class WebDriver extends WebDriverBase {

  WebDriver(host, port, path) : super(host, port, path);

  /**
   * Create a new session. The server will attempt to create a session that
   * most closely matches the desired and required capabilities. Required
   * capabilities have higher priority than desired capabilities and must be
   * set for the session to be created.
   *
   * The capabilities are:
   *
   * - browserName (String)  The name of the browser being used; should be one
   *   of chrome|firefox|htmlunit|internet explorer|iphone.
   *
   * - version (String) The browser version, or the empty string if unknown.
   *
   * - platform (String) A key specifying which platform the browser is
   *   running on. This value should be one of WINDOWS|XP|VISTA|MAC|LINUX|UNIX.
   *   When requesting a new session, the client may specify ANY to indicate
   *   any available platform may be used.
   *
   * - javascriptEnabled (bool) Whether the session supports executing user
   *   supplied JavaScript in the context of the current page.
   *
   * - takesScreenshot (bool) Whether the session supports taking screenshots
   *   of the current page.
   *
   * - handlesAlerts (bool) Whether the session can interact with modal popups,
   *   such as window.alert and window.confirm.
   *
   * - databaseEnabled (bool) Whether the session can interact database storage.
   *
   * - locationContextEnabled (bool) Whether the session can set and query the
   *   browser's location context.
   *
   * - applicationCacheEnabled (bool) Whether the session can interact with
   *   the application cache.
   *
   * - browserConnectionEnabled (bool) Whether the session can query for the
   *   browser's connectivity and disable it if desired.
   *
   * - cssSelectorsEnabled (bool) Whether the session supports CSS selectors
   *   when searching for elements.
   *
   * - webStorageEnabled (bool) Whether the session supports interactions with
   *   storage objects.
   *
   * - rotatable (bool) Whether the session can rotate the current page's
   *   current layout between portrait and landscape orientations (only applies
   *   to mobile platforms).
   *
   * - acceptSslCerts (bool) Whether the session should accept all SSL certs
   *   by default.
   *
   * - nativeEvents (bool) Whether the session is capable of generating native
   *   events when simulating user input.
   *
   * - proxy (proxy object) Details of any proxy to use. If no proxy is
   *   specified, whatever the system's current or default state is used.
   *
   * The format of the proxy object is:
   *
   * - proxyType (String) The type of proxy being used. Possible values are:
   *
   *   direct - A direct connection - no proxy in use,
   *
   *   manual - Manual proxy settings configured,
   *
   *   pac - Proxy autoconfiguration from a URL),
   *
   *   autodetect (proxy autodetection, probably with WPAD),
   *
   *   system - Use system settings
   *
   * - proxyAutoconfigUrl (String) Required if proxyType == pac, Ignored
   *   otherwise. Specifies the URL to be used for proxy autoconfiguration.
   *
   * - ftpProxy, httpProxy, sslProxy (String) (Optional, Ignored if
   *   proxyType != manual) Specifies the proxies to be used for FTP, HTTP
   *   and HTTPS requests respectively. Behaviour is undefined if a request
   *   is made, where the proxy for the particular protocol is undefined,
   *   if proxyType is manual.
   *
   * Potential Errors: SessionNotCreatedException (if a required capability
   * could not be set).
   */
  Future<WebDriverSession> newSession([
      browser = 'chrome', Map additional_capabilities]) {
    var completer = new Completer();
    if (additional_capabilities == null) {
      additional_capabilities = {};
    }

    additional_capabilities['browserName'] = browser;

    _serverRequest('POST', '${_path}/session', null, [ 302 ],
        customHandler: (r, v) {
          var url = r.headers.value(HttpHeaders.LOCATION);
          var session = new WebDriverSession.fromUrl(url);
          completer.complete(session);
        }, params: { 'desiredCapabilities': additional_capabilities });
    return completer.future;
  }

  /** Get the set of currently active sessions. */
  Future<List<WebDriverSession>> getSessions() {
    var completer = new Completer();
    _get('sessions', (result) {
      var _sessions = [];
      for (var session in result) {
        _sessions.add(new WebDriverSession.fromUrl(
          '${this._path}/session/${session["id"]}'));
      }
      completer.complete(_sessions);
    });
    return completer.future;
  }

  /** Query the server's current status. */
  Future<Map> getStatus() => _get('status');
}