/*

 * Copyright (c) 2013, 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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.

 */

package sun.management.jdp;

import java.io.ByteArrayInputStream;

import java.io.DataInputStream;

import java.io.EOFException;

import java.io.IOException;

import java.io.UnsupportedEncodingException;

import java.util.Collections;

import java.util.HashMap;

import java.util.Map;

/**

 * JdpPacketReader responsible for reading a packet <p>This class gets a byte

 * array as it came from a Net, validates it and breaks a part </p>

 */

public final class JdpPacketReader {

    private final DataInputStream pkt;

    private Map<String, String> pmap = null;

    /**

     * Create packet reader, extract and check magic and version

     *

     * @param packet - packet received from a Net

     * @throws JdpException

     */

    public JdpPacketReader(byte[] packet)

            throws JdpException {

        ByteArrayInputStream bais = new ByteArrayInputStream(packet);

        pkt = new DataInputStream(bais);

        try {

            int magic = pkt.readInt();

            JdpGenericPacket.checkMagic(magic);

        } catch (IOException e) {

            throw new JdpException("Invalid JDP packet received, bad magic");

        }

        try {

            short version = pkt.readShort();

            JdpGenericPacket.checkVersion(version);

        } catch (IOException e) {

            throw new JdpException("Invalid JDP packet received, bad protocol version");

        }

    }

    /**

     * Get next entry from packet

     *

     * @return the entry

     * @throws EOFException

     * @throws JdpException

     */

    public String getEntry()

            throws EOFException, JdpException {

        try {

            short len = pkt.readShort();

            // Artificial setting the "len" field to Short.MAX_VALUE may cause a reader to allocate

            // to much memory. Prevent this possible DOS attack.

            if (len < 1 && len > pkt.available()) {

                throw new JdpException("Broken JDP packet. Invalid entry length field.");

            }

            byte[] b = new byte[len];

            if (pkt.read(b) != len) {

                throw new JdpException("Broken JDP packet. Unable to read entry.");

            }

            return new String(b, "UTF-8");

        } catch (EOFException e) {

            throw e;

        } catch (UnsupportedEncodingException ex) {

            throw new JdpException("Broken JDP packet. Unable to decode entry.");

        } catch (IOException e) {

            throw new JdpException("Broken JDP packet. Unable to read entry.");

        }

    }

    /**

     * return packet content as a key/value map

     *

     * @return map containing packet entries pair of entries treated as

     * key,value

     * @throws IOException

     * @throws JdpException

     */

    public Map<String, String> getDiscoveryDataAsMap()

            throws JdpException {

        // return cached map if possible

        if (pmap != null) {

            return pmap;

        }

        String key = null, value = null;

        final Map<String, String> tmpMap = new HashMap<>();

        try {

            while (true) {

                key = getEntry();

                value = getEntry();

                tmpMap.put(key, value);

            }

        } catch (EOFException e) {

            // EOF reached on reading value, report broken packet

            // otherwise ignore it.

            if (value == null) {

                throw new JdpException("Broken JDP packet. Key without value." + key);

            }

        }

        pmap = Collections.unmodifiableMap(tmpMap);

        return pmap;

    }

}