Dead code removal 3 (#79)

* fix: remove dead code and fix double client.close() bug

Dead code removal:
- Remove DateTimeX.timestamp getter (unused)
- Remove GhIdX.markdownLink getter (unused)
- Remove Pfs.separator and Pfs.homeDir (unused)
- Remove SettingsService.applySpeedSettingsToBuiltin() (unused)
- Remove 28 unused individual Settings.set*() methods (setRpcListenPort,
  setRpcSecret, setMaxConcurrentDownloads, setSplit, etc.) - only setBtTracker
  and setLastSyncTrackerTime are used by TrackerSyncService

Bug fix:
- Remove redundant client.close() in try block of file selection save handler;
  the finally block already handles cleanup, causing double-close on success

* perf: optimize hot-path allocations and exception-based control flow

Performance:
- Cache RegExp as static finals in TaskDetailsBtHelpers (azureus pattern,
  digit/letter patterns) instead of recompiling per-peer per-second
- Cache UnmodifiableListView in DownloadDataService.tasks getter (was
  creating a new wrapper on every access, dozens of times per second)
- Precompute lowercase names map before sort in _compareTasks (eliminates
  O(n log n) toLowerCase() allocations per refresh cycle)
- Precompute lowercase instance names map before search filtering (saves
  1x toLowerCase() per task per keystroke)
- Replace firstWhere+catch with simple for-loop in getInstanceById and
  getBuiltinInstance (avoids expensive stack trace capture for control flow)
- Use getBuiltinInstance() in initialize() instead of bare firstWhere

Author: GT-610

lib/constants/github_id.dart

@@ -10,6 +10,4 @@ typedef GhId = String;
 
 extension GhIdX on GhId {
   String get url => 'https://github.com/$this';
-
-  String get markdownLink => '[$this]($url)';
 }

lib/kit/core/ext/datetime.dart

@@ -2,6 +2,4 @@ extension DateTimeX on DateTime {
   String get hourMinute {
     return '${hour.toString().padLeft(2, '0')}:${minute.toString().padLeft(2, '0')}';
   }
-
-  static int get timestamp => DateTime.now().millisecondsSinceEpoch;
 }

lib/kit/core/platform.dart

@@ -24,18 +24,6 @@ enum Pfs {
       _ => unknown,
     };
   }();
-
-  static final String separator = isWindows ? '\\' : '/';
-
-  static final String? homeDir = () {
-    final envVars = Platform.environment;
-    if (isMacOS || isLinux) {
-      return envVars['HOME'];
-    } else if (isWindows) {
-      return envVars['UserProfile'];
-    }
-    return null;
-  }();
 }
 
 final isLinux = Pfs.type == Pfs.linux;

lib/models/settings.dart

@@ -578,203 +578,18 @@ class Settings extends ChangeNotifier with Loggable {
   }
 
   // Built-in Aria2 instance setters
-  // Connection settings
-  Future<void> setRpcListenPort(int port) async {
-    _rpcListenPort = port;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setRpcSecret(String secret) async {
-    _rpcSecret = secret;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  // Transfer settings
-  Future<void> setMaxConcurrentDownloads(int value) async {
-    _maxConcurrentDownloads = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setMaxConnectionPerServer(int value) async {
-    _maxConnectionPerServer = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setSplit(int value) async {
-    _split = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setContinueDownloads(bool value) async {
-    _continueDownloads = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setDownloadDir(String value) async {
-    _downloadDir = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  // Speed settings
-  Future<void> setMaxOverallDownloadLimit(int limit) async {
-    _maxOverallDownloadLimit = limit;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setMaxOverallUploadLimit(int limit) async {
-    _maxOverallUploadLimit = limit;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  // BT settings
-  Future<void> setBtSaveMetadata(bool value) async {
-    _btSaveMetadata = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setBtForceEncryption(bool value) async {
-    _btForceEncryption = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setBtLoadSavedMetadata(bool value) async {
-    _btLoadSavedMetadata = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setKeepSeeding(bool value) async {
-    _keepSeeding = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setSeedRatio(double ratio) async {
-    _seedRatio = ratio;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setSeedTime(int minutes) async {
-    _seedTime = minutes;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setBtListenPort(String port) async {
-    _btListenPort = port;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
   Future<void> setBtTracker(String trackers) async {
     _btTracker = _normalizeBtTracker(trackers);
     notifyListeners();
     await _saveAllSettings();
   }
 
-  Future<void> setBtExcludeTracker(String trackers) async {
-    _btExcludeTracker = trackers;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  // Advanced settings
-  Future<void> setProxyEnabled(bool value) async {
-    _proxyEnabled = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setAllProxy(String proxy) async {
-    _allProxy = proxy;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setNoProxy(String noProxy) async {
-    _noProxy = noProxy;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setDhtListenPort(int port) async {
-    _dhtListenPort = port;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setEnableDht6(bool value) async {
-    _enableDht6 = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setEnableUpnp(bool value) async {
-    _enableUpnp = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setSessionPath(String path) async {
-    _sessionPath = path;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setLogPath(String path) async {
-    _logPath = path;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setAutoSyncTracker(bool value) async {
-    _autoSyncTracker = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
   Future<void> setLastSyncTrackerTime(int value) async {
     _lastSyncTrackerTime = value;
     notifyListeners();
     await _saveAllSettings();
   }
 
-  Future<void> setTrackerSource(String value) async {
-    _trackerSource = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setAutoFileRenaming(bool value) async {
-    _autoFileRenaming = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setAllowOverwrite(bool value) async {
-    _allowOverwrite = value;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
-  Future<void> setUserAgent(String userAgent) async {
-    _userAgent = userAgent;
-    notifyListeners();
-    await _saveAllSettings();
-  }
-
   Future<void> updateBuiltinInstanceSettings({
     required int rpcListenPort,
     required String rpcSecret,

lib/pages/download_page/components/task_details_bt_helpers.dart

@@ -7,6 +7,9 @@ import '../../../utils/format_utils.dart';
 import '../models/download_task.dart';
 
 class TaskDetailsBtHelpers {
+  static final _azureusPattern = RegExp(r'^-([A-Za-z~]{2})(.{4})-');
+  static final _digitPattern = RegExp(r'[0-9]');
+  static final _letterPattern = RegExp(r'[A-Za-z]');
   static Widget buildBitfieldVisualization(
     BuildContext context,
     DownloadTask task,
@@ -327,7 +330,7 @@ class TaskDetailsBtHelpers {
       return 'unknown';
     }
 
-    final azureusMatch = RegExp(r'^-([A-Za-z~]{2})(.{4})-').firstMatch(decoded);
+    final azureusMatch = _azureusPattern.firstMatch(decoded);
     if (azureusMatch != null) {
       final clientCode = azureusMatch.group(1)!;
       final versionRaw = azureusMatch.group(2)!;
@@ -370,9 +373,9 @@ class TaskDetailsBtHelpers {
   static String _formatPeerVersion(String rawVersion) {
     final segments = <String>[];
     for (final char in rawVersion.split('')) {
-      if (RegExp(r'[0-9]').hasMatch(char)) {
+      if (_digitPattern.hasMatch(char)) {
         segments.add(char);
-      } else if (RegExp(r'[A-Za-z]').hasMatch(char)) {
+      } else if (_letterPattern.hasMatch(char)) {
         segments.add(char.toLowerCase());
       }
     }

lib/pages/download_page/components/task_details_dialog.dart

@@ -604,7 +604,6 @@ class TaskDetailsDialog {
                                                                       ),
                                                             },
                                                           );
-                                                          client.close();
 
                                                           onTaskUpdated?.call();
 

lib/pages/download_page/download_page.dart

@@ -377,9 +377,12 @@ class DownloadPageState extends State<DownloadPage>
 
     if (_searchQuery.isNotEmpty) {
       final query = _searchQuery.toLowerCase();
+      final lowerInstanceNames = <String, String>{
+        for (final entry in _instanceNames.entries)
+          entry.key: entry.value.toLowerCase(),
+      };
       tasks = tasks.where((task) {
-        final instanceName = (_instanceNames[task.instanceId] ?? '')
-            .toLowerCase();
+        final instanceName = lowerInstanceNames[task.instanceId] ?? '';
         final taskDir = (task.dir ?? '').toLowerCase();
         final taskName = task.name.toLowerCase();
         return taskName.contains(query) ||

lib/services/download_data_service.dart

@@ -34,6 +34,7 @@ class DownloadDataService extends ChangeNotifier with Loggable {
   Timer? _refreshTimer;
 
   List<DownloadTask> _tasks = [];
+  List<DownloadTask> _tasksView = const [];
   bool _isRefreshing = false;
   String? _lastError;
   final List<DownloadTaskNotification> _pendingNotifications = [];
@@ -44,7 +45,7 @@ class DownloadDataService extends ChangeNotifier with Loggable {
   final Map<String, Aria2RpcClient> _clientCache = {};
   List<Aria2Instance> Function()? _connectedInstancesProvider;
 
-  List<DownloadTask> get tasks => UnmodifiableListView(_tasks);
+  List<DownloadTask> get tasks => _tasksView;
   int get tasksVersion => _tasksVersion;
   bool get isRefreshing => _isRefreshing;
   String? get lastError => _lastError;
@@ -86,6 +87,7 @@ class DownloadDataService extends ChangeNotifier with Loggable {
       final hadTasks = _tasks.isNotEmpty;
       final hadError = _lastError != null;
       _tasks = [];
+      _tasksView = UnmodifiableListView(_tasks);
       _tasksVersion++;
       _lastError = null;
       if (hadTasks || hadError) {
@@ -102,14 +104,18 @@ class DownloadDataService extends ChangeNotifier with Loggable {
       final taskGroups = await Future.wait(
         connectedInstances.map(_fetchTasksForInstance),
       );
-      final newTasks = taskGroups.expand((tasks) => tasks).toList()
-        ..sort(_compareTasks);
+      final newTasks = taskGroups.expand((tasks) => tasks).toList();
+      final lowerCaseNames = <String, String>{
+        for (final t in newTasks) t.name: t.name.toLowerCase(),
+      };
+      newTasks.sort((a, b) => _compareTasks(a, b, lowerCaseNames));
 
       final terminalTransitionInstanceIds = _collectTaskNotifications(
         previousTasks,
         newTasks,
       );
       _tasks = newTasks;
+      _tasksView = UnmodifiableListView(_tasks);
       _tasksVersion++;
       _saveSessionsForTerminalTransitions(
         connectedInstances,
@@ -217,7 +223,11 @@ class DownloadDataService extends ChangeNotifier with Loggable {
     DownloadStatus.stopped: 2,
   };
 
-  int _compareTasks(DownloadTask left, DownloadTask right) {
+  int _compareTasks(
+    DownloadTask left,
+    DownloadTask right,
+    Map<String, String> lowerCaseNames,
+  ) {
     final leftOrder = _statusOrder[left.status] ?? 99;
     final rightOrder = _statusOrder[right.status] ?? 99;
     if (leftOrder != rightOrder) {
@@ -228,12 +238,8 @@ class DownloadDataService extends ChangeNotifier with Loggable {
       return left.instanceId.compareTo(right.instanceId);
     }
 
-    return _compareIgnoreCase(left.name, right.name);
-  }
-
-  static int _compareIgnoreCase(String a, String b) {
-    final aLower = a.toLowerCase();
-    final bLower = b.toLowerCase();
+    final aLower = lowerCaseNames[left.name] ?? left.name.toLowerCase();
+    final bLower = lowerCaseNames[right.name] ?? right.name.toLowerCase();
     return aLower.compareTo(bLower);
   }