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/*_############################################################################
  _## 
  _##  SNMP4J - DummyTransport.java  
  _## 
  _##  Copyright (C) 2003-2024  Frank Fock (SNMP4J.org)
  _##  
  _##  Licensed 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.snmp4j.transport;

import org.snmp4j.SNMP4JSettings;
import org.snmp4j.TransportStateReference;
import org.snmp4j.log.LogAdapter;
import org.snmp4j.log.LogFactory;
import org.snmp4j.security.SecurityLevel;
import org.snmp4j.smi.Address;
import org.snmp4j.smi.IpAddress;
import org.snmp4j.smi.OctetString;
import org.snmp4j.util.WorkerTask;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.HashMap;
import java.util.Map;
import java.util.Queue;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.TimeUnit;

/**
 * The {@code DummyTransport} is a test TransportMapping for Command Generators
 * which actually does not sent messages over the network. Instead it provides the message
 * transparently as incoming message over the {@link DummyTransportResponder} on a virtual
 * listen address, regardless to which outbound address the message was sent. The messages
 * are returned even if the {@code listenAddress} is left {@code null}.
 *
 * @author Frank Fock
 * @since 2.0
 */
public class DummyTransport extends AbstractTransportMapping {

    private static final LogAdapter logger = LogFactory.getLogger(DummyTransport.class);

    private final Queue requests = new ConcurrentLinkedQueue();
    private final Queue responses = new ConcurrentLinkedQueue();
    private boolean listening;
    private A listenAddress;
    private A receiverAddress;
    private WorkerTask listenThread;
    private long sessionID = 0;

    public DummyTransport() {
        this.listening = false;
    }

    public DummyTransport(A senderAddress) {
        this.listenAddress = senderAddress;
    }

    public DummyTransport(A senderAddress, A receiverAddress) {
        this.listenAddress = senderAddress;
        this.receiverAddress = receiverAddress;
    }

    @Override
    public Class getSupportedAddressClass() {
        return IpAddress.class;
    }

    @Override
    public A getListenAddress() {
        return listenAddress;
    }

    public void setListenAddress(A listenAddress) {
        this.listenAddress = listenAddress;
    }

    @Override
    public void sendMessage(A address, byte[] message, TransportStateReference tmStateReference,
                            long timeoutMillis, int retries) throws IOException {
        synchronized (requests) {
            if (logger.isDebugEnabled()) {
                logger.debug("Send request message to '" + address + "': " + new OctetString(message).toHexString());
            }
            requests.add(new MessageContainer(address, new OctetString(message)));
        }
    }

    @Override
    public void close() throws IOException {
        if (listening) {
            listening = false;
            listenThread.terminate();
            try {
                listenThread.join();
            } catch (InterruptedException e) {
                // ignore
            }
        }
        responses.clear();
    }

    @Override
    public void listen() throws IOException {
        listening = true;
        sessionID++;
        QueueProcessor listener = new QueueProcessor(responses, this);
        this.listenThread = SNMP4JSettings.getThreadFactory().createWorkerThread(
                "DummyTransportMapping_" + getListenAddress(), listener, true);
        this.listenThread.run();
    }

    @Override
    public boolean isListening() {
        return listening;
    }

    public AbstractTransportMapping getResponder(A receiverAddress) {
        this.receiverAddress = receiverAddress;
        return new DummyTransportResponder();
    }

    private class QueueProcessor implements WorkerTask {

        private volatile boolean stop;
        private final Queue queue;
        private final AbstractTransportMapping tm;

        public QueueProcessor(Queue queue, AbstractTransportMapping tm) {
            this.queue = queue;
            this.tm = tm;
        }

        @Override
        public void run() {
            while (!stop) {
                MessageContainer nextMessage = null;
                nextMessage = queue.poll();
                if (nextMessage != null) {
                    TransportStateReference stateReference =
                            new TransportStateReference(DummyTransport.this, listenAddress, null,
                                    SecurityLevel.undefined, SecurityLevel.undefined,
                                    false, sessionID);
                    tm.fireProcessMessage(listenAddress,
                            ByteBuffer.wrap(nextMessage.getPayload().getValue()), stateReference);
                } else {
                    try {
                        Thread.sleep(50);
                    } catch (InterruptedException e) {
                        logger.warn("Interrupted QueueProcessor: " + e.getMessage());
                    }
                }
            }
        }

        @Override
        public void terminate() {
            stop = true;
        }

        @Override
        public void join() throws InterruptedException {
            stop = true;
            synchronized (this) {
                // wait until run is stopped
            }
        }

        @Override
        public void interrupt() {
            stop = true;
        }
    }

    public class DummyTransportResponder extends AbstractTransportMapping {

        private boolean listening;
        private WorkerTask listenThread;

        @Override
        public Class getSupportedAddressClass() {
            return DummyTransport.this.getSupportedAddressClass();
        }

        @Override
        public A getListenAddress() {
            return receiverAddress;
        }

        @Override
        public void sendMessage(A address, byte[] message, TransportStateReference tmStateReference,
                                long timeoutMillis, int retries) throws IOException {
            if (logger.isDebugEnabled()) {
                logger.debug("Send response message to '" + address + "': " + new OctetString(message).toHexString());
            }
            responses.add(new MessageContainer(address, new OctetString(message)));
        }

        @Override
        public void close() throws IOException {
            this.listening = false;
            this.listenThread.terminate();
            try {
                this.listenThread.join();
            } catch (InterruptedException e) {
                // ignore
            }
            requests.clear();
        }

        @Override
        public void listen() throws IOException {
            this.listening = true;
            sessionID++;
            QueueProcessor listener = new QueueProcessor(requests, this);
            this.listenThread = SNMP4JSettings.getThreadFactory().createWorkerThread(
                    "DummyResponseTransportMapping_" + getListenAddress(), listener, true);
            this.listenThread.run();
        }

        @Override
        public WorkerTask getListenWorkerTask() {
            return listenThread;
        }

        @Override
        public boolean isListening() {
            return this.listening;
        }
    }

    @Override
    public String toString() {
        return "DummyTransport{" +
                "requests=" + requests +
                ", responses=" + responses +
                ", listening=" + listening +
                ", listenAddress=" + listenAddress +
                ", receiverAddress=" + receiverAddress +
                ", listenThread=" + listenThread +
                ", sessionID=" + sessionID +
                '}';
    }

    @Override
    public WorkerTask getListenWorkerTask() {
        return listenThread;
    }

    private static class MessageContainer {
        private final Address sourceAddress;
        private final OctetString payload;

        public MessageContainer(Address sourceAddress, OctetString payload) {
            this.payload = payload;
            this.sourceAddress = sourceAddress;
        }

        public OctetString getPayload() {
            return payload;
        }

        public Address getSourceAddress() {
            return sourceAddress;
        }
    }
}