New feat

- SFTP download
- open downloaded files in other apps

lib/data/model/sftp/download_worker.dart

@@ -0,0 +1,107 @@
+import 'dart:async';
+import 'dart:io';
+import 'dart:isolate';
+
+import 'package:dartssh2/dartssh2.dart';
+import 'package:easy_isolate/easy_isolate.dart';
+import 'package:toolbox/data/model/server/server_private_info.dart';
+import 'package:toolbox/data/model/sftp/download_status.dart';
+
+class DownloadItem {
+  DownloadItem(this.spi, this.remotePath, this.localPath);
+
+  final ServerPrivateInfo spi;
+  final String remotePath;
+  final String localPath;
+}
+
+class SftpDownloadWorker {
+  SftpDownloadWorker(
+      {required this.onNotify, required this.item, this.privateKey});
+
+  final Function(Object event) onNotify;
+  final DownloadItem item;
+  final worker = Worker();
+  final String? privateKey;
+
+  /// Initiate the worker (new thread) and start listen from messages between
+  /// the threads
+  Future<void> init() async {
+    if (worker.isInitialized) worker.dispose();
+    await worker.init(
+      mainMessageHandler,
+      isolateMessageHandler,
+      errorHandler: print,
+    );
+    worker.sendMessage(DownloadItemEvent(item, privateKey));
+  }
+
+  /// Handle the messages coming from the isolate
+  void mainMessageHandler(dynamic data, SendPort isolateSendPort) {
+    onNotify(data);
+  }
+
+  /// Handle the messages coming from the main
+  static isolateMessageHandler(
+      dynamic data, SendPort mainSendPort, SendErrorFunction sendError) async {
+    if (data is DownloadItemEvent) {
+      try {
+        mainSendPort.send(SftpWorkerStatus.preparing);
+        final watch = Stopwatch()..start();
+        final item = data.item;
+        final spi = item.spi;
+        final socket = await SSHSocket.connect(spi.ip, spi.port);
+        SSHClient client;
+        if (spi.pubKeyId == null) {
+          client = SSHClient(socket,
+              username: spi.user,
+              onPasswordRequest: () => spi.authorization as String);
+        } else {
+          client = SSHClient(socket,
+              username: spi.user,
+              identities: SSHKeyPair.fromPem(data.privateKey!));
+        }
+        mainSendPort.send(SftpWorkerStatus.sshConnectted);
+
+        final remotePath = item.remotePath;
+        final localPath = item.localPath;
+        await Directory(localPath.substring(0, item.localPath.lastIndexOf('/')))
+            .create(recursive: true);
+        final local = File(localPath);
+        if (await local.exists()) {
+          await local.delete();
+        }
+        final localFile = local.openWrite(mode: FileMode.append);
+        final file = await (await client.sftp()).open(remotePath);
+        final size = (await file.stat()).size;
+        if (size == null) {
+          mainSendPort.send(Exception('can not get file size'));
+          return;
+        }
+        const defaultChunkSize = 1024 * 512;
+        final chunkSize = size > defaultChunkSize ? defaultChunkSize : size;
+        mainSendPort.send(size);
+        mainSendPort.send(SftpWorkerStatus.downloading);
+        for (var i = 0; i < size; i += chunkSize) {
+          final fileData = file.read(length: chunkSize);
+          await for (var form in fileData) {
+            localFile.add(form);
+            mainSendPort.send((i + form.length) / size * 100);
+          }
+        }
+        mainSendPort.send(SftpWorkerStatus.finished);
+        localFile.close();
+        mainSendPort.send(watch.elapsed);
+      } catch (e) {
+        mainSendPort.send(e);
+      }
+    }
+  }
+}
+
+class DownloadItemEvent {
+  DownloadItemEvent(this.item, this.privateKey);
+
+  final DownloadItem item;
+  final String? privateKey;
+}