pkgs/cupertino_http/lib/src/cupertino_api.dart

// Copyright (c) 2022, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

/// Provides access to the
/// [Foundation URL Loading System](https://developer.apple.com/documentation/foundation/url_loading_system).
///
/// For example:
/// ```
/// void main() {
///   final url = Uri.https('www.example.com', '/');
///   final session = URLSession.sharedSession();
///   final task = session.dataTaskWithCompletionHandler(
///     URLRequest.fromUrl(url),
///       (data, response, error) {
///     if (error == null) {
///       if (response != null && response.statusCode == 200) {
///         print(response);  // Do something with the response.
///         return;
///       }
///     }
///     print(error);  // Handle errors.
///   });
///   task.resume();
/// }
/// ```
library;

import 'dart:async';

import 'package:objective_c/objective_c.dart' as objc;

import 'native_cupertino_bindings.dart' as ncb;
import 'native_cupertino_bindings.dart'
    show
        NSHTTPCookieAcceptPolicy,
        NSURLRequestCachePolicy,
        NSURLRequestNetworkServiceType,
        NSURLSessionMultipathServiceType,
        NSURLSessionResponseDisposition,
        NSURLSessionTaskState,
        NSURLSessionWebSocketMessageType;

export 'native_cupertino_bindings.dart'
    show
        NSHTTPCookieAcceptPolicy,
        NSURLRequestCachePolicy,
        NSURLRequestNetworkServiceType,
        NSURLSessionMultipathServiceType,
        NSURLSessionResponseDisposition,
        NSURLSessionTaskState,
        NSURLSessionWebSocketCloseCode,
        NSURLSessionWebSocketMessageType;

objc.NSURL _uriToNSURL(Uri uri) =>
    objc.NSURL.URLWithString(uri.toString().toNSString())!;
Uri _nsurlToUri(objc.NSURL url) =>
    Uri.parse(url.absoluteString!.toDartString());

/// Callback for HTTP redirect handling.
typedef OnRedirect =
    URLRequest? Function(
      URLSession session,
      URLSessionTask task,
      HTTPURLResponse response,
      URLRequest newRequest,
    );

/// Callback invoked when the initial response (headers) is received.
typedef OnResponse =
    NSURLSessionResponseDisposition Function(
      URLSession session,
      URLSessionTask task,
      URLResponse response,
    );

/// Callback invoked when a data chunk is received.
typedef OnData =
    void Function(URLSession session, URLSessionTask task, objc.NSData data);

/// Callback invoked when a download task finishes writing to disk.
typedef OnFinishedDownloading =
    void Function(URLSession session, URLSessionDownloadTask task, Uri uri);

/// Callback invoked when a task completes (successfully or with an error).
typedef OnComplete =
    void Function(URLSession session, URLSessionTask task, objc.NSError? error);

/// Callback invoked when a WebSocket handshake succeeds.
typedef OnWebSocketTaskOpened =
    void Function(
      URLSession session,
      URLSessionWebSocketTask task,
      String? protocol,
    );

/// Callback invoked when a WebSocket receives a close frame from the peer.
typedef OnWebSocketTaskClosed =
    void Function(
      URLSession session,
      URLSessionWebSocketTask task,
      int closeCode,
      objc.NSData? reason,
    );

@pragma('vm:prefer-inline')
objc.ObjCProtocolBuilder _buildDelegate(
  bool isBackground, {
  OnRedirect? onRedirect,
  OnResponse? onResponse,
  OnData? onData,
  OnFinishedDownloading? onFinishedDownloading,
  OnComplete? onComplete,
  OnWebSocketTaskOpened? onWebSocketTaskOpened,
  OnWebSocketTaskClosed? onWebSocketTaskClosed,
}) {
  final protoBuilder = objc.ObjCProtocolBuilder();

  if (onComplete != null) {
    ncb.NSURLSessionDataDelegate$Builder.URLSession_task_didCompleteWithError_
        .implementAsListener(protoBuilder, (nsSession, nsTask, nsError) {
          onComplete(
            URLSession._(nsSession, isBackground: isBackground),
            URLSessionTask._(nsTask),
            nsError,
          );
        });
  }

  if (onRedirect != null) {
    ncb
        .NSURLSessionDataDelegate$Builder
        // ignore: lines_longer_than_80_chars
        .URLSession_task_willPerformHTTPRedirection_newRequest_completionHandler_
        .implementAsListener(
          protoBuilder,

          // ignore: lines_longer_than_80_chars
          (nsSession, nsTask, nsResponse, nsRequest, nsRequestCompleter) {
            final request = URLRequest._(nsRequest);
            final response =
                URLResponse._exactURLResponseType(nsResponse)
                    as HTTPURLResponse;
            final redirectRequest = onRedirect(
              URLSession._(nsSession, isBackground: isBackground),
              URLSessionTask._(nsTask),
              response,
              request,
            );
            nsRequestCompleter.call(redirectRequest?._nsObject);
          },
        );
  }

  if (onResponse != null) {
    ncb
        .NSURLSessionDataDelegate$Builder
        .URLSession_dataTask_didReceiveResponse_completionHandler_
        .implementAsListener(protoBuilder, (
          nsSession,
          nsDataTask,
          nsResponse,
          nsCompletionHandler,
        ) {
          final exactResponse = URLResponse._exactURLResponseType(nsResponse);
          final disposition = onResponse(
            URLSession._(nsSession, isBackground: isBackground),
            URLSessionTask._(nsDataTask),
            exactResponse,
          );
          nsCompletionHandler.call(disposition);
        });
  }

  if (onData != null) {
    ncb.NSURLSessionDataDelegate$Builder.URLSession_dataTask_didReceiveData_
        .implementAsListener(protoBuilder, (nsSession, nsDataTask, nsData) {
          onData(
            URLSession._(nsSession, isBackground: isBackground),
            URLSessionTask._(nsDataTask),
            nsData,
          );
        });
  }

  if (onFinishedDownloading != null) {
    ncb
        .NSURLSessionDownloadDelegate$Builder
        .URLSession_downloadTask_didFinishDownloadingToURL_
        .implementAsBlocking(protoBuilder, (nsSession, nsTask, nsUrl) {
          onFinishedDownloading(
            URLSession._(nsSession, isBackground: isBackground),
            URLSessionDownloadTask._(nsTask),
            _nsurlToUri(nsUrl),
          );
        });
  }

  if (onWebSocketTaskOpened != null) {
    ncb
        .NSURLSessionWebSocketDelegate$Builder
        .URLSession_webSocketTask_didOpenWithProtocol_
        .implementAsListener(protoBuilder, (nsSession, nsTask, nsProtocol) {
          onWebSocketTaskOpened(
            URLSession._(nsSession, isBackground: isBackground),
            URLSessionWebSocketTask._(nsTask),
            nsProtocol?.toDartString(),
          );
        });
  }

  if (onWebSocketTaskClosed != null) {
    ncb
        .NSURLSessionWebSocketDelegate$Builder
        .URLSession_webSocketTask_didCloseWithCode_reason_
        .implementAsListener(protoBuilder, (
          nsSession,
          nsTask,
          closeCode,
          reason,
        ) {
          onWebSocketTaskClosed(
            URLSession._(nsSession, isBackground: isBackground),
            URLSessionWebSocketTask._(nsTask),
            closeCode,
            reason,
          );
        });
  }

  return protoBuilder;
}

abstract class _ObjectHolder<T extends objc.NSObject> {
  final T _nsObject;

  _ObjectHolder(this._nsObject);

  @override
  bool operator ==(Object other) {
    if (other is _ObjectHolder) {
      return _nsObject == other._nsObject;
    }
    return false;
  }

  @override
  int get hashCode => _nsObject.hashCode;
}

/// A cache for [URLRequest]s. Used by [URLSessionConfiguration.cache].
///
/// See [NSURLCache](https://developer.apple.com/documentation/foundation/nsurlcache)
class URLCache extends _ObjectHolder<ncb.NSURLCache> {
  URLCache._(super.c);

  /// The default URLCache.
  ///
  /// See [NSURLCache.sharedURLCache](https://developer.apple.com/documentation/foundation/nsurlcache/1413377-sharedurlcache)
  static URLCache? get sharedURLCache {
    final sharedCache = ncb.NSURLCache.getSharedURLCache();
    return URLCache._(sharedCache);
  }

  /// Create a new [URLCache] with the given memory and disk cache sizes.
  ///
  /// [memoryCapacity] and [diskCapacity] are specified in bytes.
  ///
  /// [directory] is the file system location where the disk cache will be
  /// stored. If `null` then the default directory will be used.
  ///
  /// See [NSURLCache initWithMemoryCapacity:diskCapacity:directoryURL:](https://developer.apple.com/documentation/foundation/nsurlcache/3240612-initwithmemorycapacity)
  factory URLCache.withCapacity({
    int memoryCapacity = 0,
    int diskCapacity = 0,
    Uri? directory,
  }) => URLCache._(
    ncb.NSURLCache.alloc().initWithMemoryCapacity(
      memoryCapacity,
      diskCapacity: diskCapacity,
      directoryURL: directory == null ? null : _uriToNSURL(directory),
    ),
  );
}

/// Controls the behavior of a URLSession.
///
/// See [NSURLSessionConfiguration](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration)
class URLSessionConfiguration
    extends _ObjectHolder<ncb.NSURLSessionConfiguration> {
  // A configuration created with
  // [`backgroundSessionConfigurationWithIdentifier`](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1407496-backgroundsessionconfigurationwi)
  final bool _isBackground;

  URLSessionConfiguration._(super.c, {required bool isBackground})
    : _isBackground = isBackground;

  /// A configuration suitable for performing HTTP uploads and downloads in
  /// the background.
  ///
  /// See [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1407496-backgroundsessionconfigurationwi)
  factory URLSessionConfiguration.backgroundSession(
    String identifier,
  ) => URLSessionConfiguration._(
    ncb.NSURLSessionConfiguration.backgroundSessionConfigurationWithIdentifier(
      identifier.toNSString(),
    ),
    isBackground: true,
  );

  /// A configuration that uses caching and saves cookies and credentials.
  ///
  /// See [NSURLSessionConfiguration defaultSessionConfiguration](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1411560-defaultsessionconfiguration)
  factory URLSessionConfiguration.defaultSessionConfiguration() =>
      URLSessionConfiguration._(
        ncb.NSURLSessionConfiguration.as(
          ncb.NSURLSessionConfiguration.getDefaultSessionConfiguration(),
        ),
        isBackground: false,
      );

  /// A session configuration that uses no persistent storage for caches,
  /// cookies, or credentials.
  ///
  /// See [NSURLSessionConfiguration ephemeralSessionConfiguration](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1410529-ephemeralsessionconfiguration)
  factory URLSessionConfiguration.ephemeralSessionConfiguration() =>
      URLSessionConfiguration._(
        ncb.NSURLSessionConfiguration.as(
          ncb.NSURLSessionConfiguration.getEphemeralSessionConfiguration(),
        ),
        isBackground: false,
      );

  /// Whether connections over a cellular network are allowed.
  ///
  /// See [NSURLSessionConfiguration.allowsCellularAccess](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1409406-allowscellularaccess)
  bool get allowsCellularAccess => _nsObject.allowsCellularAccess;
  set allowsCellularAccess(bool value) =>
      _nsObject.allowsCellularAccess = value;

  /// Whether connections are allowed when the user has selected Low Data Mode.
  ///
  /// See [NSURLSessionConfiguration.allowsConstrainedNetworkAccess](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/3235751-allowsconstrainednetworkaccess)
  bool get allowsConstrainedNetworkAccess =>
      _nsObject.allowsConstrainedNetworkAccess;
  set allowsConstrainedNetworkAccess(bool value) =>
      _nsObject.allowsConstrainedNetworkAccess = value;

  /// Whether connections are allowed over expensive networks.
  ///
  /// See [NSURLSessionConfiguration.allowsExpensiveNetworkAccess](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/3235752-allowsexpensivenetworkaccess)
  bool get allowsExpensiveNetworkAccess =>
      _nsObject.allowsExpensiveNetworkAccess;
  set allowsExpensiveNetworkAccess(bool value) =>
      _nsObject.allowsExpensiveNetworkAccess = value;

  /// The [URLCache] used to cache the results of [URLSessionTask]s.
  ///
  /// A value of `nil` indicates that no cache will be used.
  ///
  /// See [NSURLSessionConfiguration.URLCache](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1410148-urlcache)
  URLCache? get cache =>
      _nsObject.URLCache == null ? null : URLCache._(_nsObject.URLCache!);
  set cache(URLCache? cache) => _nsObject.URLCache = cache?._nsObject;

  /// Whether background tasks can be delayed by the system.
  ///
  /// See [NSURLSessionConfiguration.discretionary](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1411552-discretionary)
  bool get discretionary => _nsObject.isDiscretionary;
  set discretionary(bool value) => _nsObject.isDiscretionary = value;

  /// Additional headers to send with each request.
  ///
  /// Note that the getter for this field returns a **copy** of the headers.
  ///
  /// See [NSURLSessionConfiguration.HTTPAdditionalHeaders](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1411532-httpadditionalheaders)
  Map<String, String>? get httpAdditionalHeaders {
    if (_nsObject.HTTPAdditionalHeaders case var additionalHeaders?) {
      final headers = objc.NSDictionary.as(additionalHeaders);
      return (objc.toDartObject(headers) as Map).cast<String, String>();
    }
    return null;
  }

  set httpAdditionalHeaders(Map<String, String>? headers) {
    if (headers == null) {
      _nsObject.HTTPAdditionalHeaders = null;
      return;
    }
    _nsObject.HTTPAdditionalHeaders =
        objc.toObjCObject(headers) as objc.NSMutableDictionary;
  }

  /// What policy to use when deciding whether to accept cookies.
  ///
  /// See [NSURLSessionConfiguration.HTTPCookieAcceptPolicy](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1408933-httpcookieacceptpolicy).
  NSHTTPCookieAcceptPolicy get httpCookieAcceptPolicy =>
      _nsObject.HTTPCookieAcceptPolicy;
  set httpCookieAcceptPolicy(NSHTTPCookieAcceptPolicy value) =>
      _nsObject.HTTPCookieAcceptPolicy = value;

  /// The maximum number of connections that a URLSession can have open to the
  /// same host.
  //
  /// See [NSURLSessionConfiguration.HTTPMaximumConnectionsPerHost](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1407597-httpmaximumconnectionsperhost).
  int get httpMaximumConnectionsPerHost =>
      _nsObject.HTTPMaximumConnectionsPerHost;
  set httpMaximumConnectionsPerHost(int value) =>
      _nsObject.HTTPMaximumConnectionsPerHost = value;

  /// Whether requests should include cookies from the cookie store.
  ///
  /// See [NSURLSessionConfiguration.HTTPShouldSetCookies](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1411589-httpshouldsetcookies)
  bool get httpShouldSetCookies => _nsObject.HTTPShouldSetCookies;
  set httpShouldSetCookies(bool value) =>
      _nsObject.HTTPShouldSetCookies = value;

  /// Whether to use [HTTP pipelining](https://en.wikipedia.org/wiki/HTTP_pipelining).
  ///
  /// See [NSURLSessionConfiguration.HTTPShouldUsePipelining](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1411657-httpshouldusepipelining)
  bool get httpShouldUsePipelining => _nsObject.HTTPShouldUsePipelining;
  set httpShouldUsePipelining(bool value) =>
      _nsObject.HTTPShouldUsePipelining = value;

  /// What type of Multipath TCP connections to use.
  ///
  /// See [NSURLSessionConfiguration.multipathServiceType](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/2875967-multipathservicetype)
  NSURLSessionMultipathServiceType get multipathServiceType =>
      _nsObject.multipathServiceType;
  set multipathServiceType(NSURLSessionMultipathServiceType value) =>
      _nsObject.multipathServiceType = value;

  /// Provides in indication to the operating system on what type of requests
  /// are being sent.
  ///
  /// See [NSURLSessionConfiguration.networkServiceType](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1411606-networkservicetype).
  NSURLRequestNetworkServiceType get networkServiceType =>
      _nsObject.networkServiceType;
  set networkServiceType(NSURLRequestNetworkServiceType value) =>
      _nsObject.networkServiceType = value;

  /// Controls how to deal with response caching.
  ///
  /// See [NSURLSessionConfiguration.requestCachePolicy](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1411655-requestcachepolicy)
  NSURLRequestCachePolicy get requestCachePolicy =>
      _nsObject.requestCachePolicy;
  set requestCachePolicy(NSURLRequestCachePolicy value) =>
      _nsObject.requestCachePolicy = value;

  /// Whether the app should be resumed when background tasks complete.
  ///
  /// See [NSURLSessionConfiguration.sessionSendsLaunchEvents](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1617174-sessionsendslaunchevents)
  bool get sessionSendsLaunchEvents => _nsObject.sessionSendsLaunchEvents;
  set sessionSendsLaunchEvents(bool value) =>
      _nsObject.sessionSendsLaunchEvents = value;

  /// The timeout interval if data is not received.
  ///
  /// See [NSURLSessionConfiguration.timeoutIntervalForRequest](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1408259-timeoutintervalforrequest)
  Duration get timeoutIntervalForRequest => Duration(
    microseconds:
        (_nsObject.timeoutIntervalForRequest * Duration.microsecondsPerSecond)
            .round(),
  );

  set timeoutIntervalForRequest(Duration interval) {
    _nsObject.timeoutIntervalForRequest =
        interval.inMicroseconds.toDouble() / Duration.microsecondsPerSecond;
  }

  /// Whether tasks should wait for connectivity or fail immediately.
  ///
  /// See [NSURLSessionConfiguration.waitsForConnectivity](https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/2908812-waitsforconnectivity)
  bool get waitsForConnectivity => _nsObject.waitsForConnectivity;
  set waitsForConnectivity(bool value) =>
      _nsObject.waitsForConnectivity = value;

  @override
  String toString() =>
      '[URLSessionConfiguration '
      'allowsCellularAccess=$allowsCellularAccess '
      'allowsConstrainedNetworkAccess=$allowsConstrainedNetworkAccess '
      'allowsExpensiveNetworkAccess=$allowsExpensiveNetworkAccess '
      'discretionary=$discretionary '
      'httpAdditionalHeaders=$httpAdditionalHeaders '
      'httpCookieAcceptPolicy=$httpCookieAcceptPolicy '
      'httpShouldSetCookies=$httpShouldSetCookies '
      'httpMaximumConnectionsPerHost=$httpMaximumConnectionsPerHost '
      'httpShouldUsePipelining=$httpShouldUsePipelining '
      'requestCachePolicy=$requestCachePolicy '
      'sessionSendsLaunchEvents=$sessionSendsLaunchEvents '
      'shouldUseExtendedBackgroundIdleMode='
      'timeoutIntervalForRequest=$timeoutIntervalForRequest '
      'waitsForConnectivity=$waitsForConnectivity'
      ']';
}

/// The response associated with loading an URL.
///
/// See [NSURLResponse](https://developer.apple.com/documentation/foundation/nsurlresponse)
class URLResponse extends _ObjectHolder<ncb.NSURLResponse> {
  URLResponse._(super.c);

  factory URLResponse._exactURLResponseType(ncb.NSURLResponse response) {
    if (ncb.NSHTTPURLResponse.isA(response)) {
      return HTTPURLResponse._(ncb.NSHTTPURLResponse.as(response));
    }
    return URLResponse._(response);
  }

  /// The expected amount of data returned with the response.
  ///
  /// See [NSURLResponse.expectedContentLength](https://developer.apple.com/documentation/foundation/nsurlresponse/1413507-expectedcontentlength)
  int get expectedContentLength => _nsObject.expectedContentLength;

  /// The MIME type of the response.
  ///
  /// See [NSURLResponse.MIMEType](https://developer.apple.com/documentation/foundation/nsurlresponse/1411613-mimetype)
  String? get mimeType => _nsObject.MIMEType?.toDartString();

  @override
  String toString() =>
      '[URLResponse '
      'mimeType=$mimeType '
      'expectedContentLength=$expectedContentLength'
      ']';
}

/// The response associated with loading a HTTP URL.
///
/// See [NSHTTPURLResponse](https://developer.apple.com/documentation/foundation/nshttpurlresponse)
class HTTPURLResponse extends URLResponse {
  final ncb.NSHTTPURLResponse _httpUrlResponse;

  HTTPURLResponse._(ncb.NSHTTPURLResponse super.c)
    : _httpUrlResponse = c,
      super._();

  /// The HTTP status code of the response (e.g. 200).
  ///
  /// See [HTTPURLResponse.statusCode](https://developer.apple.com/documentation/foundation/nshttpurlresponse/1409395-statuscode)
  int get statusCode => _httpUrlResponse.statusCode;

  /// The HTTP headers of the response.
  ///
  /// See [HTTPURLResponse.allHeaderFields](https://developer.apple.com/documentation/foundation/nshttpurlresponse/1417930-allheaderfields)
  Map<String, String> get allHeaderFields =>
      (objc.toDartObject(_httpUrlResponse.allHeaderFields) as Map)
          .cast<String, String>();

  @override
  String toString() =>
      '[HTTPURLResponse '
      'statusCode=$statusCode '
      'mimeType=$mimeType '
      'expectedContentLength=$expectedContentLength'
      ']';
}

/// A WebSocket message.
///
/// See [NSURLSessionWebSocketMessage](https://developer.apple.com/documentation/foundation/nsurlsessionwebsocketmessage)
class URLSessionWebSocketMessage
    extends _ObjectHolder<ncb.NSURLSessionWebSocketMessage> {
  URLSessionWebSocketMessage._(super.nsObject);

  /// Create a WebSocket data message.
  ///
  /// See [NSURLSessionWebSocketMessage initWithData:](https://developer.apple.com/documentation/foundation/nsurlsessionwebsocketmessage/3181192-initwithdata)
  factory URLSessionWebSocketMessage.fromData(objc.NSData d) =>
      URLSessionWebSocketMessage._(
        ncb.NSURLSessionWebSocketMessage.alloc().initWithData(d),
      );

  /// Create a WebSocket string message.
  ///
  /// See [NSURLSessionWebSocketMessage initWitString:](https://developer.apple.com/documentation/foundation/nsurlsessionwebsocketmessage/3181193-initwithstring)
  factory URLSessionWebSocketMessage.fromString(String s) =>
      URLSessionWebSocketMessage._(
        ncb.NSURLSessionWebSocketMessage.alloc().initWithString(s.toNSString()),
      );

  /// The data associated with the WebSocket message.
  ///
  /// Will be `null` if the [URLSessionWebSocketMessage] is a string message.
  ///
  /// See [NSURLSessionWebSocketMessage.data](https://developer.apple.com/documentation/foundation/nsurlsessionwebsocketmessage/3181191-data)
  objc.NSData? get data => _nsObject.data;

  /// The string associated with the WebSocket message.
  ///
  /// Will be `null` if the [URLSessionWebSocketMessage] is a data message.
  ///
  /// See [NSURLSessionWebSocketMessage.string](https://developer.apple.com/documentation/foundation/nsurlsessionwebsocketmessage/3181194-string)
  String? get string => _nsObject.string?.toDartString();

  /// The type of the WebSocket message.
  ///
  /// See [NSURLSessionWebSocketMessage.type](https://developer.apple.com/documentation/foundation/nsurlsessionwebsocketmessage/3181195-type)
  NSURLSessionWebSocketMessageType get type => _nsObject.type;

  @override
  String toString() =>
      '[URLSessionWebSocketMessage type=$type string=$string data=$data]';
}

/// A task associated with downloading a URI.
///
/// See [NSURLSessionTask](https://developer.apple.com/documentation/foundation/nsurlsessiontask)
class URLSessionTask extends _ObjectHolder<ncb.NSURLSessionTask> {
  URLSessionTask._(super.c);

  /// Cancels the task.
  ///
  /// See [NSURLSessionTask cancel](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1411591-cancel)
  void cancel() {
    _nsObject.cancel();
  }

  /// Resumes a suspended task (new tasks start as suspended).
  ///
  /// See [NSURLSessionTask resume](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1411121-resume)
  void resume() {
    _nsObject.resume();
  }

  /// Suspends a task (prevents it from transferring data).
  ///
  /// See [NSURLSessionTask suspend](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1411565-suspend)
  void suspend() {
    _nsObject.suspend();
  }

  /// The current state of the task.
  ///
  /// See [NSURLSessionTask.state](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1409888-state)
  NSURLSessionTaskState get state => _nsObject.state;

  /// The relative priority [0, 1] that the host should use to handle the
  /// request.
  ///
  /// See [NSURLSessionTask.priority](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1410569-priority)
  double get priority => _nsObject.priority;

  /// The relative priority [0, 1] that the host should use to handle the
  /// request.
  ///
  /// See [NSURLSessionTask.priority](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1410569-priority)
  set priority(double value) => _nsObject.priority = value;

  /// The request currently being handled by the task.
  ///
  /// May be different from [originalRequest] if the server responds with a
  /// redirect.
  ///
  /// See [NSURLSessionTask.currentRequest](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1411649-currentrequest)
  URLRequest? get currentRequest {
    final request = _nsObject.currentRequest;
    if (request == null) {
      return null;
    } else {
      return URLRequest._(request);
    }
  }

  /// The original request associated with the task.
  ///
  /// May be different from [currentRequest] if the server responds with a
  /// redirect.
  ///
  /// See [NSURLSessionTask.originalRequest](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1411572-originalrequest)
  URLRequest? get originalRequest {
    final request = _nsObject.originalRequest;
    if (request == null) {
      return null;
    } else {
      return URLRequest._(request);
    }
  }

  /// The server response to the request associated with this task.
  ///
  /// See [NSURLSessionTask.response](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1410586-response)
  URLResponse? get response {
    final nsResponse = _nsObject.response;
    if (nsResponse == null) {
      return null;
    }
    return URLResponse._exactURLResponseType(nsResponse);
  }

  /// An error indicating why the task failed or `null` on success.
  ///
  /// See [NSURLSessionTask.error](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1408145-error)
  objc.NSError? get error => _nsObject.error;

  /// The user-assigned description for the task.
  ///
  /// See [NSURLSessionTask.taskDescription](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1409798-taskdescription)
  String get taskDescription => _nsObject.taskDescription?.toDartString() ?? '';

  /// The user-assigned description for the task.
  ///
  /// See [NSURLSessionTask.taskDescription](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1409798-taskdescription)
  set taskDescription(String value) =>
      _nsObject.taskDescription = value.toNSString();

  /// A unique ID for the [URLSessionTask] in a [URLSession].
  ///
  /// See [NSURLSessionTask.taskIdentifier](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1411231-taskidentifier)
  int get taskIdentifier => _nsObject.taskIdentifier;

  /// The number of content bytes that are expected to be received from the
  /// server.
  ///
  /// See [NSURLSessionTask.countOfBytesReceived](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1410663-countofbytesexpectedtoreceive)
  int get countOfBytesExpectedToReceive =>
      _nsObject.countOfBytesExpectedToReceive;

  /// The number of content bytes that have been received from the server.
  ///
  /// See [NSURLSessionTask.countOfBytesReceived](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1411581-countofbytesreceived)
  int get countOfBytesReceived => _nsObject.countOfBytesReceived;

  /// The number of content bytes that the task expects to send to the server.
  ///
  /// See [NSURLSessionTask.countOfBytesExpectedToSend](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1411534-countofbytesexpectedtosend)
  int get countOfBytesExpectedToSend => _nsObject.countOfBytesExpectedToSend;

  /// Whether the body of the response should be delivered incrementally or not.
  ///
  /// [NSURLSessionTask.countOfBytesSent](https://developer.apple.com/documentation/foundation/nsurlsessiontask/1410444-countofbytessent)
  int get countOfBytesSent => _nsObject.countOfBytesSent;

  /// Whether the body of the response should be delivered incrementally or not.
  ///
  /// See [NSURLSessionTask.prefersIncrementalDelivery](https://developer.apple.com/documentation/foundation/nsurlsessiontask/3735881-prefersincrementaldelivery)
  bool get prefersIncrementalDelivery => _nsObject.prefersIncrementalDelivery;

  /// Whether the body of the response should be delivered incrementally or not.
  ///
  /// See [NSURLSessionTask.prefersIncrementalDelivery](https://developer.apple.com/documentation/foundation/nsurlsessiontask/3735881-prefersincrementaldelivery)
  set prefersIncrementalDelivery(bool value) =>
      _nsObject.prefersIncrementalDelivery = value;

  @pragma('vm:prefer-inline')
  static ncb.NSURLSessionTaskDelegate delegate({
    OnRedirect? onRedirect,
    OnResponse? onResponse,
    OnData? onData,
    OnFinishedDownloading? onFinishedDownloading,
    OnComplete? onComplete,
    OnWebSocketTaskOpened? onWebSocketTaskOpened,
    OnWebSocketTaskClosed? onWebSocketTaskClosed,
  }) {
    final builder = _buildDelegate(
      false,
      onRedirect: onRedirect,
      onResponse: onResponse,
      onData: onData,
      onFinishedDownloading: onFinishedDownloading,
      onComplete: onComplete,
      onWebSocketTaskOpened: onWebSocketTaskOpened,
      onWebSocketTaskClosed: onWebSocketTaskClosed,
    );
    return ncb.NSURLSessionTaskDelegate.as(builder.build());
  }

  /// Sets a task-specific delegate.
  ///
  /// Methods not implemented on this delegate will still be forwarded to the
  /// session delegate. Cannot be modified after the task resumes. Not
  /// supported on background sessions.
  ///
  /// See [NSURLSessionTask.delegate](https://developer.apple.com/documentation/foundation/nsurlsessiontask/3746977-delegate)
  set taskDelegate(ncb.NSURLSessionTaskDelegate value) =>
      _nsObject.delegate = value;

  String _toStringHelper(String className) =>
      '[$className '
      'taskDescription=$taskDescription '
      'taskIdentifier=$taskIdentifier '
      'countOfBytesExpectedToReceive=$countOfBytesExpectedToReceive '
      'countOfBytesReceived=$countOfBytesReceived '
      'countOfBytesExpectedToSend=$countOfBytesExpectedToSend '
      'countOfBytesSent=$countOfBytesSent '
      'priority=$priority '
      'state=$state '
      'prefersIncrementalDelivery=$prefersIncrementalDelivery'
      ']';

  @override
  String toString() => _toStringHelper('URLSessionTask');
}

/// A task associated with downloading a URI to a file.
///
/// See [NSURLSessionDownloadTask](https://developer.apple.com/documentation/foundation/nsurlsessiondownloadtask)
class URLSessionDownloadTask extends URLSessionTask {
  URLSessionDownloadTask._(ncb.NSURLSessionDownloadTask super.c) : super._();

  @override
  String toString() => _toStringHelper('URLSessionDownloadTask');
}

/// A task associated with a WebSocket connection.
///
/// See [NSURLSessionWebSocketTask](https://developer.apple.com/documentation/foundation/nsurlsessionwebsockettask)
class URLSessionWebSocketTask extends URLSessionTask {
  final ncb.NSURLSessionWebSocketTask _urlSessionWebSocketTask;

  URLSessionWebSocketTask._(ncb.NSURLSessionWebSocketTask super.c)
    : _urlSessionWebSocketTask = c,
      super._();

  /// The close code set when the WebSocket connection is closed.
  ///
  /// See [NSURLSessionWebSocketTask.closeCode](https://developer.apple.com/documentation/foundation/nsurlsessionwebsockettask/3181201-closecode)
  int get closeCode => _urlSessionWebSocketTask.closeCode;

  /// The close reason set when the WebSocket connection is closed.
  /// If there is no close reason available this property will be null.
  ///
  /// See [NSURLSessionWebSocketTask.closeReason](https://developer.apple.com/documentation/foundation/nsurlsessionwebsockettask/3181202-closereason)
  objc.NSData? get closeReason => _urlSessionWebSocketTask.closeReason;

  /// Sends a single WebSocket message.
  ///
  /// The returned future will complete successfully when the message is sent
  /// and with an [Error] on failure.
  ///
  /// See [NSURLSessionWebSocketTask.sendMessage:completionHandler:](https://developer.apple.com/documentation/foundation/nsurlsessionwebsockettask/3181205-sendmessage)
  Future<void> sendMessage(URLSessionWebSocketMessage message) async {
    final completer = Completer<void>();
    _urlSessionWebSocketTask.sendMessage(
      message._nsObject,
      completionHandler: ncb.ObjCBlock_ffiVoid_NSError.listener((error) {
        if (error == null) {
          completer.complete();
        } else {
          completer.completeError(error);
        }
      }),
    );

    await completer.future;
  }

  /// Receives a single WebSocket message.
  ///
  /// Throws an [Error] on failure.
  ///
  /// See [NSURLSessionWebSocketTask.receiveMessageWithCompletionHandler:](https://developer.apple.com/documentation/foundation/nsurlsessionwebsockettask/3181204-receivemessagewithcompletionhand)
  Future<URLSessionWebSocketMessage> receiveMessage() async {
    final completer = Completer<URLSessionWebSocketMessage>();
    _urlSessionWebSocketTask.receiveMessageWithCompletionHandler(
      ncb.ObjCBlock_ffiVoid_NSURLSessionWebSocketMessage_NSError.listener((
        message,
        error,
      ) {
        if (error != null) {
          completer.completeError(error);
        } else if (message != null) {
          completer.complete(URLSessionWebSocketMessage._(message));
        } else {
          completer.completeError(
            StateError('one of message or error must be non-null'),
          );
        }
      }),
    );
    return completer.future;
  }

  /// Sends close frame with the given code and optional reason.
  ///
  /// See [NSURLSessionWebSocketTask.cancelWithCloseCode:reason:](https://developer.apple.com/documentation/foundation/nsurlsessionwebsockettask/3181200-cancelwithclosecode)
  void cancelWithCloseCode(int closeCode, objc.NSData? reason) {
    _urlSessionWebSocketTask.cancelWithCloseCode(closeCode, reason: reason);
  }

  @override
  String toString() => _toStringHelper('NSURLSessionWebSocketTask');
}

/// A request to load a URL.
///
/// See [NSURLRequest](https://developer.apple.com/documentation/foundation/nsurlrequest)
class URLRequest extends _ObjectHolder<ncb.NSURLRequest> {
  URLRequest._(super.c);

  /// Creates a request for a URL.
  ///
  /// See [NSURLRequest.requestWithURL:](https://developer.apple.com/documentation/foundation/nsurlrequest/1528603-requestwithurl)
  factory URLRequest.fromUrl(Uri uri) =>
      URLRequest._(ncb.NSURLRequest.requestWithURL(_uriToNSURL(uri)));

  /// Returns all of the HTTP headers for the request.
  ///
  /// See [NSURLRequest.allHTTPHeaderFields](https://developer.apple.com/documentation/foundation/nsurlrequest/1418477-allhttpheaderfields)
  Map<String, String>? get allHttpHeaderFields {
    if (_nsObject.allHTTPHeaderFields == null) {
      return null;
    } else {
      return (objc.toDartObject(_nsObject.allHTTPHeaderFields!) as Map)
          .cast<String, String>();
    }
  }

  /// Controls how to deal with caching for the request.
  ///
  /// See [NSURLSession.cachePolicy](https://developer.apple.com/documentation/foundation/nsurlrequest/1407944-cachepolicy)
  NSURLRequestCachePolicy get cachePolicy => _nsObject.cachePolicy;

  /// The body of the request.
  ///
  /// See [NSURLRequest.HTTPBody](https://developer.apple.com/documentation/foundation/nsurlrequest/1411317-httpbody)
  objc.NSData? get httpBody => _nsObject.HTTPBody;

  /// The HTTP request method (e.g. 'GET').
  ///
  /// See [NSURLRequest.HTTPMethod](https://developer.apple.com/documentation/foundation/nsurlrequest/1413030-httpmethod)
  ///
  /// NOTE: The documentation for `NSURLRequest.HTTPMethod` says that the
  /// property is nullable but, in practice, assigning it to null will produce
  /// an error.
  String get httpMethod => _nsObject.HTTPMethod!.toDartString();

  /// The timeout interval during the connection attempt.
  ///
  /// See [NSURLSession.timeoutInterval](https://developer.apple.com/documentation/foundation/nsurlrequest/1418229-timeoutinterval)
  Duration get timeoutInterval => Duration(
    microseconds: (_nsObject.timeoutInterval * Duration.microsecondsPerSecond)
        .round(),
  );

  /// The requested URL.
  ///
  /// See [URLRequest.URL](https://developer.apple.com/documentation/foundation/nsurlrequest/1408996-url)
  Uri? get url {
    final nsUrl = _nsObject.URL;
    if (nsUrl == null) {
      return null;
    }
    return _nsurlToUri(nsUrl);
  }

  @override
  String toString() =>
      '[URLRequest '
      'allHttpHeaderFields=$allHttpHeaderFields '
      'cachePolicy=$cachePolicy '
      'httpBody=$httpBody '
      'httpMethod=$httpMethod '
      'timeoutInterval=$timeoutInterval '
      'url=$url '
      ']';
}

/// A mutable request to load a URL.
///
/// See [NSMutableURLRequest](https://developer.apple.com/documentation/foundation/nsmutableurlrequest)
class MutableURLRequest extends URLRequest {
  final ncb.NSMutableURLRequest _mutableUrlRequest;

  MutableURLRequest._(ncb.NSMutableURLRequest super.c)
    : _mutableUrlRequest = c,
      super._();

  /// Creates a request for a URL.
  ///
  /// See [NSMutableURLRequest.requestWithURL:](https://developer.apple.com/documentation/foundation/nsmutableurlrequest/1414617-allhttpheaderfields)
  factory MutableURLRequest.fromUrl(Uri uri) {
    final url = objc.NSURL.URLWithString(uri.toString().toNSString())!;
    return MutableURLRequest._(ncb.NSMutableURLRequest.requestWithURL(url));
  }

  set cachePolicy(NSURLRequestCachePolicy value) =>
      _mutableUrlRequest.cachePolicy$1 = value;

  set httpBody(objc.NSData? data) {
    _mutableUrlRequest.HTTPBody = data;
  }

  /// Sets the body of the request to the given [Stream].
  ///
  /// See [NSMutableURLRequest.HTTPBodyStream](https://developer.apple.com/documentation/foundation/nsurlrequest/1407341-httpbodystream).
  set httpBodyStream(objc.NSInputStream stream) {
    _mutableUrlRequest.HTTPBodyStream = stream;
  }

  set httpMethod(String method) {
    _mutableUrlRequest.HTTPMethod = method.toNSString();
  }

  set timeoutInterval(Duration interval) {
    _mutableUrlRequest.timeoutInterval$1 =
        interval.inMicroseconds.toDouble() / Duration.microsecondsPerSecond;
  }

  /// Set the value of a header field.
  ///
  /// See [NSMutableURLRequest setValue:forHTTPHeaderField:](https://developer.apple.com/documentation/foundation/nsmutableurlrequest/1408793-setvalue)
  void setValueForHttpHeaderField(String value, String field) {
    _mutableUrlRequest.setValue(
      field.toNSString(),
      forHTTPHeaderField: value.toNSString(),
    );
  }

  @override
  String toString() =>
      '[MutableURLRequest '
      'allHttpHeaderFields=$allHttpHeaderFields '
      'cachePolicy=$cachePolicy '
      'httpBody=$httpBody '
      'httpMethod=$httpMethod '
      'timeoutInterval=$timeoutInterval '
      'url=$url '
      ']';
}

/// A client that can make network requests to a server.
///
/// See [NSURLSession](https://developer.apple.com/documentation/foundation/nsurlsession)
class URLSession extends _ObjectHolder<ncb.NSURLSession> {
  // Provide our own native delegate to `NSURLSession` because delegates can be
  // called on arbitrary threads and Dart code cannot be.
  // Indicates if the session is a background session. Copied from the
  // [URLSessionConfiguration._isBackground] associated with this [URLSession].
  final bool _isBackground;

  @pragma('vm:prefer-inline')
  static ncb.NSURLSessionDelegate delegate(
    bool isBackground, {
    OnRedirect? onRedirect,
    OnResponse? onResponse,
    OnData? onData,
    OnFinishedDownloading? onFinishedDownloading,
    OnComplete? onComplete,
    OnWebSocketTaskOpened? onWebSocketTaskOpened,
    OnWebSocketTaskClosed? onWebSocketTaskClosed,
  }) {
    final builder = _buildDelegate(
      isBackground,
      onRedirect: onRedirect,
      onResponse: onResponse,
      onData: onData,
      onFinishedDownloading: onFinishedDownloading,
      onComplete: onComplete,
      onWebSocketTaskOpened: onWebSocketTaskOpened,
      onWebSocketTaskClosed: onWebSocketTaskClosed,
    );
    return ncb.NSURLSessionDelegate.as(builder.build());
  }

  URLSession._(super.c, {required bool isBackground})
    : _isBackground = isBackground;

  /// A client with reasonable default behavior.
  ///
  /// See [NSURLSession.sharedSession](https://developer.apple.com/documentation/foundation/nsurlsession/1409000-sharedsession)
  factory URLSession.sharedSession() =>
      URLSession._(ncb.NSURLSession.getSharedSession(), isBackground: false);

  /// A client with a given configuration.
  ///
  /// If [onRedirect] is set then it will be called whenever a HTTP
  /// request returns a redirect response (e.g. 302). The `response` parameter
  /// contains the response from the server. The `newRequest` parameter contains
  /// a follow-up request that would honor the server's redirect. If the return
  /// value of this function is `null` then the redirect will not occur.
  /// Otherwise, the returned [URLRequest] (usually `newRequest`) will be
  /// executed. [onRedirect] should not throw. [onRedirect] will not be called
  /// for background sessions, which automatically follow redirects. See
  /// [URLSession:task:willPerformHTTPRedirection:newRequest:completionHandler:](https://developer.apple.com/documentation/foundation/nsurlsessiontaskdelegate/1411626-urlsession)
  ///
  /// If [onResponse] is set then it will be called whenever a valid response
  /// is received. The returned [NSURLSessionResponseDisposition] will decide
  /// how the content of the response is processed. [onResponse] should not
  /// throw. See
  /// [URLSession:dataTask:didReceiveResponse:completionHandler:](https://developer.apple.com/documentation/foundation/nsurlsessiondatadelegate/1410027-urlsession).
  ///
  /// If [onData] is set then it will be called whenever response data is
  /// received. If the amount of received data is large, then it may be
  /// called more than once. See
  /// [URLSession:dataTask:didReceiveData:](https://developer.apple.com/documentation/foundation/nsurlsessiondatadelegate/1411528-urlsession)
  ///
  /// If [onFinishedDownloading] is set then it will be called whenever a
  /// [URLSessionDownloadTask] has finished downloading.
  ///
  /// If [onComplete] is set then it will be called when a task completes. If
  /// `error` is `null` then the request completed successfully. See
  /// [URLSession:task:didCompleteWithError:](https://developer.apple.com/documentation/foundation/nsurlsessiontaskdelegate/1411610-urlsession)
  ///
  /// See [sessionWithConfiguration:delegate:delegateQueue:](https://developer.apple.com/documentation/foundation/nsurlsession/1411597-sessionwithconfiguration)
  ///
  /// If [onWebSocketTaskOpened] is set then it will be called when a
  /// [URLSessionWebSocketTask] successfully negotiated the handshake with the
  /// server.
  ///
  /// If [onWebSocketTaskClosed] is set then it will be called if a
  /// [URLSessionWebSocketTask] receives a close control frame from the server.
  /// NOTE: A [URLSessionWebSocketTask.receiveMessage] must be in flight for
  /// [onWebSocketTaskClosed] to be called.
  factory URLSession.sessionWithConfiguration(
    URLSessionConfiguration config, {
    OnRedirect? onRedirect,
    OnResponse? onResponse,
    OnData? onData,
    OnFinishedDownloading? onFinishedDownloading,
    OnComplete? onComplete,
    OnWebSocketTaskOpened? onWebSocketTaskOpened,
    OnWebSocketTaskClosed? onWebSocketTaskClosed,
  }) {
    // Avoid the complexity of simultaneous or out-of-order delegate callbacks
    // by only allowing callbacks to execute sequentially.
    // See https://developer.apple.com/forums/thread/47252
    final queue = ncb.NSOperationQueue()
      ..maxConcurrentOperationCount = 1
      ..name = 'cupertino_http.NSURLSessionDelegateQueue'.toNSString();

    final hasDelegate =
        (onRedirect ??
            onResponse ??
            onData ??
            onFinishedDownloading ??
            onComplete ??
            onWebSocketTaskOpened ??
            onWebSocketTaskClosed) !=
        null;

    if (hasDelegate) {
      return URLSession._(
        ncb.NSURLSession.sessionWithConfiguration$1(
          config._nsObject,
          delegate: delegate(
            config._isBackground,
            onRedirect: onRedirect,
            onResponse: onResponse,
            onData: onData,
            onFinishedDownloading: onFinishedDownloading,
            onComplete: onComplete,
            onWebSocketTaskOpened: onWebSocketTaskOpened,
            onWebSocketTaskClosed: onWebSocketTaskClosed,
          ),
          delegateQueue: queue,
        ),
        isBackground: config._isBackground,
      );
    } else {
      return URLSession._(
        ncb.NSURLSession.sessionWithConfiguration(config._nsObject),
        isBackground: config._isBackground,
      );
    }
  }

  /// A **copy** of the configuration for this session.
  ///
  /// See [NSURLSession.configuration](https://developer.apple.com/documentation/foundation/nsurlsession/1411477-configuration)
  URLSessionConfiguration get configuration => URLSessionConfiguration._(
    ncb.NSURLSessionConfiguration.as(_nsObject.configuration),
    isBackground: _isBackground,
  );

  /// A description of the session that may be useful for debugging.
  ///
  /// See [NSURLSession.sessionDescription](https://developer.apple.com/documentation/foundation/nsurlsession/1408277-sessiondescription)
  String? get sessionDescription =>
      _nsObject.sessionDescription?.toDartString();
  set sessionDescription(String? value) =>
      _nsObject.sessionDescription = value?.toNSString();

  /// Create a [URLSessionTask] that accesses a server URL.
  ///
  /// See [NSURLSession dataTaskWithRequest:](https://developer.apple.com/documentation/foundation/nsurlsession/1410592-datataskwithrequest)
  URLSessionTask dataTaskWithRequest(URLRequest request) =>
      URLSessionTask._(_nsObject.dataTaskWithRequest(request._nsObject));

  /// Creates a [URLSessionTask] that accesses a server URL and calls
  /// [completion] when done.
  ///
  /// See [NSURLSession dataTaskWithRequest:completionHandler:](https://developer.apple.com/documentation/foundation/nsurlsession/1407613-datataskwithrequest)
  URLSessionTask dataTaskWithCompletionHandler(
    URLRequest request,
    void Function(objc.NSData? data, URLResponse? response, objc.NSError? error)
    completion,
  ) {
    if (_isBackground) {
      throw UnsupportedError(
        'dataTaskWithCompletionHandler is not supported in background '
        'sessions',
      );
    }
    final completer =
        ncb.ObjCBlock_ffiVoid_NSData_NSURLResponse_NSError.listener((
          data,
          response,
          error,
        ) {
          completion(
            data,
            response == null
                ? null
                : URLResponse._exactURLResponseType(response),
            error,
          );
        });

    final task = ncb.NSURLSessionAsynchronousConvenience(
      _nsObject,
    ).dataTaskWithRequest$1(request._nsObject, completionHandler: completer);

    return URLSessionTask._(task);
  }

  /// Creates a [URLSessionDownloadTask] that downloads the data from a server
  /// URL.
  ///
  /// Provide a `onFinishedDownloading` handler in the [URLSession] factory to
  /// receive notifications when the data has completed downloaded.
  ///
  /// See [NSURLSession downloadTaskWithRequest:](https://developer.apple.com/documentation/foundation/nsurlsession/1411481-downloadtaskwithrequest)
  URLSessionDownloadTask downloadTaskWithRequest(URLRequest request) =>
      URLSessionDownloadTask._(
        _nsObject.downloadTaskWithRequest(request._nsObject),
      );

  /// Creates a [URLSessionWebSocketTask] that represents a connection to a
  /// WebSocket endpoint.
  ///
  /// To add custom protocols, add a "Sec-WebSocket-Protocol" header with a list
  /// of protocols to [request].
  ///
  /// See [NSURLSession webSocketTaskWithRequest:](https://developer.apple.com/documentation/foundation/nsurlsession/3235750-websockettaskwithrequest)
  URLSessionWebSocketTask webSocketTaskWithRequest(URLRequest request) {
    if (_isBackground) {
      throw UnsupportedError(
        'WebSocket tasks are not supported in background sessions',
      );
    }
    return URLSessionWebSocketTask._(
      _nsObject.webSocketTaskWithRequest(request._nsObject),
    );
  }

  /// Creates a [URLSessionWebSocketTask] that represents a connection to a
  /// WebSocket endpoint.
  ///
  /// See [NSURLSession webSocketTaskWithURL:protocols:](https://developer.apple.com/documentation/foundation/nsurlsession/3181172-websockettaskwithurl)
  URLSessionWebSocketTask webSocketTaskWithURL(
    Uri uri, {
    Iterable<String>? protocols,
  }) {
    if (_isBackground) {
      throw UnsupportedError(
        'WebSocket tasks are not supported in background sessions',
      );
    }
    final URLSessionWebSocketTask task;
    if (protocols == null) {
      task = URLSessionWebSocketTask._(
        _nsObject.webSocketTaskWithURL(_uriToNSURL(uri)),
      );
    } else {
      task = URLSessionWebSocketTask._(
        _nsObject.webSocketTaskWithURL$1(
          _uriToNSURL(uri),
          protocols: objc.toObjCObject(protocols) as objc.NSArray,
        ),
      );
    }
    return task;
  }

  /// Free resources related to this session after the last task completes.
  /// Returns immediately.
  ///
  /// See [NSURLSession finishTasksAndInvalidate](https://developer.apple.com/documentation/foundation/nsurlsession/1407428-finishtasksandinvalidate)
  void finishTasksAndInvalidate() {
    _nsObject.finishTasksAndInvalidate();
  }
}

const _nsurlErrorCancelled = -999;
final _urlError = objc.NSString('NSURLErrorDomain');

extension NSErrorExtension on objc.NSError {
  /// Whether the error was caused by a cancelled `NSURLSession` request.
  bool get isCancelled =>
      code == _nsurlErrorCancelled && _urlError.isEqualToString(domain);
}