/*

 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

import java.io.IOException;

import java.nio.ByteBuffer;

/**

 * Generic JDWP command

 * @param <T> the corresponding JDWP reply class, to construct a reply object

 */

public abstract class JdwpCmd<T extends JdwpReply> {

    private ByteBuffer data;

    private static int id = 1;

    private final byte FLAGS = 0;

    private T reply;

    private final int dataLen;

    private final int HEADER_LEN = 11;

    /**

     * JDWWp command

     * @param cmd command code

     * @param cmdSet command set

     * @param replyClz command reply class

     * @param dataLen length of additional data for the command

     */

    JdwpCmd(int cmd, int cmdSet, Class<T> replyClz, int dataLen) {

        this.dataLen = dataLen;

        data = ByteBuffer.allocate(HEADER_LEN + dataLen);

        data.putInt(HEADER_LEN + dataLen);

        data.putInt(id++);

        data.put(FLAGS);

        data.put((byte) cmdSet);

        data.put((byte) cmd);

        if (replyClz != null) {

            try {

                reply = replyClz.newInstance();

            } catch (Exception ex) {

                ex.printStackTrace();

            }

        }

    }

    JdwpCmd(int cmd, int cmdSet, Class<T> replyClz) {

        this(cmd, cmdSet, replyClz, 0);

    }

    int getDataLength() {

        return dataLen;

    }

    public final T send(JdwpChannel channel) throws IOException {

        channel.write(data.array(), HEADER_LEN + getDataLength());

        if (reply != null) {

            reply.initFromStream(channel.getInputStream());

        }

        return (T) reply;

    }

    protected void putRefId(long refId) {

        data.putLong(refId);

    }

    protected void putInt(int val) {

        data.putInt(val);

    }

    protected static int refLen() {

        return 8;

    }

}