Node smtp server

/*
 
  smtpd.js is SMTP server written for node.js
 
  MIT License
*/
 
var tcp = require('tcp');
var sys = require('sys');
 
var enable_debug = true;
 
var server = tcp.createServer( function( socket ) 
{
	var eol = "\r\n";

	// patterns for commands
	var command_patterns = 
	{
		helo: /^HELO\s*/i,
		ehlo: /^EHLO\s*/i,
		quit: /^QUIT/i,
		from: /^MAIL FROM:\s*/i,
		rcpt: /^RCPT TO:\s*/i,
		data: /^DATA/i,
		noop: /^NOOP/i,
		rset: /^RSET/i,
		vrfy: /^VRFY\s+/i,
		expn: /^EXPN\s+/,
		help: /^HELP/i,
		tls: /^STARTTLS/i,
		auth: /^AUTH\s+/i
	}
 
	// our replies
	var reply =
	{
		send: function(s) {
		  debug( "reply: '" + (s || "null") + "'" );
		  socket.write( s + eol );
		},
		banner: function() {
		  reply.send("220 <hostname> ESMTP smtpd.js");
		},
		error: function(s) {
		  reply.send("500 " + s);
		},
		ok: function() {
		  reply.send("250 OK");
		}
  }
 
	function Command( line ) 
	{
		function parseCommand( line ) 
		{
			for( var cmd in command_patterns) 
			{
				if (command_patterns[ cmd ].test( buffer ) ) 
				{
					return cmd;
				}
			}
		}

		function extractArguments( command ) 
		{
			return this.line.replace( command, '' ).replace(/^\s\s*/, '').replace(/\s\s*$/, '');
		}
		
		this.cmd     = parseCommand( line ).toLowerCase();
		this.line    = line;
		this.in_data = false;
		this.data    = [];

		this.isRecognized = function() 
		{
			return typeof this.cmd != "undefined";
		}

		this.exec = function() 
		{
			if ( callbacks[this.cmd] ) 
			{
				callbacks[this.cmd].callback(this.line);
			}
			else 
			{
				reply.error("command not implemented");
			}
		}
		
		var that = this;

		var callbacks = {
			quit: {
				callback: function () 
				{
					reply.send( '221 <hostname> closing connection' );
					socket.close();
				}
			},
			ehlo: {
				callback: function() 
				{
					var hostname = extractArguments( 'EHLO' );
					reply.send('250-<hostname> Hello ' + socket.remoteAddress );
					reply.send('250 8BITMIME');
				}
			},
			helo: {
				callback: function() 
				{
					reply.send('250 <hostname> Hello ' + socket.remoteAddress );
				}
			},
			from: {
				callback: function() 
				{
					this.from = extractArguments( 'MAIL FROM:' );
					reply.ok();
				}
			},
			rcpt: {
				callback: function() 
				{
					this.recipient = extractArguments( 'RCPT TO:' );
					reply.ok();
				}
			},
			data: {
				callback: function() 
				{
					that.in_data = true;
					reply.send("354 Terminate with line containing only '.'");
				}
			}
		}

		this.appendData = function( buffer ) 
		{
			var size = buffer.length;
			var line = "";

			for( var i = 0; i < buffer.length; i++ )
			{
				var chr = buffer[i];
				
				if( chr + buffer[i + 1] == eol ) 
				{
					if(line[0] == '.' && line.length == 1)
					{
						this.in_data = false;
						break;
					}
					else
					{
						// http://tools.ietf.org/html/rfc5321#section-4.5.2
						if(line[0] == '.' && line.length > 1) line = line.substr(1);
						
						sys.puts("INSERTING LINE INTO DATA: "+line)
						this.data.push( line );
						line = "";
						i++;
						continue;
					}
				}
				
				line += chr;
			}
			
			/*var size = this.data.length - 1;
			
			if( this.data[size] == '.')// && this.data[size - 1] == '' ) 
			{
				this.in_data = false;
				this.data.pop();
				this.data.pop();
			}
			*/
		}
		
		return this;
	}
 
	function debug(s) 
	{
		if( enable_debug && s != null ) 
		{
			sys.print( s.toString() + eol );
			sys.print('----------------------------' + eol );
		}
	}
 
	socket.addListener('connect', function() 
	{
		reply.banner();
	});
 
	var buffer = "";
	var cmd = {};

	socket.addListener('data', function(packet)
	{
		buffer += packet;
		
		while( buffer.indexOf(eol) != -1 ) 
		{
			if ( cmd.in_data )
			{
				cmd.appendData( buffer );
				
				// we're finished
				if( !cmd.in_data )
				{
					reply.ok();
				}
			}
			else 
			{
				cmd = Command( buffer );

				if ( cmd.isRecognized() )
				{
					cmd.exec();
				} 
				else 
				{
					reply.error('unrecognized command');
				}
			}
			
			buffer = "";
		}
	});
	
	socket.addListener('end', function()
	{
		socket.close();
		sys.puts("Closing Connection");
	});
});
 
exports.runServer = function() 
{
	server.listen( 25 );
	sys.puts("SMTMP server running on port 25");
}

server.listen( 25 );
sys.puts("SMTMP server running on port 25");