apidash/packages/better_networking/lib/services/http_client_manager.dart

import 'dart:io';
import 'package:flutter/foundation.dart';
import 'package:http/http.dart' as http;
import 'package:http/io_client.dart';

http.Client createHttpClientWithNoSSL() {
  var ioClient = HttpClient()
    ..badCertificateCallback = (X509Certificate cert, String host, int port) =>
        true;
  return IOClient(ioClient);
}

class _JsonAcceptClient extends http.BaseClient {
  final http.Client _inner;

  _JsonAcceptClient(this._inner);

  @override
  Future<http.StreamedResponse> send(http.BaseRequest request) {
    request.headers['Accept'] = 'application/json';
    return _inner.send(request);
  }

  @override
  void close() {
    _inner.close();
  }
}

class HttpClientManager {
  static final HttpClientManager _instance = HttpClientManager._internal();
  static const int _maxCancelledRequests = 100;
  final Map<String, http.Client> _clients = {};
  final Set<String> _cancelledRequests = {};

  factory HttpClientManager() {
    return _instance;
  }

  HttpClientManager._internal();

  http.Client createClient(String requestId, {bool noSSL = false}) {
    final client = (noSSL && !kIsWeb)
        ? createHttpClientWithNoSSL()
        : http.Client();
    _clients[requestId] = client;
    return client;
  }

  void cancelRequest(String? requestId) {
    if (requestId != null && _clients.containsKey(requestId)) {
      _clients[requestId]?.close();
      _clients.remove(requestId);

      _cancelledRequests.add(requestId);
      if (_cancelledRequests.length > _maxCancelledRequests) {
        _cancelledRequests.remove(_cancelledRequests.first);
      }
    }
  }

  bool wasRequestCancelled(String requestId) {
    return _cancelledRequests.contains(requestId);
  }

  void removeCancelledRequest(String requestId) {
    _cancelledRequests.remove(requestId);
  }

  void closeClient(String requestId) {
    if (_clients.containsKey(requestId)) {
      _clients[requestId]?.close();
      _clients.remove(requestId);
    }
  }

  bool hasActiveClient(String requestId) {
    return _clients.containsKey(requestId);
  }

  http.Client createClientWithJsonAccept(
    String requestId, {
    bool noSSL = false,
  }) {
    final baseClient = (noSSL && !kIsWeb)
        ? createHttpClientWithNoSSL()
        : http.Client();

    final client = _JsonAcceptClient(baseClient);
    _clients[requestId] = client;
    return client;
  }
}