Distributed Command Pattern - an extension of command pattern for connected systems

using System;
using System.Net.Sockets;
using System.Collections;
using System.Text;
using System.IO;

namespace DistributedCommand.HTTPProvider
{
	public class HttpMessageException : Exception
	{
		public HttpMessageException( String status, String reason )
		{
			Error = new HttpMessage( );
			Error.Status = status;
			Error.Reason = reason;
			Error.Version = "HTTP/1.1";
		}

		public HttpMessage Error;
	}

	public class HttpMessage
	{
		public HttpMessage( )
		{
			CorrelationID = String.Empty;
		}

		public void Send( NetworkStream stream )
		{
			StringBuilder sb = new StringBuilder( );
			// build first line
			if ( IsResponse )
			{
				sb.Append( Version );
				sb.Append( ' ' );
				sb.Append( Status );
				sb.Append( ' ' );
				sb.Append( Reason );
			}
			else
			{
				sb.Append( Verb );
				sb.Append( ' ' );
				sb.Append( RequestUri );
				sb.Append( ' ' );
				sb.Append( Version );
				if ( CorrelationID == String.Empty )
					CorrelationID = Guid.NewGuid( ).ToString( );
			}
			sb.Append( "\r\n" );

			if ( body.Length > 0 )
				ContentLength = body.Length;

			// build headers
			IDictionaryEnumerator itr = Headers.GetEnumerator( );
			while ( itr.MoveNext( ) )
			{
				sb.Append( itr.Key as String );
				sb.Append( ": " );
				sb.Append( itr.Value as String );
				sb.Append( "\r\n" );
			}
			sb.Append( "\r\n" );

			// convert to bytes
			Byte[] bytes = Encoding.UTF8.GetBytes( sb.ToString( ) );

			stream.Write( bytes, 0, bytes.Length );
			stream.Write( body, 0, body.Length );
			stream.Flush( );

		}

		private void ThrowBadRequest( )
		{
			throw new HttpMessageException( "400", "Bad request" );
		}

		public void Receive( NetworkStream stream )
		{
			// allocate inital buffer
			MemoryStream mem = new MemoryStream( );

			// read the HTTP headers
			bool completed = false;
			do
			{
				int b = 0;
				b = stream.ReadByte( );

				if ( b == 0x0d )
				{
					mem.WriteByte( (byte) b ); // add '\r'
					b = stream.ReadByte( );
					mem.WriteByte( (byte) b ); // add '\n'
					completed = true;
					break;
				}

				while ( b != 0x0d )
				{
					mem.WriteByte( (byte) b );
					b = stream.ReadByte( );
				}
				mem.WriteByte( (byte) b ); // add '\r'
				b = stream.ReadByte( );
				mem.WriteByte( (byte) b ); // add '\n'

			} while ( stream.DataAvailable );

			if ( !completed )
				ThrowBadRequest( );

			mem.Position = 0;
			StreamReader reader = new StreamReader( mem, Encoding.UTF8 );

			// read and process first line
			String line = reader.ReadLine( );

			int n = line.IndexOf( ' ' );
			if ( n == -1 )
				ThrowBadRequest( );

			String str = line.Substring( 0, n );
			if ( str.ToUpper( ).StartsWith( "HTTP" ) )
			{
				Version = str;

				line = line.Substring( n + 1 );
				n = line.IndexOf( ' ' );
				if ( n == -1 )
					ThrowBadRequest( );

				Status = line.Substring( 0, n );
				Reason = line.Substring( n + 1 );

			}
			else
			{
				Verb = str;

				line = line.Substring( n + 1 );
				n = line.IndexOf( ' ' );
				if ( n == -1 )
					ThrowBadRequest( );

				RequestUri = line.Substring( 0, n );
				Version = line.Substring( n + 1 );
			}


			// read all the headers
			String[] tokens;
			line = reader.ReadLine( );
			while ( line != null && line != String.Empty )
			{
				tokens = line.Split( ':' );
				String name = tokens[0].Trim( );
				Headers[name] = tokens[1].Trim( );
				line = reader.ReadLine( );
			}

			// now go for the message body if there is one
			int len = ContentLength;
			if ( len == 0 )
				return;

			int totalBytesRead = 0;

			// Read until specified content length is fully read
			MemoryStream bodyStream = new MemoryStream(ContentLength);
			Byte[] buffer = new Byte[len];
			while( totalBytesRead < ContentLength )
			{
				int bytesRead = stream.Read( buffer, 0, buffer.Length );
				bodyStream.Write( buffer, 0, bytesRead );

				totalBytesRead += bytesRead;
			}

			body = bodyStream.GetBuffer();
		}


		public bool IsResponse
		{
			get { return Verb == null || Verb == String.Empty; }
		}


		public Hashtable Headers = new Hashtable( );

		public String CorrelationID
		{
			get { return Headers["Correlation-Id"] as String; }
			set { Headers["Correlation-Id"] = value; }
		}


		public int ContentLength
		{
			get
			{
				String tmp = Headers["Content-Length"] as String;
				return (tmp != null) ? int.Parse( tmp ) : 0;
			}
			set { Headers["Content-Length"] = value.ToString( ); }
		}


		private Byte[] body = new Byte[0];

		public Byte[] Body
		{
			get { return body; }
			set
			{
				body = value;
				if ( body.Length > 0 )
					ContentLength = body.Length;
			}
		}

		// first line tokens 
		public String Verb;
		public String RequestUri;
		public String Version;
		public String Status;
		public String Reason;
	}
}