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/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 2001
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Akkana Peck <akkana@netscape.com> (original author)
 *   Darin Fisher <darin@meer.net>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
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 * ***** END LICENSE BLOCK ***** */

#include "nsIRequest.idl"

interface nsIURI;
interface nsIChannel;
interface nsIRequestObserver;

/**
 * nsIURIChecker
 *
 * The URI checker is a component that can be used to verify the existance
 * 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);
};