# Axis2ServerPushListener.java

    /*
     *  Copyright (c) 2022, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
     *
     *  WSO2 Inc. licenses this file to you under the Apache License,
     *  Version 2.0 (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.apache.org/licenses/LICENSE-2.0
     *
     *  Unless required by applicable law or agreed to in writing,
     *  software distributed under the License is distributed on an
     *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
     *  KIND, either express or implied.  See the License for the
     *  specific language governing permissions and limitations
     *  under the License.
     */

    package org.apache.synapse.transport.netty.sender;

    import org.apache.axis2.context.MessageContext;
    import org.apache.axis2.transport.base.threads.WorkerPool;
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.apache.synapse.transport.netty.BridgeConstants;
    import org.wso2.transport.http.netty.contract.HttpClientConnectorListener;
    import org.wso2.transport.http.netty.contract.HttpResponseFuture;
    import org.wso2.transport.http.netty.message.Http2PushPromise;
    import org.wso2.transport.http.netty.message.HttpCarbonMessage;

    /**
     * {@code Axis2ServerPushListener} is the class which listens for HTTP/2 server pushes from the backend.
     */
    public class Axis2ServerPushListener implements HttpClientConnectorListener {

        private static final Log LOG = LogFactory.getLog(Axis2ServerPushListener.class);

        private final HttpResponseFuture future;
        private final MessageContext requestMsgCtx;
        private final WorkerPool workerPool;
        private Http2PushPromise pushPromise;

        public Axis2ServerPushListener(HttpResponseFuture future, MessageContext requestMsgCtx, WorkerPool workerPool) {

            this.future = future;
            this.requestMsgCtx = requestMsgCtx;
            this.workerPool = workerPool;
        }

        public Axis2ServerPushListener(Http2PushPromise pushPromise, HttpResponseFuture future,
                                       MessageContext requestMsgCtx, WorkerPool workerPool) {

            this.pushPromise = pushPromise;
            this.future = future;
            this.requestMsgCtx = requestMsgCtx;
            this.workerPool = workerPool;
        }

        @Override
        public void onPushPromiseAvailability(boolean isPromiseAvailable) {

            if (isPromiseAvailable) {
                future.setPushPromiseListener(new Axis2ServerPushListener(future, requestMsgCtx, workerPool));
            }
        }

        @Override
        public void onPushPromise(Http2PushPromise pushPromise) {

            if (LOG.isDebugEnabled()) {
                LOG.debug(BridgeConstants.BRIDGE_LOG_PREFIX + "HTTP/2 push promise received");
            }
            workerPool.execute(new HttpServerPushWorker(requestMsgCtx, pushPromise));
            future.setPushResponseListener(new Axis2ServerPushListener(pushPromise, future, requestMsgCtx, workerPool),
                    pushPromise.getPromisedStreamId());
            future.setPromiseAvailabilityListener(new Axis2ServerPushListener(future, requestMsgCtx, workerPool));
        }

        @Override
        public void onPushResponse(int promiseId, HttpCarbonMessage httpMessage) {

            if (LOG.isDebugEnabled()) {
                LOG.debug(BridgeConstants.BRIDGE_LOG_PREFIX + "HTTP/2 push response received");
            }
            workerPool.execute(new HttpServerPushWorker(requestMsgCtx, pushPromise, httpMessage));
        }
    }