// System.Runtime.Remoting.Channels.Tcp.TcpMessageIO.cs
//
// Author: Lluis Sanchez Gual (lluis@ideary.com)
//
// (C) 2002 Lluis Sanchez Gual

//
// 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.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
using System.Collections;
using System.IO;
using System.Text;
using System.Net.Sockets;

namespace System.Runtime.Remoting.Channels.Tcp 
{
	enum MessageStatus { MethodMessage = 0, CancelSignal = 1, Unknown = 10}

	internal class TcpMessageIO
	{
		static byte[][] _msgHeaders = 
			  {
				  new byte[] { (byte)'.', (byte)'N', (byte)'E', (byte)'T', 1, 0 },
				  new byte[] { 255, 255, 255, 255, 255, 255 }
			  };
							
		public static int DefaultStreamBufferSize = 1000;

		// Identifies an incoming message
		public static MessageStatus ReceiveMessageStatus (Stream networkStream, byte[] buffer)
		{
			try {
				StreamRead (networkStream, buffer, 6);
			} catch (Exception ex) {
				throw new RemotingException ("Tcp transport error.", ex);
			}

			try
			{
				bool[] isOnTrack = new bool[_msgHeaders.Length];
				bool atLeastOneOnTrack = true;
				int i = 0;

				while (atLeastOneOnTrack)
				{
					atLeastOneOnTrack = false;
					byte c = buffer [i];
					for (int n = 0; n<_msgHeaders.Length; n++)
					{
						if (i > 0 && !isOnTrack[n]) continue;

						isOnTrack[n] = (c == _msgHeaders[n][i]);
						if (isOnTrack[n] && (i == _msgHeaders[n].Length-1)) return (MessageStatus) n;
						atLeastOneOnTrack = atLeastOneOnTrack || isOnTrack[n];
					}
					i++;
				}
				return MessageStatus.Unknown;
			}
			catch (Exception ex) {
				throw new RemotingException ("Tcp transport error.", ex);
			}
		}
		
		static bool StreamRead (Stream networkStream, byte[] buffer, int count)
		{
			int nr = 0;
			do {
				int pr = networkStream.Read (buffer, nr, count - nr);
				if (pr == 0)
					throw new RemotingException ("Connection closed");
				nr += pr;
			} while (nr < count);
			return true;
		}

		public static void SendMessageStream (Stream networkStream, Stream data, ITransportHeaders requestHeaders, byte[] buffer)
		{
			if (buffer == null) buffer = new byte[DefaultStreamBufferSize];

			// Writes the message start header
			byte[] dotnetHeader = _msgHeaders[(int) MessageStatus.MethodMessage];
			networkStream.Write(dotnetHeader, 0, dotnetHeader.Length);

			// Writes header tag (0x0000 if request stream, 0x0002 if response stream)
			if(requestHeaders[CommonTransportKeys.RequestUri]!=null) buffer [0] = (byte) 0;
			else buffer[0] = (byte) 2;
			buffer [1] = (byte) 0 ;

			// Writes ID
			buffer [2] = (byte) 0;

			// Writes assemblyID????
			buffer [3] = (byte) 0;

			// Writes the length of the stream being sent (not including the headers)
			int num = (int)data.Length;
			buffer [4] = (byte) num;
			buffer [5] = (byte) (num >> 8);
			buffer [6] = (byte) (num >> 16);
			buffer [7] = (byte) (num >> 24);
			networkStream.Write(buffer, 0, 8);
	
			// Writes the message headers
			SendHeaders (networkStream, requestHeaders, buffer);

			// Writes the stream
			if (data is MemoryStream)
			{
				// The copy of the stream can be optimized. The internal
				// buffer of MemoryStream can be used.
				MemoryStream memStream = (MemoryStream)data;
				networkStream.Write (memStream.GetBuffer(), 0, (int)memStream.Length);
			}
			else
			{
				int nread = data.Read (buffer, 0, buffer.Length);
				while (nread > 0)
				{
					networkStream.Write (buffer, 0, nread);
					nread = data.Read (buffer, 0, buffer.Length);
				}
			}
		}
		
		static byte[] msgUriTransportKey = new byte[] { 4, 0, 1, 1 };
		static byte[] msgContentTypeTransportKey = new byte[] { 6, 0, 1, 1 };
		static byte[] msgDefaultTransportKey = new byte[] { 1, 0, 1 };
		static byte[] msgHeaderTerminator = new byte[] { 0, 0 };

		private static void SendHeaders(Stream networkStream, ITransportHeaders requestHeaders, byte[] buffer)
		{
			// Writes the headers as a sequence of strings
			if (networkStream != null)
			{
				IEnumerator e = requestHeaders.GetEnumerator();
				while (e.MoveNext())
				{
					DictionaryEntry hdr = (DictionaryEntry)e.Current;
					switch (hdr.Key.ToString())
					{
						case CommonTransportKeys.RequestUri: 
							networkStream.Write (msgUriTransportKey, 0, 4);
							break;
						case "Content-Type": 
							networkStream.Write (msgContentTypeTransportKey, 0, 4);
							break;
						default: 
							networkStream.Write (msgDefaultTransportKey, 0, 3);
							SendString (networkStream, hdr.Key.ToString(), buffer);
							networkStream.WriteByte (1);
							break;
					}
					SendString (networkStream, hdr.Value.ToString(), buffer);
				}
			}
			networkStream.Write (msgHeaderTerminator, 0, 2);	// End of headers
		}
		
		public static ITransportHeaders ReceiveHeaders (Stream networkStream, byte[] buffer)
		{
			StreamRead (networkStream, buffer, 2);
			
			byte headerType = buffer [0];
			TransportHeaders headers = new TransportHeaders ();

			while (headerType != 0)
			{
				string key;
				StreamRead (networkStream, buffer, 1);	// byte 1
				switch (headerType)
				{
					case 4: key = CommonTransportKeys.RequestUri; break;
					case 6: key = "Content-Type"; break;
					case 1: key = ReceiveString (networkStream, buffer); break;
					default: throw new NotSupportedException ("Unknown header code: " + headerType);
				}
				StreamRead (networkStream, buffer, 1);	// byte 1
				headers[key] = ReceiveString (networkStream, buffer);

				StreamRead (networkStream, buffer, 2);
				headerType = buffer [0];
			}

			return headers;
		}
		
		public static Stream ReceiveMessageStream (Stream networkStream, out ITransportHeaders headers, byte[] buffer)
		{
			headers = null;

			if (buffer == null) buffer = new byte[DefaultStreamBufferSize];

			// Reads header tag:  0 -> Stream with headers or 2 -> Response Stream
			// +
			// Gets the length of the data stream
			StreamRead (networkStream, buffer, 8);

			int byteCount = (buffer [4] | (buffer [5] << 8) |
				(buffer [6] << 16) | (buffer [7] << 24));

			// Reads the headers
			headers = ReceiveHeaders (networkStream, buffer);

			byte[] resultBuffer = new byte[byteCount];
			StreamRead (networkStream, resultBuffer, byteCount);

			return new MemoryStream (resultBuffer);
		}		

		private static void SendString (Stream networkStream, string str, byte[] buffer)
		{
			// Allocates a buffer. Use the internal buffer if it is 
			// big enough. If not, create a new one.

			int maxBytes = Encoding.UTF8.GetMaxByteCount(str.Length)+4;	//+4 bytes for storing the string length
			if (maxBytes > buffer.Length)
				buffer = new byte[maxBytes];

			int num = Encoding.UTF8.GetBytes (str, 0, str.Length, buffer, 4);

			// store number of bytes (not number of chars!)

			buffer [0] = (byte) num;
			buffer [1] = (byte) (num >> 8);
			buffer [2] = (byte) (num >> 16);
			buffer [3] = (byte) (num >> 24);

			// Write the string bytes
			networkStream.Write (buffer, 0, num + 4);
		}

		private static string ReceiveString (Stream networkStream, byte[] buffer)
		{
			StreamRead (networkStream, buffer, 4);

			// Reads the number of bytes (not chars!)

			int byteCount = (buffer [0] | (buffer [1] << 8) |
				(buffer [2] << 16) | (buffer [3] << 24));

			if (byteCount == 0) return string.Empty;

			// Allocates a buffer of the correct size. Use the
			// internal buffer if it is big enough

			if (byteCount > buffer.Length)
				buffer = new byte[byteCount];

			// Reads the string

			StreamRead (networkStream, buffer, byteCount);
			char[] chars = Encoding.UTF8.GetChars (buffer, 0, byteCount);
	
			return new string (chars);
		}
		
	}
}