/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* ***** 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) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
 * 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 "nsIInputStream.idl"
#include "nsIStreamListener.idl"

%{C++
#define NS_ISTREAMCONVERTER_KEY         "@mozilla.org/streamconv;1"
%}

/**
 * The nsIStreamConverterService is a higher level stream converter factory
 * responsible for locating and creating stream converters
 * (nsIStreamConverter).
 *
 * This service retrieves an interface that can convert data from a particular
 * MIME type, to a particular MIME type. It is responsible for any intermediary
 * conversion required in order to get from X to Z, assuming direct conversion
 * is not possible.
 *
 * @author Jud Valeski
 * @see nsIStreamConverter
 */
[scriptable, uuid(f2b1ab53-f0bd-4adb-9365-e59b1701a258)]
interface nsIStreamConverterService : nsISupports {
    /**
     * Tests whether conversion between the two specified types is possible.
     * This is cheaper than calling convert()/asyncConvertData(); it is not
     * necessary to call this function before calling one of those, though.
     */
    boolean canConvert(in string aFromType, in string aToType);

    /**
     * <b>SYNCHRONOUS VERSION</b>
     * Converts a stream of one type, to a stream of another type.
     *
     * Use this method when you have a stream you want to convert.
     *
     * @param aFromStream   The stream representing the original/raw data.
     * @param aFromType     The MIME type of aFromStream.
     * @param aToType       The MIME type of the returned stream.
     * @param aContext      Either an opaque context, or a converter specific
     *                      context (implementation specific).
     * @return              The converted stream. NOTE: The returned stream
     *                      may not already be converted. An efficient stream
     *                      converter implementation will convert data on
     *                      demand rather than buffering the converted data
     *                      until it is used.
     */
    nsIInputStream convert(in nsIInputStream aFromStream,
                           in string aFromType,
                           in string aToType,
                           in nsISupports aContext);

    /**
     * <b>ASYNCHRONOUS VERSION</b>
     * Retrieves a nsIStreamListener that receives the original/raw data via its
     * nsIStreamListener::OnDataAvailable() callback, then converts and pushes 
     * the data to aListener.
     *
     * Use this method when you want to proxy (and convert) nsIStreamListener
     * callbacks asynchronously.
     *
     * @param aFromType     The MIME type of the original/raw data.
     * @param aToType       The MIME type of the converted data.
     * @param aListener     The listener that receives the converted data.
     * @param aCtxt         Either an opaque context, or a converter specific
     *                      context (implementation specific).
     * @return              A nsIStreamListener that receives data via its
     *                      OnDataAvailable() method.
     */
    nsIStreamListener asyncConvertData(in string aFromType, 
                                       in string aToType, 
                                       in nsIStreamListener aListener,
                                       in nsISupports aContext);
};