/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* 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 "nsIRunnable.idl"

%{C++
#include "mozilla/AlreadyAddRefed.h"
%}

native alreadyAddRefed_nsIRunnable(already_AddRefed<nsIRunnable>);

/*
 * The primary use of this interface is to allow any nsISerialEventTarget to
 * provide Direct Task dispatching which is similar (but not identical to) the
 * microtask semantics of JS promises.
 * New direct task may be dispatched when a current direct task is running. In
 * which case they will be run in FIFO order.
 */
[uuid(e05bf0fe-94b7-4e28-8462-a8368da9c136)]
interface nsIDirectTaskDispatcher : nsISupports
{
  /**
   * Dispatch an event for the nsISerialEventTarget, using the direct task
   * queue.
   *
   * This function must be called from the same nsISerialEventTarget
   * implementing direct task dispatching.
   *
   * @param event
   *   The alreadyAddRefed<> event to dispatch.
   *
   */
  [noscript] void dispatchDirectTask(in alreadyAddRefed_nsIRunnable event);

  /**
   * Synchronously run any pending direct tasks queued.
   */
  [noscript] void drainDirectTasks();

  /**
   * Returns true if any direct tasks are pending.
   */
  [noscript] bool haveDirectTasks();

  %{C++
  // Infallible version of the above. Will assert that it is successful.
  bool HaveDirectTasks() {
    bool value = false;
    MOZ_ALWAYS_SUCCEEDS(HaveDirectTasks(&value));
    return value;
  }
  %}

};
