import 'dart:async';
import 'package:web_socket_channel/web_socket_channel.dart';

abstract interface class RelayConnection {
  Future<void> connect();
  Future<void> send(String message);
  Stream<String> get messages;
  Future<void> close();
}

final class WebSocketRelayConnection implements RelayConnection {
  final String _url;
  WebSocketChannel? _channel;
  StreamController<String>? _controller;

  WebSocketRelayConnection(String url) : _url = url;

  @override
  Future<void> connect() async {
    _channel = WebSocketChannel.connect(Uri.parse(_url));
    await _channel!.ready;
    _controller = StreamController<String>();
    _channel!.stream.cast<String>().listen(
          _controller!.add,
          onError: _controller!.addError,
          onDone: _controller!.close,
        );
  }

  @override
  Future<void> send(String message) async => _channel!.sink.add(message);

  @override
  Stream<String> get messages => _controller!.stream;

  @override
  Future<void> close() async {
    await _channel?.sink.close();
    _channel = null;
    _controller = null;
  }
}