// 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.

library http_io;

import 'dart:async';
import 'dart:collection'
    show HashMap, HashSet, Queue, ListQueue, LinkedList, LinkedListEntry;
import 'dart:convert';
import 'dart:io'
    show
        ConnectionTask,
        BytesBuilder,
        gzip,
        HandshakeException,
        InternetAddress,
        IOSink,
        Platform,
        RawSocketOption,
        SecureServerSocket,
        SecureSocket,
        SecurityContext,
        ServerSocket,
        Socket,
        SocketException,
        SocketOption,
        stderr,
        TlsException,
        X509Certificate,
        ZLibEncoder;
import 'dart:typed_data';

import 'src/char_code.dart';
import 'src/crypto.dart';
import 'src/http_exception.dart';
import 'src/http_headers_impl.dart';
import 'src/http_incoming.dart';
import 'src/http_parser.dart';
import 'src/http_session.dart';
import 'src/http_session_impl.dart';
import 'src/http_status.dart';

export 'src/http_date.dart';
export 'src/http_exception.dart';
export 'src/http_session.dart';
export 'src/http_status.dart';

part 'src/http_impl.dart';
part 'src/http_overrides.dart';

/// A server that delivers content, such as web pages, using the HTTP protocol.
///
/// The HttpServer is a [Stream] that provides [HttpRequest] objects. Each
/// HttpRequest has an associated [HttpResponse] object.
/// The server responds to a request by writing to that HttpResponse object.
/// The following example shows how to bind an HttpServer to an IPv6
/// [InternetAddress] on port 80 (the standard port for HTTP servers)
/// and how to listen for requests.
/// Port 80 is the default HTTP port. However, on most systems accessing
/// this requires super-user privileges. For local testing consider
/// using a non-reserved port (1024 and above).
///
///     import 'dart:io';
///
///     main() {
///       HttpServer
///           .bind(InternetAddress.anyIPv6, 80)
///           .then((server) {
///             server.listen((HttpRequest request) {
///               request.response.write('Hello, world!');
///               request.response.close();
///             });
///           });
///     }
///
/// Incomplete requests, in which all or part of the header is missing, are
/// ignored, and no exceptions or HttpRequest objects are generated for them.
/// Likewise, when writing to an HttpResponse, any [Socket] exceptions are
/// ignored and any future writes are ignored.
///
/// The HttpRequest exposes the request headers and provides the request body,
/// if it exists, as a Stream of data. If the body is unread, it is drained
/// when the server writes to the HttpResponse or closes it.
///
/// ## Bind with a secure HTTPS connection
///
/// Use [bindSecure] to create an HTTPS server.
///
/// The server presents a certificate to the client. The certificate
/// chain and the private key are set in the [SecurityContext]
/// object that is passed to [bindSecure].
///
///     import 'dart:io';
///     import "dart:isolate";
///
///     main() {
///       SecurityContext context = new SecurityContext();
///       var chain =
///           Platform.script.resolve('certificates/server_chain.pem')
///           .toFilePath();
///       var key =
///           Platform.script.resolve('certificates/server_key.pem')
///           .toFilePath();
///       context.useCertificateChain(chain);
///       context.usePrivateKey(key, password: 'dartdart');
///
///       HttpServer
///           .bindSecure(InternetAddress.anyIPv6,
///                       443,
///                       context)
///           .then((server) {
///             server.listen((HttpRequest request) {
///               request.response.write('Hello, world!');
///               request.response.close();
///             });
///           });
///     }
///
///  The certificates and keys are PEM files, which can be created and
///  managed with the tools in OpenSSL.
///
/// ## Connect to a server socket
///
/// You can use the [HttpServer.listenOn] constructor to attach an HTTP server to
/// a [ServerSocket].
///
///     import 'dart:io';
///
///     main() {
///       ServerSocket.bind(InternetAddress.anyIPv6, 80)
///         .then((serverSocket) {
///           HttpServer httpserver = new HttpServer.listenOn(serverSocket);
///           serverSocket.listen((Socket socket) {
///             socket.write('Hello, client.');
///           });
///         });
///     }
///
/// ## Other resources
///
/// * HttpServer is a Stream. Refer to the [Stream] class for information
/// about the streaming qualities of an HttpServer.
/// Pausing the subscription of the stream, pauses at the OS level.
///
/// * The [shelf](https://pub.dartlang.org/packages/shelf)
/// package on pub.dartlang.org contains a set of high-level classes that,
/// together with this class, makes it easy to provide content through HTTP
/// servers.
abstract class HttpServer implements Stream<HttpRequest> {
  /// Gets and sets the default value of the `Server` header for all responses
  /// generated by this [HttpServer].
  ///
  /// If [serverHeader] is `null`, no `Server` header will be added to each
  /// response.
  ///
  /// The default value is `null`.
  String serverHeader;

  /// Default set of headers added to all response objects.
  ///
  /// By default the following headers are in this set:
  ///
  ///     Content-Type: text/plain; charset=utf-8
  ///     X-Frame-Options: SAMEORIGIN
  ///     X-Content-Type-Options: nosniff
  ///     X-XSS-Protection: 1; mode=block
  ///
  /// If the `Server` header is added here and the `serverHeader` is set as
  /// well then the value of `serverHeader` takes precedence.
  HttpHeaders get defaultResponseHeaders;

  /// Whether the [HttpServer] should compress the content, if possible.
  ///
  /// The content can only be compressed when the response is using
  /// chunked Transfer-Encoding and the incoming request has `gzip`
  /// as an accepted encoding in the Accept-Encoding header.
  ///
  /// The default value is `false` (compression disabled).
  /// To enable, set `autoCompress` to `true`.
  bool autoCompress;

  /// Gets or sets the timeout used for idle keep-alive connections. If no
  /// further request is seen within [idleTimeout] after the previous request was
  /// completed, the connection is dropped.
  ///
  /// Default is 120 seconds.
  ///
  /// Note that it may take up to `2 * idleTimeout` before a idle connection is
  /// aborted.
  ///
  /// To disable, set [idleTimeout] to `null`.
  Duration idleTimeout;

  /// Starts listening for HTTP requests on the specified [address] and
  /// [port].
  ///
  /// The [address] can either be a [String] or an
  /// [InternetAddress]. If [address] is a [String], [bind] will
  /// perform a [InternetAddress.lookup] and use the first value in the
  /// list. To listen on the loopback adapter, which will allow only
  /// incoming connections from the local host, use the value
  /// [InternetAddress.loopbackIPv4] or
  /// [InternetAddress.loopbackIPv6]. To allow for incoming
  /// connection from the network use either one of the values
  /// [InternetAddress.anyIPv4] or [InternetAddress.anyIPv6] to
  /// bind to all interfaces or the IP address of a specific interface.
  ///
  /// If an IP version 6 (IPv6) address is used, both IP version 6
  /// (IPv6) and version 4 (IPv4) connections will be accepted. To
  /// restrict this to version 6 (IPv6) only, use [v6Only] to set
  /// version 6 only. However, if the address is
  /// [InternetAddress.loopbackIPv6], only IP version 6 (IPv6) connections
  /// will be accepted.
  ///
  /// If [port] has the value [:0:] an ephemeral port will be chosen by
  /// the system. The actual port used can be retrieved using the
  /// [port] getter.
  ///
  /// The optional argument [backlog] can be used to specify the listen
  /// backlog for the underlying OS listen setup. If [backlog] has the
  /// value of [:0:] (the default) a reasonable value will be chosen by
  /// the system.
  ///
  /// The optional argument [shared] specifies whether additional HttpServer
  /// objects can bind to the same combination of `address`, `port` and `v6Only`.
  /// If `shared` is `true` and more `HttpServer`s from this isolate or other
  /// isolates are bound to the port, then the incoming connections will be
  /// distributed among all the bound `HttpServer`s. Connections can be
  /// distributed over multiple isolates this way.
  static Future<HttpServer> bind(address, int port,
          {int backlog = 0, bool v6Only = false, bool shared = false}) =>
      _HttpServer.bind(address, port, backlog, v6Only, shared);

  /// The [address] can either be a [String] or an
  /// [InternetAddress]. If [address] is a [String], [bind] will
  /// perform a [InternetAddress.lookup] and use the first value in the
  /// list. To listen on the loopback adapter, which will allow only
  /// incoming connections from the local host, use the value
  /// [InternetAddress.loopbackIPv4] or
  /// [InternetAddress.loopbackIPv6]. To allow for incoming
  /// connection from the network use either one of the values
  /// [InternetAddress.anyIPv4] or [InternetAddress.anyIPv6] to
  /// bind to all interfaces or the IP address of a specific interface.
  ///
  /// If an IP version 6 (IPv6) address is used, both IP version 6
  /// (IPv6) and version 4 (IPv4) connections will be accepted. To
  /// restrict this to version 6 (IPv6) only, use [v6Only] to set
  /// version 6 only.
  ///
  /// If [port] has the value [:0:] an ephemeral port will be chosen by
  /// the system. The actual port used can be retrieved using the
  /// [port] getter.
  ///
  /// The optional argument [backlog] can be used to specify the listen
  /// backlog for the underlying OS listen setup. If [backlog] has the
  /// value of [:0:] (the default) a reasonable value will be chosen by
  /// the system.
  ///
  /// If [requestClientCertificate] is true, the server will
  /// request clients to authenticate with a client certificate.
  /// The server will advertise the names of trusted issuers of client
  /// certificates, getting them from a [SecurityContext], where they have been
  /// set using [SecurityContext.setClientAuthorities].
  ///
  /// The optional argument [shared] specifies whether additional HttpServer
  /// objects can bind to the same combination of `address`, `port` and `v6Only`.
  /// If `shared` is `true` and more `HttpServer`s from this isolate or other
  /// isolates are bound to the port, then the incoming connections will be
  /// distributed among all the bound `HttpServer`s. Connections can be
  /// distributed over multiple isolates this way.

  static Future<HttpServer> bindSecure(
          address, int port, SecurityContext context,
          {int backlog = 0,
          bool v6Only = false,
          bool requestClientCertificate = false,
          bool shared = false}) =>
      _HttpServer.bindSecure(address, port, context, backlog, v6Only,
          requestClientCertificate, shared);

  /// Attaches the HTTP server to an existing [ServerSocket]. When the
  /// [HttpServer] is closed, the [HttpServer] will just detach itself,
  /// closing current connections but not closing [serverSocket].
  factory HttpServer.listenOn(ServerSocket serverSocket) =>
      _HttpServer.listenOn(serverSocket);

  /// Permanently stops this [HttpServer] from listening for new
  /// connections.  This closes the [Stream] of [HttpRequest]s with a
  /// done event. The returned future completes when the server is
  /// stopped. For a server started using [bind] or [bindSecure] this
  /// means that the port listened on no longer in use.
  ///
  /// If [force] is `true`, active connections will be closed immediately.
  Future close({bool force = false});

  /// Returns the port that the server is listening on. This can be
  /// used to get the actual port used when a value of 0 for [:port:] is
  /// specified in the [bind] or [bindSecure] call.
  int get port;

  /// Returns the address that the server is listening on. This can be
  /// used to get the actual address used, when the address is fetched by
  /// a lookup from a hostname.
  InternetAddress get address;

  /// Sets the timeout, in seconds, for sessions of this [HttpServer].
  /// The default timeout is 20 minutes.
  set sessionTimeout(int timeout);

  /// Returns an [HttpConnectionsInfo] object summarizing the number of
  /// current connections handled by the server.
  HttpConnectionsInfo connectionsInfo();
}

/// Summary statistics about an [HttpServer]s current socket connections.
class HttpConnectionsInfo {
  /// Total number of socket connections.
  int total = 0;

  /// Number of active connections where actual request/response
  /// processing is active.
  int active = 0;

  /// Number of idle connections held by clients as persistent connections.
  int idle = 0;

  /// Number of connections which are preparing to close. Note: These
  /// connections are also part of the [:active:] count as they might
  /// still be sending data to the client before finally closing.
  int closing = 0;
}

/// Headers for HTTP requests and responses.
///
/// In some situations, headers are immutable:
///
/// * HttpRequest and HttpClientResponse always have immutable headers.
///
/// * HttpResponse and HttpClientRequest have immutable headers
///   from the moment the body is written to.
///
/// In these situations, the mutating methods throw exceptions.
///
/// For all operations on HTTP headers the header name is
/// case-insensitive.
///
/// To set the value of a header use the `set()` method:
///
///     request.headers.set(HttpHeaders.CACHE_CONTROL,
///                         'max-age=3600, must-revalidate');
///
/// To retrieve the value of a header use the `value()` method:
///
///     print(request.headers.value(HttpHeaders.USER_AGENT));
///
/// An HttpHeaders object holds a list of values for each name
/// as the standard allows. In most cases a name holds only a single value,
/// The most common mode of operation is to use `set()` for setting a value,
/// and `value()` for retrieving a value.
abstract class HttpHeaders {
  static const ACCEPT = "accept";
  static const ACCEPT_CHARSET = "accept-charset";
  static const ACCEPT_ENCODING = "accept-encoding";
  static const ACCEPT_LANGUAGE = "accept-language";
  static const ACCEPT_RANGES = "accept-ranges";
  static const AGE = "age";
  static const ALLOW = "allow";
  static const AUTHORIZATION = "authorization";
  static const CACHE_CONTROL = "cache-control";
  static const CONNECTION = "connection";
  static const CONTENT_ENCODING = "content-encoding";
  static const CONTENT_LANGUAGE = "content-language";
  static const CONTENT_LENGTH = "content-length";
  static const CONTENT_LOCATION = "content-location";
  static const CONTENT_MD5 = "content-md5";
  static const CONTENT_RANGE = "content-range";
  static const CONTENT_TYPE = "content-type";
  static const DATE = "date";
  static const ETAG = "etag";
  static const EXPECT = "expect";
  static const EXPIRES = "expires";
  static const FROM = "from";
  static const HOST = "host";
  static const IF_MATCH = "if-match";
  static const IF_MODIFIED_SINCE = "if-modified-since";
  static const IF_NONE_MATCH = "if-none-match";
  static const IF_RANGE = "if-range";
  static const IF_UNMODIFIED_SINCE = "if-unmodified-since";
  static const LAST_MODIFIED = "last-modified";
  static const LOCATION = "location";
  static const MAX_FORWARDS = "max-forwards";
  static const PRAGMA = "pragma";
  static const PROXY_AUTHENTICATE = "proxy-authenticate";
  static const PROXY_AUTHORIZATION = "proxy-authorization";
  static const RANGE = "range";
  static const REFERER = "referer";
  static const RETRY_AFTER = "retry-after";
  static const SERVER = "server";
  static const TE = "te";
  static const TRAILER = "trailer";
  static const TRANSFER_ENCODING = "transfer-encoding";
  static const UPGRADE = "upgrade";
  static const USER_AGENT = "user-agent";
  static const VARY = "vary";
  static const VIA = "via";
  static const WARNING = "warning";
  static const WWW_AUTHENTICATE = "www-authenticate";

  // Cookie headers from RFC 6265.
  static const COOKIE = "cookie";
  static const SET_COOKIE = "set-cookie";

  static const GENERAL_HEADERS = [
    CACHE_CONTROL,
    CONNECTION,
    DATE,
    PRAGMA,
    TRAILER,
    TRANSFER_ENCODING,
    UPGRADE,
    VIA,
    WARNING
  ];

  static const ENTITY_HEADERS = [
    ALLOW,
    CONTENT_ENCODING,
    CONTENT_LANGUAGE,
    CONTENT_LENGTH,
    CONTENT_LOCATION,
    CONTENT_MD5,
    CONTENT_RANGE,
    CONTENT_TYPE,
    EXPIRES,
    LAST_MODIFIED
  ];

  static const RESPONSE_HEADERS = [
    ACCEPT_RANGES,
    AGE,
    ETAG,
    LOCATION,
    PROXY_AUTHENTICATE,
    RETRY_AFTER,
    SERVER,
    VARY,
    WWW_AUTHENTICATE
  ];

  static const REQUEST_HEADERS = [
    ACCEPT,
    ACCEPT_CHARSET,
    ACCEPT_ENCODING,
    ACCEPT_LANGUAGE,
    AUTHORIZATION,
    EXPECT,
    FROM,
    HOST,
    IF_MATCH,
    IF_MODIFIED_SINCE,
    IF_NONE_MATCH,
    IF_RANGE,
    IF_UNMODIFIED_SINCE,
    MAX_FORWARDS,
    PROXY_AUTHORIZATION,
    RANGE,
    REFERER,
    TE,
    USER_AGENT
  ];

  /// Gets and sets the date. The value of this property will
  /// reflect the 'date' header.
  DateTime date;

  /// Gets and sets the expiry date. The value of this property will
  /// reflect the 'expires' header.
  DateTime expires;

  /// Gets and sets the "if-modified-since" date. The value of this property will
  /// reflect the "if-modified-since" header.
  DateTime ifModifiedSince;

  /// Gets and sets the host part of the 'host' header for the
  /// connection.
  String host;

  /// Gets and sets the port part of the 'host' header for the
  /// connection.
  int port;

  /// Gets the protocol version for the connection.
  String get protocolVersion;

  /// Gets and sets the content type. Note that the content type in the
  /// header will only be updated if this field is set
  /// directly. Mutating the returned current value will have no
  /// effect.
  ContentType contentType;

  /// Gets and sets the content length header value.
  int contentLength;

  /// Gets and sets the persistent connection header value.
  bool persistentConnection;

  /// Gets and sets the chunked transfer encoding header value.
  bool chunkedTransferEncoding;

  /// Returns the list of values for the header named [name]. If there
  /// is no header with the provided name, [:null:] will be returned.
  List<String> operator [](String name);

  /// Convenience method for the value for a single valued header. If
  /// there is no header with the provided name, [:null:] will be
  /// returned. If the header has more than one value an exception is
  /// thrown.
  String value(String name);

  /// Adds a header value. The header named [name] will have the value
  /// [value] added to its list of values. Some headers are single
  /// valued, and for these adding a value will replace the previous
  /// value. If the value is of type DateTime a HTTP date format will be
  /// applied. If the value is a [:List:] each element of the list will
  /// be added separately. For all other types the default [:toString:]
  /// method will be used.
  void add(String name, Object value);

  /// Sets a header. The header named [name] will have all its values
  /// cleared before the value [value] is added as its value.
  void set(String name, Object value);

  /// Removes a specific value for a header name. Some headers have
  /// system supplied values and for these the system supplied values
  /// will still be added to the collection of values for the header.
  void remove(String name, Object value);

  /// Removes all values for the specified header name. Some headers
  /// have system supplied values and for these the system supplied
  /// values will still be added to the collection of values for the
  /// header.
  void removeAll(String name);

  /// Enumerates the headers, applying the function [f] to each
  /// header. The header name passed in [:name:] will be all lower
  /// case.
  void forEach(void f(String name, List<String> values));

  /// Disables folding for the header named [name] when sending the HTTP
  /// header. By default, multiple header values are folded into a
  /// single header line by separating the values with commas. The
  /// 'set-cookie' header has folding disabled by default.
  void noFolding(String name);

  /// Remove all headers. Some headers have system supplied values and
  /// for these the system supplied values will still be added to the
  /// collection of values for the header.
  void clear();
}

/// Representation of a header value in the form:
///
///   [:value; parameter1=value1; parameter2=value2:]
///
/// [HeaderValue] can be used to conveniently build and parse header
/// values on this form.
///
/// To build an [:accepts:] header with the value
///
///     text/plain; q=0.3, text/html
///
/// use code like this:
///
///     HttpClientRequest request = ...;
///     var v = new HeaderValue("text/plain", {"q": "0.3"});
///     request.headers.add(HttpHeaders.ACCEPT, v);
///     request.headers.add(HttpHeaders.ACCEPT, "text/html");
///
/// To parse the header values use the [:parse:] static method.
///
///     HttpRequest request = ...;
///     List<String> values = request.headers[HttpHeaders.ACCEPT];
///     values.forEach((value) {
///       HeaderValue v = HeaderValue.parse(value);
///       // Use v.value and v.parameters
///     });
///
/// An instance of [HeaderValue] is immutable.
abstract class HeaderValue {
  /// Creates a new header value object setting the value and parameters.
  factory HeaderValue([String value = "", Map<String, String> parameters]) {
    return HeaderValueImpl(value, parameters);
  }

  /// Creates a new header value object from parsing a header value
  /// string with both value and optional parameters.
  static HeaderValue parse(String value,
      {String parameterSeparator = ";",
      String valueSeparator,
      bool preserveBackslash = false}) {
    return HeaderValueImpl.parse(value,
        parameterSeparator: parameterSeparator,
        valueSeparator: valueSeparator,
        preserveBackslash: preserveBackslash);
  }

  /// Gets the header value.
  String get value;

  /// Gets the map of parameters.
  ///
  /// This map cannot be modified. Invoking any operation which would
  /// modify the map will throw [UnsupportedError].
  Map<String, String> get parameters;

  /// Returns the formatted string representation in the form:
  ///
  ///     value; parameter1=value1; parameter2=value2
  String toString();
}

/// Representation of a content type. An instance of [ContentType] is
/// immutable.
abstract class ContentType implements HeaderValue {
  /// Content type for plain text using UTF-8 encoding.
  ///
  ///     text/plain; charset=utf-8
  static final TEXT = ContentType("text", "plain", charset: "utf-8");

  ///  Content type for HTML using UTF-8 encoding.
  ///
  ///     text/html; charset=utf-8
  static final HTML = ContentType("text", "html", charset: "utf-8");

  ///  Content type for JSON using UTF-8 encoding.
  ///
  ///     application/json; charset=utf-8
  static final JSON = ContentType("application", "json", charset: "utf-8");

  ///  Content type for binary data.
  ///
  ///     application/octet-stream
  static final BINARY = ContentType("application", "octet-stream");

  /// Creates a new content type object setting the primary type and
  /// sub type. The charset and additional parameters can also be set
  /// using [charset] and [parameters]. If charset is passed and
  /// [parameters] contains charset as well the passed [charset] will
  /// override the value in parameters. Keys passed in parameters will be
  /// converted to lower case. The `charset` entry, whether passed as `charset`
  /// or in `parameters`, will have its value converted to lower-case.
  factory ContentType(String primaryType, String subType,
      {String charset, Map<String, String> parameters}) {
    return ContentTypeImpl(primaryType, subType, charset, parameters);
  }

  /// Creates a new content type object from parsing a Content-Type
  /// header value. As primary type, sub type and parameter names and
  /// values are not case sensitive all these values will be converted
  /// to lower case. Parsing this string
  ///
  ///     text/html; charset=utf-8
  ///
  /// will create a content type object with primary type [:text:], sub
  /// type [:html:] and parameter [:charset:] with value [:utf-8:].
  static ContentType parse(String value) {
    return ContentTypeImpl.parse(value);
  }

  /// Gets the mime-type, without any parameters.
  String get mimeType;

  /// Gets the primary type.
  String get primaryType;

  /// Gets the sub type.
  String get subType;

  /// Gets the character set.
  String get charset;
}

/// Representation of a cookie. For cookies received by the server as
/// Cookie header values only [:name:] and [:value:] fields will be
/// set. When building a cookie for the 'set-cookie' header in the server
/// and when receiving cookies in the client as 'set-cookie' headers all
/// fields can be used.
abstract class Cookie {
  /// Gets and sets the name.
  String name;

  /// Gets and sets the value.
  String value;

  /// Gets and sets the expiry date.
  DateTime expires;

  /// Gets and sets the max age. A value of [:0:] means delete cookie
  /// now.
  int maxAge;

  /// Gets and sets the domain.
  String domain;

  /// Gets and sets the path.
  String path;

  /// Gets and sets whether this cookie is secure.
  bool secure;

  /// Gets and sets whether this cookie is HTTP only.
  bool httpOnly;

  /// Creates a new cookie optionally setting the name and value.
  ///
  /// By default the value of `httpOnly` will be set to `true`.
  factory Cookie([String name, String value]) => CookieImpl(name, value);

  /// Creates a new cookie by parsing a header value from a 'set-cookie'
  /// header.
  factory Cookie.fromSetCookieValue(String value) {
    return CookieImpl.fromSetCookieValue(value);
  }

  /// Returns the formatted string representation of the cookie. The
  /// string representation can be used for for setting the Cookie or
  /// 'set-cookie' headers
  String toString();
}

/// A server-side object
/// that contains the content of and information about an HTTP request.
///
/// __Note__: Check out the
/// [http_server](http://pub.dartlang.org/packages/http_server)
/// package, which makes working with the low-level
/// dart:io HTTP server subsystem easier.
///
/// `HttpRequest` objects are generated by an [HttpServer],
/// which listens for HTTP requests on a specific host and port.
/// For each request received, the HttpServer, which is a [Stream],
/// generates an `HttpRequest` object and adds it to the stream.
///
/// An `HttpRequest` object delivers the body content of the request
/// as a stream of byte lists.
/// The object also contains information about the request,
/// such as the method, URI, and headers.
///
/// In the following code, an HttpServer listens
/// for HTTP requests. When the server receives a request,
/// it uses the HttpRequest object's `method` property to dispatch requests.
///
///     final HOST = InternetAddress.loopbackIPv4;
///     final PORT = 80;
///
///     HttpServer.bind(HOST, PORT).then((_server) {
///       _server.listen((HttpRequest request) {
///         switch (request.method) {
///           case 'GET':
///             handleGetRequest(request);
///             break;
///           case 'POST':
///             ...
///         }
///       },
///       onError: handleError);    // listen() failed.
///     }).catchError(handleError);
///
/// An HttpRequest object provides access to the associated [HttpResponse]
/// object through the response property.
/// The server writes its response to the body of the HttpResponse object.
/// For example, here's a function that responds to a request:
///
///     void handleGetRequest(HttpRequest req) {
///       HttpResponse res = req.response;
///       res.write('Received request ${req.method}: ${req.uri.path}');
///       res.close();
///     }
abstract class HttpRequest implements Stream<List<int>> {
  /// The content length of the request body.
  ///
  /// If the size of the request body is not known in advance,
  /// this value is -1.
  int get contentLength;

  /// The method, such as 'GET' or 'POST', for the request.
  String get method;

  /// The URI for the request.
  ///
  /// This provides access to the
  /// path and query string for the request.
  Uri get uri;

  /// The requested URI for the request.
  ///
  /// The returned URI is reconstructed by using http-header fields, to access
  /// otherwise lost information, e.g. host and scheme.
  ///
  /// To reconstruct the scheme, first 'X-Forwarded-Proto' is checked, and then
  /// falling back to server type.
  ///
  /// To reconstruct the host, first 'X-Forwarded-Host' is checked, then 'Host'
  /// and finally calling back to server.
  Uri get requestedUri;

  /// The request headers.
  ///
  /// The returned [HttpHeaders] are immutable.
  HttpHeaders get headers;

  /// The cookies in the request, from the Cookie headers.
  List<Cookie> get cookies;

  /// The persistent connection state signaled by the client.
  bool get persistentConnection;

  /// The client certificate of the client making the request.
  ///
  /// This value is null if the connection is not a secure TLS or SSL connection,
  /// or if the server does not request a client certificate, or if the client
  /// does not provide one.
  X509Certificate get certificate;

  /// The session for the given request.
  ///
  /// If the session is
  /// being initialized by this call, [:isNew:] is true for the returned
  /// session.
  /// See [HttpServer.sessionTimeout] on how to change default timeout.
  HttpSession get session;

  /// The HTTP protocol version used in the request,
  /// either "1.0" or "1.1".
  String get protocolVersion;

  /// Information about the client connection.
  ///
  /// Returns [:null:] if the socket is not available.
  HttpConnectionInfo get connectionInfo;

  /// The [HttpResponse] object, used for sending back the response to the
  /// client.
  ///
  /// If the [contentLength] of the body isn't 0, and the body isn't being read,
  /// any write calls on the [HttpResponse] automatically drain the request
  /// body.
  HttpResponse get response;
}

/// An HTTP response, which returns the headers and data
/// from the server to the client in response to an HTTP request.
///
/// Every HttpRequest object provides access to the associated [HttpResponse]
/// object through the `response` property.
/// The server sends its response to the client by writing to the
/// HttpResponse object.
///
/// ## Writing the response
///
/// This class implements [IOSink].
/// After the header has been set up, the methods
/// from IOSink, such as `writeln()`, can be used to write
/// the body of the HTTP response.
/// Use the `close()` method to close the response and send it to the client.
///
///     server.listen((HttpRequest request) {
///       request.response.write('Hello, world!');
///       request.response.close();
///     });
///
/// When one of the IOSink methods is used for the
/// first time, the request header is sent. Calling any methods that
/// change the header after it is sent throws an exception.
///
/// ## Setting the headers
///
/// The HttpResponse object has a number of properties for setting up
/// the HTTP headers of the response.
/// When writing string data through the IOSink, the encoding used
/// is determined from the "charset" parameter of the
/// "Content-Type" header.
///
///     HttpResponse response = ...
///     response.headers.contentType
///         = new ContentType("application", "json", charset: "utf-8");
///     response.write(...);  // Strings written will be UTF-8 encoded.
///
/// If no charset is provided the default of ISO-8859-1 (Latin 1) will
/// be used.
///
///     HttpResponse response = ...
///     response.headers.add(HttpHeaders.CONTENT_TYPE, "text/plain");
///     response.write(...);  // Strings written will be ISO-8859-1 encoded.
///
/// An exception is thrown if you use the `write()` method
/// while an unsupported content-type is set.
abstract class HttpResponse implements IOSink {
  // TODO(ajohnsen): Add documentation of how to pipe a file to the response.
  /// Gets and sets the content length of the response. If the size of
  /// the response is not known in advance set the content length to
  /// -1 - which is also the default if not set.
  int contentLength;

  /// Gets and sets the status code. Any integer value is accepted. For
  /// the official HTTP status codes use the fields from
  /// [HttpStatus]. If no status code is explicitly set the default
  /// value [HttpStatus.OK] is used.
  ///
  /// The status code must be set before the body is written
  /// to. Setting the status code after writing to the response body or
  /// closing the response will throw a `StateError`.
  int statusCode;

  /// Gets and sets the reason phrase. If no reason phrase is explicitly
  /// set a default reason phrase is provided.
  ///
  /// The reason phrase must be set before the body is written
  /// to. Setting the reason phrase after writing to the response body
  /// or closing the response will throw a `StateError`.
  String reasonPhrase;

  /// Gets and sets the persistent connection state. The initial value
  /// of this property is the persistent connection state from the
  /// request.
  bool persistentConnection;

  /// Set and get the [deadline] for the response. The deadline is timed from the
  /// time it's set. Setting a new deadline will override any previous deadline.
  /// When a deadline is exceeded, the response will be closed and any further
  /// data ignored.
  ///
  /// To disable a deadline, set the [deadline] to `null`.
  ///
  /// The [deadline] is `null` by default.
  Duration deadline;

  /// Gets or sets if the [HttpResponse] should buffer output.
  ///
  /// Default value is `true`.
  ///
  /// __Note__: Disabling buffering of the output can result in very poor
  /// performance, when writing many small chunks.
  bool bufferOutput;

  /// Returns the response headers.
  ///
  /// The response headers can be modified until the response body is
  /// written to or closed. After that they become immutable.
  HttpHeaders get headers;

  /// Cookies to set in the client (in the 'set-cookie' header).
  List<Cookie> get cookies;

  /// Respond with a redirect to [location].
  ///
  /// The URI in [location] should be absolute, but there are no checks
  /// to enforce that.
  ///
  /// By default the HTTP status code `HttpStatus.MOVED_TEMPORARILY`
  /// (`302`) is used for the redirect, but an alternative one can be
  /// specified using the [status] argument.
  ///
  /// This method will also call `close`, and the returned future is
  /// the future returned by `close`.
  Future redirect(Uri location, {int status = HttpStatus.MOVED_TEMPORARILY});

  /// Detaches the underlying socket from the HTTP server. When the
  /// socket is detached the HTTP server will no longer perform any
  /// operations on it.
  ///
  /// This is normally used when a HTTP upgrade request is received
  /// and the communication should continue with a different protocol.
  ///
  /// If [writeHeaders] is `true`, the status line and [headers] will be written
  /// to the socket before it's detached. If `false`, the socket is detached
  /// immediately, without any data written to the socket. Default is `true`.
  Future<Socket> detachSocket({bool writeHeaders = true});

  /// Gets information about the client connection. Returns [:null:] if the
  /// socket is not available.
  HttpConnectionInfo get connectionInfo;
}

/// A client that receives content, such as web pages, from
/// a server using the HTTP protocol.
///
/// HttpClient contains a number of methods to send an [HttpClientRequest]
/// to an Http server and receive an [HttpClientResponse] back.
/// For example, you can use the [get], [getUrl], [post], and [postUrl] methods
/// for GET and POST requests, respectively.
///
/// ## Making a simple GET request: an example
///
/// A `getUrl` request is a two-step process, triggered by two [Future]s.
/// When the first future completes with a [HttpClientRequest], the underlying
/// network connection has been established, but no data has been sent.
/// In the callback function for the first future, the HTTP headers and body
/// can be set on the request. Either the first write to the request object
/// or a call to [close] sends the request to the server.
///
/// When the HTTP response is received from the server,
/// the second future, which is returned by close,
/// completes with an [HttpClientResponse] object.
/// This object provides access to the headers and body of the response.
/// The body is available as a stream implemented by HttpClientResponse.
/// If a body is present, it must be read. Otherwise, it leads to resource
/// leaks. Consider using [HttpClientResponse.drain] if the body is unused.
///
///     HttpClient client = new HttpClient();
///     client.getUrl(Uri.parse("http://www.example.com/"))
///         .then((HttpClientRequest request) {
///           // Optionally set up headers...
///           // Optionally write to the request object...
///           // Then call close.
///           ...
///           return request.close();
///         })
///         .then((HttpClientResponse response) {
///           // Process the response.
///           ...
///         });
///
/// The future for [HttpClientRequest] is created by methods such as
/// [getUrl] and [open].
///
/// ## HTTPS connections
///
/// An HttpClient can make HTTPS requests, connecting to a server using
/// the TLS (SSL) secure networking protocol. Calling [getUrl] with an
/// https: scheme will work automatically, if the server's certificate is
/// signed by a root CA (certificate authority) on the default list of
/// well-known trusted CAs, compiled by Mozilla.
///
/// To add a custom trusted certificate authority, or to send a client
/// certificate to servers that request one, pass a [SecurityContext] object
/// as the optional `context` argument to the `HttpClient` constructor.
/// The desired security options can be set on the [SecurityContext] object.
///
/// ## Headers
///
/// All HttpClient requests set the following header by default:
///
///     Accept-Encoding: gzip
///
/// This allows the HTTP server to use gzip compression for the body if
/// possible. If this behavior is not desired set the
/// `Accept-Encoding` header to something else.
/// To turn off gzip compression of the response, clear this header:
///
///      request.headers.removeAll(HttpHeaders.ACCEPT_ENCODING)
///
/// ## Closing the HttpClient
///
/// The HttpClient supports persistent connections and caches network
/// connections to reuse them for multiple requests whenever
/// possible. This means that network connections can be kept open for
/// some time after a request has completed. Use HttpClient.close
/// to force the HttpClient object to shut down and to close the idle
/// network connections.
///
/// ## Turning proxies on and off
///
/// By default the HttpClient uses the proxy configuration available
/// from the environment, see [findProxyFromEnvironment]. To turn off
/// the use of proxies set the [findProxy] property to
/// [:null:].
///
///     HttpClient client = new HttpClient();
///     client.findProxy = null;
abstract class HttpClient {
  static const int DEFAULT_HTTP_PORT = 80;
  static const int DEFAULT_HTTPS_PORT = 443;

  /// Gets and sets the idle timeout of non-active persistent (keep-alive)
  /// connections.
  ///
  /// The default value is 15 seconds.
  Duration idleTimeout;

  /// Gets and sets the connection timeout.
  ///
  /// When connecting to a new host exceeds this timeout, a [SocketException]
  /// is thrown. The timeout applies only to connections initiated after the
  /// timeout is set.
  ///
  /// When this is `null`, the OS default timeout is used. The default is
  /// `null`.
  Duration connectionTimeout;

  /// Gets and sets the maximum number of live connections, to a single host.
  ///
  /// Increasing this number may lower performance and take up unwanted
  /// system resources.
  ///
  /// To disable, set to `null`.
  ///
  /// Default is `null`.
  int maxConnectionsPerHost;

  /// Gets and sets whether the body of a response will be automatically
  /// uncompressed.
  ///
  /// The body of an HTTP response can be compressed. In most
  /// situations providing the un-compressed body is most
  /// convenient. Therefore the default behavior is to un-compress the
  /// body. However in some situations (e.g. implementing a transparent
  /// proxy) keeping the uncompressed stream is required.
  ///
  /// NOTE: Headers in the response are never modified. This means
  /// that when automatic un-compression is turned on the value of the
  /// header `Content-Length` will reflect the length of the original
  /// compressed body. Likewise the header `Content-Encoding` will also
  /// have the original value indicating compression.
  ///
  /// NOTE: Automatic un-compression is only performed if the
  /// `Content-Encoding` header value is `gzip`.
  ///
  /// This value affects all responses produced by this client after the
  /// value is changed.
  ///
  /// To disable, set to `false`.
  ///
  /// Default is `true`.
  bool autoUncompress;

  /// Gets and sets the default value of the `User-Agent` header for all requests
  /// generated by this [HttpClient].
  ///
  /// The default value is `Dart/<version> (dart:io)`.
  ///
  /// If the userAgent is set to `null`, no default `User-Agent` header will be
  /// added to each request.
  String userAgent;

  factory HttpClient({SecurityContext context}) {
    HttpOverrides overrides = HttpOverrides.current;
    if (overrides == null) {
      return _HttpClient(context);
    }
    return overrides.createHttpClient(context);
  }

  /// Opens a HTTP connection.
  ///
  /// The HTTP method to use is specified in [method], the server is
  /// specified using [host] and [port], and the path (including
  /// a possible query) is specified using [path].
  /// The path may also contain a URI fragment, which will be ignored.
  ///
  /// The `Host` header for the request will be set to the value
  /// [host]:[port]. This can be overridden through the
  /// [HttpClientRequest] interface before the request is sent.  NOTE
  /// if [host] is an IP address this will still be set in the `Host`
  /// header.
  ///
  /// For additional information on the sequence of events during an
  /// HTTP transaction, and the objects returned by the futures, see
  /// the overall documentation for the class [HttpClient].
  Future<HttpClientRequest> open(
      String method, String host, int port, String path);

  /// Opens a HTTP connection.
  ///
  /// The HTTP method is specified in [method] and the URL to use in
  /// [url].
  ///
  /// The `Host` header for the request will be set to the value
  /// [Uri.host]:[Uri.port] from [url]. This can be overridden through the
  /// [HttpClientRequest] interface before the request is sent.  NOTE
  /// if [Uri.host] is an IP address this will still be set in the `Host`
  /// header.
  ///
  /// For additional information on the sequence of events during an
  /// HTTP transaction, and the objects returned by the futures, see
  /// the overall documentation for the class [HttpClient].
  Future<HttpClientRequest> openUrl(String method, Uri url);

  /// Opens a HTTP connection using the GET method.
  ///
  /// The server is specified using [host] and [port], and the path
  /// (including a possible query) is specified using
  /// [path].
  ///
  /// See [open] for details.
  Future<HttpClientRequest> get(String host, int port, String path);

  /// Opens a HTTP connection using the GET method.
  ///
  /// The URL to use is specified in [url].
  ///
  /// See [openUrl] for details.
  Future<HttpClientRequest> getUrl(Uri url);

  /// Opens a HTTP connection using the POST method.
  ///
  /// The server is specified using [host] and [port], and the path
  /// (including a possible query) is specified using
  /// [path].
  ///
  /// See [open] for details.
  Future<HttpClientRequest> post(String host, int port, String path);

  /// Opens a HTTP connection using the POST method.
  ///
  /// The URL to use is specified in [url].
  ///
  /// See [openUrl] for details.
  Future<HttpClientRequest> postUrl(Uri url);

  /// Opens a HTTP connection using the PUT method.
  ///
  /// The server is specified using [host] and [port], and the path
  /// (including a possible query) is specified using [path].
  ///
  /// See [open] for details.
  Future<HttpClientRequest> put(String host, int port, String path);

  /// Opens a HTTP connection using the PUT method.
  ///
  /// The URL to use is specified in [url].
  ///
  /// See [openUrl] for details.
  Future<HttpClientRequest> putUrl(Uri url);

  /// Opens a HTTP connection using the DELETE method.
  ///
  /// The server is specified using [host] and [port], and the path
  /// (including a possible query) is specified using [path].
  ///
  /// See [open] for details.
  Future<HttpClientRequest> delete(String host, int port, String path);

  /// Opens a HTTP connection using the DELETE method.
  ///
  /// The URL to use is specified in [url].
  ///
  /// See [openUrl] for details.
  Future<HttpClientRequest> deleteUrl(Uri url);

  /// Opens a HTTP connection using the PATCH method.
  ///
  /// The server is specified using [host] and [port], and the path
  /// (including a possible query) is specified using [path].
  ///
  /// See [open] for details.
  Future<HttpClientRequest> patch(String host, int port, String path);

  /// Opens a HTTP connection using the PATCH method.
  ///
  /// The URL to use is specified in [url].
  ///
  /// See [openUrl] for details.
  Future<HttpClientRequest> patchUrl(Uri url);

  /// Opens a HTTP connection using the HEAD method.
  ///
  /// The server is specified using [host] and [port], and the path
  /// (including a possible query) is specified using [path].
  ///
  /// See [open] for details.
  Future<HttpClientRequest> head(String host, int port, String path);

  /// Opens a HTTP connection using the HEAD method.
  ///
  /// The URL to use is specified in [url].
  ///
  /// See [openUrl] for details.
  Future<HttpClientRequest> headUrl(Uri url);

  /// Sets the function to be called when a site is requesting
  /// authentication. The URL requested and the security realm from the
  /// server are passed in the arguments `url` and `realm`.
  ///
  /// The function returns a [Future] which should complete when the
  /// authentication has been resolved. If credentials cannot be
  /// provided the [Future] should complete with [:false:]. If
  /// credentials are available the function should add these using
  /// [addCredentials] before completing the [Future] with the value
  /// [:true:].
  ///
  /// If the [Future] completes with true the request will be retried
  /// using the updated credentials. Otherwise response processing will
  /// continue normally.
  set authenticate(Future<bool> f(Uri url, String scheme, String realm));

  /// Add credentials to be used for authorizing HTTP requests.
  void addCredentials(Uri url, String realm, HttpClientCredentials credentials);

  /// Sets the function used to resolve the proxy server to be used for
  /// opening a HTTP connection to the specified `url`. If this
  /// function is not set, direct connections will always be used.
  ///
  /// The string returned by [f] must be in the format used by browser
  /// PAC (proxy auto-config) scripts. That is either
  ///
  ///     "DIRECT"
  ///
  /// for using a direct connection or
  ///
  ///     "PROXY host:port"
  ///
  /// for using the proxy server [:host:] on port [:port:].
  ///
  /// A configuration can contain several configuration elements
  /// separated by semicolons, e.g.
  ///
  ///     "PROXY host:port; PROXY host2:port2; DIRECT"
  ///
  /// The static function [findProxyFromEnvironment] on this class can
  /// be used to implement proxy server resolving based on environment
  /// variables.
  set findProxy(String f(Uri url));

  /// Function for resolving the proxy server to be used for a HTTP
  /// connection from the proxy configuration specified through
  /// environment variables.
  ///
  /// The following environment variables are taken into account:
  ///
  ///     http_proxy
  ///     https_proxy
  ///     no_proxy
  ///     HTTP_PROXY
  ///     HTTPS_PROXY
  ///     NO_PROXY
  ///
  /// [:http_proxy:] and [:HTTP_PROXY:] specify the proxy server to use for
  /// http:// urls. Use the format [:hostname:port:]. If no port is used a
  /// default of 1080 will be used. If both are set the lower case one takes
  /// precedence.
  ///
  /// [:https_proxy:] and [:HTTPS_PROXY:] specify the proxy server to use for
  /// https:// urls. Use the format [:hostname:port:]. If no port is used a
  /// default of 1080 will be used. If both are set the lower case one takes
  /// precedence.
  ///
  /// [:no_proxy:] and [:NO_PROXY:] specify a comma separated list of
  /// postfixes of hostnames for which not to use the proxy
  /// server. E.g. the value "localhost,127.0.0.1" will make requests
  /// to both "localhost" and "127.0.0.1" not use a proxy. If both are set
  /// the lower case one takes precedence.
  ///
  /// To activate this way of resolving proxies assign this function to
  /// the [findProxy] property on the [HttpClient].
  ///
  ///     HttpClient client = new HttpClient();
  ///     client.findProxy = HttpClient.findProxyFromEnvironment;
  ///
  /// If you don't want to use the system environment you can use a
  /// different one by wrapping the function.
  ///
  ///     HttpClient client = new HttpClient();
  ///     client.findProxy = (url) {
  ///       return HttpClient.findProxyFromEnvironment(
  ///           url, environment: {"http_proxy": ..., "no_proxy": ...});
  ///     }
  ///
  /// If a proxy requires authentication it is possible to configure
  /// the username and password as well. Use the format
  /// [:username:password@hostname:port:] to include the username and
  /// password. Alternatively the API [addProxyCredentials] can be used
  /// to set credentials for proxies which require authentication.
  static String findProxyFromEnvironment(Uri url,
      {Map<String, String> environment}) {
    HttpOverrides overrides = HttpOverrides.current;
    if (overrides == null) {
      return _HttpClient._findProxyFromEnvironment(url, environment);
    }
    return overrides.findProxyFromEnvironment(url, environment);
  }

  /// Sets the function to be called when a proxy is requesting
  /// authentication. Information on the proxy in use and the security
  /// realm for the authentication are passed in the arguments `host`,
  /// `port` and `realm`.
  ///
  /// The function returns a [Future] which should complete when the
  /// authentication has been resolved. If credentials cannot be
  /// provided the [Future] should complete with [:false:]. If
  /// credentials are available the function should add these using
  /// [addProxyCredentials] before completing the [Future] with the value
  /// [:true:].
  ///
  /// If the [Future] completes with [:true:] the request will be retried
  /// using the updated credentials. Otherwise response processing will
  /// continue normally.
  set authenticateProxy(
      Future<bool> f(String host, int port, String scheme, String realm));

  /// Add credentials to be used for authorizing HTTP proxies.
  void addProxyCredentials(
      String host, int port, String realm, HttpClientCredentials credentials);

  /// Sets a callback that will decide whether to accept a secure connection
  /// with a server certificate that cannot be authenticated by any of our
  /// trusted root certificates.
  ///
  /// When an secure HTTP request if made, using this HttpClient, and the
  /// server returns a server certificate that cannot be authenticated, the
  /// callback is called asynchronously with the [X509Certificate] object and
  /// the server's hostname and port.  If the value of [badCertificateCallback]
  /// is [:null:], the bad certificate is rejected, as if the callback
  /// returned [:false:]
  ///
  /// If the callback returns true, the secure connection is accepted and the
  /// [:Future<HttpClientRequest>:] that was returned from the call making the
  /// request completes with a valid HttpRequest object. If the callback returns
  /// false, the [:Future<HttpClientRequest>:] completes with an exception.
  ///
  /// If a bad certificate is received on a connection attempt, the library calls
  /// the function that was the value of badCertificateCallback at the time
  /// the request is made, even if the value of badCertificateCallback
  /// has changed since then.
  set badCertificateCallback(
      bool callback(X509Certificate cert, String host, int port));

  /// Shuts down the HTTP client.
  ///
  /// If [force] is `false` (the default) the [HttpClient] will be kept alive
  /// until all active connections are done. If [force] is `true` any active
  /// connections will be closed to immediately release all resources. These
  /// closed connections will receive an error event to indicate that the client
  /// was shut down. In both cases trying to establish a new connection after
  /// calling [close] will throw an exception.
  void close({bool force = false});
}

/// HTTP request for a client connection.
///
/// To set up a request, set the headers using the headers property
/// provided in this class and write the data to the body of the request.
/// HttpClientRequest is an [IOSink]. Use the methods from IOSink,
/// such as writeCharCode(), to write the body of the HTTP
/// request. When one of the IOSink methods is used for the first
/// time, the request header is sent. Calling any methods that
/// change the header after it is sent throws an exception.
///
/// When writing string data through the [IOSink] the
/// encoding used is determined from the "charset" parameter of
/// the "Content-Type" header.
///
///     HttpClientRequest request = ...
///     request.headers.contentType
///         = new ContentType("application", "json", charset: "utf-8");
///     request.write(...);  // Strings written will be UTF-8 encoded.
///
/// If no charset is provided the default of ISO-8859-1 (Latin 1) is
/// be used.
///
///     HttpClientRequest request = ...
///     request.headers.add(HttpHeaders.CONTENT_TYPE, "text/plain");
///     request.write(...);  // Strings written will be ISO-8859-1 encoded.
///
/// An exception is thrown if you use an unsupported encoding and the
/// `write()` method being used takes a string parameter.
abstract class HttpClientRequest implements IOSink {
  /// Gets and sets the requested persistent connection state.
  ///
  /// The default value is [:true:].
  bool persistentConnection;

  /// Set this property to [:true:] if this request should
  /// automatically follow redirects. The default is [:true:].
  ///
  /// Automatic redirect will only happen for "GET" and "HEAD" requests
  /// and only for the status codes [:HttpStatus.MOVED_PERMANENTLY:]
  /// (301), [:HttpStatus.FOUND:] (302),
  /// [:HttpStatus.MOVED_TEMPORARILY:] (302, alias for
  /// [:HttpStatus.FOUND:]), [:HttpStatus.SEE_OTHER:] (303) and
  /// [:HttpStatus.TEMPORARY_REDIRECT:] (307). For
  /// [:HttpStatus.SEE_OTHER:] (303) automatic redirect will also happen
  /// for "POST" requests with the method changed to "GET" when
  /// following the redirect.
  ///
  /// All headers added to the request will be added to the redirection
  /// request(s). However, any body send with the request will not be
  /// part of the redirection request(s).
  bool followRedirects;

  /// Set this property to the maximum number of redirects to follow
  /// when [followRedirects] is `true`. If this number is exceeded
  /// an error event will be added with a [RedirectException].
  ///
  /// The default value is 5.
  int maxRedirects;

  /// The method of the request.
  String get method;

  /// The uri of the request.
  Uri get uri;

  /// Gets and sets the content length of the request.
  ///
  /// If the size of the request is not known in advance set content length to
  /// -1, which is also the default.
  int contentLength;

  /// Gets or sets if the [HttpClientRequest] should buffer output.
  ///
  /// Default value is `true`.
  ///
  /// __Note__: Disabling buffering of the output can result in very poor
  /// performance, when writing many small chunks.
  bool bufferOutput;

  /// Returns the client request headers.
  ///
  /// The client request headers can be modified until the client
  /// request body is written to or closed. After that they become
  /// immutable.
  HttpHeaders get headers;

  /// Cookies to present to the server (in the 'cookie' header).
  List<Cookie> get cookies;

  /// A [HttpClientResponse] future that will complete once the response is
  /// available.
  ///
  /// If an error occurs before the response is available, this future will
  /// complete with an error.
  Future<HttpClientResponse> get done;

  /// Close the request for input. Returns the value of [done].
  Future<HttpClientResponse> close();

  /// Gets information about the client connection.
  ///
  /// Returns [:null:] if the socket is not available.
  HttpConnectionInfo get connectionInfo;
}

/// HTTP response for a client connection.
///
/// The body of a [HttpClientResponse] object is a
/// [Stream] of data from the server. Listen to the body to handle
/// the data and be notified when the entire body is received.
///
///     new HttpClient().get('localhost', 80, '/file.txt')
///          .then((HttpClientRequest request) => request.close())
///          .then((HttpClientResponse response) {
///            response.transform(utf8.decoder).listen((contents) {
///              // handle data
///            });
///          });
abstract class HttpClientResponse implements Stream<List<int>> {
  /// Returns the status code.
  ///
  /// The status code must be set before the body is written
  /// to. Setting the status code after writing to the body will throw
  /// a `StateError`.
  int get statusCode;

  /// Returns the reason phrase associated with the status code.
  ///
  /// The reason phrase must be set before the body is written
  /// to. Setting the reason phrase after writing to the body will throw
  /// a `StateError`.
  String get reasonPhrase;

  /// Returns the content length of the response body. Returns -1 if the size of
  /// the response body is not known in advance.
  ///
  /// If the content length needs to be set, it must be set before the
  /// body is written to. Setting the reason phrase after writing to
  /// the body will throw a `StateError`.
  int get contentLength;

  /// Gets the persistent connection state returned by the server.
  ///
  /// if the persistent connection state needs to be set, it must be
  /// set before the body is written to. Setting the reason phrase
  /// after writing to the body will throw a `StateError`.
  bool get persistentConnection;

  /// Returns whether the status code is one of the normal redirect
  /// codes [HttpStatus.MOVED_PERMANENTLY], [HttpStatus.FOUND],
  /// [HttpStatus.MOVED_TEMPORARILY], [HttpStatus.SEE_OTHER] and
  /// [HttpStatus.TEMPORARY_REDIRECT].
  bool get isRedirect;

  /// Returns the series of redirects this connection has been through. The
  /// list will be empty if no redirects were followed. [redirects] will be
  /// updated both in the case of an automatic and a manual redirect.
  List<RedirectInfo> get redirects;

  /// Redirects this connection to a new URL. The default value for
  /// [method] is the method for the current request. The default value
  /// for [url] is the value of the [HttpHeaders.LOCATION] header of
  /// the current response. All body data must have been read from the
  /// current response before calling [redirect].
  ///
  /// All headers added to the request will be added to the redirection
  /// request. However, any body sent with the request will not be
  /// part of the redirection request.
  ///
  /// If [followLoops] is set to [:true:], redirect will follow the redirect,
  /// even if the URL was already visited. The default value is [:false:].
  ///
  /// The method will ignore [HttpClientRequest.maxRedirects]
  /// and will always perform the redirect.
  Future<HttpClientResponse> redirect(
      [String method, Uri url, bool followLoops]);

  /// Returns the client response headers.
  ///
  /// The client response headers are immutable.
  HttpHeaders get headers;

  /// Detach the underlying socket from the HTTP client. When the
  /// socket is detached the HTTP client will no longer perform any
  /// operations on it.
  ///
  /// This is normally used when a HTTP upgrade is negotiated and the
  /// communication should continue with a different protocol.
  Future<Socket> detachSocket();

  /// Cookies set by the server (from the 'set-cookie' header).
  List<Cookie> get cookies;

  /// Returns the certificate of the HTTPS server providing the response.
  /// Returns null if the connection is not a secure TLS or SSL connection.
  X509Certificate get certificate;

  /// Gets information about the client connection. Returns [:null:] if the socket
  /// is not available.
  HttpConnectionInfo get connectionInfo;
}

abstract class HttpClientCredentials {}

/// Represents credentials for basic authentication.
abstract class HttpClientBasicCredentials extends HttpClientCredentials {
  factory HttpClientBasicCredentials(String username, String password) =>
      _HttpClientBasicCredentials(username, password);
}

/// Represents credentials for digest authentication. Digest
/// authentication is only supported for servers using the MD5
/// algorithm and quality of protection (qop) of either "none" or
/// "auth".
abstract class HttpClientDigestCredentials extends HttpClientCredentials {
  factory HttpClientDigestCredentials(String username, String password) =>
      _HttpClientDigestCredentials(username, password);
}

/// Information about an [HttpRequest], [HttpResponse], [HttpClientRequest], or
/// [HttpClientResponse] connection.
abstract class HttpConnectionInfo {
  InternetAddress get remoteAddress;
  int get remotePort;
  int get localPort;
}

/// Redirect information.
abstract class RedirectInfo {
  /// Returns the status code used for the redirect.
  int get statusCode;

  /// Returns the method used for the redirect.
  String get method;

  /// Returns the location for the redirect.
  Uri get location;
}

/// When detaching a socket from either the [:HttpServer:] or the
/// [:HttpClient:] due to a HTTP connection upgrade there might be
/// unparsed data already read from the socket. This unparsed data
/// together with the detached socket is returned in an instance of
/// this class.
abstract class DetachedSocket {
  Socket get socket;
  List<int> get unparsedData;
}

class RedirectException implements HttpException {
  final String message;
  final List<RedirectInfo> redirects;

  const RedirectException(this.message, this.redirects);

  String toString() => "RedirectException: $message";

  Uri get uri => redirects.last.location;
}