/* This file is part of VoltDB.
 * Copyright (C) 2008-2010 VoltDB Inc.
 *
 * VoltDB is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * VoltDB 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with VoltDB.  If not, see <http://www.gnu.org/licenses/>.
 */

package org.voltdb.network;

import java.util.concurrent.atomic.AtomicLong;
import java.nio.ByteBuffer;
import java.io.IOException;

public abstract class VoltProtocolHandler implements InputHandler {
    /** VoltProtocolPorts each have a unique id */
    private static AtomicLong m_globalConnectionCounter = new AtomicLong(0);

    /** messages read by this connection */
    private int m_sequenceId;
    /** serial number of this VoltPort */
    private final long m_connectionId;
    private int m_nextLength;

    public VoltProtocolHandler() {
        m_sequenceId = 0;
        m_connectionId = m_globalConnectionCounter.incrementAndGet();
    }

    @Override
    public ByteBuffer retrieveNextMessage(Connection c) throws IOException {
        final NIOReadStream inputStream = c.readStream();

        /*
         * Note that access to the read stream is not synchronized. In this application
         * the VoltPort will invoke this input handler to interact with the read stream guaranteeing
         * thread safety. That said the Connection interface does allow other parts of the application
         * access to the read stream.
         */
        ByteBuffer result = null;

        if (m_nextLength == 0 && inputStream.dataAvailable() > (Integer.SIZE/8)) {
            m_nextLength = inputStream.getInt();
            if (m_nextLength < 1) {
                throw new IOException(
                        "Next message length is " + m_nextLength + " which is less than 1 and is nonsense");
            }
            if (m_nextLength > 52428800) {
                throw new IOException(
                        "Next message length is " + m_nextLength + " which is greater then the hard coded " +
                        "max of 52428800. Break up the work into smaller chunks (2 megabytes is reasonable) " +
                        "and send as multiple messages or stored procedure invocations");
            }
            assert m_nextLength > 0;
        }
        if (m_nextLength > 0 && inputStream.dataAvailable() >= m_nextLength) {
            result = ByteBuffer.allocate(m_nextLength);
            inputStream.getBytes(result.array());
            m_nextLength = 0;
            m_sequenceId++;
        }
        return result;
    }

    @Override
    public void started(Connection c) {
    }

    @Override
    public void starting(Connection c) {
    }

    @Override
    public void stopped(Connection c) {
    }

    @Override
    public void stopping(Connection c) {
    }

    @Override
    public long connectionId() {
        return m_connectionId;
    }

    public int sequenceId() {
        return m_sequenceId;
    }

    protected int getNextMessageLength() {
        return m_nextLength;
    }

}