/* -*- Mode: C++; tab-width: 4; 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 "nsISupports.idl"

interface nsIStreamListener;

/**
 * A channel implementing this interface allows one to intercept its data by
 * inserting intermediate stream listeners.
 */
[scriptable, uuid(68167b0b-ef34-4d79-a09a-8045f7c5140e)]
interface nsITraceableChannel : nsISupports
{
    /*
     * Replace the channel's listener with a new one, and return the listener 
     * the channel used to have. The new listener intercepts OnStartRequest, 
     * OnDataAvailable and OnStopRequest calls and must pass them to 
     * the original listener after examination. If multiple callers replace 
     * the channel's listener, a chain of listeners is created.
     * The caller of setNewListener has no way to control at which place 
     * in the chain its listener is placed.
     *
     * Note: The caller of setNewListener must not delay passing 
     * OnStartRequest to the original listener.
     *
     * Note2: A channel may restrict when the listener can be replaced.
     * It is not recommended to allow listener replacement after OnStartRequest
     * has been called.
     */
    nsIStreamListener setNewListener(in nsIStreamListener aListener);
};