jsonDecode(jsonString);
+        var needsSave = false;
 
         // Global settings
         _autoStart = settingsMap['autoStart'] ?? false;
@@ -306,7 +315,14 @@ class Settings extends ChangeNotifier with Loggable {
         _maxConnectionPerServer = settingsMap['maxConnectionPerServer'] ?? 16;
         _split = settingsMap['split'] ?? 16;
         _continueDownloads = settingsMap['continueDownloads'] ?? true;
-        _downloadDir = settingsMap['downloadDir'] ?? '';
+        final configuredDownloadDir =
+            (settingsMap['downloadDir'] as String? ?? '').trim();
+        if (configuredDownloadDir.isEmpty) {
+          _downloadDir = await _defaultDownloadDirectory();
+          needsSave = true;
+        } else {
+          _downloadDir = p.normalize(configuredDownloadDir);
+        }
 
         // Speed settings
         _maxOverallDownloadLimit = settingsMap['maxOverallDownloadLimit'] ?? 0;
@@ -344,8 +360,12 @@ class Settings extends ChangeNotifier with Loggable {
         _userAgent =
             settingsMap['userAgent'] ??
             'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36';
+
+        if (needsSave) {
+          await _saveAllSettings();
+        }
       } else {
-        _applyDefaultSettings();
+        await _applyDefaultSettings(save: true);
       }
 
       _isLoaded = true;
@@ -357,14 +377,19 @@ class Settings extends ChangeNotifier with Loggable {
     } catch (e) {
       this.e('Failed to load settings', error: e);
       // Apply default settings
-      _applyDefaultSettings();
+      await _applyDefaultSettings(save: true);
       _isLoaded = true;
     }
   }
 
   // Apply default settings
-  void _applyDefaultSettings() {
-    _assignDefaultSettings();
+  Future<void> _applyDefaultSettings({bool save = false}) async {
+    _assignDefaultSettings(
+      defaultDownloadDir: await _defaultDownloadDirectory(),
+    );
+    if (save) {
+      await _saveAllSettings();
+    }
     // Schedule notifyListeners to run after the current frame is built
     SchedulerBinding.instance.addPostFrameCallback((_) {
       notifyListeners();
@@ -448,7 +473,9 @@ class Settings extends ChangeNotifier with Loggable {
   }
 
   Future<void> resetToDefaults() async {
-    _assignDefaultSettings();
+    _assignDefaultSettings(
+      defaultDownloadDir: await _defaultDownloadDirectory(),
+    );
     _isLoaded = true;
     notifyListeners();
     await _saveAllSettings();

lib/services/aria2_rpc_client.dart

@@ -352,16 +352,16 @@ class Aria2RpcClient with Loggable {
     } on ConnectionFailedException catch (e) {
       w('Connection test failed: $e');
       return false;
-  } on UnauthorizedException {
-    rethrow;
-  } catch (err, stackTrace) {
-    e(
-      'Unexpected error during connection test',
-      error: err,
-      stackTrace: stackTrace,
-    );
-    rethrow;
-  }
+    } on UnauthorizedException {
+      rethrow;
+    } catch (err, stackTrace) {
+      e(
+        'Unexpected error during connection test',
+        error: err,
+        stackTrace: stackTrace,
+      );
+      rethrow;
+    }
   }
 
   /// Pause a download task
@@ -547,6 +547,24 @@ class Aria2RpcClient with Loggable {
     }
   }
 
+  /// Shut down aria2 through RPC so it can flush its session state.
+  Future<bool> shutdown({bool force = false}) async {
+    try {
+      final response = await callRpc(
+        force ? 'aria2.forceShutdown' : 'aria2.shutdown',
+        [],
+      );
+      return response['result'] == 'OK';
+    } catch (e, stackTrace) {
+      this.e(
+        'Failed to shut down ${instance.name} through RPC',
+        error: e,
+        stackTrace: stackTrace,
+      );
+      rethrow;
+    }
+  }
+
   /// Purge all stopped download results from aria2.
   Future<bool> purgeDownloadResult() async {
     try {

lib/services/builtin_instance_service.dart

@@ -3,16 +3,21 @@ import 'dart:convert';
 import 'dart:io';
 
 import 'package:flutter/foundation.dart';
+import 'package:path/path.dart' as p;
 
 import '../models/aria2_instance.dart';
 import '../utils/app_data_dir.dart';
-import 'builtin_upnp_service.dart';
+import '../utils/default_download_directory.dart';
 import '../utils/logging.dart';
+import 'aria2_rpc_client.dart';
+import 'builtin_upnp_service.dart';
 
 enum BuiltinInstanceApplyMode { none, liveApply, restartRequired }
 
 /// Service class for managing the built-in Aria2 instance
 class BuiltinInstanceService with Loggable {
+  static const Duration _rpcShutdownTimeout = Duration(seconds: 5);
+
   static BuiltinInstanceService? _instance;
   Process? _aria2Process;
   String? _aria2cPath;
@@ -36,27 +41,30 @@ class BuiltinInstanceService with Loggable {
 
   void _initializePaths() {
     final dataDir = getAppDataDirectory();
-    final coreDirPath = '${dataDir.path}/core';
+    final coreDirPath = p.join(dataDir.path, 'core');
     final coreDir = Directory(coreDirPath);
 
     if (!coreDir.existsSync()) {
       this.w('Core directory does not exist: $coreDirPath, creating it...');
       coreDir.createSync(recursive: true);
     }
 
-    _aria2cPath = '$coreDirPath/aria2c${Platform.isWindows ? '.exe' : ''}';
-    _aria2ConfPath = '$coreDirPath/aria2.conf';
-    _sessionPath = '$coreDirPath/aria2.session';
-    _logPath = '$coreDirPath/aria2.log';
+    _aria2cPath = p.join(
+      coreDirPath,
+      'aria2c${Platform.isWindows ? '.exe' : ''}',
+    );
+    _aria2ConfPath = p.join(coreDirPath, 'aria2.conf');
+    _sessionPath = p.join(coreDirPath, 'aria2.session');
+    _logPath = p.join(coreDirPath, 'aria2.log');
   }
 
   String _getSettingsFilePath() {
     final dataDir = getAppDataDirectory();
-    final configDir = Directory('${dataDir.path}/config');
+    final configDir = Directory(p.join(dataDir.path, 'config'));
     if (!configDir.existsSync()) {
       configDir.createSync(recursive: true);
     }
-    return '${configDir.path}/settings.json';
+    return p.join(configDir.path, 'settings.json');
   }
 
   Map<String, dynamic> _readSettingsSnapshot() {
@@ -101,8 +109,7 @@ class BuiltinInstanceService with Loggable {
   }
 
   String _defaultDownloadDir() {
-    final dataDir = getAppDataDirectory();
-    return '${dataDir.path}/downloads';
+    return getDefaultDownloadDirectorySync();
   }
 
   String _resolveEffectiveBtListenPort(Map<String, dynamic> settings) {
@@ -328,6 +335,8 @@ class BuiltinInstanceService with Loggable {
       '--enable-dht6=${settings['enableDht6'] ?? true}',
       '--conf-path=$_aria2ConfPath',
       '--save-session=$sessionPath',
+      '--save-session-interval=30',
+      '--force-save=false',
       '--log-level=info',
       '--log=$logPath',
     ];
@@ -427,8 +436,26 @@ class BuiltinInstanceService with Loggable {
       await _stdoutSubscription?.cancel();
       await _stderrSubscription?.cancel();
 
-      _aria2Process!.kill();
-      await _aria2Process!.exitCode.timeout(const Duration(seconds: 5));
+      try {
+        await _shutdownThroughRpcIfPossible().timeout(_rpcShutdownTimeout);
+      } on TimeoutException {
+        this.w(
+          'Timed out waiting for built-in Aria2 RPC shutdown, terminating process',
+        );
+        _aria2Process?.kill();
+      }
+
+      if (_aria2Process != null) {
+        try {
+          await _aria2Process!.exitCode.timeout(const Duration(seconds: 5));
+        } on TimeoutException {
+          this.w(
+            'Built-in Aria2 did not exit after RPC shutdown, terminating process',
+          );
+          _aria2Process!.kill();
+          await _aria2Process!.exitCode.timeout(const Duration(seconds: 5));
+        }
+      }
 
       _aria2Process = null;
       _isConnected = false;
@@ -448,6 +475,30 @@ class BuiltinInstanceService with Loggable {
     return _aria2Process != null;
   }
 
+  int? get pid => _aria2Process?.pid;
+
+  Future<void> _shutdownThroughRpcIfPossible() async {
+    final client = Aria2RpcClient(getBuiltinInstanceConfig());
+    try {
+      await client.saveSession().timeout(_rpcShutdownTimeout);
+      await client.shutdown(force: true).timeout(_rpcShutdownTimeout);
+    } on TimeoutException {
+      this.w(
+        'Timed out during built-in Aria2 RPC shutdown; falling back to process termination',
+      );
+      _aria2Process?.kill();
+    } catch (e, stackTrace) {
+      this.w(
+        'Failed to stop built-in Aria2 through RPC; falling back to process termination',
+        error: e,
+        stackTrace: stackTrace,
+      );
+      _aria2Process?.kill();
+    } finally {
+      client.close();
+    }
+  }
+
   void _monitorProcessOutput() {
     if (_aria2Process == null) return;