functional carplay experience in simulators

lib/carplay_bridge.dart

@@ -0,0 +1,77 @@
+import 'package:flutter/services.dart';
+
+import 'streaming_audio_business_object.dart';
+
+class CarPlayBridge {
+  CarPlayBridge({required StreamingAudioBusinessObject audio}) : _audio = audio;
+
+  static const MethodChannel _channel = MethodChannel(
+    'kryz_go_flutter/carplay/methods',
+  );
+
+  final StreamingAudioBusinessObject _audio;
+  bool _isStarted = false;
+
+  Future<void> start() async {
+    if (_isStarted) {
+      return;
+    }
+
+    _isStarted = true;
+    _channel.setMethodCallHandler(_handleNativeMethodCall);
+    _audio.addListener(_onAudioChanged);
+    await _pushSnapshotToNative();
+  }
+
+  Future<void> dispose() async {
+    if (!_isStarted) {
+      return;
+    }
+
+    _isStarted = false;
+    _audio.removeListener(_onAudioChanged);
+    _channel.setMethodCallHandler(null);
+  }
+
+  Map<String, dynamic> _snapshot() {
+    final String playbackStatus = switch (_audio.playbackStatus) {
+      StreamingPlaybackStatus.playing => 'playing',
+      StreamingPlaybackStatus.buffering => 'buffering',
+      StreamingPlaybackStatus.stopped => 'stopped',
+    };
+
+    return <String, dynamic>{
+      'playbackStatus': playbackStatus,
+      'isPlaying': _audio.isPlaying,
+      'isBuffering': _audio.isBuffering,
+      'isLive': true,
+      'seekable': false,
+      'title': _audio.currentTitle,
+      'subtitle': _audio.currentSubtitle,
+      'album': 'Live',
+    };
+  }
+
+  Future<dynamic> _handleNativeMethodCall(MethodCall call) async {
+    switch (call.method) {
+      case 'getStateSnapshot':
+        return _snapshot();
+      default:
+        throw MissingPluginException('Unknown CarPlay bridge method: ${call.method}');
+    }
+  }
+
+  void _onAudioChanged() {
+    _pushSnapshotToNative();
+  }
+
+  Future<void> _pushSnapshotToNative() async {
+    try {
+      await _channel.invokeMethod<void>('syncState', _snapshot());
+    } on MissingPluginException {
+      // CarPlay bridge only exists on iOS native builds.
+    } on PlatformException {
+      // Keep playback working even if native sync temporarily fails.
+    }
+  }
+}