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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2013-2014 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * http://glassfish.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at packager/legal/LICENSE.txt.
 *
 * GPL Classpath Exception:
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 *
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 */

package org.glassfish.tyrus.core;

import java.util.List;
import java.util.Map;

import javax.websocket.Extension;

/**
 * WebSocket {@link Extension}.
 * 
 * Capable of parameters negotiation, incoming and outgoing frames processing.
 * 

 * Extensions are ordered as they appear in handshake response headers, as per RFC 6455, chapter 9.1. It does not state
 * any ordering in regards of sender/receiver side and current implementation reflects that. See TODO below for possible
 * issue related to ordering.
 * 

 * Let's say we have negotiated two extensions, ext1 and ext2 in this order without parameters, so handshake response
 * headers will be: "sec-websocket-extensions: ext1, ext2". Prefix "c_" means client side, prefix "s_" server side.
 * 
 *   client -> server
 *
 *                +--------+   +--------+                  +--------+   +--------+
 *   client  >----| c_ext1 |-->| c_ext2 |--> [network] --> | s_ext1 |-->| s_ext2 |--> server
 *                +--------+   +--------+                  +--------+   +--------+
 *
 *   client <- server
 *
 *                +--------+   +--------+                  +--------+   +--------+
 *   client  <----| c_ext2 |<--| c_ext1 |<-- [network] <-- | s_ext2 |<--| s_ext1 |<-- server
 *                +--------+   +--------+                  +--------+   +--------+
 * 
 * 
 *


 * 
 * Any exception thrown from processIncoming or processOutgoing will be logged. Rest of extension chain will be invoked
 * without any modifications done in "faulty" extension. {@link javax.websocket.OnError} won't be triggered. (this might change).
 * 

 * 

 * 
TODO:
 * - naming.
 * - ordering - we might need to ensure that compression/decompression is invoked first when receiving and last when
 * sending message (to enable access to uncompressed data for other extensions).
 * - param negotiation.
 * - param validation.
 * - general validation - two extensions using same rsv bit cannot be "negotiated" for same session/connection.
 * - negotiation exception handling (onExtensionNegotiation)
 * 
 *
 * @author Pavel Bucek (pavel.bucek at oracle.com)
 */
public interface ExtendedExtension extends Extension {

    /**
     * Process incoming frame.
     * 
     * Passed frame is unmasked in case it was masked when received (server to client communication).
     *
     * @param context per-connection/session context.
     * @param frame   websocket frame representation.
     * @return processed frame. Can be new instance.
     */
    Frame processIncoming(ExtensionContext context, Frame frame);

    /**
     * Process outgoing frame.
     * 

     * Passed frame is unmasked. Frame payload will be masked when required (server to client communication).
     *
     * @param context per-connection/session context.
     * @param frame   websocket frame representation.
     * @return processed frame. Can be new instance.
     */
    Frame processOutgoing(ExtensionContext context, Frame frame);

    /**
     * Parameter negotiation. Executed before handshake response is sent to the client (server only). Returned
     * list of parameters will be present in handshake response headers.
     *
     * @param context             extension context.
     * @param requestedParameters requested parameters (from handshake request).
     * @return parameters to be present in handshake response.
     */
    List onExtensionNegotiation(ExtensionContext context, List requestedParameters);

    /**
     * Called only client side when handshake response arrives.
     * 

     * Can be used to process extension parameters returned from server side.
     *
     * @param context            extension context.
     * @param responseParameters extension parameters returned from the server.
     */
    void onHandshakeResponse(ExtensionContext context, List responseParameters);

    /**
     * Context lifecycle method. {@link org.glassfish.tyrus.core.ExtendedExtension.ExtensionContext} won't be used
     * after this method is called.
     *
     * @param context extension context to be destroyed.
     */
    void destroy(ExtensionContext context);

    /**
     * Context present as a parameter in all {@link org.glassfish.tyrus.core.ExtendedExtension} methods. Maintains per
     * connection state of current extension.
     * 

     * Context is created right before {@link #onExtensionNegotiation(org.glassfish.tyrus.core.ExtendedExtension.ExtensionContext, java.util.List)} method
     * call (server-side) or {@link #onHandshakeResponse(org.glassfish.tyrus.core.ExtendedExtension.ExtensionContext, java.util.List)} method call (client-side).
     * Last chance to access it is within {@link #destroy(org.glassfish.tyrus.core.ExtendedExtension.ExtensionContext)}
     * method invocation.
     */
    interface ExtensionContext {

        /**
         * Mutable, not synchronised property map.
         *

* Synchronisation is not necessary if you are accessing this map only during {@link org.glassfish.tyrus.core.ExtendedExtension} * methods invocation. * * @return property map. */ Map getProperties(); } }