/**
 *    Copyright 2011, Big Switch Networks, Inc.
 *    Originally created by David Erickson, Stanford University
 *
 *    Licensed under the Apache License, Version 2.0 (the "License"); you may
 *    not use this file except in compliance with the License. You may obtain
 *    a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 *    License for the specific language governing permissions and limitations
 *    under the License.
 **/

package net.onrc.onos.core.packet;

import java.nio.ByteBuffer;

/**
 * @author shudong.zhou@bigswitch.com
 */
public class TCP extends BasePacket {
    protected short sourcePort;
    protected short destinationPort;
    protected int sequence;
    protected int acknowledge;
    protected byte dataOffset;
    protected short flags;
    protected short windowSize;
    protected short checksum;
    protected short urgentPointer;
    protected byte[] options;

    /**
     * @return the sourcePort
     */
    public short getSourcePort() {
        return sourcePort;
    }

    /**
     * @param sourcePort the sourcePort to set
     */
    public TCP setSourcePort(short sourcePort) {
        this.sourcePort = sourcePort;
        return this;
    }

    /**
     * @return the destinationPort
     */
    public short getDestinationPort() {
        return destinationPort;
    }

    /**
     * @param destinationPort the destinationPort to set
     */
    public TCP setDestinationPort(short destinationPort) {
        this.destinationPort = destinationPort;
        return this;
    }

    /**
     * @return the checksum
     */
    public short getChecksum() {
        return checksum;
    }

    public int getSequence() {
        return this.sequence;
    }

    public TCP setSequence(int seq) {
        this.sequence = seq;
        return this;
    }

    public int getAcknowledge() {
        return this.acknowledge;
    }

    public TCP setAcknowledge(int ack) {
        this.acknowledge = ack;
        return this;
    }

    public byte getDataOffset() {
        return this.dataOffset;
    }

    public TCP setDataOffset(byte offset) {
        this.dataOffset = offset;
        return this;
    }

    public short getFlags() {
        return this.flags;
    }

    public TCP setFlags(short flags) {
        this.flags = flags;
        return this;
    }

    public short getWindowSize() {
        return this.windowSize;
    }

    public TCP setWindowSize(short windowSize) {
        this.windowSize = windowSize;
        return this;
    }

    public short getTcpChecksum() {
        return this.checksum;
    }

    public TCP setTcpChecksum(short checksum) {
        this.checksum = checksum;
        return this;
    }

    @Override
    public void resetChecksum() {
        this.checksum = 0;
        super.resetChecksum();
    }

    public short getUrgentPointer(short urgentPointer) {
        return this.urgentPointer;
    }

    public TCP setUrgentPointer(short urgentPointer) {
        this.urgentPointer = urgentPointer;
        return this;
    }

    public byte[] getOptions() {
        return this.options;
    }

    public TCP setOptions(byte[] options) {
        this.options = options;
        this.dataOffset = (byte) ((20 + options.length + 3) >> 2);
        return this;
    }

    /**
     * @param checksum the checksum to set
     */
    public TCP setChecksum(short checksum) {
        this.checksum = checksum;
        return this;
    }

    /**
     * Serializes the packet. Will compute and set the following fields if they
     * are set to specific values at the time serialize is called:
     * -checksum : 0
     * -length : 0
     */
    public byte[] serialize() {
        int length;
        if (dataOffset == 0)
            dataOffset = 5;  // default header length
        length = dataOffset << 2;
        byte[] payloadData = null;
        if (payload != null) {
            payload.setParent(this);
            payloadData = payload.serialize();
            length += payloadData.length;
        }

        byte[] data = new byte[length];
        ByteBuffer bb = ByteBuffer.wrap(data);

        bb.putShort(this.sourcePort);
        bb.putShort(this.destinationPort);
        bb.putInt(this.sequence);
        bb.putInt(this.acknowledge);
        bb.putShort((short) (this.flags | (dataOffset << 12)));
        bb.putShort(this.windowSize);
        bb.putShort(this.checksum);
        bb.putShort(this.urgentPointer);
        if (dataOffset > 5) {
            int padding;
            bb.put(options);
            padding = (dataOffset << 2) - 20 - options.length;
            for (int i = 0; i < padding; i++)
                bb.put((byte) 0);
        }
        if (payloadData != null)
            bb.put(payloadData);

        if (this.parent != null && this.parent instanceof IPv4)
            ((IPv4) this.parent).setProtocol(IPv4.PROTOCOL_TCP);

        // compute checksum if needed
        if (this.checksum == 0) {
            bb.rewind();
            int accumulation = 0;

            // compute pseudo header mac
            if (this.parent != null && this.parent instanceof IPv4) {
                IPv4 ipv4 = (IPv4) this.parent;
                accumulation += ((ipv4.getSourceAddress() >> 16) & 0xffff)
                        + (ipv4.getSourceAddress() & 0xffff);
                accumulation += ((ipv4.getDestinationAddress() >> 16) & 0xffff)
                        + (ipv4.getDestinationAddress() & 0xffff);
                accumulation += ipv4.getProtocol() & 0xff;
                accumulation += length & 0xffff;
            }

            for (int i = 0; i < length / 2; ++i) {
                accumulation += 0xffff & bb.getShort();
            }
            // pad to an even number of shorts
            if (length % 2 > 0) {
                accumulation += (bb.get() & 0xff) << 8;
            }

            accumulation = ((accumulation >> 16) & 0xffff)
                    + (accumulation & 0xffff);
            this.checksum = (short) (~accumulation & 0xffff);
            bb.putShort(16, this.checksum);
        }
        return data;
    }

    /* (non-Javadoc)
     * @see java.lang.Object#hashCode()
     */
    @Override
    public int hashCode() {
        final int prime = 5807;
        int result = super.hashCode();
        result = prime * result + checksum;
        result = prime * result + destinationPort;
        result = prime * result + sourcePort;
        return result;
    }

    /* (non-Javadoc)
     * @see java.lang.Object#equals(java.lang.Object)
     */
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (!super.equals(obj))
            return false;
        if (!(obj instanceof TCP))
            return false;
        TCP other = (TCP) obj;
        // May want to compare fields based on the flags set
        return (checksum == other.checksum) &&
                (destinationPort == other.destinationPort) &&
                (sourcePort == other.sourcePort) &&
                (sequence == other.sequence) &&
                (acknowledge == other.acknowledge) &&
                (dataOffset == other.dataOffset) &&
                (flags == other.flags) &&
                (windowSize == other.windowSize) &&
                (urgentPointer == other.urgentPointer) &&
                (dataOffset == 5 || options.equals(other.options));
    }

    @Override
    public IPacket deserialize(byte[] data, int offset, int length) {
        ByteBuffer bb = ByteBuffer.wrap(data, offset, length);
        this.sourcePort = bb.getShort();
        this.destinationPort = bb.getShort();
        this.sequence = bb.getInt();
        this.acknowledge = bb.getInt();
        this.flags = bb.getShort();
        this.dataOffset = (byte) ((this.flags >> 12) & 0xf);
        this.flags = (short) (this.flags & 0x1ff);
        this.windowSize = bb.getShort();
        this.checksum = bb.getShort();
        this.urgentPointer = bb.getShort();
        if (this.dataOffset > 5) {
            int optLength = (dataOffset << 2) - 20;
            if (bb.limit() < bb.position() + optLength) {
                optLength = bb.limit() - bb.position();
            }
            try {
                this.options = new byte[optLength];
                bb.get(this.options, 0, optLength);
            } catch (IndexOutOfBoundsException e) {
                this.options = null;
            }
        }

        this.payload = new Data();
        this.payload = payload.deserialize(data, bb.position(), bb.limit() - bb.position());
        this.payload.setParent(this);
        return this;
    }
}