New feat

- SFTP download
- open downloaded files in other apps

lib/data/model/app/path_with_prefix.dart

@@ -0,0 +1,38 @@
+class PathWithPrefix {
+  late String _prefixPath;
+  String _path = '/';
+  String? _prePath;
+  String get path => _prefixPath + _path;
+
+  PathWithPrefix(String prefixPath) {
+    if (prefixPath.endsWith('/')) {
+      _prefixPath = prefixPath.substring(0, prefixPath.length - 1);
+    } else {
+      _prefixPath = prefixPath;
+    }
+  }
+
+  void update(String newPath) {
+    _prePath = _path;
+    if (newPath == '..') {
+      _path = _path.substring(0, _path.lastIndexOf('/'));
+      if (_path == '') {
+        _path = '/';
+      }
+      return;
+    }
+    if (newPath == '/') {
+      _path = '/';
+      return;
+    }
+    _path = _path + (_path.endsWith('/') ? '' : '/') + newPath;
+  }
+
+  bool undo() {
+    if (_prePath == null || _path == _prePath) {
+      return false;
+    }
+    _path = _prePath!;
+    return true;
+  }
+}