Rework shell installer script writer s.t. fish shell doesn't rely on sftp

lib/core/extension/ssh_client.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:typed_data';
 
 import 'package:dartssh2/dartssh2.dart';
 import 'package:flutter/foundation.dart';
@@ -85,4 +86,42 @@ extension SSHClientX on SSHClient {
       stdin: stdin,
     );
   }
+
+  Future<Uint8List> runWithSessionAction(
+    String command, {
+    bool runInPty = false,
+    bool stdout = true,
+    bool stderr = true,
+    Map<String, String>? environment,
+    Future<void> Function(SSHSession)? action,
+  }) async {
+    final session = await execute(
+      command,
+      pty: runInPty ? const SSHPtyConfig() : null,
+      environment: environment,
+    );
+
+    final result = BytesBuilder(copy: false);
+    final stdoutDone = Completer<void>();
+    final stderrDone = Completer<void>();
+
+    session.stdout.listen(
+      stdout ? result.add : (_) {},
+      onDone: stdoutDone.complete,
+      onError: stderrDone.completeError,
+    );
+
+    session.stderr.listen(
+      stderr ? result.add : (_) {},
+      onDone: stderrDone.complete,
+      onError: stderrDone.completeError,
+    );
+
+    if (action != null) await action(session);
+
+    await stdoutDone.future;
+    await stderrDone.future;
+
+    return result.takeBytes();
+  }
 }

lib/data/model/app/shell_func.dart

@@ -33,13 +33,17 @@ enum ShellFunc {
 
   /// Issue #168
   /// Use `sh` for compatibility
-  static final installShellCmd = """
+  // static final installShellCmd = """
-mkdir -p $_homeVar/$_srvBoxDir
+// mkdir -p $_homeVar/$_srvBoxDir
-cat << 'EOF' > $_installShellPath
+// cat << 'EOF' > $_installShellPath
-${ShellFunc.allScript}
+// ${ShellFunc.allScript}
-EOF
+// EOF
-chmod +x $_installShellPath
+// chmod +x $_installShellPath
-""";
+// """;
+
+  static const installerMkdirs = "mkdir -p $_homeVar/$_srvBoxDir";
+  static const installerShellWriter = "cat > $_installShellPath";
+  static const installerPermissionModifier = "chmod +x $_installShellPath";
 
   String get flag {
     switch (this) {

lib/data/provider/server.dart

@@ -1,9 +1,12 @@
 import 'dart:async';
 import 'dart:io';
+import 'dart:typed_data';
+import 'dart:convert';
 
 import 'package:computer/computer.dart';
 import 'package:dartssh2/dartssh2.dart';
 import 'package:flutter/material.dart';
+import 'package:toolbox/core/extension/ssh_client.dart';
 import 'package:toolbox/core/utils/platform/path.dart';
 import 'package:toolbox/data/model/app/shell_func.dart';
 import 'package:toolbox/data/model/server/system.dart';
@@ -256,6 +259,29 @@ class ServerProvider extends ChangeNotifier {
     notifyListeners();
   }
 
+  Future<void> _writeInstallerScript(Server s) async {
+    void ensure(String? writeResult) {
+      if (writeResult == null || writeResult.isNotEmpty) {
+        throw Exception("Failed to write installer script: $writeResult");
+      }
+    }
+
+    final client = s.client;
+    if (client == null) {
+      throw Exception("Invalid state: s.client cannot be null");
+    }
+
+    ensure(await client.run(ShellFunc.installerMkdirs).string);
+
+    ensure(await client.runWithSessionAction(ShellFunc.installerShellWriter,
+            action: (session) async {
+              session.stdin.add(utf8.encode(ShellFunc.allScript));
+            })
+        .string);
+
+    ensure(await client.run(ShellFunc.installerPermissionModifier).string);
+  }
+
   Future<void> _getData(ServerPrivateInfo spi) async {
     final sid = spi.id;
     final s = _servers[sid];
@@ -304,11 +330,7 @@ class ServerProvider extends ChangeNotifier {
       // Write script to server
       // by ssh
       try {
-        final writeResult =
+        await _writeInstallerScript(s);
-            await s.client?.run(ShellFunc.installShellCmd).string;
-        if (writeResult == null || writeResult.isNotEmpty) {
-          throw Exception('$writeResult');
-        }
       } on SSHAuthAbortError catch (e) {
         TryLimiter.inc(sid);
         s.status.err = e.toString();