using System;

namespace Cosmos.Sys.Network.TCPIP.UDP
{
    internal class UDPPacket : IPPacket
    {
        protected UInt16 sourcePort;
        protected UInt16 destPort;
        protected UInt16 udpLen;
        protected UInt16 udpCRC;

        internal UDPPacket(byte[] rawData)
            : base(rawData)
        {}

        internal UDPPacket(IPv4Address source, IPv4Address dest, UInt16 srcPort, UInt16 destPort, byte[] data)
            : base((UInt16)(data.Length+8), 17, source, dest)
        {
            mRawData[this.dataOffset + 0] = (byte)((srcPort >> 8) & 0xFF);
            mRawData[this.dataOffset + 1] = (byte)((srcPort >> 0) & 0xFF);
            mRawData[this.dataOffset + 2] = (byte)((destPort >> 8) & 0xFF);
            mRawData[this.dataOffset + 3] = (byte)((destPort >> 0) & 0xFF);
            udpLen = (UInt16)(data.Length + 8);
            mRawData[this.dataOffset + 4] = (byte)((udpLen >> 8) & 0xFF);
            mRawData[this.dataOffset + 5] = (byte)((udpLen >> 0) & 0xFF);
            mRawData[this.dataOffset + 6] = 0;
            mRawData[this.dataOffset + 7] = 0;
            for (int b = 0; b < data.Length; b++)
            {
                mRawData[this.dataOffset + 8 + b] = data[b];
            }

            initFields();
        }

        protected override void initFields()
        {
            base.initFields();
            sourcePort = (UInt16)((mRawData[this.dataOffset] << 8) | mRawData[this.dataOffset + 1]);
            destPort = (UInt16)((mRawData[this.dataOffset + 2] << 8) | mRawData[this.dataOffset + 3]);
            udpLen = (UInt16)((mRawData[this.dataOffset + 4] << 8) | mRawData[this.dataOffset + 5]);
            udpCRC = (UInt16)((mRawData[this.dataOffset + 6] << 8) | mRawData[this.dataOffset + 7]);
        }

        internal UInt16 DestinationPort
        {
            get { return this.destPort; }
        }
        internal UInt16 SourcePort
        {
            get { return this.sourcePort; }
        }
        internal UInt16 UDP_Length
        {
            get { return this.udpLen; }
        }
        internal UInt16 UDP_DataLength
        {
            get { return (UInt16)(this.udpLen - 8); }
        }
        internal byte[] UDP_Data
        {
            get
            {
                byte[] data = new byte[this.udpLen - 8];

                for (int b = 0; b < data.Length; b++)
                {
                    data[b] = this.mRawData[this.dataOffset + 8 + b];
                }

                return data;
            }
        }

        public override string ToString()
        {
            return "UDP Packet Src=" + sourceIP + ":" + sourcePort + ", Dest=" + destIP + ":" + destPort + ", DataLen=" + UDP_DataLength;
        }
    }
}