import 'dart:async';
import 'dart:convert';

import 'package:web_socket_channel/web_socket_channel.dart';

import '../models/chain_event.dart';

/// WebSocket JSON-RPC 客户端（用于事件订阅）
class GenexWebSocketClient {
  final String wsUrl;
  WebSocketChannel? _channel;
  int _requestId = 0;
  final Map<int, Completer<dynamic>> _pendingRequests = {};
  final Map<String, StreamController<ChainEvent>> _subscriptions = {};
  bool _connected = false;

  GenexWebSocketClient(this.wsUrl);

  /// 连接 WebSocket
  Future<void> connect() async {
    if (_connected) return;

    _channel = WebSocketChannel.connect(Uri.parse(wsUrl));
    _connected = true;

    _channel!.stream.listen(
      _onMessage,
      onError: _onError,
      onDone: _onDone,
    );
  }

  /// 订阅事件
  Stream<ChainEvent> subscribe(
      String eventType, Map<String, dynamic> params) {
    final controller = StreamController<ChainEvent>.broadcast();

    _ensureConnected().then((_) {
      _requestId++;
      final id = _requestId;
      final completer = Completer<dynamic>();
      _pendingRequests[id] = completer;

      _channel!.sink.add(jsonEncode({
        'jsonrpc': '2.0',
        'id': id,
        'method': 'eth_subscribe',
        'params': [eventType, if (params.isNotEmpty) params],
      }));

      completer.future.then((subscriptionId) {
        _subscriptions[subscriptionId as String] = controller;
      });
    });

    return controller.stream;
  }

  /// 取消订阅
  Future<void> unsubscribe(String subscriptionId) async {
    await _ensureConnected();
    _requestId++;
    final id = _requestId;
    final completer = Completer<dynamic>();
    _pendingRequests[id] = completer;

    _channel!.sink.add(jsonEncode({
      'jsonrpc': '2.0',
      'id': id,
      'method': 'eth_unsubscribe',
      'params': [subscriptionId],
    }));

    await completer.future;
    _subscriptions[subscriptionId]?.close();
    _subscriptions.remove(subscriptionId);
  }

  Future<void> _ensureConnected() async {
    if (!_connected) await connect();
  }

  void _onMessage(dynamic message) {
    final json = jsonDecode(message as String) as Map<String, dynamic>;

    // 处理 RPC 响应
    if (json.containsKey('id') && json['id'] != null) {
      final id = json['id'] as int;
      final completer = _pendingRequests.remove(id);
      if (completer != null) {
        if (json.containsKey('error')) {
          completer.completeError(
            Exception(json['error'].toString()),
          );
        } else {
          completer.complete(json['result']);
        }
      }
      return;
    }

    // 处理订阅推送
    if (json['method'] == 'eth_subscription') {
      final params = json['params'] as Map<String, dynamic>;
      final subId = params['subscription'] as String;
      final controller = _subscriptions[subId];
      if (controller != null) {
        controller.add(ChainEvent.fromSubscription(params));
      }
    }
  }

  void _onError(Object error) {
    for (final controller in _subscriptions.values) {
      controller.addError(error);
    }
  }

  void _onDone() {
    _connected = false;
    for (final controller in _subscriptions.values) {
      controller.close();
    }
    _subscriptions.clear();
    _pendingRequests.clear();
  }

  void close() {
    _channel?.sink.close();
    _connected = false;
    for (final controller in _subscriptions.values) {
      controller.close();
    }
    _subscriptions.clear();
  }
}