/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* 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 "nsIRequest.idl"

interface nsIURI;
interface nsIChannel;
interface nsIRequestObserver;

/**
 * nsIURIChecker
 *
 * The URI checker is a component that can be used to verify the existence
 * of a resource at the location specified by a given URI.  It will use
 * protocol specific methods to verify the URI (e.g., use of HEAD request
 * for HTTP URIs).
 */
[scriptable, uuid(4660c1a1-be2d-4c78-9baf-c22984176c28)]
interface nsIURIChecker : nsIRequest
{
    /**
     * Initializes the URI checker.  After this method is called, it is valid
     * to further configure the URI checker by calling its nsIRequest methods.
     * This method creates the channel that will be used to verify the URI.
     * In the case of the HTTP protocol, only a HEAD request will be issued.
     *
     * @param aURI
     *        The URI to be checked.
     */
    void init(in nsIURI aURI);

    /**
     * Returns the base channel that will be used to verify the URI.
     */
    readonly attribute nsIChannel baseChannel;

    /**
     * Begin asynchronous checking URI for validity.  Notification will be
     * asynchronous through the nsIRequestObserver callback interface.  When
     * OnStartRequest is fired, the baseChannel attribute will have been
     * updated to reflect the final channel used (corresponding to any redirects
     * that may have been followed).
     *
     * Our interpretations of the nsIRequestObserver status codes:
     *   NS_BINDING_SUCCEEDED:   link is valid
     *   NS_BINDING_FAILED:      link is invalid (gave an error)
     *   NS_BINDING_ABORTED:     timed out, or cancelled
     *
     * @param aObserver
     *        The object to notify when the link is verified.  We will
     *        call aObserver.OnStartRequest followed immediately by
     *        aObserver.OnStopRequest.  It is recommended that the caller use
     *        OnStopRequest to act on the link's status.  The underlying request
     *        will not be cancelled until after OnStopRequest has been called.
     * @param aContext
     *        A closure that will be passed back to the nsIRequestObserver
     *        methods.
     */
    void asyncCheck(in nsIRequestObserver aObserver, in nsISupports aContext);
};