﻿/* Copyright (c) 2010 Michael Lidgren

Permission is hereby granted, free of charge, to any person obtaining a copy of this software
and associated documentation files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom
the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or
substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
USE OR OTHER DEALINGS IN THE SOFTWARE.

*/
using System;
using System.Diagnostics;

namespace Lidgren.Network
{
	/// <summary>
	/// Outgoing message used to send data to remote peer(s)
	/// </summary>
	[DebuggerDisplay("LengthBits={LengthBits}")]
	public sealed partial class NetOutgoingMessage
	{
		internal NetMessageType m_messageType;
		internal bool m_isSent;
		internal int m_recyclingCount;

		internal int m_fragmentGroup;             // which group of fragments ths belongs to
		internal int m_fragmentGroupTotalBits;    // total number of bits in this group
		internal int m_fragmentChunkByteSize;	  // size, in bytes, of every chunk but the last one
		internal int m_fragmentChunkNumber;       // which number chunk this is, starting with 0

		internal NetOutgoingMessage()
		{
		}

		internal void Reset()
		{
			m_messageType = NetMessageType.LibraryError;
			m_bitLength = 0;
			m_isSent = false;
			m_recyclingCount = 0;
			m_fragmentGroup = 0;
		}

		internal int Encode(byte[] intoBuffer, int ptr, int sequenceNumber)
		{
			//  8 bits - NetMessageType
			//  1 bit  - Fragment?
			// 15 bits - Sequence number
			// 16 bits - Payload length in bits
			
			intoBuffer[ptr++] = (byte)m_messageType;

			byte low = (byte)((sequenceNumber << 1) | (m_fragmentGroup == 0 ? 0 : 1));
			intoBuffer[ptr++] = low;
			intoBuffer[ptr++] = (byte)(sequenceNumber >> 7);

			if (m_fragmentGroup == 0)
			{
				intoBuffer[ptr++] = (byte)m_bitLength;
				intoBuffer[ptr++] = (byte)(m_bitLength >> 8);

				int byteLen = NetUtility.BytesToHoldBits(m_bitLength);
				if (byteLen > 0)
				{
					Buffer.BlockCopy(m_data, 0, intoBuffer, ptr, byteLen);
					ptr += byteLen;
				}
			}
			else
			{
				int wasPtr = ptr;
				intoBuffer[ptr++] = (byte)m_bitLength;
				intoBuffer[ptr++] = (byte)(m_bitLength >> 8);

				//
				// write fragmentation header
				//
				ptr = NetFragmentationHelper.WriteHeader(intoBuffer, ptr, m_fragmentGroup, m_fragmentGroupTotalBits, m_fragmentChunkByteSize, m_fragmentChunkNumber);
				int hdrLen = ptr - wasPtr - 2;

				// update length
				int realBitLength = m_bitLength + (hdrLen * 8);
				intoBuffer[wasPtr] = (byte)realBitLength;
				intoBuffer[wasPtr + 1] = (byte)(realBitLength >> 8);

				int byteLen = NetUtility.BytesToHoldBits(m_bitLength);
				if (byteLen > 0)
				{
					Buffer.BlockCopy(m_data, (int)(m_fragmentChunkNumber * m_fragmentChunkByteSize), intoBuffer, ptr, byteLen);
					ptr += byteLen;
				}
			}

			NetException.Assert(ptr > 0);
			return ptr;
		}

		internal int GetEncodedSize()
		{
			int retval = 5; // regular headers
			if (m_fragmentGroup != 0)
				retval += NetFragmentationHelper.GetFragmentationHeaderSize(m_fragmentGroup, m_fragmentGroupTotalBits / 8, m_fragmentChunkByteSize, m_fragmentChunkNumber);
			retval += this.LengthBytes;

			return retval;
		}

		/// <summary>
		/// Encrypt this message using the XTEA algorithm; no more writing can be done before sending it
		/// </summary>
		public void Encrypt(NetXtea tea)
		{
			// need blocks of 8 bytes
			WritePadBits();
			int blocksNeeded = (m_bitLength + 63) / 64;
			int missingBits = (blocksNeeded * 64) - m_bitLength;
			int missingBytes = NetUtility.BytesToHoldBits(missingBits);
			for (int i = 0; i < missingBytes; i++)
				Write((byte)0);

			byte[] result = new byte[m_data.Length];
			for (int i = 0; i < blocksNeeded; i++)
				tea.EncryptBlock(m_data, (i * 8), result, (i * 8));
			m_data = result;
		}

		/// <summary>
		/// Returns a string that represents this object
		/// </summary>
		public override string ToString()
		{
			return "[NetOutgoingMessage " + m_messageType + " " + this.LengthBytes + " bytes]";
		}
	}
}
