/*
 * JBoss, Home of Professional Open Source
 * Copyright 2011, Red Hat, Inc. and individual contributors
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.mobicents.protocols.ss7.m3ua.impl;

import java.io.IOException;
import java.nio.channels.spi.AbstractSelectableChannel;
import java.util.concurrent.ConcurrentLinkedQueue;
import org.mobicents.protocols.ss7.m3ua.M3UAChannel;
import org.mobicents.protocols.ss7.m3ua.impl.message.M3UAMessageImpl;
import org.mobicents.protocols.ss7.m3ua.message.M3UAMessage;

/**
 * The base implementation for the M3UAChannel based on NIO.
 * 
 * @author kulikov
 */
public abstract class M3UAChannelImpl extends M3UASelectableChannelImpl implements M3UAChannel {
    
    //Queue for incoming messages
    protected ConcurrentLinkedQueue<M3UAMessageImpl> rxQueue = new ConcurrentLinkedQueue();
    //Queue for outgoing messages
    protected ConcurrentLinkedQueue<M3UAMessageImpl> txQueue = new ConcurrentLinkedQueue();
    
    protected IOException ioException;
    
    /**
     * Constructs new M3UA channel.
     * 
     * @param channel the underlying network channel.
     * @throws java.io.IOException
     */
    protected M3UAChannelImpl(AbstractSelectableChannel channel) throws IOException {
        this.channel = channel;
        this.channel.configureBlocking(false);
    }

    /**
     * (Non Java-doc.)
     * 
     * @see org.mobicents.protocols.ss7.m3ua.M3UAChannel#receive() 
     */
    public M3UAMessage receive() throws IOException {
        //If underlying channel raised Exception at IO, throw the same here
        if(ioException != null){
            throw ioException;
        }
        //extracts next message from queue
        return rxQueue.poll();
    }
    
    /**
     * (Non Java-doc.)
     * 
     * @see org.mobicents.protocols.ss7.m3ua.M3UAChannel#send(org.mobicents.protocols.ss7.m3ua.message.M3UAMessage)  
     */
    public void send(M3UAMessage message) throws IOException {
        //If underlying channel raised Exception at IO, throw the same here
        if(ioException != null){
            throw ioException;
        }
        
        //queue next message for sending
        txQueue.offer((M3UAMessageImpl) message);
    }
    
    /**
     * Implements undelying network read operation.
     * 
     * @throws java.io.IOException
     */
    protected abstract void doRead() throws IOException;
    
    /**
     * Implements undelying network write operation.
     * 
     * @throws java.io.IOException
     */
    protected abstract void doWrite() throws IOException;
    
    /**
     * Tests if this channel contains data available for reading
     * 
     * @return true if this channel contains data which can be read by user.
     */
    protected boolean isReadable() {
        return !rxQueue.isEmpty();
    }
    
    /**
     * Tests if write operation available for this channel
     * 
     * @return true if this channel allows to user to use write operation.
     */
    protected boolean isWritable() {
        return txQueue.isEmpty();
    }
    
    
}