/*
 * Copyright 2011-17 Fraunhofer ISE, energy & meteo Systems GmbH and other contributors
 *
 * 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.openmuc.josistack;

import java.io.IOException;
import java.net.InetAddress;
import java.nio.ByteBuffer;
import java.util.concurrent.TimeoutException;

import javax.net.ServerSocketFactory;

import org.openmuc.jositransport.ServerTSap;
import org.openmuc.jositransport.TConnection;
import org.openmuc.jositransport.TConnectionListener;

/**
 * This class implements the server Service Access Point (SAP) for the Application Control Service Element (ACSE)
 * protocol as defined by ISO 8650 or ITU X.217/X.227. The ACSE provides services for establishing and releasing
 * application-associations. The class also realizes the lower ISO Presentation Layer as defined by ISO 8823/ITU X226
 * and the ISO Session Layer as defined by 8327/ITU X.225.
 * 
 */
public final class ServerAcseSap implements TConnectionListener {

    private AcseAssociationListener associationListener = null;
    public ServerTSap serverTSap = null;

    public byte[] pSelLocal = ClientAcseSap.P_SEL_DEFAULT;

    /**
     * Use this constructor to create a server ACSE SAP that listens on a fixed port.
     * 
     * @param port
     *            the local port listen on
     * @param backlog
     *            the backlog
     * @param bindAddr
     *            the InetAddress to bind to
     * @param associationListener
     *            the AssociationListener that will be notified when remote clients have associated. Once constructed
     *            the AcseSAP contains a public TSAP that can be accessed to set its configuration.
     */
    public ServerAcseSap(int port, int backlog, InetAddress bindAddr, AcseAssociationListener associationListener) {
        this(port, backlog, bindAddr, associationListener, ServerSocketFactory.getDefault());
    }

    /**
     * Use this constructor to create a server ACSE SAP that listens on a fixed port. The server socket is created with
     * the given socket factory.
     * 
     * @param port
     *            the local port listen on
     * @param backlog
     *            the backlog
     * @param bindAddr
     *            the InetAddress to bind to
     * @param associationListener
     *            the AssociationListener that will be notified when remote clients have associated. Once constructed
     *            the AcseSAP contains a public TSAP that can be accessed to set its configuration.
     * @param serverSocketFactory
     *            the server socket factory to create the socket
     */
    public ServerAcseSap(int port, int backlog, InetAddress bindAddr, AcseAssociationListener associationListener,
            ServerSocketFactory serverSocketFactory) {
        this.associationListener = associationListener;
        serverTSap = new ServerTSap(port, backlog, bindAddr, this, serverSocketFactory);
    }

    /**
     * Start listening for incoming connections. Only for server SAPs.
     * 
     * @throws IOException
     *             if an error occures starting to listen
     */
    public void startListening() throws IOException {
        if (associationListener == null || serverTSap == null) {
            throw new IllegalStateException("AcseSAP is unable to listen because it was not initialized.");
        }
        serverTSap.startListening();
    }

    public void stopListening() {
        serverTSap.stopListening();
    }

    /**
     * This function is internal and should not be called by users of this class.
     */
    @Override
    public void serverStoppedListeningIndication(IOException e) {
        associationListener.serverStoppedListeningIndication(e);
    }

    /**
     * This function is internal and should not be called by users of this class.
     * 
     */
    @Override
    public void connectionIndication(TConnection tConnection) {

        try {

            AcseAssociation acseAssociation = new AcseAssociation(tConnection, pSelLocal);

            ByteBuffer asdu = ByteBuffer.allocate(1000);
            try {
                asdu = acseAssociation.listenForCn(asdu);
            } catch (IOException e) {
                // Server: Connection unsuccessful.
                tConnection.close();
                return;
            } catch (TimeoutException e) {
                // Illegal state: Timeout should not occur here
                tConnection.close();
                return;
            }

            associationListener.connectionIndication(acseAssociation, asdu);

        } catch (Exception e) {
            // Association closed because of an unexpected exception.
            tConnection.close();
        }

    }
}