mclarens.js

/*
 * Mclarens Bar: Redis based Instant Messaging
 * Nikhil Marathe - 22/04/2010

 * A simple example of an IM client implemented using
 * Redis PUB/SUB commands so that all the communication
 * is offloaded to Redis, and the node.js code only
 * handles command interpretation,presentation and subscribing.
 * 
 * Requires redis-node-client and a recent version of Redis
 *    http://code.google.com/p/redis
 *    http://github.com/fictorial/redis-node-client
 *
 * Start the server then telnet to port 8000
 * Register with NICK <nick>, use WHO to see others
 * Use TALKTO <nick> to initiate a chat. Send a message
 * using MSG <nick> <msg>. Note its important to do a
 * TALKTO so that both sides are listening. Use STOP <nick>
 * to stop talking to someone, and QUIT to exit.
 *
 * This code is in the public domain.
 */
var redis = require('./redis-node-client/lib/redis-client');

var sys = require('sys');
var net = require('net');

var server = net.createServer(function(stream) {
    var sub; // redis connection
    var pub;
    var registered = false;
    var nick = "";

    function channel(a,b) {
	return [a,b].sort().join(':');
    }

    function shareTable(other) {
	sys.debug(nick + ": Subscribing to "+channel(nick,other));
	sub.subscribeTo(channel(nick,other), function(channel, message) {
	    var str = message.toString();
	    var sender = str.slice(0, str.indexOf(':'));
	    if( sender != nick )
		stream.write("[" + sender + "] " + str.substr(str.indexOf(':')+1) + "\n");
	});
    }

    function leaveTable(other) {
	sub.unsubscribeFrom(channel(nick,other), function(err) {
	    stream.write("Stopped talking to " + other+ "\n");
	});
    }

    stream.addListener("connect", function() {
	sub = redis.createClient();
	pub = redis.createClient();
    });

    stream.addListener("data", function(data) {
	if( !registered ) {
	    var msg = data.toString().match(/^NICK (\w*)/);
	    if(msg) {
		stream.write("SERVER: Hi " + msg[1] + "\n");
		pub.sadd('mclarens:inside', msg[1], function(err) {
		    if(err) {
			stream.end();
		    }
		    registered = true;
		    nick = msg[1];
// server messages
		    sub.subscribeTo( nick + ":info", function(nick, message) {
			var m = message.toString().split(' ');
			var cmd = m[0];
			var who = m[1];
			if( cmd == "start" ) {
			    stream.write( who + " is now talking to you\n");
			    shareTable(who);
			}
			else if( cmd == "stop" ) {
			    stream.write( who + " stopped talking to you\n");
			    leaveTable(who);
			}
		    });
		});
	    }
	    else {
		stream.write("Please register with NICK <nickname>\n");
	    }
	    return;
	}

	var fragments = data.toString().replace('\r\n', '').split(' ');
	switch(fragments[0]) {
	case 'TALKTO':
	    pub.publish(fragments[1]+":info", "start " + nick, function(a,b) {
	    });
	    shareTable(fragments[1]);
	    break;
	case 'MSG':
	    pub.publish(channel(nick, fragments[1]),
			nick + ':' +fragments.slice(2).join(' '),
		      function(err, reply) {
			  if(err) {
			      stream.write("ERROR!");
			  }
		      });
	    break;
	case 'WHO':
	    pub.smembers('mclarens:inside', function(err, users) {
		stream.write("Online:\n" + users.join('\n') + "\n");
	    });
	    break;
	case 'STOP':
	    leaveTable(fragments[1]);
	    pub.publish(fragments[1]+":info", "stop " + nick, function() {});
	    break;
	case 'QUIT':
	    stream.end();
	    break;
	}
    });

    stream.addListener("end", function() {
	pub.publish(nick, nick + " is offline");
	pub.srem('mclarens:inside', nick, function(err) {
	    if(err) {
		sys.debug("Could not remove client");
	    }
	});
    });
});

server.listen(8000, "localhost");