/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsISupports.idl"

interface nsIEventTarget;

/**
 * nsIThreadRetargetableRequest
 *
 * Should be implemented by requests that support retargeting delivery of
 * data off the main thread.
 */
[uuid(27b84c48-5a73-4ba4-a8a4-8b5e649a145e)]
interface nsIThreadRetargetableRequest : nsISupports
{
  /**
   * Called to retarget delivery of OnDataAvailable to another thread. Should
   * only be called before AsyncOpen for nsIWebsocketChannels, or during
   * OnStartRequest for nsIChannels.
   * Note: For nsIChannels, OnStartRequest and OnStopRequest will still be
   * delivered on the main thread.
   *
   * @param aNewTarget New event target, e.g. thread or threadpool.
   *
   * Note: no return value is given. If the retargeting cannot be handled,
   * normal delivery to the main thread will continue. As such, listeners
   * should be ready to deal with OnDataAvailable on either the main thread or
   * the new target thread.
   */
  void retargetDeliveryTo(in nsIEventTarget aNewTarget);

  /**
   * Returns the event target where OnDataAvailable events will be dispatched.
   *
   * This is only valid after OnStartRequest has been called. Any time before
   * that point, the value may be changed by `retargetDeliveryTo` calls.
   */
  readonly attribute nsIEventTarget deliveryTarget;
};
