// Copyright (c) 2013, 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.

part of dart._http;

abstract final class HttpProfiler {
  static const _kType = 'HttpProfile';

  static final Map<String, _HttpProfileData> _profile = {};

  static _HttpProfileData? startRequest(
    String method,
    Uri uri, {
    _HttpProfileData? parentRequest,
  }) {
    if (const bool.fromEnvironment("dart.vm.product")) return null;
    final data = _HttpProfileData(method, uri, parentRequest?._timeline);
    _profile[data.id] = data;
    return data;
  }

  static _HttpProfileData? getHttpProfileRequest(String id) => _profile[id];

  static void clear() => _profile.clear();

  /// Returns a list of Maps, where each map conforms to the @HttpProfileRequest
  /// type defined in the dart:io service extension spec.
  static List<Map<String, dynamic>> serializeHttpProfileRequests(
    int? updatedSince,
  ) {
    return _profile.values
        .where(
          (e) => (updatedSince == null) || e.lastUpdateTime >= updatedSince,
        )
        .map((e) => e.toJson(ref: true))
        .toList();
  }
}

class _HttpProfileEvent {
  _HttpProfileEvent(this.name, this.arguments);
  final int timestamp = DateTime.now().microsecondsSinceEpoch;
  final String name;
  final Map? arguments;

  Map<String, dynamic> toJson() {
    return <String, dynamic>{
      'timestamp': timestamp,
      'event': name,
      if (arguments != null) 'arguments': arguments,
    };
  }
}

class _HttpProfileData {
  _HttpProfileData(String method, this.uri, TimelineTask? parent)
    : method = method.toUpperCase(),
      _timeline = TimelineTask(filterKey: 'HTTP/client', parent: parent) {
    // Grab the ID from the timeline event so HTTP profile IDs can be matched
    // to the timeline.
    id = _timeline.pass().toString();
    requestInProgress = true;
    requestStartTimestamp = DateTime.now().microsecondsSinceEpoch;
    _timeline.start(
      'HTTP CLIENT $method',
      arguments: {'method': method.toUpperCase(), 'uri': uri.toString()},
    );
    _updated();
  }

  /// Adds an HTTP request event to the timeline and the list of events.
  void requestEvent(String name, {Map? arguments}) {
    _timeline.instant(name, arguments: arguments);
    requestEvents.add(_HttpProfileEvent(name, arguments));
    _updated();
  }

  void proxyEvent(_Proxy proxy) {
    proxyDetails = {
      if (proxy.host != null) 'host': proxy.host,
      if (proxy.port != null) 'port': proxy.port,
      if (proxy.username != null) 'username': proxy.username,
    };
    _timeline.instant(
      'Establishing proxy tunnel',
      arguments: {'proxyDetails': proxyDetails},
    );
    _updated();
  }

  void appendRequestData(Uint8List data) {
    requestBody.addAll(data);
    _updated();
  }

  Map formatHeaders(HttpHeaders headers) {
    final newHeaders = <String, List<String>>{};
    headers.forEach((name, values) {
      newHeaders[name] = values;
    });
    return newHeaders;
  }

  Map? formatConnectionInfo(HttpConnectionInfo? connectionInfo) =>
      connectionInfo == null
      ? null
      : {
          'localPort': connectionInfo.localPort,
          'remoteAddress': connectionInfo.remoteAddress.address,
          'remotePort': connectionInfo.remotePort,
        };

  void finishRequest({required HttpClientRequest request}) {
    // TODO(bkonyi): include encoding?
    requestInProgress = false;
    requestEndTimestamp = DateTime.now().microsecondsSinceEpoch;
    requestDetails = <String, dynamic>{
      // TODO(bkonyi): consider exposing certificate information?
      // 'certificate': response.certificate,
      'headers': formatHeaders(request.headers),
      'connectionInfo': formatConnectionInfo(request.connectionInfo),
      'contentLength': request.contentLength,
      'cookies': [for (final cookie in request.cookies) cookie.toString()],
      'followRedirects': request.followRedirects,
      'maxRedirects': request.maxRedirects,
      'method': request.method,
      'persistentConnection': request.persistentConnection,
      'uri': request.uri.toString(),
    };
    _timeline.finish(arguments: requestDetails);
    _updated();
  }

  /// Marks the response as "started."
  void startResponse({required HttpClientResponse response}) {
    responseDetails = <String, dynamic>{
      'headers': formatHeaders(response.headers),
      'compressionState': response.compressionState.toString(),
      'connectionInfo': formatConnectionInfo(response.connectionInfo),
      'contentLength': response.contentLength,
      'cookies': [for (final cookie in response.cookies) cookie.toString()],
      'isRedirect': response.isRedirect,
      'persistentConnection': response.persistentConnection,
      'reasonPhrase': response.reasonPhrase,
      'redirects': [
        for (final redirect in response.redirects)
          {
            'location': redirect.location.toString(),
            'method': redirect.method,
            'statusCode': redirect.statusCode,
          },
      ],
      'statusCode': response.statusCode,
    };

    assert(!requestInProgress);
    responseInProgress = true;
    _responseTimeline = TimelineTask(
      parent: _timeline,
      filterKey: 'HTTP/client',
    );

    responseStartTimestamp = DateTime.now().microsecondsSinceEpoch;
    _responseTimeline.start(
      'HTTP CLIENT response of $method',
      arguments: {'requestUri': uri.toString(), ...responseDetails!},
    );
    _updated();
  }

  void finishRequestWithError(String error) {
    requestInProgress = false;
    requestEndTimestamp = DateTime.now().microsecondsSinceEpoch;
    requestError = error;
    _timeline.finish(arguments: {'error': error});
    _updated();
  }

  /// Marks the response as "finished."
  void finishResponse() {
    // Guard against the response being completed more than once or being
    // completed before the response actually finished starting.
    if (responseInProgress != true) return;
    responseInProgress = false;
    responseEndTimestamp = DateTime.now().microsecondsSinceEpoch;
    requestEvent('Content Download');
    _responseTimeline.finish();
    _updated();
  }

  /// Marks the response as "finished" with an error.
  void finishResponseWithError(String error) {
    // Return if `finishResponseWithError` has already been called. Can happen
    // if the response stream is listened to with `cancelOnError: false`.
    if (!responseInProgress!) return;
    responseInProgress = false;
    responseEndTimestamp = DateTime.now().microsecondsSinceEpoch;
    responseError = error;
    _responseTimeline.finish(arguments: {'error': error});
    _updated();
  }

  void appendResponseData(Uint8List data) {
    responseBody.addAll(data);
    _updated();
  }

  Map<String, dynamic> toJson({required bool ref}) {
    return <String, dynamic>{
      'type': '${ref ? '@' : ''}HttpProfileRequest',
      'id': id,
      'isolateId': isolateId,
      'method': method,
      'uri': uri.toString(),
      'events': <Map<String, dynamic>>[
        for (final event in requestEvents) event.toJson(),
      ],
      'startTime': requestStartTimestamp,
      if (!requestInProgress) 'endTime': requestEndTimestamp,
      if (!requestInProgress)
        'request': {
          if (proxyDetails != null) 'proxyDetails': proxyDetails!,
          if (requestDetails != null) ...requestDetails!,
          if (requestError != null) 'error': requestError,
        },
      if (responseInProgress != null)
        'response': <String, dynamic>{
          'startTime': responseStartTimestamp,
          ...responseDetails!,
          if (!responseInProgress!) 'endTime': responseEndTimestamp,
          if (responseError != null) 'error': responseError,
        },
      if (!ref) ...{
        if (!requestInProgress) 'requestBody': requestBody,
        if (responseInProgress != null) 'responseBody': responseBody,
      },
    };
  }

  void _updated() => _lastUpdateTime = DateTime.now().microsecondsSinceEpoch;

  static final String isolateId = Service.getIsolateId(Isolate.current)!;

  bool requestInProgress = true;

  /// Whether the response-processing has started, and has not yet finished.
  ///
  /// This field has three meaningful states:
  /// * `null`: processing the response has not started.
  /// * `true`: processing the response has started.
  /// * `false`: processing the response has finished.
  bool? responseInProgress;

  late final String id;
  final String method;
  final Uri uri;

  late final int requestStartTimestamp;
  late final int requestEndTimestamp;
  Map<String, dynamic>? requestDetails;
  Map<String, dynamic>? proxyDetails;
  final requestBody = <int>[];
  String? requestError;
  final requestEvents = <_HttpProfileEvent>[];

  late final int responseStartTimestamp;
  late final int responseEndTimestamp;
  Map<String, dynamic>? responseDetails;
  final responseBody = <int>[];
  String? responseError;

  int get lastUpdateTime => _lastUpdateTime;
  int _lastUpdateTime = 0;

  final TimelineTask _timeline;
  late TimelineTask _responseTimeline;
}

int _nextServiceId = 1;

// TODO(ajohnsen): Use other way of getting a unique id.
mixin _ServiceObject {
  int __serviceId = 0;
  int get _serviceId {
    if (__serviceId == 0) __serviceId = _nextServiceId++;
    return __serviceId;
  }

  String get _servicePath => "$_serviceTypePath/$_serviceId";

  String get _serviceTypePath;

  String get _serviceTypeName;

  String _serviceType(bool ref) {
    if (ref) return "@$_serviceTypeName";
    return _serviceTypeName;
  }
}

class _CopyingBytesBuilder implements BytesBuilder {
  // Start with 1024 bytes.
  static const int _INIT_SIZE = 1024;

  static final _emptyList = Uint8List(0);

  int _length = 0;
  Uint8List _buffer;

  _CopyingBytesBuilder([int initialCapacity = 0])
    : _buffer = (initialCapacity <= 0)
          ? _emptyList
          : Uint8List(_pow2roundup(initialCapacity));

  void add(List<int> bytes) {
    int bytesLength = bytes.length;
    if (bytesLength == 0) return;
    int required = _length + bytesLength;
    if (_buffer.length < required) {
      _grow(required);
    }
    assert(_buffer.length >= required);
    if (bytes is Uint8List) {
      _buffer.setRange(_length, required, bytes);
    } else {
      for (int i = 0; i < bytesLength; i++) {
        _buffer[_length + i] = bytes[i];
      }
    }
    _length = required;
  }

  void addByte(int byte) {
    if (_buffer.length == _length) {
      // The grow algorithm always at least doubles.
      // If we added one to _length it would quadruple unnecessarily.
      _grow(_length);
    }
    assert(_buffer.length > _length);
    _buffer[_length] = byte;
    _length++;
  }

  void _grow(int required) {
    // We will create a list in the range of 2-4 times larger than
    // required.
    int newSize = required * 2;
    if (newSize < _INIT_SIZE) {
      newSize = _INIT_SIZE;
    } else {
      newSize = _pow2roundup(newSize);
    }
    var newBuffer = Uint8List(newSize);
    newBuffer.setRange(0, _buffer.length, _buffer);
    _buffer = newBuffer;
  }

  Uint8List takeBytes() {
    if (_length == 0) return _emptyList;
    var buffer = Uint8List.view(_buffer.buffer, _buffer.offsetInBytes, _length);
    clear();
    return buffer;
  }

  Uint8List toBytes() {
    if (_length == 0) return _emptyList;
    return Uint8List.fromList(
      Uint8List.view(_buffer.buffer, _buffer.offsetInBytes, _length),
    );
  }

  int get length => _length;

  bool get isEmpty => _length == 0;

  bool get isNotEmpty => _length != 0;

  void clear() {
    _length = 0;
    _buffer = _emptyList;
  }

  static int _pow2roundup(int x) {
    assert(x > 0);
    --x;
    x |= x >> 1;
    x |= x >> 2;
    x |= x >> 4;
    x |= x >> 8;
    x |= x >> 16;
    return x + 1;
  }
}

const int _OUTGOING_BUFFER_SIZE = 8 * 1024;

typedef _BytesConsumer = void Function(List<int> bytes);

class _HttpIncoming extends Stream<Uint8List> {
  final int _transferLength;
  final _dataCompleter = Completer<bool>();
  final Stream<Uint8List> _stream;

  bool fullBodyRead = false;

  // Common properties.
  final _HttpHeaders headers;
  bool upgraded = false;

  // ClientResponse properties.
  int? statusCode;
  String? reasonPhrase;

  // Request properties.
  String? method;
  Uri? uri;

  bool hasSubscriber = false;

  // The transfer length if the length of the message body as it
  // appears in the message (RFC 2616 section 4.4). This can be -1 if
  // the length of the massage body is not known due to transfer
  // codings.
  int get transferLength => _transferLength;

  _HttpIncoming(this.headers, this._transferLength, this._stream);

  StreamSubscription<Uint8List> listen(
    void Function(Uint8List event)? onData, {
    Function? onError,
    void Function()? onDone,
    bool? cancelOnError,
  }) {
    hasSubscriber = true;
    return _stream
        .handleError((error) {
          throw HttpException((error as HttpException).message, uri: uri);
        }, test: (error) => error is HttpException)
        .listen(
          onData,
          onError: onError,
          onDone: onDone,
          cancelOnError: cancelOnError,
        );
  }

  // Is completed once all data have been received.
  Future<bool> get dataDone => _dataCompleter.future;

  void close(bool closing) {
    fullBodyRead = true;
    hasSubscriber = true;
    _dataCompleter.complete(closing);
  }
}

abstract class _HttpInboundMessageListInt extends Stream<List<int>> {
  final _HttpIncoming _incoming;
  List<Cookie>? _cookies;

  _HttpInboundMessageListInt(this._incoming);

  List<Cookie> get cookies => _cookies ??= headers._parseCookies();

  _HttpHeaders get headers => _incoming.headers;
  String get protocolVersion => headers.protocolVersion;
  int get contentLength => headers.contentLength;
  bool get persistentConnection => headers.persistentConnection;
}

abstract class _HttpInboundMessage extends Stream<Uint8List> {
  final _HttpIncoming _incoming;
  List<Cookie>? _cookies;

  _HttpInboundMessage(this._incoming);

  List<Cookie> get cookies => _cookies ??= headers._parseCookies();

  _HttpHeaders get headers => _incoming.headers;
  String get protocolVersion => headers.protocolVersion;
  int get contentLength => headers.contentLength;
  bool get persistentConnection => headers.persistentConnection;
}

class _HttpRequest extends _HttpInboundMessage implements HttpRequest {
  final HttpResponse response;

  final _HttpServer _httpServer;

  final _HttpConnection _httpConnection;

  _HttpSession? _session;

  Uri? _requestedUri;

  _HttpRequest(
    this.response,
    _HttpIncoming _incoming,
    this._httpServer,
    this._httpConnection,
  ) : super(_incoming) {
    if (headers.protocolVersion == "1.1") {
      response.headers
        ..chunkedTransferEncoding = true
        ..persistentConnection = headers.persistentConnection;
    }

    if (_httpServer._sessionManagerInstance != null) {
      // Map to session if exists.
      var sessionIds = cookies
          .where((cookie) => cookie.name.toUpperCase() == _DART_SESSION_ID)
          .map<String>((cookie) => cookie.value);
      for (var sessionId in sessionIds) {
        var session = _httpServer._sessionManager.getSession(sessionId);
        _session = session;
        if (session != null) {
          session._markSeen();
          break;
        }
      }
    }
  }

  StreamSubscription<Uint8List> listen(
    void Function(Uint8List event)? onData, {
    Function? onError,
    void Function()? onDone,
    bool? cancelOnError,
  }) {
    return _incoming.listen(
      onData,
      onError: onError,
      onDone: onDone,
      cancelOnError: cancelOnError,
    );
  }

  Uri get uri => _incoming.uri!;

  Uri get requestedUri {
    var requestedUri = _requestedUri;
    if (requestedUri != null) return requestedUri;

    // `uri` can be an absoluteURI or an abs_path (RFC 2616 section 5.1.2).
    // If `uri` is already absolute then use it as-is. Otherwise construct an
    // absolute URI using `uri` and header information.

    // RFC 3986 section 4.3 says that an absolute URI must have a scheme and
    // cannot have a fragment. But any URI with a scheme is sufficient for the
    // purpose of providing the `requestedUri`.
    if (uri.hasScheme) {
      return _requestedUri = uri;
    }

    var proto = headers['x-forwarded-proto'];
    var scheme = proto != null
        ? proto.first
        : _httpConnection._socket is SecureSocket
        ? "https"
        : "http";
    var hostList = headers['x-forwarded-host'];
    String host;
    if (hostList != null) {
      host = hostList.first;
    } else {
      hostList = headers[HttpHeaders.hostHeader];
      if (hostList != null) {
        host = hostList.first;
      } else {
        host = "${_httpServer.address.host}:${_httpServer.port}";
      }
    }
    return _requestedUri = Uri.parse("$scheme://$host$uri");
  }

  String get method => _incoming.method!;

  HttpSession get session {
    var session = _session;
    if (session != null && !session._destroyed) {
      return session;
    }
    // Create session, store it in connection, and return.
    return _session = _httpServer._sessionManager.createSession();
  }

  HttpConnectionInfo? get connectionInfo => _httpConnection.connectionInfo;

  X509Certificate? get certificate {
    var socket = _httpConnection._socket;
    if (socket is SecureSocket) return socket.peerCertificate;
    return null;
  }
}

class _HttpClientResponse extends _HttpInboundMessageListInt
    implements HttpClientResponse {
  List<RedirectInfo> get redirects => _httpRequest._responseRedirects;

  // The HttpClient this response belongs to.
  final _HttpClient _httpClient;

  // The HttpClientRequest of this response.
  final _HttpClientRequest _httpRequest;

  // The compression state of this response.
  final HttpClientResponseCompressionState compressionState;

  final _HttpProfileData? _profileData;

  _HttpClientResponse(
    _HttpIncoming _incoming,
    this._httpRequest,
    this._httpClient,
    this._profileData,
  ) : compressionState = _getCompressionState(_httpClient, _incoming.headers),
      super(_incoming) {
    // Set uri for potential exceptions.
    _incoming.uri = _httpRequest.uri;
  }

  static HttpClientResponseCompressionState _getCompressionState(
    _HttpClient httpClient,
    _HttpHeaders headers,
  ) {
    if (headers.value(HttpHeaders.contentEncodingHeader) == "gzip") {
      return httpClient.autoUncompress
          ? HttpClientResponseCompressionState.decompressed
          : HttpClientResponseCompressionState.compressed;
    } else {
      return HttpClientResponseCompressionState.notCompressed;
    }
  }

  int get statusCode => _incoming.statusCode!;
  String get reasonPhrase => _incoming.reasonPhrase!;

  X509Certificate? get certificate {
    var socket = _httpRequest._httpClientConnection._socket;
    if (socket is SecureSocket) return socket.peerCertificate;
    return null;
  }

  List<Cookie> get cookies {
    var cookies = _cookies;
    if (cookies != null) return cookies;
    cookies = <Cookie>[];
    List<String>? values = headers[HttpHeaders.setCookieHeader];
    if (values != null) {
      for (var value in values) {
        cookies.add(Cookie.fromSetCookieValue(value));
      }
    }
    _cookies = cookies;
    return cookies;
  }

  bool get isRedirect {
    if (_httpRequest.method == "GET" || _httpRequest.method == "HEAD") {
      return statusCode == HttpStatus.movedPermanently ||
          statusCode == HttpStatus.permanentRedirect ||
          statusCode == HttpStatus.found ||
          statusCode == HttpStatus.seeOther ||
          statusCode == HttpStatus.temporaryRedirect;
    } else if (_httpRequest.method == "POST") {
      return statusCode == HttpStatus.seeOther;
    }
    return false;
  }

  Future<HttpClientResponse> redirect([
    String? method,
    Uri? url,
    bool? followLoops,
  ]) {
    if (method == null) {
      // Set method as defined by RFC 2616 section 10.3.4.
      if (statusCode == HttpStatus.seeOther && _httpRequest.method == "POST") {
        method = "GET";
      } else {
        method = _httpRequest.method;
      }
    }
    if (url == null) {
      String? location = headers.value(HttpHeaders.locationHeader);
      if (location == null) {
        throw RedirectException(
          "Server response has no Location header for redirect",
          redirects,
        );
      }
      url = Uri.parse(location);
    }
    if (followLoops != true) {
      for (var redirect in redirects) {
        if (redirect.location == url) {
          return Future.error(
            RedirectException("Redirect loop detected", redirects),
          );
        }
      }
    }
    return _httpClient
        ._openUrlFromRequest(method, url, _httpRequest, isRedirect: true)
        .then((request) {
          request._responseRedirects
            ..addAll(redirects)
            ..add(_RedirectInfo(statusCode, method!, url!));
          return request.close();
        });
  }

  StreamSubscription<Uint8List> listen(
    void Function(Uint8List event)? onData, {
    Function? onError,
    void Function()? onDone,
    bool? cancelOnError,
  }) {
    if (_incoming.upgraded) {
      _profileData?.finishResponseWithError('Connection was upgraded');
      // If upgraded, the connection is already 'removed' form the client.
      // Since listening to upgraded data is 'bogus', simply close and
      // return empty stream subscription.
      _httpRequest._httpClientConnection.destroy();
      return Stream<Uint8List>.empty().listen(null, onDone: onDone);
    }
    Stream<Uint8List> stream = _incoming;
    if (compressionState == HttpClientResponseCompressionState.decompressed) {
      stream = stream
          .cast<List<int>>()
          .transform(gzip.decoder)
          .transform(const _ToUint8List());
    }
    if (_profileData != null) {
      // If _timeline is not set up, don't add unnecessary map() to the stream.
      stream = stream.map((data) {
        _profileData.appendResponseData(data);
        return data;
      });
    }
    return stream.listen(
      onData,
      onError: (e, st) {
        _profileData?.finishResponseWithError(e.toString());
        if (onError == null) {
          return;
        }
        if (onError is void Function(Object, StackTrace)) {
          onError(e, st);
        } else {
          (onError as void Function(Object))(e);
        }
      },
      onDone: onDone,
      cancelOnError: cancelOnError,
    );
  }

  Future<Socket> detachSocket() {
    _profileData?.finishResponseWithError('Socket has been detached');
    _httpClient._connectionClosed(_httpRequest._httpClientConnection);
    return _httpRequest._httpClientConnection.detachSocket();
  }

  HttpConnectionInfo? get connectionInfo => _httpRequest.connectionInfo;

  bool get _shouldAuthenticateProxy {
    // Only try to authenticate if there is a challenge in the response.
    List<String>? challenge = headers[HttpHeaders.proxyAuthenticateHeader];
    return statusCode == HttpStatus.proxyAuthenticationRequired &&
        challenge != null &&
        challenge.length == 1;
  }

  bool get _shouldAuthenticate {
    // Only try to authenticate if there is a challenge in the response and
    // the client has credentials or an authentication function.
    List<String>? challenge = headers[HttpHeaders.wwwAuthenticateHeader];
    return statusCode == HttpStatus.unauthorized &&
        challenge != null &&
        challenge.length == 1 &&
        (_httpClient._credentials.isNotEmpty ||
            _httpClient._authenticate != null);
  }

  Future<HttpClientResponse> _authenticate(bool proxyAuth) {
    _httpRequest._profileData?.requestEvent('Authentication');
    Future<HttpClientResponse> retry() {
      _httpRequest._profileData?.requestEvent('Retrying');
      // Drain body and retry.
      return drain().then((_) {
        return _httpClient
            ._openUrlFromRequest(
              _httpRequest.method,
              _httpRequest.uri,
              _httpRequest,
              isRedirect: false,
            )
            .then((request) => request.close());
      });
    }

    List<String>? authChallenge() {
      return proxyAuth
          ? headers[HttpHeaders.proxyAuthenticateHeader]
          : headers[HttpHeaders.wwwAuthenticateHeader];
    }

    _Credentials? findCredentials(_AuthenticationScheme scheme) {
      return proxyAuth
          ? _httpClient._findProxyCredentials(_httpRequest._proxy, scheme)
          : _httpClient._findCredentials(_httpRequest.uri, scheme);
    }

    void removeCredentials(_Credentials cr) {
      if (proxyAuth) {
        _httpClient._removeProxyCredentials(cr);
      } else {
        _httpClient._removeCredentials(cr);
      }
    }

    Future<bool> requestAuthentication(
      _AuthenticationScheme scheme,
      String? realm,
    ) {
      if (proxyAuth) {
        var authenticateProxy = _httpClient._authenticateProxy;
        if (authenticateProxy == null) {
          return Future.value(false);
        }
        var proxy = _httpRequest._proxy;
        if (!proxy.isDirect) {
          return authenticateProxy(
            proxy.host!,
            proxy.port!,
            scheme.toString(),
            realm,
          );
        }
      }
      var authenticate = _httpClient._authenticate;
      if (authenticate == null) {
        return Future.value(false);
      }
      return authenticate(_httpRequest.uri, scheme.toString(), realm);
    }

    List<String> challenge = authChallenge()!;
    assert(challenge.length == 1);
    final _HeaderValue header;
    try {
      header = _HeaderValue.parse(challenge[0], parameterSeparator: ",");
    } on HttpException catch (_, s) {
      Error.throwWithStackTrace(
        HttpException(
          'The authentication challenge sent by the server is '
          'not correctly formatted.',
        ),
        s,
      );
    }
    _AuthenticationScheme scheme = _AuthenticationScheme.fromString(
      header.value,
    );
    String? realm = header.parameters["realm"];

    // See if any matching credentials are available.
    var cr = findCredentials(scheme);
    if (cr != null) {
      // For basic authentication don't retry already used credentials
      // as they must have already been added to the request causing
      // this authenticate response.
      if (cr.scheme == _AuthenticationScheme.Basic && !cr.used) {
        // Credentials were found, prepare for retrying the request.
        return retry();
      }

      // Digest authentication only supports the MD5 algorithm.
      if (cr.scheme == _AuthenticationScheme.Digest) {
        var algorithm = header.parameters["algorithm"];
        if (algorithm == null || algorithm.toLowerCase() == "md5") {
          var nonce = cr.nonce;
          if (nonce == null || nonce == header.parameters["nonce"]) {
            // If the nonce is not set then this is the first authenticate
            // response for these credentials. Set up authentication state.
            if (nonce == null) {
              cr
                ..nonce = header.parameters["nonce"]
                ..algorithm = "MD5"
                ..qop = header.parameters["qop"]
                ..nonceCount = 0;
            }
            // Credentials were found, prepare for retrying the request.
            return retry();
          } else {
            var staleHeader = header.parameters["stale"];
            if (staleHeader != null && staleHeader.toLowerCase() == "true") {
              // If stale is true retry with new nonce.
              cr.nonce = header.parameters["nonce"];
              // Credentials were found, prepare for retrying the request.
              return retry();
            }
          }
        }
      }
    }

    // Ask for more credentials if none found or the one found has
    // already been used. If it has already been used it must now be
    // invalid and is removed.
    if (cr != null) {
      removeCredentials(cr);
      cr = null;
    }
    return requestAuthentication(scheme, realm).then((credsAvailable) {
      if (credsAvailable) {
        cr = _httpClient._findCredentials(_httpRequest.uri, scheme);
        return retry();
      } else {
        // No credentials available, complete with original response.
        return this;
      }
    });
  }
}

class _ToUint8List extends Converter<List<int>, Uint8List> {
  const _ToUint8List();

  Uint8List convert(List<int> input) => Uint8List.fromList(input);

  Sink<List<int>> startChunkedConversion(Sink<Uint8List> sink) {
    return _Uint8ListConversionSink(sink);
  }
}

class _Uint8ListConversionSink implements Sink<List<int>> {
  const _Uint8ListConversionSink(this._target);

  final Sink<Uint8List> _target;

  void add(List<int> data) {
    _target.add(Uint8List.fromList(data));
  }

  void close() {
    _target.close();
  }
}

class _StreamSinkImpl<T> implements StreamSink<T> {
  final StreamConsumer<T> _target;
  final _doneCompleter = Completer<void>();
  StreamController<T>? _controllerInstance;
  Completer? _controllerCompleter;
  bool _isClosed = false;
  bool _isBound = false;
  bool _hasError = false;

  _StreamSinkImpl(this._target);

  void add(T data) {
    if (_isClosed) {
      throw StateError("StreamSink is closed");
    }
    _controller.add(data);
  }

  void addError(Object error, [StackTrace? stackTrace]) {
    if (_isClosed) {
      throw StateError("StreamSink is closed");
    }
    _controller.addError(error, stackTrace);
  }

  Future addStream(Stream<T> stream) {
    if (_isBound) {
      throw StateError("StreamSink is already bound to a stream");
    }
    _isBound = true;
    if (_hasError) return done;
    // Wait for any sync operations to complete.
    Future targetAddStream() {
      return _target.addStream(stream).whenComplete(() {
        _isBound = false;
      });
    }

    var controller = _controllerInstance;
    if (controller == null) return targetAddStream();
    var future = _controllerCompleter!.future;
    controller.close();
    return future.then((_) => targetAddStream());
  }

  Future flush() {
    if (_isBound) {
      throw StateError("StreamSink is bound to a stream");
    }
    var controller = _controllerInstance;
    if (controller == null) return Future.value(this);
    // Adding an empty stream-controller will return a future that will complete
    // when all data is done.
    _isBound = true;
    var future = _controllerCompleter!.future;
    controller.close();
    return future.whenComplete(() {
      _isBound = false;
    });
  }

  Future close() {
    if (_isBound) {
      throw StateError("StreamSink is bound to a stream");
    }
    if (!_isClosed) {
      _isClosed = true;
      var controller = _controllerInstance;
      if (controller != null) {
        controller.close();
      } else {
        _closeTarget();
      }
    }
    return done;
  }

  void _closeTarget() {
    _target.close().then(_completeDoneValue, onError: _completeDoneError);
  }

  Future get done => _doneCompleter.future;

  void _completeDoneValue(value) {
    if (!_doneCompleter.isCompleted) {
      _doneCompleter.complete(value);
    }
  }

  void _completeDoneError(Object error, StackTrace stackTrace) {
    if (!_doneCompleter.isCompleted) {
      _hasError = true;
      _doneCompleter.completeError(error, stackTrace);
    }
  }

  StreamController<T> get _controller {
    if (_isBound) {
      throw StateError("StreamSink is bound to a stream");
    }
    if (_isClosed) {
      throw StateError("StreamSink is closed");
    }
    if (_controllerInstance == null) {
      _controllerInstance = StreamController<T>(sync: true);
      _controllerCompleter = Completer();
      _target
          .addStream(_controller.stream)
          .then(
            (_) {
              if (_isBound) {
                // A new stream takes over - forward values to that stream.
                _controllerCompleter!.complete(this);
                _controllerCompleter = null;
                _controllerInstance = null;
              } else {
                // No new stream, .close was called. Close _target.
                _closeTarget();
              }
            },
            onError: (Object error, StackTrace stackTrace) {
              if (_isBound) {
                // A new stream takes over - forward errors to that stream.
                _controllerCompleter!.completeError(error, stackTrace);
                _controllerCompleter = null;
                _controllerInstance = null;
              } else {
                // No new stream. No need to close target, as it has already
                // failed.
                _completeDoneError(error, stackTrace);
              }
            },
          );
    }
    return _controllerInstance!;
  }
}

class _IOSinkImpl extends _StreamSinkImpl<List<int>> implements IOSink {
  Encoding _encoding;
  bool _encodingMutable = true;

  final _HttpProfileData? _profileData;
  _IOSinkImpl(
    StreamConsumer<List<int>> target,
    this._encoding,
    this._profileData,
  ) : super(target);

  Encoding get encoding => _encoding;

  void set encoding(Encoding value) {
    if (!_encodingMutable) {
      throw StateError("IOSink encoding is not mutable");
    }
    _encoding = value;
  }

  void _writeString(String string) {
    Uint8List? utf8Encoding;
    _profileData?.appendRequestData(utf8Encoding = utf8.encode(string));
    super.add(
      utf8Encoding != null && identical(_encoding, utf8)
          ? utf8Encoding
          : _encoding.encode(string),
    );
  }

  void write(Object? obj) {
    String string = '$obj';
    if (string.isEmpty) return;
    _writeString(string);
  }

  void writeAll(Iterable objects, [String separator = ""]) {
    Iterator iterator = objects.iterator;
    if (!iterator.moveNext()) return;
    if (separator.isEmpty) {
      do {
        write(iterator.current);
      } while (iterator.moveNext());
    } else {
      write(iterator.current);
      while (iterator.moveNext()) {
        write(separator);
        write(iterator.current);
      }
    }
  }

  void writeln([Object? object = ""]) {
    write('$object\n');
  }

  void writeCharCode(int charCode) {
    write(String.fromCharCode(charCode));
  }
}

abstract class _HttpOutboundMessage<T> extends _IOSinkImpl {
  // Used to mark when the body should be written. This is used for HEAD
  // requests and in error handling.
  bool _encodingSet = false;

  bool _bufferOutput = true;

  final Uri _uri;
  final _HttpOutgoing _outgoing;

  final _HttpHeaders headers;

  _HttpOutboundMessage(
    Uri uri,
    String protocolVersion,
    _HttpOutgoing outgoing,
    _HttpProfileData? profileData, {
    _HttpHeaders? initialHeaders,
  }) : _uri = uri,
       headers = _HttpHeaders(
         protocolVersion,
         defaultPortForScheme: uri.isScheme('https')
             ? HttpClient.defaultHttpsPort
             : HttpClient.defaultHttpPort,
         initialHeaders: initialHeaders,
       ),
       _outgoing = outgoing,
       super(outgoing, latin1, profileData) {
    _outgoing.outbound = this;
    _encodingMutable = false;
  }

  int get contentLength => headers.contentLength;
  void set contentLength(int contentLength) {
    headers.contentLength = contentLength;
  }

  bool get persistentConnection => headers.persistentConnection;
  void set persistentConnection(bool p) {
    headers.persistentConnection = p;
  }

  bool get bufferOutput => _bufferOutput;
  void set bufferOutput(bool bufferOutput) {
    if (_outgoing.headersWritten) throw StateError("Header already sent");
    _bufferOutput = bufferOutput;
  }

  Encoding get encoding {
    if (_encodingSet && _outgoing.headersWritten) {
      return _encoding;
    }
    String charset;
    var contentType = headers.contentType;
    if (contentType != null && contentType.charset != null) {
      charset = contentType.charset!;
    } else {
      charset = "iso-8859-1";
    }
    return Encoding.getByName(charset) ?? latin1;
  }

  void add(List<int> data) {
    if (data.isEmpty) return;
    _profileData?.appendRequestData(Uint8List.fromList(data));
    super.add(data);
  }

  Future addStream(Stream<List<int>> s) {
    if (_profileData == null) {
      return super.addStream(s);
    }
    return super.addStream(
      s.map((data) {
        _profileData.appendRequestData(Uint8List.fromList(data));
        return data;
      }),
    );
  }

  void write(Object? obj) {
    if (!_encodingSet) {
      _encoding = encoding;
      _encodingSet = true;
    }
    super.write(obj);
  }

  void _writeHeader();

  bool get _isConnectionClosed => false;
}

class _HttpResponse extends _HttpOutboundMessage<HttpResponse>
    implements HttpResponse {
  int _statusCode = 200;
  String? _reasonPhrase;
  List<Cookie>? _cookies;
  _HttpRequest? _httpRequest;
  Duration? _deadline;
  Timer? _deadlineTimer;

  _HttpResponse(
    Uri uri,
    String protocolVersion,
    _HttpOutgoing outgoing,
    HttpHeaders defaultHeaders,
    String? serverHeader,
  ) : super(
        uri,
        protocolVersion,
        outgoing,
        null,
        initialHeaders: defaultHeaders as _HttpHeaders,
      ) {
    if (serverHeader != null) {
      headers.set(HttpHeaders.serverHeader, serverHeader);
    }
  }

  bool get _isConnectionClosed => _httpRequest!._httpConnection._isClosing;

  List<Cookie> get cookies => _cookies ??= <Cookie>[];

  int get statusCode => _statusCode;
  void set statusCode(int statusCode) {
    if (_outgoing.headersWritten) throw StateError("Header already sent");
    _statusCode = statusCode;
  }

  String get reasonPhrase => _findReasonPhrase(statusCode);
  void set reasonPhrase(String reasonPhrase) {
    if (_outgoing.headersWritten) throw StateError("Header already sent");
    _reasonPhrase = reasonPhrase;
  }

  Future redirect(Uri location, {int status = HttpStatus.movedTemporarily}) {
    if (_outgoing.headersWritten) throw StateError("Header already sent");
    statusCode = status;
    headers.set(HttpHeaders.locationHeader, location.toString());
    return close();
  }

  Future<Socket> detachSocket({bool writeHeaders = true}) {
    if (_outgoing.headersWritten) throw StateError("Headers already sent");
    deadline = null; // Be sure to stop any deadline.
    var future = _httpRequest!._httpConnection.detachSocket();
    if (writeHeaders) {
      var headersFuture = _outgoing.writeHeaders(
        drainRequest: false,
        setOutgoing: false,
      );
      assert(headersFuture == null);
    } else {
      // Imitate having written the headers.
      _outgoing.headersWritten = true;
    }
    // Close connection so the socket is 'free'.
    close();
    done.catchError((_) {
      // Catch any error on done, as they automatically will be
      // propagated to the websocket.
    });
    return future;
  }

  HttpConnectionInfo? get connectionInfo => _httpRequest!.connectionInfo;

  Duration? get deadline => _deadline;

  void set deadline(Duration? d) {
    _deadlineTimer?.cancel();
    _deadline = d;

    if (d == null) return;
    _deadlineTimer = Timer(d, () {
      _httpRequest!._httpConnection.destroy();
    });
  }

  void _writeHeader() {
    BytesBuilder buffer = _CopyingBytesBuilder(_OUTGOING_BUFFER_SIZE);

    // Write status line.
    if (headers.protocolVersion == "1.1") {
      buffer.add(_Const.HTTP11);
    } else {
      buffer.add(_Const.HTTP10);
    }
    buffer.addByte(_CharCode.SP);
    buffer.add(statusCode.toString().codeUnits);
    buffer.addByte(_CharCode.SP);
    buffer.add(reasonPhrase.codeUnits);
    buffer.addByte(_CharCode.CR);
    buffer.addByte(_CharCode.LF);

    var session = _httpRequest!._session;
    if (session != null && !session._destroyed) {
      // Mark as not new.
      session._isNew = false;
      // Make sure we only send the current session id.
      bool found = false;
      for (int i = 0; i < cookies.length; i++) {
        if (cookies[i].name.toUpperCase() == _DART_SESSION_ID) {
          cookies[i]
            ..value = session.id
            ..httpOnly = true
            ..path = "/";
          found = true;
        }
      }
      if (!found) {
        var cookie = Cookie(_DART_SESSION_ID, session.id);
        cookies.add(
          cookie
            ..httpOnly = true
            ..path = "/",
        );
      }
    }
    // Add all the cookies set to the headers.
    _cookies?.forEach((cookie) {
      headers.add(HttpHeaders.setCookieHeader, cookie);
    });

    headers._finalize();

    // Write headers.
    headers._build(buffer);
    buffer.addByte(_CharCode.CR);
    buffer.addByte(_CharCode.LF);
    Uint8List headerBytes = buffer.takeBytes();
    _outgoing.setHeader(headerBytes, headerBytes.length);
  }

  String _findReasonPhrase(int statusCode) {
    var reasonPhrase = _reasonPhrase;
    if (reasonPhrase != null) {
      return reasonPhrase;
    }

    switch (statusCode) {
      case HttpStatus.continue_:
        return "Continue";
      case HttpStatus.switchingProtocols:
        return "Switching Protocols";
      case HttpStatus.ok:
        return "OK";
      case HttpStatus.created:
        return "Created";
      case HttpStatus.accepted:
        return "Accepted";
      case HttpStatus.nonAuthoritativeInformation:
        return "Non-Authoritative Information";
      case HttpStatus.noContent:
        return "No Content";
      case HttpStatus.resetContent:
        return "Reset Content";
      case HttpStatus.partialContent:
        return "Partial Content";
      case HttpStatus.multipleChoices:
        return "Multiple Choices";
      case HttpStatus.movedPermanently:
        return "Moved Permanently";
      case HttpStatus.found:
        return "Found";
      case HttpStatus.seeOther:
        return "See Other";
      case HttpStatus.notModified:
        return "Not Modified";
      case HttpStatus.useProxy:
        return "Use Proxy";
      case HttpStatus.temporaryRedirect:
        return "Temporary Redirect";
      case HttpStatus.badRequest:
        return "Bad Request";
      case HttpStatus.unauthorized:
        return "Unauthorized";
      case HttpStatus.paymentRequired:
        return "Payment Required";
      case HttpStatus.forbidden:
        return "Forbidden";
      case HttpStatus.notFound:
        return "Not Found";
      case HttpStatus.methodNotAllowed:
        return "Method Not Allowed";
      case HttpStatus.notAcceptable:
        return "Not Acceptable";
      case HttpStatus.proxyAuthenticationRequired:
        return "Proxy Authentication Required";
      case HttpStatus.requestTimeout:
        return "Request Time-out";
      case HttpStatus.conflict:
        return "Conflict";
      case HttpStatus.gone:
        return "Gone";
      case HttpStatus.lengthRequired:
        return "Length Required";
      case HttpStatus.preconditionFailed:
        return "Precondition Failed";
      case HttpStatus.requestEntityTooLarge:
        return "Request Entity Too Large";
      case HttpStatus.requestUriTooLong:
        return "Request-URI Too Long";
      case HttpStatus.unsupportedMediaType:
        return "Unsupported Media Type";
      case HttpStatus.requestedRangeNotSatisfiable:
        return "Requested range not satisfiable";
      case HttpStatus.expectationFailed:
        return "Expectation Failed";
      case HttpStatus.internalServerError:
        return "Internal Server Error";
      case HttpStatus.notImplemented:
        return "Not Implemented";
      case HttpStatus.badGateway:
        return "Bad Gateway";
      case HttpStatus.serviceUnavailable:
        return "Service Unavailable";
      case HttpStatus.gatewayTimeout:
        return "Gateway Time-out";
      case HttpStatus.httpVersionNotSupported:
        return "Http Version not supported";
      default:
        return "Status $statusCode";
    }
  }
}

class _HttpClientRequest extends _HttpOutboundMessage<HttpClientResponse>
    implements HttpClientRequest {
  final String method;
  final Uri uri;
  final List<Cookie> cookies = [];

  // The HttpClient this request belongs to.
  final _HttpClient _httpClient;
  final _HttpClientConnection _httpClientConnection;

  /// A [Completer] that completes when the response has been fully received,
  /// including any redirects and authentications.
  final Completer<HttpClientResponse> _responseCompleter =
      Completer<HttpClientResponse>();

  final _Proxy _proxy;

  Future<HttpClientResponse>? _response;

  // TODO(ajohnsen): Get default value from client?
  bool _followRedirects = true;

  int _maxRedirects = 5;

  final List<RedirectInfo> _responseRedirects = [];

  bool _aborted = false;

  _HttpClientRequest(
    _HttpOutgoing outgoing,
    this.uri,
    this.method,
    this._proxy,
    this._httpClient,
    this._httpClientConnection,
    _HttpProfileData? _profileData,
  ) : super(uri, "1.1", outgoing, _profileData) {
    _profileData?.requestEvent('Request sent');
    // GET and HEAD have 'content-length: 0' by default.
    if (method == "GET" || method == "HEAD") {
      contentLength = 0;
    } else {
      headers.chunkedTransferEncoding = true;
    }

    _responseCompleter.future.then((response) {
      _profileData?.requestEvent('Waiting (TTFB)');
      _profileData?.startResponse(
        // TODO(bkonyi): consider exposing certificate information?
        // 'certificate': response.certificate,
        response: response,
      );
      (response as _HttpClientResponse)._incoming.dataDone.then(
        // Ensure the response profile is finished, even if the response stream
        // is never listened to.
        (_) => _profileData?.finishResponse(),
      );
    }, onError: (e) {});
  }

  Future<HttpClientResponse> get done => _response ??= Future.wait([
    _responseCompleter.future,
    super.done,
  ], eagerError: true).then((list) => list[0]);

  Future<HttpClientResponse> close() {
    if (!_aborted) {
      // It will send out the request.
      super.close();
    }
    return done;
  }

  int get maxRedirects => _maxRedirects;
  void set maxRedirects(int maxRedirects) {
    if (_outgoing.headersWritten) throw StateError("Request already sent");
    _maxRedirects = maxRedirects;
  }

  bool get followRedirects => _followRedirects;
  void set followRedirects(bool followRedirects) {
    if (_outgoing.headersWritten) throw StateError("Request already sent");
    _followRedirects = followRedirects;
  }

  HttpConnectionInfo? get connectionInfo =>
      _httpClientConnection.connectionInfo;

  /// Handles [incoming] by possibly following redirects, possibly
  /// authenticating, and completing [_responseCompleter] when the response is
  /// complete.
  void _handleIncoming(_HttpIncoming incoming) {
    if (_aborted) {
      return;
    }
    final response = _HttpClientResponse(
      incoming,
      this,
      _httpClient,
      _profileData,
    );
    Future<HttpClientResponse> future;
    if (followRedirects && response.isRedirect) {
      if (response.redirects.length < maxRedirects) {
        // Redirect and drain response.
        future = response.drain().then<HttpClientResponse>(
          (_) => response.redirect(),
        );
      } else {
        // End with exception, too many redirects.
        future = response.drain().then<HttpClientResponse>((_) {
          return Future<HttpClientResponse>.error(
            RedirectException("Redirect limit exceeded", response.redirects),
          );
        });
      }
    } else if (response._shouldAuthenticateProxy) {
      future = response._authenticate(true);
    } else if (response._shouldAuthenticate) {
      future = response._authenticate(false);
    } else {
      future = Future<HttpClientResponse>.value(response);
    }
    future.then(
      (v) {
        if (!_responseCompleter.isCompleted) {
          _responseCompleter.complete(v);
        }
      },
      onError: (e, s) {
        if (!_responseCompleter.isCompleted) {
          _responseCompleter.completeError(e, s);
        }
      },
    );
  }

  void _onError(error, StackTrace stackTrace) {
    if (!_responseCompleter.isCompleted) {
      _responseCompleter.completeError(error, stackTrace);
    }
  }

  // Generate the request URI based on the method and proxy.
  String _requestUri() {
    // Generate the request URI starting from the path component.
    String uriStartingFromPath() {
      String result = uri.path;
      if (result.isEmpty) result = "/";
      if (uri.hasQuery) {
        result = "$result?${uri.query}";
      }
      return result;
    }

    if (_proxy.isDirect) {
      return uriStartingFromPath();
    } else {
      if (method == "CONNECT") {
        // For the connect method the request URI is the host:port of
        // the requested destination of the tunnel (see RFC 2817
        // section 5.2)
        return "${uri.host}:${uri.port}";
      } else {
        if (_httpClientConnection._proxyTunnel) {
          return uriStartingFromPath();
        } else {
          return uri.removeFragment().toString();
        }
      }
    }
  }

  void add(List<int> data) {
    if (data.isEmpty || _aborted) return;
    super.add(data);
  }

  void write(Object? obj) {
    if (_aborted) return;
    super.write(obj);
  }

  void _writeHeader() {
    if (_aborted) {
      _outgoing.setHeader(Uint8List(0), 0);
      return;
    }
    BytesBuilder buffer = _CopyingBytesBuilder(_OUTGOING_BUFFER_SIZE);

    // Write the request method.
    buffer.add(method.codeUnits);
    buffer.addByte(_CharCode.SP);
    // Write the request URI.
    buffer.add(_requestUri().codeUnits);
    buffer.addByte(_CharCode.SP);
    // Write HTTP/1.1.
    buffer.add(_Const.HTTP11);
    buffer.addByte(_CharCode.CR);
    buffer.addByte(_CharCode.LF);

    // Add the cookies to the headers.
    if (cookies.isNotEmpty) {
      StringBuffer sb = StringBuffer();
      for (int i = 0; i < cookies.length; i++) {
        if (i > 0) sb.write("; ");
        sb
          ..write(cookies[i].name)
          ..write("=")
          ..write(cookies[i].value);
      }
      headers.add(HttpHeaders.cookieHeader, sb.toString());
    }

    headers._finalize();

    // Write headers.
    headers._build(
      buffer,
      skipZeroContentLength:
          method == "CONNECT" ||
          method == "DELETE" ||
          method == "GET" ||
          method == "HEAD",
    );
    buffer.addByte(_CharCode.CR);
    buffer.addByte(_CharCode.LF);
    Uint8List headerBytes = buffer.takeBytes();
    _outgoing.setHeader(headerBytes, headerBytes.length);
  }

  void abort([Object? exception, StackTrace? stackTrace]) {
    _aborted = true;
    if (!_responseCompleter.isCompleted) {
      exception ??= HttpException("Request has been aborted");
      _responseCompleter.completeError(exception, stackTrace);
      _httpClientConnection.destroy();
    }
  }
}

// Used by _HttpOutgoing as a target of a chunked converter for gzip
// compression.
class _HttpGZipSink extends ByteConversionSink {
  final _BytesConsumer _consume;
  _HttpGZipSink(this._consume);

  void add(List<int> chunk) {
    _consume(chunk);
  }

  void addSlice(List<int> chunk, int start, int end, bool isLast) {
    if (chunk is Uint8List) {
      _consume(
        Uint8List.view(chunk.buffer, chunk.offsetInBytes + start, end - start),
      );
    } else {
      _consume(chunk.sublist(start, end - start));
    }
  }

  void close() {}
}

// The _HttpOutgoing handles all of the following:
//  - Buffering
//  - GZip compression
//  - Content-Length validation.
//  - Errors.
//
// Most notable is the GZip compression, that uses a double-buffering system,
// one before gzip (_gzipBuffer) and one after (_buffer).
class _HttpOutgoing implements StreamConsumer<List<int>> {
  static const List<int> _footerAndChunk0Length = [
    _CharCode.CR,
    _CharCode.LF,
    0x30,
    _CharCode.CR,
    _CharCode.LF,
    _CharCode.CR,
    _CharCode.LF,
  ];

  static const List<int> _chunk0Length = [
    0x30,
    _CharCode.CR,
    _CharCode.LF,
    _CharCode.CR,
    _CharCode.LF,
  ];

  final Completer<Socket> _doneCompleter = Completer<Socket>();
  final Socket socket;

  bool ignoreBody = false;
  bool headersWritten = false;

  Uint8List? _buffer;
  int _length = 0;

  Future? _closeFuture;

  bool chunked = false;
  int _pendingChunkedFooter = 0;

  int? contentLength;
  int _bytesWritten = 0;

  bool _gzip = false;
  ByteConversionSink? _gzipSink;
  // _gzipAdd is set iff the sink is being added to. It's used to specify where
  // gzipped data should be taken (sometimes a controller, sometimes a socket).
  _BytesConsumer? _gzipAdd;
  Uint8List? _gzipBuffer;
  int _gzipBufferLength = 0;

  bool _socketError = false;

  _HttpOutboundMessage? outbound;

  _HttpOutgoing(this.socket);

  // Returns either a future or 'null', if it was able to write headers
  // immediately.
  Future<void>? writeHeaders({
    bool drainRequest = true,
    bool setOutgoing = true,
  }) {
    if (headersWritten) return null;
    headersWritten = true;
    Future<void>? drainFuture;
    bool gzip = false;
    var response = outbound!;
    if (response is _HttpResponse) {
      // Server side.
      if (response._httpRequest!._httpServer.autoCompress &&
          response.bufferOutput &&
          response.headers.chunkedTransferEncoding) {
        List<String>? acceptEncodings =
            response._httpRequest!.headers[HttpHeaders.acceptEncodingHeader];
        List<String>? contentEncoding =
            response.headers[HttpHeaders.contentEncodingHeader];
        if (acceptEncodings != null &&
            contentEncoding == null &&
            acceptEncodings
                .expand((list) => list.split(","))
                .any((encoding) => encoding.trim().toLowerCase() == "gzip")) {
          response.headers.set(HttpHeaders.contentEncodingHeader, "gzip");
          gzip = true;
        }
      }
      if (drainRequest && !response._httpRequest!._incoming.hasSubscriber) {
        drainFuture = response._httpRequest!.drain<void>().catchError((_) {});
      }
    } else {
      drainRequest = false;
    }
    if (!ignoreBody) {
      if (setOutgoing) {
        int contentLength = response.headers.contentLength;
        if (response.headers.chunkedTransferEncoding) {
          chunked = true;
          if (gzip) this.gzip = true;
        } else if (contentLength >= 0) {
          this.contentLength = contentLength;
        }
      }
      if (drainFuture != null) {
        return drainFuture.then((_) => response._writeHeader());
      }
    }
    response._writeHeader();
    return null;
  }

  Future addStream(Stream<List<int>> stream) {
    if (_socketError) {
      stream.listen(null).cancel();
      return Future.value(outbound);
    }
    if (ignoreBody) {
      stream.drain().catchError((_) {});
      var future = writeHeaders();
      if (future != null) {
        return future.then((_) => close());
      }
      return close();
    }
    // Use new stream so we are able to pause (see below listen). The
    // alternative is to use stream.expand, but that won't give us a way of
    // pausing.
    var controller = StreamController<List<int>>(sync: true);

    void onData(List<int> data) {
      if (_socketError) return;
      if (data.isEmpty) return;
      if (chunked) {
        if (_gzip) {
          _gzipAdd = controller.add;
          _addGZipChunk(data, _gzipSink!.add);
          _gzipAdd = null;
          return;
        }
        _addChunk(_chunkHeader(data.length), controller.add);
        _pendingChunkedFooter = 2;
      } else {
        var contentLength = this.contentLength;
        if (contentLength != null) {
          _bytesWritten += data.length;
          if (_bytesWritten > contentLength) {
            controller.addError(
              HttpException(
                "Content size exceeds specified contentLength. "
                "$_bytesWritten bytes written while expected "
                "$contentLength. "
                "[${String.fromCharCodes(data)}]",
              ),
            );
            return;
          }
        }
      }
      _addChunk(data, controller.add);
    }

    var sub = stream.listen(
      onData,
      onError: controller.addError,
      onDone: controller.close,
      cancelOnError: true,
    );
    controller.onCancel = sub.cancel;
    controller.onPause = sub.pause;
    controller.onResume = sub.resume;
    // Write headers now that we are listening to the stream.
    if (!headersWritten) {
      var future = writeHeaders();
      if (future != null) {
        // While incoming is being drained, the pauseFuture is non-null. Pause
        // output until it's drained.
        sub.pause(future);
      }
    }
    return socket
        .addStream(controller.stream)
        .then(
          (_) {
            return outbound;
          },
          onError: (error, stackTrace) {
            // Be sure to close it in case of an error.
            if (_gzip) _gzipSink!.close();
            _socketError = true;
            _doneCompleter.completeError(error, stackTrace);
            if (_ignoreError(error)) {
              return outbound;
            } else {
              throw error;
            }
          },
        );
  }

  Future close() {
    // If we are already closed, return that future.
    var closeFuture = _closeFuture;
    if (closeFuture != null) return closeFuture;

    var outbound = this.outbound!;
    // If we earlier saw an error, return immediate. The notification to
    // _Http*Connection is already done.
    if (_socketError) return Future.value(outbound);
    if (outbound._isConnectionClosed) return Future.value(outbound);
    if (!headersWritten && !ignoreBody) {
      if (outbound.headers.contentLength == -1) {
        // If no body was written, ignoreBody is false (it's not a HEAD
        // request) and the content-length is unspecified, set contentLength to
        // 0.
        outbound.headers.chunkedTransferEncoding = false;
        outbound.headers.contentLength = 0;
      } else if (outbound.headers.contentLength > 0) {
        var error = HttpException(
          "No content even though contentLength was specified to be "
          "greater than 0: ${outbound.headers.contentLength}.",
          uri: outbound._uri,
        );
        _doneCompleter.completeError(error);
        return _closeFuture = Future.error(error);
      }
    }
    // If contentLength was specified, validate it.
    var contentLength = this.contentLength;
    if (contentLength != null) {
      if (_bytesWritten < contentLength) {
        var error = HttpException(
          "Content size below specified contentLength. "
          " $_bytesWritten bytes written but expected "
          "$contentLength.",
          uri: outbound._uri,
        );
        _doneCompleter.completeError(error);
        return _closeFuture = Future.error(error);
      }
    }

    Future finalize() {
      // In case of chunked encoding (and gzip), handle remaining gzip data and
      // append the 'footer' for chunked encoding.
      if (chunked) {
        if (_gzip) {
          _gzipAdd = socket.add;
          if (_gzipBufferLength > 0) {
            _gzipSink!.add(
              Uint8List.view(
                _gzipBuffer!.buffer,
                _gzipBuffer!.offsetInBytes,
                _gzipBufferLength,
              ),
            );
          }
          _gzipBuffer = null;
          _gzipSink!.close();
          _gzipAdd = null;
        }
        _addChunk(_chunkHeader(0), socket.add);
      }
      // Add any remaining data in the buffer.
      if (_length > 0) {
        socket.add(
          Uint8List.view(_buffer!.buffer, _buffer!.offsetInBytes, _length),
        );
      }
      // Clear references, for better GC.
      _buffer = null;
      // And finally flush it. As we support keep-alive, never close it from
      // here. Once the socket is flushed, we'll be able to reuse it (signaled
      // by the 'done' future).
      return socket.flush().then(
        (_) {
          _doneCompleter.complete(socket);
          return outbound;
        },
        onError: (error, stackTrace) {
          _doneCompleter.completeError(error, stackTrace);
          if (_ignoreError(error)) {
            return outbound;
          } else {
            throw error;
          }
        },
      );
    }

    var future = writeHeaders();
    if (future != null) {
      return _closeFuture = future.whenComplete(finalize);
    }
    return _closeFuture = finalize();
  }

  Future<Socket> get done => _doneCompleter.future;

  void setHeader(List<int> data, int length) {
    assert(_length == 0);
    _buffer = data as Uint8List;
    _length = length;
  }

  void set gzip(bool value) {
    _gzip = value;
    if (value) {
      _gzipBuffer = Uint8List(_OUTGOING_BUFFER_SIZE);
      assert(_gzipSink == null);
      _gzipSink = ZLibEncoder(gzip: true).startChunkedConversion(
        _HttpGZipSink((data) {
          // We are closing down prematurely, due to an error. Discard.
          if (_gzipAdd == null) return;
          _addChunk(_chunkHeader(data.length), _gzipAdd!);
          _pendingChunkedFooter = 2;
          _addChunk(data, _gzipAdd!);
        }),
      );
    }
  }

  bool _ignoreError(error) =>
      (error is SocketException || error is TlsException) &&
      outbound is HttpResponse;

  void _addGZipChunk(List<int> chunk, void Function(List<int> data) add) {
    var bufferOutput = outbound!.bufferOutput;
    if (!bufferOutput) {
      add(chunk);
      return;
    }
    var gzipBuffer = _gzipBuffer!;
    if (chunk.length > gzipBuffer.length - _gzipBufferLength) {
      add(
        Uint8List.view(
          gzipBuffer.buffer,
          gzipBuffer.offsetInBytes,
          _gzipBufferLength,
        ),
      );
      _gzipBuffer = Uint8List(_OUTGOING_BUFFER_SIZE);
      _gzipBufferLength = 0;
    }
    if (chunk.length > _OUTGOING_BUFFER_SIZE) {
      add(chunk);
    } else {
      var currentLength = _gzipBufferLength;
      var newLength = currentLength + chunk.length;
      _gzipBuffer!.setRange(currentLength, newLength, chunk);
      _gzipBufferLength = newLength;
    }
  }

  void _addChunk(List<int> chunk, void Function(List<int> data) add) {
    var bufferOutput = outbound!.bufferOutput;
    if (!bufferOutput) {
      if (_buffer != null) {
        // If _buffer is not null, we have not written the header yet. Write
        // it now.
        add(Uint8List.view(_buffer!.buffer, _buffer!.offsetInBytes, _length));
        _buffer = null;
        _length = 0;
      }
      add(chunk);
      return;
    }
    if (chunk.length > _buffer!.length - _length) {
      add(Uint8List.view(_buffer!.buffer, _buffer!.offsetInBytes, _length));
      _buffer = Uint8List(_OUTGOING_BUFFER_SIZE);
      _length = 0;
    }
    if (chunk.length > _OUTGOING_BUFFER_SIZE) {
      add(chunk);
    } else {
      _buffer!.setRange(_length, _length + chunk.length, chunk);
      _length += chunk.length;
    }
  }

  List<int> _chunkHeader(int length) {
    const hexDigits = [
      0x30,
      0x31,
      0x32,
      0x33,
      0x34,
      0x35,
      0x36,
      0x37,
      0x38,
      0x39,
      0x41,
      0x42,
      0x43,
      0x44,
      0x45,
      0x46,
    ];
    if (length == 0) {
      if (_pendingChunkedFooter == 2) return _footerAndChunk0Length;
      return _chunk0Length;
    }
    int size = _pendingChunkedFooter;
    int len = length;
    // Compute a fast integer version of (log(length + 1) / log(16)).ceil().
    while (len > 0) {
      size++;
      len >>= 4;
    }
    var footerAndHeader = Uint8List(size + 2);
    if (_pendingChunkedFooter == 2) {
      footerAndHeader[0] = _CharCode.CR;
      footerAndHeader[1] = _CharCode.LF;
    }
    int index = size;
    while (index > _pendingChunkedFooter) {
      footerAndHeader[--index] = hexDigits[length & 15];
      length = length >> 4;
    }
    footerAndHeader[size + 0] = _CharCode.CR;
    footerAndHeader[size + 1] = _CharCode.LF;
    return footerAndHeader;
  }
}

class _HttpClientConnection {
  final String key;
  final Socket _socket;
  final bool _proxyTunnel;
  final SecurityContext? _context;
  final _HttpParser _httpParser;
  StreamSubscription? _subscription;
  final _HttpClient _httpClient;
  bool _dispose = false;
  Timer? _idleTimer;
  bool closed = false;
  Uri? _currentUri;

  Completer<_HttpIncoming>? _nextResponseCompleter;
  Future<Socket>? _streamFuture;

  _HttpClientConnection(
    this.key,
    this._socket,
    this._httpClient, [
    this._proxyTunnel = false,
    this._context,
  ]) : _httpParser = _HttpParser.responseParser() {
    _httpParser.listenToStream(_socket);

    // Set up handlers on the parser here, so we are sure to get 'onDone' from
    // the parser.
    _subscription = _httpParser.listen(
      (incoming) {
        // Only handle one incoming response at the time. Keep the
        // stream paused until the response have been processed.
        _subscription!.pause();
        // We assume the response is not here, until we have send the request.
        if (_nextResponseCompleter == null) {
          throw HttpException(
            "Unexpected response (unsolicited response without request). This "
            "can be caused when a malformed request is sent to the server "
            "(e.g. a GET request containing a body) or if the server is not "
            "correctly implemented. Future requests to this server, using the "
            "same HttpClient, are likely to fail.",
            uri: _currentUri,
          );
        }

        // Check for status code '100 Continue'. In that case just
        // consume that response as the final response will follow
        // it. There is currently no API for the client to wait for
        // the '100 Continue' response.
        if (incoming.statusCode == 100) {
          incoming
              .drain()
              .then((_) {
                _subscription!.resume();
              })
              .catchError(
                (dynamic error, StackTrace stackTrace) {
                  String message;
                  if (error is HttpException) {
                    message = error.message;
                  } else if (error is SocketException) {
                    message = error.message;
                  } else if (error is TlsException) {
                    message = error.message;
                  } else {
                    throw error;
                  }
                  _nextResponseCompleter!.completeError(
                    HttpException(message, uri: _currentUri),
                    stackTrace,
                  );
                  _nextResponseCompleter = null;
                },
                test: (error) =>
                    error is HttpException ||
                    error is SocketException ||
                    error is TlsException,
              );
        } else {
          _nextResponseCompleter!.complete(incoming);
          _nextResponseCompleter = null;
        }
      },
      onError: (dynamic error, StackTrace stackTrace) {
        String message;
        if (error is HttpException) {
          message = error.message;
        } else if (error is SocketException) {
          message = error.message;
        } else if (error is TlsException) {
          message = error.message;
        } else {
          throw error;
        }
        _nextResponseCompleter?.completeError(
          HttpException(message, uri: _currentUri),
          stackTrace,
        );
        _nextResponseCompleter = null;
      },
      onDone: () {
        _nextResponseCompleter?.completeError(
          HttpException(
            "Connection closed before response was received",
            uri: _currentUri,
          ),
        );
        _nextResponseCompleter = null;
        if (!closed) {
          _close();
        }
      },
    );
  }

  _HttpClientRequest send(
    Uri uri,
    int port,
    String method,
    _Proxy proxy,
    _HttpProfileData? profileData,
  ) {
    if (closed) {
      throw HttpException("Socket closed before request was sent", uri: uri);
    }
    _currentUri = uri;
    // Start with pausing the parser.
    _subscription!.pause();
    if (method == "CONNECT") {
      // Parser will ignore Content-Length or Transfer-Encoding header
      _httpParser.connectMethod = true;
    }
    _ProxyCredentials? proxyCreds; // Credentials used to authorize proxy.
    _SiteCredentials? creds; // Credentials used to authorize this request.
    var outgoing = _HttpOutgoing(_socket);

    // Create new request object, wrapping the outgoing connection.
    var request = _HttpClientRequest(
      outgoing,
      uri,
      method,
      proxy,
      _httpClient,
      this,
      profileData,
    );
    // For the Host header an IPv6 address must be enclosed in []'s.
    var host = uri.host;
    if (host.contains(':')) host = "[$host]";
    request.headers
      ..host = host
      ..port = port
      ..add(HttpHeaders.acceptEncodingHeader, "gzip");
    if (_httpClient.userAgent != null) {
      request.headers.add(HttpHeaders.userAgentHeader, _httpClient.userAgent!);
    }
    if (proxy.isAuthenticated) {
      // If the proxy configuration contains user information use that
      // for proxy basic authorization.
      String auth = base64Encode(
        utf8.encode("${proxy.username}:${proxy.password}"),
      );
      request.headers.set(HttpHeaders.proxyAuthorizationHeader, "Basic $auth");
    } else if (!proxy.isDirect && _httpClient._proxyCredentials.isNotEmpty) {
      proxyCreds = _httpClient._findProxyCredentials(proxy);
      if (proxyCreds != null) {
        proxyCreds.authorize(request);
      }
    }
    if (uri.userInfo != null && uri.userInfo.isNotEmpty) {
      // If the URL contains user information use that for basic
      // authorization.
      String auth = base64Encode(utf8.encode(uri.userInfo));
      request.headers.set(HttpHeaders.authorizationHeader, "Basic $auth");
    } else {
      // Look for credentials.
      creds = _httpClient._findCredentials(uri);
      if (creds != null) {
        creds.authorize(request);
      }
    }

    // Start sending the request (lazy, delayed until the user provides
    // data).
    _httpParser.isHead = method == "HEAD";
    _streamFuture = outgoing.done.then<Socket>((Socket s) {
      // Request sent, details available for profiling
      profileData?.finishRequest(request: request);

      // Request sent, set up response completer.
      var nextResponseCompleter = Completer<_HttpIncoming>();
      _nextResponseCompleter = nextResponseCompleter;

      // Listen for response.
      nextResponseCompleter.future
          .then((incoming) {
            _currentUri = null;
            incoming.dataDone.then((closing) {
              if (incoming.upgraded) {
                _httpClient._connectionClosed(this);
                startTimer();
                return;
              }
              // Keep the connection open if the CONNECT request was successful.
              if (closed ||
                  (method == 'CONNECT' &&
                      incoming.statusCode == HttpStatus.ok)) {
                return;
              }
              if (!closing &&
                  !_dispose &&
                  incoming.headers.persistentConnection &&
                  request.persistentConnection) {
                // Return connection, now we are done.
                _httpClient._returnConnection(this);
                _subscription!.resume();
              } else {
                destroy();
              }
            });
            // For digest authentication if proxy check if the proxy
            // requests the client to start using a new nonce for proxy
            // authentication.
            if (proxyCreds != null &&
                proxyCreds.scheme == _AuthenticationScheme.Digest) {
              var authInfo = incoming.headers["proxy-authentication-info"];
              if (authInfo != null && authInfo.length == 1) {
                var header = _HeaderValue.parse(
                  authInfo[0],
                  parameterSeparator: ',',
                );
                var nextnonce = header.parameters["nextnonce"];
                if (nextnonce != null) proxyCreds.nonce = nextnonce;
              }
            }
            // For digest authentication check if the server requests the
            // client to start using a new nonce.
            if (creds != null && creds.scheme == _AuthenticationScheme.Digest) {
              var authInfo = incoming.headers["authentication-info"];
              if (authInfo != null && authInfo.length == 1) {
                var header = _HeaderValue.parse(
                  authInfo[0],
                  parameterSeparator: ',',
                );
                var nextnonce = header.parameters["nextnonce"];
                if (nextnonce != null) creds.nonce = nextnonce;
              }
            }
            request._handleIncoming(incoming);
          })
          // If we see a state error, we failed to get the 'first'
          // element.
          .catchError((error) {
            throw HttpException(
              "Connection closed before data was received",
              uri: uri,
            );
          }, test: (error) => error is StateError)
          .catchError((error, stackTrace) {
            // We are done with the socket.
            destroy();
            request._onError(error, stackTrace);
          });

      // Resume the parser now we have a handler.
      _subscription!.resume();
      return s;
    });
    Future<Socket?>.value(_streamFuture).catchError((e) {
      destroy();
      return null;
    });
    return request;
  }

  Future<Socket> detachSocket() {
    return _streamFuture!.then(
      (_) => _DetachedSocket(_socket, _httpParser.detachIncoming()),
    );
  }

  void destroy() {
    closed = true;
    _httpClient._connectionClosed(this);
    _socket.destroy();
  }

  void destroyFromExternal() {
    closed = true;
    _httpClient._connectionClosedNoFurtherClosing(this);
    _socket.destroy();
  }

  void _close() {
    closed = true;
    _httpClient._connectionClosed(this);
    _streamFuture!
        .timeout(_httpClient.idleTimeout)
        .then((_) => _socket.destroy());
  }

  void closeFromExternal() {
    closed = true;
    _httpClient._connectionClosedNoFurtherClosing(this);
    _streamFuture!
        .timeout(_httpClient.idleTimeout)
        .then((_) => _socket.destroy());
  }

  Future<_HttpClientConnection> createProxyTunnel(
    String host,
    int port,
    _Proxy proxy,
    bool Function(X509Certificate certificate) callback,
    _HttpProfileData? profileData,
  ) {
    final method = "CONNECT";
    final uri = Uri(host: host, port: port);

    profileData?.proxyEvent(proxy);

    // Notify the profiler that we're starting a sub request.
    _HttpProfileData? proxyProfileData;
    if (profileData != null) {
      proxyProfileData = HttpProfiler.startRequest(
        method,
        uri,
        parentRequest: profileData,
      );
    }
    _HttpClientRequest request = send(
      Uri(host: host, port: port),
      port,
      method,
      proxy,
      proxyProfileData,
    );
    if (proxy.isAuthenticated) {
      // If the proxy configuration contains user information use that
      // for proxy basic authorization.
      String auth = base64Encode(
        utf8.encode("${proxy.username}:${proxy.password}"),
      );
      request.headers.set(HttpHeaders.proxyAuthorizationHeader, "Basic $auth");
    }
    return request
        .close()
        .then((response) {
          if (response.statusCode != HttpStatus.ok) {
            final error =
                "Proxy failed to establish tunnel "
                "(${response.statusCode} ${response.reasonPhrase})";
            profileData?.requestEvent(error);
            throw HttpException(error, uri: request.uri);
          }
          var socket = (response as _HttpClientResponse)
              ._httpRequest
              ._httpClientConnection
              ._socket;
          return SecureSocket.secure(
            socket,
            host: host,
            context: _context,
            onBadCertificate: callback,
          );
        })
        .then((secureSocket) {
          String key = _HttpClientConnection.makeKey(true, host, port);
          profileData?.requestEvent('Proxy tunnel established');
          return _HttpClientConnection(
            key,
            secureSocket,
            request._httpClient,
            true,
          );
        });
  }

  HttpConnectionInfo? get connectionInfo => _HttpConnectionInfo.create(_socket);

  static makeKey(bool isSecure, String host, int port) {
    return isSecure ? "ssh:$host:$port" : "$host:$port";
  }

  void stopTimer() {
    _idleTimer?.cancel();
    _idleTimer = null;
  }

  void startTimer() {
    assert(_idleTimer == null);
    _idleTimer = Timer(_httpClient.idleTimeout, () {
      _idleTimer = null;
      _close();
    });
  }
}

class _ConnectionInfo {
  final _HttpClientConnection connection;
  final _Proxy proxy;

  _ConnectionInfo(this.connection, this.proxy);
}

class _ConnectionTarget {
  // Unique key for this connection target.
  final String key;
  final String host;
  final int port;
  final bool isSecure;
  final SecurityContext? context;
  final Future<ConnectionTask<Socket>> Function(Uri, String?, int?)?
  connectionFactory;
  final Set<_HttpClientConnection> _idle = HashSet();
  final Set<_HttpClientConnection> _active = HashSet();
  final Set<ConnectionTask<Socket>> _socketTasks = HashSet();
  final _pending = ListQueue<void Function()>();
  int _connecting = 0;

  _ConnectionTarget(
    this.key,
    this.host,
    this.port,
    this.isSecure,
    this.context,
    this.connectionFactory,
  );

  bool get isEmpty => _idle.isEmpty && _active.isEmpty && _connecting == 0;

  bool get hasIdle => _idle.isNotEmpty;

  bool get hasActive => _active.isNotEmpty || _connecting > 0;

  _HttpClientConnection takeIdle() {
    assert(hasIdle);
    _HttpClientConnection connection = _idle.first;
    _idle.remove(connection);
    connection.stopTimer();
    _active.add(connection);
    return connection;
  }

  _checkPending() {
    if (_pending.isNotEmpty) {
      _pending.removeFirst()();
    }
  }

  void addNewActive(_HttpClientConnection connection) {
    _active.add(connection);
  }

  void returnConnection(_HttpClientConnection connection) {
    assert(_active.contains(connection));
    _active.remove(connection);
    _idle.add(connection);
    connection.startTimer();
    _checkPending();
  }

  void connectionClosed(_HttpClientConnection connection) {
    assert(!_active.contains(connection) || !_idle.contains(connection));
    _active.remove(connection);
    _idle.remove(connection);
    _checkPending();
  }

  void close(bool force) {
    // Always cancel pending socket connections.
    for (var t in _socketTasks.toList()) {
      // Make sure the socket is destroyed if the ConnectionTask is cancelled.
      t.socket.then((s) {
        s.destroy();
      }, onError: (e) {});
      t.cancel();
    }
    if (force) {
      for (var c in _idle.toList()) {
        c.destroyFromExternal();
      }
      for (var c in _active.toList()) {
        c.destroyFromExternal();
      }
    } else {
      for (var c in _idle.toList()) {
        c.closeFromExternal();
      }
    }
  }

  Future<_ConnectionInfo> connect(
    Uri uri,
    String uriHost,
    int uriPort,
    _Proxy proxy,
    _HttpClient client,
    _HttpProfileData? profileData,
  ) {
    if (hasIdle) {
      var connection = takeIdle();
      client._connectionsChanged();
      return Future.value(_ConnectionInfo(connection, proxy));
    }
    var maxConnectionsPerHost = client.maxConnectionsPerHost;
    if (maxConnectionsPerHost != null &&
        _active.length + _connecting >= maxConnectionsPerHost) {
      var completer = Completer<_ConnectionInfo>();
      _pending.add(() {
        completer.complete(
          connect(uri, uriHost, uriPort, proxy, client, profileData),
        );
      });
      return completer.future;
    }
    var currentBadCertificateCallback = client._badCertificateCallback;

    bool callback(X509Certificate certificate) {
      if (currentBadCertificateCallback == null) return false;
      return currentBadCertificateCallback(certificate, uriHost, uriPort);
    }

    Future<ConnectionTask<Socket>> connectionTask;
    final cf = connectionFactory;
    if (cf != null) {
      if (proxy.isDirect) {
        connectionTask = cf(uri, null, null);
      } else {
        connectionTask = cf(uri, host, port);
      }
    } else {
      connectionTask = (isSecure && proxy.isDirect
          ? SecureSocket.startConnect(
              host,
              port,
              context: context,
              onBadCertificate: callback,
              keyLog: client._keyLog,
            )
          : Socket.startConnect(host, port));
    }
    _connecting++;
    return connectionTask.then(
      (ConnectionTask<Socket> task) {
        _socketTasks.add(task);
        Future<Socket> socketFuture = task.socket;
        final Duration? connectionTimeout = client.connectionTimeout;
        if (connectionTimeout != null) {
          socketFuture = socketFuture.timeout(connectionTimeout);
        }
        return socketFuture.then(
          (socket) {
            _connecting--;
            if (socket.address.type != InternetAddressType.unix) {
              socket.setOption(SocketOption.tcpNoDelay, true);
            }
            var connection = _HttpClientConnection(
              key,
              socket,
              client,
              false,
              context,
            );
            if (isSecure && !proxy.isDirect) {
              connection._dispose = true;
              return connection
                  .createProxyTunnel(
                    uriHost,
                    uriPort,
                    proxy,
                    callback,
                    profileData,
                  )
                  .then((tunnel) {
                    client
                        ._getConnectionTarget(uriHost, uriPort, true)
                        .addNewActive(tunnel);
                    _socketTasks.remove(task);
                    return _ConnectionInfo(tunnel, proxy);
                  });
            } else {
              addNewActive(connection);
              _socketTasks.remove(task);
              return _ConnectionInfo(connection, proxy);
            }
          },
          onError: (error) {
            _connecting--;
            _socketTasks.remove(task);
            _checkPending();
            // When there is a timeout, cancel the ConnectionTask and propagate a
            // SocketException as specified by the HttpClient.connectionTimeout
            // docs.
            if (error is TimeoutException) {
              assert(connectionTimeout != null);
              task.cancel();
              throw SocketException(
                "HTTP connection timed out after $connectionTimeout, "
                "host: $host, port: $port",
              );
            }
            throw error;
          },
        );
      },
      onError: (error) {
        _connecting--;
        _checkPending();
        throw error;
      },
    );
  }
}

typedef BadCertificateCallback =
    bool Function(X509Certificate cr, String host, int port);

class _HttpClient implements HttpClient {
  bool _closing = false;
  bool _closingForcefully = false;
  final Map<String, _ConnectionTarget> _connectionTargets =
      HashMap<String, _ConnectionTarget>();
  final List<_Credentials> _credentials = [];
  final List<_ProxyCredentials> _proxyCredentials = [];
  final SecurityContext? _context;
  Future<ConnectionTask<Socket>> Function(Uri, String?, int?)?
  _connectionFactory;
  Future<bool> Function(Uri, String scheme, String? realm)? _authenticate;
  Future<bool> Function(String host, int port, String scheme, String? realm)?
  _authenticateProxy;
  String Function(Uri)? _findProxy = HttpClient.findProxyFromEnvironment;
  Duration _idleTimeout = const Duration(seconds: 15);
  BadCertificateCallback? _badCertificateCallback;
  Function(String line)? _keyLog;

  Duration get idleTimeout => _idleTimeout;

  Duration? connectionTimeout;

  int? maxConnectionsPerHost;

  bool autoUncompress = true;

  String? userAgent = _getHttpVersion();

  _HttpClient(this._context);

  void set idleTimeout(Duration timeout) {
    _idleTimeout = timeout;
    for (var c in _connectionTargets.values) {
      for (var idle in c._idle) {
        // Reset timer. This is fine, as it's not happening often.
        idle.stopTimer();
        idle.startTimer();
      }
    }
  }

  set badCertificateCallback(
    bool Function(X509Certificate cert, String host, int port)? callback,
  ) {
    _badCertificateCallback = callback;
  }

  void set keyLog(Function(String line)? callback) {
    _keyLog = callback;
  }

  Future<HttpClientRequest> open(
    String method,
    String host,
    int port,
    String path,
  ) {
    const int hashMark = 0x23;
    const int questionMark = 0x3f;
    int fragmentStart = path.length;
    int queryStart = path.length;
    for (int i = path.length - 1; i >= 0; i--) {
      var char = path.codeUnitAt(i);
      if (char == hashMark) {
        fragmentStart = i;
        queryStart = i;
      } else if (char == questionMark) {
        queryStart = i;
      }
    }
    String? query;
    if (queryStart < fragmentStart) {
      query = path.substring(queryStart + 1, fragmentStart);
      path = path.substring(0, queryStart);
    }
    Uri uri = Uri(
      scheme: "http",
      host: host,
      port: port,
      path: path,
      query: query,
    );
    return _openUrl(method, uri);
  }

  Future<HttpClientRequest> openUrl(String method, Uri url) =>
      _openUrl(method, url);

  Future<HttpClientRequest> get(String host, int port, String path) =>
      open("get", host, port, path);

  Future<HttpClientRequest> getUrl(Uri url) => _openUrl("get", url);

  Future<HttpClientRequest> post(String host, int port, String path) =>
      open("post", host, port, path);

  Future<HttpClientRequest> postUrl(Uri url) => _openUrl("post", url);

  Future<HttpClientRequest> put(String host, int port, String path) =>
      open("put", host, port, path);

  Future<HttpClientRequest> putUrl(Uri url) => _openUrl("put", url);

  Future<HttpClientRequest> delete(String host, int port, String path) =>
      open("delete", host, port, path);

  Future<HttpClientRequest> deleteUrl(Uri url) => _openUrl("delete", url);

  Future<HttpClientRequest> head(String host, int port, String path) =>
      open("head", host, port, path);

  Future<HttpClientRequest> headUrl(Uri url) => _openUrl("head", url);

  Future<HttpClientRequest> patch(String host, int port, String path) =>
      open("patch", host, port, path);

  Future<HttpClientRequest> patchUrl(Uri url) => _openUrl("patch", url);

  void close({bool force = false}) {
    _closing = true;
    _closingForcefully = force;
    _closeConnections(_closingForcefully);
    assert(!_connectionTargets.values.any((s) => s.hasIdle));
    assert(
      !force || !_connectionTargets.values.any((s) => s._active.isNotEmpty),
    );
  }

  set authenticate(
    Future<bool> Function(Uri url, String scheme, String? realm)? f,
  ) {
    _authenticate = f;
  }

  void addCredentials(Uri url, String realm, HttpClientCredentials cr) {
    _credentials.add(
      _SiteCredentials(url, realm, cr as _HttpClientCredentials),
    );
  }

  set authenticateProxy(
    Future<bool> Function(String host, int port, String scheme, String? realm)?
    f,
  ) {
    _authenticateProxy = f;
  }

  void addProxyCredentials(
    String host,
    int port,
    String realm,
    HttpClientCredentials cr,
  ) {
    _proxyCredentials.add(
      _ProxyCredentials(host, port, realm, cr as _HttpClientCredentials),
    );
  }

  void set connectionFactory(
    Future<ConnectionTask<Socket>> Function(
      Uri url,
      String? proxyHost,
      int? proxyPort,
    )?
    f,
  ) => _connectionFactory = f;

  set findProxy(String Function(Uri uri)? f) => _findProxy = f;

  static void _startRequestTimelineEvent(
    TimelineTask? timeline,
    String method,
    Uri uri,
  ) {
    timeline?.start(
      'HTTP CLIENT ${method.toUpperCase()}',
      arguments: {'method': method.toUpperCase(), 'uri': uri.toString()},
    );
  }

  bool _isLoopback(String host) {
    if (host.isEmpty) return false;
    if ("localhost" == host) return true;
    try {
      return InternetAddress(host).isLoopback;
    } on ArgumentError {
      return false;
    }
  }

  bool _isValidToken(String token) {
    checkNotNullable(token, "token");
    // from https://www.rfc-editor.org/rfc/rfc2616#page-15
    //
    // CTL            = <any US-ASCII control character
    //                  (octets 0 - 31) and DEL (127)>
    // separators     = "(" | ")" | "<" | ">" | "@"
    //                | "," | ";" | ":" | "\" | <">
    //                | "/" | "[" | "]" | "?" | "="
    //                | "{" | "}" | SP | HT
    // token          = 1*<any CHAR except CTLs or separators>
    const _validChars =
        r"                                "
        r" ! #$%&'  *+ -. 0123456789      "
        r" ABCDEFGHIJKLMNOPQRSTUVWXYZ   ^_"
        r"`abcdefghijklmnopqrstuvwxyz | ~ ";
    for (int codeUnit in token.codeUnits) {
      if (codeUnit >= _validChars.length ||
          _validChars.codeUnitAt(codeUnit) == 0x20) {
        return false;
      }
    }
    return true;
  }

  Future<_HttpClientRequest> _openUrl(String method, Uri uri) {
    if (_closing) {
      throw StateError("Client is closed");
    }

    // Ignore any fragments on the request URI.
    uri = uri.removeFragment();

    // from https://www.rfc-editor.org/rfc/rfc2616#page-35
    if (!_isValidToken(method)) {
      throw ArgumentError.value(method, "method");
    }

    if (method != "CONNECT") {
      if (uri.host.isEmpty) {
        throw ArgumentError("No host specified in URI $uri");
      } else if (this._connectionFactory == null &&
          !uri.isScheme("http") &&
          !uri.isScheme("https")) {
        throw ArgumentError("Unsupported scheme '${uri.scheme}' in URI $uri");
      }
    }

    _httpConnectionHook(uri);

    bool isSecure = uri.isScheme("https");

    int port = uri.port;
    if (port == 0) {
      port = isSecure
          ? HttpClient.defaultHttpsPort
          : HttpClient.defaultHttpPort;
    }
    // Check to see if a proxy server should be used for this connection.
    var proxyConf = const _ProxyConfiguration.direct();
    var findProxy = _findProxy;
    if (findProxy != null) {
      // TODO(sgjesse): Keep a map of these as normally only a few
      // configuration strings will be used.
      try {
        proxyConf = _ProxyConfiguration(findProxy(uri));
      } catch (error, stackTrace) {
        return Future.error(error, stackTrace);
      }
    }
    _HttpProfileData? profileData;
    if (HttpClient.enableTimelineLogging &&
        !const bool.fromEnvironment("dart.vm.product")) {
      profileData = HttpProfiler.startRequest(method, uri);
    }
    return _getConnection(
      uri,
      uri.host,
      port,
      proxyConf,
      isSecure,
      profileData,
    ).then(
      (_ConnectionInfo info) {
        _HttpClientRequest send(_ConnectionInfo info) {
          profileData?.requestEvent('Connection established');
          return info.connection.send(
            uri,
            port,
            method.toUpperCase(),
            info.proxy,
            profileData,
          );
        }

        // If the connection was closed before the request was sent, create
        // and use another connection.
        if (info.connection.closed) {
          return _getConnection(
            uri,
            uri.host,
            port,
            proxyConf,
            isSecure,
            profileData,
          ).then(send);
        }
        return send(info);
      },
      onError: (error) {
        profileData?.finishRequestWithError(error.toString());
        throw error;
      },
    );
  }

  static bool _isSubdomain(Uri subdomain, Uri domain) {
    return (subdomain.isScheme(domain.scheme) &&
        subdomain.port == domain.port &&
        (subdomain.host == domain.host ||
            subdomain.host.endsWith("." + domain.host)));
  }

  // Only visible for testing.
  static bool shouldCopyHeaderOnRedirect(
    String headerKey,
    Uri originalUrl,
    Uri redirectUri,
  ) {
    if (_isSubdomain(redirectUri, originalUrl)) {
      return true;
    }

    const nonRedirectHeaders = [
      "authorization",
      "www-authenticate",
      "cookie",
      "cookie2",
    ];
    return !nonRedirectHeaders.contains(headerKey.toLowerCase());
  }

  Future<_HttpClientRequest> _openUrlFromRequest(
    String method,
    Uri uri,
    _HttpClientRequest previous, {
    required bool isRedirect,
  }) {
    // If the new URI is relative (to either '/' or some sub-path),
    // construct a full URI from the previous one.
    Uri resolved = previous.uri.resolveUri(uri);
    return _openUrl(method, resolved).then((_HttpClientRequest request) {
      request
        // Only follow redirects if initial request did.
        ..followRedirects = previous.followRedirects
        // Allow same number of redirects.
        ..maxRedirects = previous.maxRedirects;
      // Copy headers.
      for (var header in previous.headers._headers.keys) {
        if (request.headers[header] == null &&
            (!isRedirect ||
                shouldCopyHeaderOnRedirect(header, resolved, previous.uri))) {
          request.headers.set(header, previous.headers[header]!);
        }
      }
      return request
        ..headers.chunkedTransferEncoding = false
        ..contentLength = 0;
    });
  }

  // Return a live connection to the idle pool.
  void _returnConnection(_HttpClientConnection connection) {
    _connectionTargets[connection.key]!.returnConnection(connection);
    _connectionsChanged();
  }

  // Remove a closed connection from the active set.
  void _connectionClosed(_HttpClientConnection connection) {
    connection.stopTimer();
    var connectionTarget = _connectionTargets[connection.key];
    if (connectionTarget != null) {
      connectionTarget.connectionClosed(connection);
      if (connectionTarget.isEmpty) {
        _connectionTargets.remove(connection.key);
      }
      _connectionsChanged();
    }
  }

  // Remove a closed connection and not issue _closeConnections(). If the close
  // is signaled from user by calling close(), _closeConnections() was called
  // and prevent further calls.
  void _connectionClosedNoFurtherClosing(_HttpClientConnection connection) {
    connection.stopTimer();
    var connectionTarget = _connectionTargets[connection.key];
    if (connectionTarget != null) {
      connectionTarget.connectionClosed(connection);
      if (connectionTarget.isEmpty) {
        _connectionTargets.remove(connection.key);
      }
    }
  }

  void _connectionsChanged() {
    if (_closing) {
      _closeConnections(_closingForcefully);
    }
  }

  void _closeConnections(bool force) {
    for (var connectionTarget in _connectionTargets.values.toList()) {
      connectionTarget.close(force);
    }
  }

  _ConnectionTarget _getConnectionTarget(String host, int port, bool isSecure) {
    String key = _HttpClientConnection.makeKey(isSecure, host, port);
    return _connectionTargets.putIfAbsent(key, () {
      return _ConnectionTarget(
        key,
        host,
        port,
        isSecure,
        _context,
        _connectionFactory,
      );
    });
  }

  // Get a new _HttpClientConnection, from the matching _ConnectionTarget.
  Future<_ConnectionInfo> _getConnection(
    Uri uri,
    String uriHost,
    int uriPort,
    _ProxyConfiguration proxyConf,
    bool isSecure,
    _HttpProfileData? profileData,
  ) {
    Iterator<_Proxy> proxies = proxyConf.proxies.iterator;

    Future<_ConnectionInfo> connect(error, stackTrace) {
      if (!proxies.moveNext()) return Future.error(error, stackTrace);
      _Proxy proxy = proxies.current;
      String host = proxy.isDirect ? uriHost : proxy.host!;
      int port = proxy.isDirect ? uriPort : proxy.port!;
      return _getConnectionTarget(host, port, isSecure)
          .connect(uri, uriHost, uriPort, proxy, this, profileData)
          // On error, continue with next proxy.
          .catchError(connect);
    }

    return connect(HttpException("No proxies given"), StackTrace.current);
  }

  _SiteCredentials? _findCredentials(Uri url, [_AuthenticationScheme? scheme]) {
    // Look for credentials.
    _SiteCredentials? cr = _credentials.fold(null, (
      _SiteCredentials? prev,
      value,
    ) {
      var siteCredentials = value as _SiteCredentials;
      if (siteCredentials.applies(url, scheme)) {
        if (prev == null) return value;
        return siteCredentials.uri.path.length > prev.uri.path.length
            ? siteCredentials
            : prev;
      } else {
        return prev;
      }
    });
    return cr;
  }

  _ProxyCredentials? _findProxyCredentials(
    _Proxy proxy, [
    _AuthenticationScheme? scheme,
  ]) {
    // Look for credentials.
    for (var current in _proxyCredentials) {
      if (current.applies(proxy, scheme)) {
        return current;
      }
    }
    return null;
  }

  void _removeCredentials(_Credentials cr) {
    int index = _credentials.indexOf(cr);
    if (index != -1) {
      _credentials.removeAt(index);
    }
  }

  void _removeProxyCredentials(_Credentials cr) {
    _proxyCredentials.remove(cr);
  }

  static String _findProxyFromEnvironment(
    Uri url,
    Map<String, String>? environment,
  ) {
    String? checkNoProxy(String? option) {
      if (option == null) return null;
      Iterator<String> names = option.split(",").map((s) => s.trim()).iterator;
      while (names.moveNext()) {
        var name = names.current;
        if ((name.startsWith("[") &&
                name.endsWith("]") &&
                "[${url.host}]" == name) ||
            (name.isNotEmpty && url.host.endsWith(name))) {
          return "DIRECT";
        }
      }
      return null;
    }

    String? checkProxy(String? option) {
      if (option == null) return null;
      option = option.trim();
      if (option.isEmpty) return null;
      int pos = option.indexOf("://");
      if (pos >= 0) {
        option = option.substring(pos + 3);
      }
      pos = option.indexOf("/");
      if (pos >= 0) {
        option = option.substring(0, pos);
      }
      // Add default port if no port configured.
      if (option.indexOf("[") == 0) {
        var pos = option.lastIndexOf(":");
        if (option.indexOf("]") > pos) option = "$option:1080";
      } else {
        if (!option.contains(":")) option = "$option:1080";
      }
      return "PROXY $option";
    }

    // Default to using the process current environment.
    environment ??= _platformEnvironmentCache;

    String? proxyCfg;

    String? noProxy = environment["no_proxy"] ?? environment["NO_PROXY"];
    proxyCfg = checkNoProxy(noProxy);
    if (proxyCfg != null) {
      return proxyCfg;
    }

    if (url.isScheme("http")) {
      String? proxy = environment["http_proxy"] ?? environment["HTTP_PROXY"];
      proxyCfg = checkProxy(proxy);
      if (proxyCfg != null) {
        return proxyCfg;
      }
    } else if (url.isScheme("https")) {
      String? proxy = environment["https_proxy"] ?? environment["HTTPS_PROXY"];
      proxyCfg = checkProxy(proxy);
      if (proxyCfg != null) {
        return proxyCfg;
      }
    }
    return "DIRECT";
  }

  static final Map<String, String> _platformEnvironmentCache =
      Platform.environment;
}

final class _HttpConnection extends LinkedListEntry<_HttpConnection>
    with _ServiceObject {
  static const _ACTIVE = 0;
  static const _IDLE = 1;
  static const _CLOSING = 2;
  static const _DETACHED = 3;

  // Use HashMap, as we don't need to keep order.
  static final Map<int, _HttpConnection> _connections =
      HashMap<int, _HttpConnection>();

  final Socket _socket;
  final _HttpServer _httpServer;
  final _HttpParser _httpParser;
  int _state = _IDLE;
  StreamSubscription? _subscription;
  bool _idleMark = false;
  Future? _streamFuture;

  _HttpConnection(this._socket, this._httpServer)
    : _httpParser = _HttpParser.requestParser() {
    _connections[_serviceId] = this;
    _httpParser.listenToStream(_socket);
    _subscription = _httpParser.listen(
      (incoming) {
        _httpServer._markActive(this);
        // If the incoming was closed, close the connection.
        incoming.dataDone.then((closing) {
          if (closing) destroy();
        });
        // Only handle one incoming request at the time. Keep the
        // stream paused until the request has been send.
        _subscription!.pause();
        _state = _ACTIVE;
        var outgoing = _HttpOutgoing(_socket);
        var response = _HttpResponse(
          incoming.uri!,
          incoming.headers.protocolVersion,
          outgoing,
          _httpServer.defaultResponseHeaders,
          _httpServer.serverHeader,
        );
        // Parser found badRequest and sent out Response.
        if (incoming.statusCode == HttpStatus.badRequest) {
          response.statusCode = HttpStatus.badRequest;
        }
        var request = _HttpRequest(response, incoming, _httpServer, this);
        _streamFuture = outgoing.done.then(
          (_) {
            response.deadline = null;
            if (_state == _DETACHED) return;
            if (response.persistentConnection &&
                request.persistentConnection &&
                incoming.fullBodyRead &&
                !_httpParser.upgrade &&
                !_httpServer.closed) {
              _state = _IDLE;
              _idleMark = false;
              _httpServer._markIdle(this);
              // Resume the subscription for incoming requests as the
              // request is now processed.
              _subscription!.resume();
            } else {
              // Close socket, keep-alive not used or body sent before
              // received data was handled.
              destroy();
            }
          },
          onError: (_) {
            destroy();
          },
        );
        outgoing.ignoreBody = request.method == "HEAD";
        response._httpRequest = request;
        _httpServer._handleRequest(request);
      },
      onDone: () {
        destroy();
      },
      onError: (error) {
        // Ignore failed requests that was closed before headers was received.
        destroy();
      },
    );
  }

  void markIdle() {
    _idleMark = true;
  }

  bool get isMarkedIdle => _idleMark;

  void destroy() {
    if (_state == _CLOSING || _state == _DETACHED) return;
    _state = _CLOSING;
    _socket.destroy();
    _httpServer._connectionClosed(this);
    _connections.remove(_serviceId);
  }

  Future<Socket> detachSocket() {
    _state = _DETACHED;
    // Remove connection from server.
    _httpServer._connectionClosed(this);

    _HttpDetachedIncoming detachedIncoming = _httpParser.detachIncoming();

    return _streamFuture!.then((_) {
      _connections.remove(_serviceId);
      return _DetachedSocket(_socket, detachedIncoming);
    });
  }

  HttpConnectionInfo? get connectionInfo => _HttpConnectionInfo.create(_socket);

  bool get _isActive => _state == _ACTIVE;
  bool get _isIdle => _state == _IDLE;
  bool get _isClosing => _state == _CLOSING;
  bool get _isDetached => _state == _DETACHED;

  String get _serviceTypePath => 'io/http/serverconnections';
  String get _serviceTypeName => 'HttpServerConnection';
}

// Common interface of [ServerSocket] and [SecureServerSocket] used by
// [_HttpServer].
abstract interface class ServerSocketBase<T extends Socket>
    implements Stream<T> {
  int get port;
  InternetAddress get address;
  Future<void> close();
}

// HTTP server waiting for socket connections.
class _HttpServer extends Stream<HttpRequest>
    with _ServiceObject
    implements HttpServer {
  // Use default Map so we keep order.
  static final Map<int, _HttpServer> _servers = <int, _HttpServer>{};

  String? serverHeader;
  final HttpHeaders defaultResponseHeaders = _initDefaultResponseHeaders();
  bool autoCompress = false;

  Duration? _idleTimeout;
  Timer? _idleTimer;

  static Future<HttpServer> bind(
    address,
    int port,
    int backlog,
    bool v6Only,
    bool shared,
  ) {
    return ServerSocket.bind(
      address,
      port,
      backlog: backlog,
      v6Only: v6Only,
      shared: shared,
    ).then<HttpServer>((socket) {
      return _HttpServer._(socket, true);
    });
  }

  static Future<HttpServer> bindSecure(
    address,
    int port,
    SecurityContext? context,
    int backlog,
    bool v6Only,
    bool requestClientCertificate,
    bool shared,
  ) {
    return SecureServerSocket.bind(
      address,
      port,
      context,
      backlog: backlog,
      v6Only: v6Only,
      requestClientCertificate: requestClientCertificate,
      shared: shared,
    ).then<HttpServer>((socket) {
      return _HttpServer._(socket, true);
    });
  }

  _HttpServer._(this._serverSocket, this._closeServer)
    : _controller = StreamController<HttpRequest>(sync: true) {
    _controller.onCancel = close;
    idleTimeout = const Duration(seconds: 120);
    _servers[_serviceId] = this;
  }

  _HttpServer.listenOn(this._serverSocket)
    : _closeServer = false,
      _controller = StreamController<HttpRequest>(sync: true) {
    _controller.onCancel = close;
    idleTimeout = const Duration(seconds: 120);
    _servers[_serviceId] = this;
  }

  static HttpHeaders _initDefaultResponseHeaders() {
    var defaultResponseHeaders = _HttpHeaders('1.1');
    defaultResponseHeaders.contentType = ContentType.text;
    defaultResponseHeaders.set('X-Frame-Options', 'SAMEORIGIN');
    defaultResponseHeaders.set('X-Content-Type-Options', 'nosniff');
    defaultResponseHeaders.set('X-XSS-Protection', '1; mode=block');
    return defaultResponseHeaders;
  }

  Duration? get idleTimeout => _idleTimeout;

  void set idleTimeout(Duration? duration) {
    var idleTimer = _idleTimer;
    if (idleTimer != null) {
      idleTimer.cancel();
      _idleTimer = null;
    }
    _idleTimeout = duration;
    if (duration != null) {
      _idleTimer = Timer.periodic(duration, (_) {
        for (var idle in _idleConnections.toList()) {
          if (idle.isMarkedIdle) {
            idle.destroy();
          } else {
            idle.markIdle();
          }
        }
      });
    }
  }

  StreamSubscription<HttpRequest> listen(
    void Function(HttpRequest event)? onData, {
    Function? onError,
    void Function()? onDone,
    bool? cancelOnError,
  }) {
    _serverSocket.listen(
      (Socket socket) {
        if (socket.address.type != InternetAddressType.unix) {
          socket.setOption(SocketOption.tcpNoDelay, true);
        }
        // Accept the client connection.
        _HttpConnection connection = _HttpConnection(socket, this);
        _idleConnections.add(connection);
      },
      onError: (error, stackTrace) {
        // Ignore HandshakeExceptions as they are bound to a single request,
        // and are not fatal for the server.
        if (error is! HandshakeException) {
          _controller.addError(error, stackTrace);
        }
      },
      onDone: _controller.close,
    );
    return _controller.stream.listen(
      onData,
      onError: onError,
      onDone: onDone,
      cancelOnError: cancelOnError,
    );
  }

  Future close({bool force = false}) {
    closed = true;
    Future result;
    if (_closeServer) {
      result = _serverSocket.close();
    } else {
      result = Future.value();
    }
    idleTimeout = null;
    if (force) {
      for (var c in _activeConnections.toList()) {
        c.destroy();
      }
      assert(_activeConnections.isEmpty);
    }
    for (var c in _idleConnections.toList()) {
      c.destroy();
    }
    _maybePerformCleanup();
    return result;
  }

  void _maybePerformCleanup() {
    var sessionManager = _sessionManagerInstance;
    if (closed &&
        _idleConnections.isEmpty &&
        _activeConnections.isEmpty &&
        sessionManager != null) {
      sessionManager.close();
      _sessionManagerInstance = null;
      _servers.remove(_serviceId);
    }
  }

  int get port {
    if (closed) throw HttpException("HttpServer is not bound to a socket");
    return _serverSocket.port;
  }

  InternetAddress get address {
    if (closed) throw HttpException("HttpServer is not bound to a socket");
    return _serverSocket.address;
  }

  set sessionTimeout(int timeout) {
    _sessionManager.sessionTimeout = timeout;
  }

  void _handleRequest(_HttpRequest request) {
    if (!closed) {
      _controller.add(request);
    } else {
      request._httpConnection.destroy();
    }
  }

  void _connectionClosed(_HttpConnection connection) {
    // Remove itself from either idle or active connections.
    connection.unlink();
    _maybePerformCleanup();
  }

  void _markIdle(_HttpConnection connection) {
    _activeConnections.remove(connection);
    _idleConnections.add(connection);
  }

  void _markActive(_HttpConnection connection) {
    _idleConnections.remove(connection);
    _activeConnections.add(connection);
  }

  // Lazy init.
  _HttpSessionManager get _sessionManager =>
      _sessionManagerInstance ??= _HttpSessionManager();

  HttpConnectionsInfo connectionsInfo() {
    HttpConnectionsInfo result = HttpConnectionsInfo();
    result.total = _activeConnections.length + _idleConnections.length;
    for (var conn in _activeConnections) {
      if (conn._isActive) {
        result.active++;
      } else {
        assert(conn._isClosing);
        result.closing++;
      }
    }
    for (var conn in _idleConnections) {
      result.idle++;
      assert(conn._isIdle);
    }
    return result;
  }

  String get _serviceTypePath => 'io/http/servers';
  String get _serviceTypeName => 'HttpServer';

  _HttpSessionManager? _sessionManagerInstance;

  // Indicated if the http server has been closed.
  bool closed = false;

  final ServerSocketBase _serverSocket;
  final bool _closeServer;

  // Set of currently connected clients.
  final LinkedList<_HttpConnection> _activeConnections =
      LinkedList<_HttpConnection>();
  final LinkedList<_HttpConnection> _idleConnections =
      LinkedList<_HttpConnection>();
  final StreamController<HttpRequest> _controller;
}

class _ProxyConfiguration {
  static const String PROXY_PREFIX = "PROXY ";
  static const String DIRECT_PREFIX = "DIRECT";

  _ProxyConfiguration(String configuration) : proxies = <_Proxy>[] {
    if (configuration == null) {
      throw HttpException("Invalid proxy configuration $configuration");
    }
    List<String> list = configuration.split(";");
    for (var proxy in list) {
      proxy = proxy.trim();
      if (proxy.isNotEmpty) {
        if (proxy.startsWith(PROXY_PREFIX)) {
          String? username;
          String? password;
          // Skip the "PROXY " prefix.
          proxy = proxy.substring(PROXY_PREFIX.length).trim();
          // Look for proxy authentication.
          int at = proxy.lastIndexOf("@");
          if (at != -1) {
            String userinfo = proxy.substring(0, at).trim();
            proxy = proxy.substring(at + 1).trim();
            int colon = userinfo.indexOf(":");
            if (colon == -1 || colon == 0 || colon == proxy.length - 1) {
              throw HttpException("Invalid proxy configuration $configuration");
            }
            username = userinfo.substring(0, colon).trim();
            password = userinfo.substring(colon + 1).trim();
          }
          // Look for proxy host and port.
          int colon = proxy.lastIndexOf(":");
          if (colon == -1 || colon == 0 || colon == proxy.length - 1) {
            throw HttpException("Invalid proxy configuration $configuration");
          }
          String host = proxy.substring(0, colon).trim();
          if (host.startsWith("[") && host.endsWith("]")) {
            host = host.substring(1, host.length - 1);
          }
          String portString = proxy.substring(colon + 1).trim();
          int port;
          try {
            port = int.parse(portString);
          } on FormatException {
            throw HttpException(
              "Invalid proxy configuration $configuration, "
              "invalid port '$portString'",
            );
          }
          proxies.add(_Proxy(host, port, username, password));
        } else if (proxy.trim() == DIRECT_PREFIX) {
          proxies.add(_Proxy.direct());
        } else {
          throw HttpException("Invalid proxy configuration $configuration");
        }
      }
    }
  }

  const _ProxyConfiguration.direct() : proxies = const [_Proxy.direct()];

  final List<_Proxy> proxies;
}

class _Proxy {
  final String? host;
  final int? port;
  final String? username;
  final String? password;
  final bool isDirect;

  const _Proxy(String this.host, int this.port, this.username, this.password)
    : isDirect = false;
  const _Proxy.direct()
    : host = null,
      port = null,
      username = null,
      password = null,
      isDirect = true;

  bool get isAuthenticated => username != null;
}

class _HttpConnectionInfo implements HttpConnectionInfo {
  InternetAddress remoteAddress;
  int remotePort;
  int localPort;

  _HttpConnectionInfo(this.remoteAddress, this.remotePort, this.localPort);

  static _HttpConnectionInfo? create(Socket socket) {
    if (socket == null) return null;
    try {
      return _HttpConnectionInfo(
        socket.remoteAddress,
        socket.remotePort,
        socket.port,
      );
    } catch (e) {}
    return null;
  }
}

class _DetachedSocket extends Stream<Uint8List> implements Socket {
  final Stream<Uint8List> _incoming;
  final Socket _socket;

  _DetachedSocket(this._socket, this._incoming);

  StreamSubscription<Uint8List> listen(
    void Function(Uint8List event)? onData, {
    Function? onError,
    void Function()? onDone,
    bool? cancelOnError,
  }) {
    return _incoming.listen(
      onData,
      onError: onError,
      onDone: onDone,
      cancelOnError: cancelOnError,
    );
  }

  Encoding get encoding => _socket.encoding;

  void set encoding(Encoding value) {
    _socket.encoding = value;
  }

  void write(Object? obj) {
    _socket.write(obj);
  }

  void writeln([Object? obj = ""]) {
    _socket.writeln(obj);
  }

  void writeCharCode(int charCode) {
    _socket.writeCharCode(charCode);
  }

  void writeAll(Iterable objects, [String separator = ""]) {
    _socket.writeAll(objects, separator);
  }

  void add(List<int> bytes) {
    _socket.add(bytes);
  }

  void addError(Object error, [StackTrace? stackTrace]) =>
      _socket.addError(error, stackTrace);

  Future addStream(Stream<List<int>> stream) {
    return _socket.addStream(stream);
  }

  void destroy() {
    _socket.destroy();
  }

  Future flush() => _socket.flush();

  Future close() => _socket.close();

  Future get done => _socket.done;

  int get port => _socket.port;

  InternetAddress get address => _socket.address;

  InternetAddress get remoteAddress => _socket.remoteAddress;

  int get remotePort => _socket.remotePort;

  bool setOption(SocketOption option, bool enabled) {
    return _socket.setOption(option, enabled);
  }

  Uint8List getRawOption(RawSocketOption option) {
    return _socket.getRawOption(option);
  }

  void setRawOption(RawSocketOption option) {
    _socket.setRawOption(option);
  }
}

enum _AuthenticationScheme {
  Unknown(),
  Basic(),
  Bearer(),
  Digest();

  factory _AuthenticationScheme.fromString(String scheme) {
    final lower = scheme.toLowerCase();
    return _AuthenticationScheme.values
            .where((e) => e.name.toLowerCase() == lower)
            .singleOrNull ??
        Unknown;
  }

  String toString() => name;
}

abstract class _Credentials {
  final _HttpClientCredentials credentials;
  final String realm;
  bool used = false;

  // Digest specific fields.
  late final String? ha1;
  String? nonce;
  String? algorithm;
  String? qop;
  int? nonceCount;

  _Credentials(this.credentials, this.realm) {
    if (credentials.scheme == _AuthenticationScheme.Digest) {
      // Calculate the H(A1) value once. There is no mentioning of
      // username/password encoding in RFC 2617. However there is an
      // open draft for adding an additional accept-charset parameter to
      // the WWW-Authenticate and Proxy-Authenticate headers, see
      // http://tools.ietf.org/html/draft-reschke-basicauth-enc-06. For
      // now always use UTF-8 encoding.
      var creds = credentials as _HttpClientDigestCredentials;
      var hasher = _MD5()
        ..add(utf8.encode(creds.username))
        ..add([_CharCode.COLON])
        ..add(realm.codeUnits)
        ..add([_CharCode.COLON])
        ..add(utf8.encode(creds.password));
      ha1 = _CryptoUtils.bytesToHex(hasher.close());
    }
  }

  _AuthenticationScheme get scheme => credentials.scheme;

  void authorize(HttpClientRequest request);
}

class _SiteCredentials extends _Credentials {
  Uri uri;

  _SiteCredentials(this.uri, realm, _HttpClientCredentials creds)
    : super(creds, realm);

  bool applies(Uri uri, _AuthenticationScheme? scheme) {
    if (scheme != null && credentials.scheme != scheme) return false;
    if (uri.host != this.uri.host) return false;
    int thisPort = this.uri.port == 0
        ? HttpClient.defaultHttpPort
        : this.uri.port;
    int otherPort = uri.port == 0 ? HttpClient.defaultHttpPort : uri.port;
    if (otherPort != thisPort) return false;
    return uri.path.startsWith(this.uri.path);
  }

  void authorize(HttpClientRequest request) {
    // Digest credentials cannot be used without a nonce from the
    // server.
    if (credentials.scheme == _AuthenticationScheme.Digest && nonce == null) {
      return;
    }
    credentials.authorize(this, request as _HttpClientRequest);
    used = true;
  }
}

class _ProxyCredentials extends _Credentials {
  String host;
  int port;

  _ProxyCredentials(this.host, this.port, realm, _HttpClientCredentials creds)
    : super(creds, realm);

  bool applies(_Proxy proxy, _AuthenticationScheme? scheme) {
    if (scheme != null && credentials.scheme != scheme) return false;
    return proxy.host == host && proxy.port == port;
  }

  void authorize(HttpClientRequest request) {
    // Digest credentials cannot be used without a nonce from the
    // server.
    if (credentials.scheme == _AuthenticationScheme.Digest && nonce == null) {
      return;
    }
    credentials.authorizeProxy(this, request as _HttpClientRequest);
  }
}

abstract class _HttpClientCredentials implements HttpClientCredentials {
  _AuthenticationScheme get scheme;
  void authorize(_Credentials credentials, _HttpClientRequest request);
  void authorizeProxy(_ProxyCredentials credentials, HttpClientRequest request);
}

final class _HttpClientBasicCredentials extends _HttpClientCredentials
    implements HttpClientBasicCredentials {
  String username;
  String password;

  _HttpClientBasicCredentials(this.username, this.password);

  _AuthenticationScheme get scheme => _AuthenticationScheme.Basic;

  String authorization() {
    // There is no mentioning of username/password encoding in RFC
    // 2617. However there is an open draft for adding an additional
    // accept-charset parameter to the WWW-Authenticate and
    // Proxy-Authenticate headers, see
    // http://tools.ietf.org/html/draft-reschke-basicauth-enc-06. For
    // now always use UTF-8 encoding.
    String auth = base64Encode(utf8.encode("$username:$password"));
    return "Basic $auth";
  }

  void authorize(_Credentials _, HttpClientRequest request) {
    request.headers.set(HttpHeaders.authorizationHeader, authorization());
  }

  void authorizeProxy(_ProxyCredentials _, HttpClientRequest request) {
    request.headers.set(HttpHeaders.proxyAuthorizationHeader, authorization());
  }
}

final class _HttpClientBearerCredentials extends _HttpClientCredentials
    implements HttpClientBearerCredentials {
  String token;

  _HttpClientBearerCredentials(this.token) {
    // verify token according to RFC-6750 section 2.1
    // https://www.rfc-editor.org/rfc/rfc6750.html#section-2.1
    if (RegExp(r'[^0-9A-Za-z\-._~+/=]').hasMatch(token)) {
      throw ArgumentError.value(token, "token", "Invalid characters");
    }
  }

  _AuthenticationScheme get scheme => _AuthenticationScheme.Bearer;

  String authorization() {
    return "Bearer $token";
  }

  void authorize(_Credentials _, HttpClientRequest request) {
    request.headers.set(HttpHeaders.authorizationHeader, authorization());
  }

  void authorizeProxy(_ProxyCredentials _, HttpClientRequest request) {
    request.headers.set(HttpHeaders.proxyAuthorizationHeader, authorization());
  }
}

final class _HttpClientDigestCredentials extends _HttpClientCredentials
    implements HttpClientDigestCredentials {
  String username;
  String password;

  _HttpClientDigestCredentials(this.username, this.password);

  _AuthenticationScheme get scheme => _AuthenticationScheme.Digest;

  String authorization(_Credentials credentials, _HttpClientRequest request) {
    String requestUri = request._requestUri();
    _MD5 hasher = _MD5()
      ..add(request.method.codeUnits)
      ..add([_CharCode.COLON])
      ..add(requestUri.codeUnits);
    var ha2 = _CryptoUtils.bytesToHex(hasher.close());

    bool isAuth = false;
    String cnonce = "";
    String nc = "";
    hasher = _MD5()
      ..add(credentials.ha1!.codeUnits)
      ..add([_CharCode.COLON]);
    if (credentials.qop == "auth") {
      isAuth = true;
      cnonce = _CryptoUtils.bytesToHex(_CryptoUtils.getRandomBytes(4));
      var nonceCount = credentials.nonceCount! + 1;
      credentials.nonceCount = nonceCount;
      nc = nonceCount.toRadixString(16).padLeft(9, "0");
      hasher
        ..add(credentials.nonce!.codeUnits)
        ..add([_CharCode.COLON])
        ..add(nc.codeUnits)
        ..add([_CharCode.COLON])
        ..add(cnonce.codeUnits)
        ..add([_CharCode.COLON])
        ..add("auth".codeUnits)
        ..add([_CharCode.COLON])
        ..add(ha2.codeUnits);
    } else {
      hasher
        ..add(credentials.nonce!.codeUnits)
        ..add([_CharCode.COLON])
        ..add(ha2.codeUnits);
    }
    var response = _CryptoUtils.bytesToHex(hasher.close());

    StringBuffer buffer = StringBuffer()
      ..write('Digest ')
      ..write('username="$username"')
      ..write(', realm="${credentials.realm}"')
      ..write(', nonce="${credentials.nonce}"')
      ..write(', uri="$requestUri"')
      ..write(', algorithm="${credentials.algorithm}"');
    if (isAuth) {
      buffer
        ..write(', qop="auth"')
        ..write(', cnonce="$cnonce"')
        ..write(', nc="$nc"');
    }
    buffer.write(', response="$response"');
    return buffer.toString();
  }

  void authorize(_Credentials credentials, HttpClientRequest request) {
    request.headers.set(
      HttpHeaders.authorizationHeader,
      authorization(credentials, request as _HttpClientRequest),
    );
  }

  void authorizeProxy(
    _ProxyCredentials credentials,
    HttpClientRequest request,
  ) {
    request.headers.set(
      HttpHeaders.proxyAuthorizationHeader,
      authorization(credentials, request as _HttpClientRequest),
    );
  }
}

class _RedirectInfo implements RedirectInfo {
  final int statusCode;
  final String method;
  final Uri location;
  const _RedirectInfo(this.statusCode, this.method, this.location);
}

String _getHttpVersion() {
  var version = Platform.version;
  // Only include major and minor version numbers.
  int index = version.indexOf('.', version.indexOf('.') + 1);
  version = version.substring(0, index);
  return 'Dart/$version (dart:io)';
}