Implement xterm v3 Terminal for LXD

Ref: canonical#86

packages/lxd_terminal/lib/lxd_terminal.dart

@@ -0,0 +1,64 @@
+library lxd_terminal;
+
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:lxd/lxd.dart';
+import 'package:xterm/xterm.dart';
+
+class LxdTerminal extends Terminal {
+  LxdTerminal(this.client, {required super.maxLines});
+
+  final LxdClient client;
+
+  WebSocket? _ws0;
+  WebSocket? _wsc;
+  StreamSubscription? _sub;
+
+  Future<void> close() async {
+    await _sub?.cancel();
+    await _ws0?.close();
+    await _wsc?.close();
+  }
+
+  Future<void> execute(LxdInstance instance) async {
+    final user = instance.config['user.name'] ?? 'root';
+    final op = await client.execInstance(
+      instance.name,
+      command: ['login', '-f', user],
+      environment: {'TERM': 'xterm-256color'},
+      interactive: true,
+      waitForWebSocket: true,
+    );
+
+    Future<WebSocket> getWebSocket(String id) {
+      final fd = op.metadata!['fds'][id] as String;
+      return client.getOperationWebSocket(op.id, fd);
+    }
+
+    _wsc = await getWebSocket('control');
+    onResize = (width, height, _, __) => _wsc?.sendTermSize(width, height);
+    _wsc!.sendTermSize(viewWidth, viewHeight);
+
+    _ws0 = await getWebSocket('0');
+    onOutput = (data) => _ws0?.add(utf8.encode(data));
+
+    _sub = _ws0!.listen((data) async {
+      if (data is List<int>) {
+        write(utf8.decode(data));
+      } else if (data is String) {
+        if (data.isEmpty) {
+          // TODO: proper way to detect exit
+          await close();
+        } else {
+          write('$data\r\n');
+        }
+      } else {
+        throw UnsupportedError('$data');
+      }
+    });
+
+    await client.waitOperation(op.id);
+  }
+}

packages/lxd_terminal/pubspec.yaml

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+name: lxd_terminal
+publish_to: 'none'
+
+environment:
+  sdk: ">=2.17.0 <3.0.0"
+  flutter: ">=3.0.0"
+
+dependencies:
+  flutter:
+    sdk: flutter
+  lxd:
+    git:
+      url: https://github.com/jpnurmi/lxd.dart
+      ref: 9799464c4488f52203407169baca963f88f0e349
+  xterm: # ^3.2.7
+    git:
+      ref: actions
+      url: https://github.com/jpnurmi/xterm.dart.git
+
+dev_dependencies:
+  build_runner: ^2.1.11
+  flutter_lints: ^2.0.0
+  flutter_test:
+    sdk: flutter
+  mockito: 5.3.0
+
+flutter:
+  uses-material-design: true

packages/lxd_terminal/test/lxd_terminal_test.dart

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+import 'dart:async';
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:lxd/lxd.dart';
+import 'package:lxd_terminal/lxd_terminal.dart';
+import 'package:mockito/annotations.dart';
+import 'package:mockito/mockito.dart';
+
+import 'lxd_terminal_test.mocks.dart';
+
+@GenerateMocks([LxdClient, LxdInstance, LxdOperation, WebSocket])
+void main() {
+  test('execute', () async {
+    final instance = MockLxdInstance();
+    when(instance.name).thenReturn('mine');
+    when(instance.config).thenReturn({'user.name': 'me'});
+
+    final exec = MockLxdOperation();
+    when(exec.id).thenReturn('x');
+    when(exec.metadata).thenReturn({
+      'fds': {
+        '0': 'fd0',
+        'control': 'fdc',
+      }
+    });
+
+    final wait = MockLxdOperation();
+    when(wait.id).thenReturn('w');
+
+    final client = MockLxdClient();
+    when(client.execInstance(
+      'mine',
+      command: ['login', '-f', 'me'],
+      environment: {'TERM': 'xterm-256color'},
+      interactive: true,
+      waitForWebSocket: true,
+    )).thenAnswer((_) async => exec);
+
+    final completer = Completer<LxdOperation>();
+    when(client.waitOperation('x')).thenAnswer((_) => completer.future);
+
+    final controller = StreamController<dynamic>(sync: true);
+
+    final ws0 = MockWebSocket();
+    when(client.getOperationWebSocket('x', 'fd0')).thenAnswer((_) async => ws0);
+    when(ws0.listen(any)).thenAnswer((i) => controller.stream
+        .listen(i.positionalArguments.first as void Function(dynamic)));
+    when(ws0.close()).thenAnswer((_) => controller.close());
+
+    final wsc = MockWebSocket();
+    when(client.getOperationWebSocket('x', 'fdc')).thenAnswer((_) async => wsc);
+    when(wsc.close()).thenAnswer((_) async {});
+
+    final terminal = TestLxdTerminal(client, maxLines: 123);
+    final result = terminal.execute(instance);
+
+    await untilCalled(client.waitOperation('x'));
+
+    verify(client.execInstance(
+      'mine',
+      command: ['login', '-f', 'me'],
+      environment: {'TERM': 'xterm-256color'},
+      interactive: true,
+      waitForWebSocket: true,
+    )).called(1);
+
+    verify(client.getOperationWebSocket('x', 'fd0')).called(1);
+    verify(client.getOperationWebSocket('x', 'fdc')).called(1);
+
+    controller.add('bytes'.codeUnits);
+    expect(terminal.written, ['bytes']);
+
+    controller.add('string');
+    expect(terminal.written, ['bytes', 'string\r\n']);
+
+    controller.add('');
+    expect(terminal.written, ['bytes', 'string\r\n']);
+
+    await untilCalled(ws0.close());
+    await untilCalled(wsc.close());
+
+    completer.complete(wait);
+
+    await expectLater(result, completes);
+  });
+}
+
+class TestLxdTerminal extends LxdTerminal {
+  TestLxdTerminal(super.client, {required super.maxLines});
+
+  final written = <String>[];
+
+  @override
+  void write(String data) => written.add(data);
+}