using System;

namespace TBF.BenchControl.Network.Camera
{
	public class RtpPacket
	{
		public readonly int Version;
		public readonly bool P;
		public readonly bool X;
		public readonly int CC;
		public readonly bool Mark;
		public readonly int PayloadType;
		public readonly int SequenceNumber;
		public readonly int Timestamp;
		public readonly int SsrcId;
		public readonly Byte[] Payload;		/// Data without RTP header

		public RtpPacket(Byte[] data)
		{
			if (data.Length < 12) throw new Exception("Packet too short");

			Version = (data[0] >> 6) & 0x02;											/// 1 RTP Version
			P = ((data[0] & 0x20) != 0);												/// 2 RTP P
			X = ((data[0] & 0x10) != 0);												/// 3 RTP X
			CC = (data[0] & 0x0F);														/// 4 RTP CC
			Mark = ((data[1] & 0x80) != 0);												/// 5 RTP M
			PayloadType = (data[1] & 0x7F);												/// 6 RTP PT
			SequenceNumber = data[2] * 256 + data[3];									/// 7 RTP Seq#
			Timestamp = ((data[4] * 256 + data[5]) * 256 + data[6]) * 256 + data[7];	/// 8 RTP Timestamp
			SsrcId = ((data[8] * 256 + data[9]) * 256 + data[10]) * 256 + data[11];		/// 9 RTP SSRC Id

			int ExtensionHeaderSize = 0;
			if (X && data.Length >= 16 + 4*CC)
			{
				ExtensionHeaderSize = data[14 + 4*CC] * 256 + data[15 + 4*CC] + 4;
			}

			int payloadDataOffset = 12 + 4 * CC + ExtensionHeaderSize;
			int payloadDataCount = data.Length - 12 - 4 * CC - ExtensionHeaderSize;

			if (payloadDataCount < 0) throw new Exception("Invalid packet");

			Payload = new byte[payloadDataCount];
			Array.Copy(data, payloadDataOffset, Payload, 0, payloadDataCount);
		}
	}
}