/*
 * Copyright (c) 2013 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */

package org.opendaylight.controller.sal.packet;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.commons.lang3.tuple.Pair;
import org.opendaylight.controller.sal.utils.HexEncode;
import org.opendaylight.controller.sal.utils.NetUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Abstract class which represents the generic network packet object It provides
 * the basic methods which are common for all the packets, like serialize and
 * deserialize
 * 
 * 
 */

public abstract class Packet {
    protected static final Logger logger = LoggerFactory
            .getLogger(Packet.class);
    // Access level granted to this packet
    protected boolean writeAccess;
    // When deserialized from wire, packet could result corrupted
    protected boolean corrupted;
    // The packet that encapsulate this packet
    protected Packet parent;
    // The packet encapsulated by this packet
    protected Packet payload;
    // Bit coordinates of packet header fields
    protected Map<String, Pair<Integer, Integer>> hdrFieldCoordMap;
    // Header fields values: Map<FieldName,Value>
    protected Map<String, byte[]> hdrFieldsMap;
    // The class of the encapsulated packet object
    protected Class<? extends Packet> payloadClass;

    public Packet() {
        writeAccess = false;
        corrupted = false;
    }

    public Packet(boolean writeAccess) {
        this.writeAccess = writeAccess;
        this.corrupted = false;
    }

    public Packet getParent() {
        return parent;
    }

    public Packet getPayload() {
        return payload;
    }

    public void setParent(Packet parent) {
        this.parent = parent;
    }

    public void setPayload(Packet payload) {
        this.payload = payload;
    }

    public void setHeaderField(String headerField, byte[] readValue) {
        hdrFieldsMap.put(headerField, readValue);
    }

    /**
     * This method deserializes the data bits obtained from the wire into the
     * respective header and payload which are of type Packet
     * 
     * @param byte[] data - data from wire to deserialize
     * @param int bitOffset bit position where packet header starts in data
     *        array
     * @param int size of packet in bits
     * @return Packet
     * @throws PacketException
     */

    public Packet deserialize(byte[] data, int bitOffset, int size)
            throws PacketException {
        String hdrField;
        Integer startOffset = 0, numBits = 0;
        byte[] hdrFieldBytes;

        for (Entry<String, Pair<Integer, Integer>> pairs : hdrFieldCoordMap
                .entrySet()) {
            hdrField = pairs.getKey();
            startOffset = bitOffset + this.getfieldOffset(hdrField);
            numBits = this.getfieldnumBits(hdrField);

            try {
                hdrFieldBytes = BitBufferHelper.getBits(data, startOffset,
                        numBits);
            } catch (BufferException e) {
                throw new PacketException(e.getMessage());
            }
            /*
             * Store the raw read value, checks the payload type and set the
             * payloadClass accordingly
             */
            if (logger.isTraceEnabled()) {
              logger.trace("{}: {}: {} (offset {} bitsize {})",
                      new Object[] { this.getClass().getSimpleName(), hdrField,
                              HexEncode.bytesToHexString(hdrFieldBytes),
                              startOffset, numBits });
            }

            this.setHeaderField(hdrField, hdrFieldBytes);
        }

        postDeserializeCustomOperation(data, startOffset);

        int payloadStart = startOffset + numBits;
        // int payloadSize = size - payloadStart;
        int payloadSize = data.length * NetUtils.NumBitsInAByte - payloadStart;

        if (payloadClass != null) {
            try {
                payload = payloadClass.newInstance();
            } catch (Exception e) {
                throw new RuntimeException(
                        "Error parsing payload for Ethernet packet", e);
            }
            payload.deserialize(data, payloadStart, payloadSize);
            payload.setParent(this);
        } else {
            // For now let's discard unparsable payload
        }
        return this;
    }

    /**
     * This method serializes the header and payload bytes from the respective
     * packet class, into a single stream of bytes to be sent on the wire
     * 
     * @return byte[] - serialized bytes
     * @throws PacketException
     */

    public byte[] serialize() throws PacketException {
        byte[] payloadBytes = null;
        int payloadSize = 0;
        int headerSize = this.getHeaderSize();
        int payloadByteOffset = headerSize / NetUtils.NumBitsInAByte;
        int size = 0;

        if (payload != null) {
            payloadBytes = payload.serialize();
            payloadSize = payloadBytes.length * NetUtils.NumBitsInAByte;
        }

        size = headerSize + payloadSize;
        int length = size / NetUtils.NumBitsInAByte;
        byte headerBytes[] = new byte[length];

        if (payload != null) {
            System.arraycopy(payloadBytes, 0, headerBytes, payloadByteOffset,
                    payloadBytes.length);
        }

        String field;
        byte[] fieldBytes;
        Integer startOffset, numBits;

        for (Map.Entry<String, Pair<Integer, Integer>> pairs : hdrFieldCoordMap
                .entrySet()) {
            field = pairs.getKey();
            fieldBytes = hdrFieldsMap.get(field);
            // Let's skip optional fields when not set
            if (fieldBytes != null) {
                startOffset = this.getfieldOffset(field);
                numBits = this.getfieldnumBits(field);
                try {
                    BitBufferHelper.setBytes(headerBytes, fieldBytes,
                            startOffset, numBits);
                } catch (BufferException e) {
                    throw new PacketException(e.getMessage());
                }
            }
        }
        postSerializeCustomOperation(headerBytes);

        if (logger.isTraceEnabled()) {
          logger.trace("{}: {}", this.getClass().getSimpleName(),
                  HexEncode.bytesToHexString(headerBytes));
        }
        return headerBytes;
    }

    /**
     * This method gets called at the end of the serialization process It is
     * intended for the child packets to insert some custom data into the output
     * byte stream which cannot be done or cannot be done efficiently during the
     * normal Packet.serialize() path. An example is the checksum computation
     * for IPv4
     * 
     * @param byte[] - serialized bytes
     * @throws PacketException
     */
    protected void postSerializeCustomOperation(byte[] myBytes)
            throws PacketException {
        // no op
    }

    /**
     * This method re-computes the checksum of the bits received on the wire and
     * validates it with the checksum in the bits received Since the computation
     * of checksum varies based on the protocol, this method is overridden
     * Currently only IPv4 does checksum computation and validation TCP and UDP
     * need to implement these if required
     * 
     * @param byte[] data
     * @param int endBitOffset
     * @throws PacketException
     */
    protected void postDeserializeCustomOperation(byte[] data, int endBitOffset)
            throws PacketException {
        // no op
    }

    /**
     * Gets the header length in bits
     * 
     * @return int the header length in bits
     */
    public int getHeaderSize() {
        int size = 0;
        /*
         * We need to iterate over the fields that were read in the frame
         * (hdrFieldsMap) not all the possible ones described in
         * hdrFieldCoordMap. For ex, 802.1Q may or may not be there
         */
        for (Map.Entry<String, byte[]> fieldEntry : hdrFieldsMap.entrySet()) {
            if (fieldEntry.getValue() != null) {
                String field = fieldEntry.getKey();
                size += getfieldnumBits(field);
            }
        }
        return size;
    }

    /**
     * This method fetches the start bit offset for header field specified by
     * 'fieldname'. The offset is present in the hdrFieldCoordMap of the
     * respective packet class
     * 
     * @param String
     *            fieldName
     * @return Integer - startOffset of the requested field
     */
    public int getfieldOffset(String fieldName) {
        return (((Pair<Integer, Integer>) hdrFieldCoordMap.get(fieldName))
                .getLeft());
    }

    /**
     * This method fetches the number of bits for header field specified by
     * 'fieldname'. The numBits are present in the hdrFieldCoordMap of the
     * respective packet class
     * 
     * @param String
     *            fieldName
     * @return Integer - number of bits of the requested field
     */
    public int getfieldnumBits(String fieldName) {
        return (((Pair<Integer, Integer>) hdrFieldCoordMap.get(fieldName))
                .getRight());
    }

    @Override
    public String toString() {
        StringBuffer ret = new StringBuffer();
        for (Map.Entry<String, byte[]> entry : hdrFieldsMap.entrySet()) {
            ret.append(entry.getKey() + ": ");
            if (entry.getValue().length == 6) {
                ret.append(HexEncode.bytesToHexString(entry.getValue()) + " ");
            } else if (entry.getValue().length == 4) {
                try {
                    ret.append(InetAddress.getByAddress(entry.getValue())
                            .getHostAddress() + " ");
                } catch (UnknownHostException e) {
                    logger.error("", e);
                }
            } else {
                ret.append(((Long) BitBufferHelper.getLong(entry.getValue()))
                        .toString() + " ");
            }
        }
        return ret.toString();
    }

    /**
     * Returns true if the packet is corrupted
     * 
     * @return boolean
     */
    protected boolean isPacketCorrupted() {
        return corrupted;
    }
}