# File lib/googleauth/web_user_authorizer.rb, line 207
      def self.extract_callback_state request
        state = MultiJson.load(request[STATE_PARAM] || "{}")
        redirect_uri = state[CURRENT_URI_KEY]
        callback_state = {
          AUTH_CODE_KEY  => request[AUTH_CODE_KEY],
          ERROR_CODE_KEY => request[ERROR_CODE_KEY],
          SESSION_ID_KEY => state[SESSION_ID_KEY],
          SCOPE_KEY      => request[SCOPE_KEY]
        }
        [callback_state, redirect_uri]
      end