opt.: cancel sftp mission

lib/data/model/app/path_with_prefix.dart

@@ -24,6 +24,8 @@ class PathWithPrefix {
     _path = pathJoin(_path, newPath);
   }
 
+  bool get canBack => path != '$_prefixPath/';
+
   bool undo() {
     if (_prePath == null || _path == _prePath) {
       return false;

lib/data/model/sftp/worker.dart

@@ -94,7 +94,7 @@ Future<void> _download(
       return;
     }
     // Read 10m each time
-    const defaultChunkSize = 1024 * 1024 * 10;
+    const defaultChunkSize = 1024 * 1024;
     final chunkSize = size > defaultChunkSize ? defaultChunkSize : size;
     mainSendPort.send(size);
     mainSendPort.send(SftpWorkerStatus.downloading);

lib/data/provider/sftp.dart

@@ -8,21 +8,8 @@ class SftpProvider extends ProviderBase {
   final List<SftpReqStatus> _status = [];
   List<SftpReqStatus> get status => _status;
 
-  Iterable<SftpReqStatus> gets({int? id, String? fileName}) {
-    Iterable<SftpReqStatus> found = [];
-    if (id != null) {
-      found = _status.where((e) => e.id == id);
-    }
-    if (fileName != null) {
-      found = found.where((e) => e.req.localPath.split('/').last == fileName);
-    }
-    return found;
-  }
-
-  SftpReqStatus? get({int? id, String? name}) {
-    final found = gets(id: id, fileName: name);
-    if (found.isEmpty) return null;
-    return found.first;
+  SftpReqStatus? get(int id) {
+    return _status.singleWhere((element) => element.id == id);
   }
 
   void add(SftpReq req, {Completer? completer}) {
@@ -32,4 +19,19 @@ class SftpProvider extends ProviderBase {
       req: req,
     ));
   }
+
+  @override
+  void dispose() {
+    for (final item in _status) {
+      item.worker.dispose();
+    }
+    super.dispose();
+  }
+
+  void cancel(int id) {
+    final idx = _status.indexWhere((element) => element.id == id);
+    _status[idx].worker.dispose();
+    _status.removeAt(idx);
+    notifyListeners();
+  }
 }