server.js

// Dependencies
//
var express = require('express')
  , http = require('http')
  , path = require('path')
  , WebSocket = require('ws')
  , WebSocketServer = WebSocket.Server
  , TwitterFinder = require('./tfinder');


// Get the Twitter access keys from
// the environment variable TWITTER_KEYS
//
var TwitterKeys = {};

if ( process.env.TWITTER_KEYS ) {
  console.log('Got TWITTER_KEYS');
  var k = JSON.parse(process.env.TWITTER_KEYS);

  TwitterKeys.consumer_key = k.consumer_key;
  TwitterKeys.consumer_secret = k.consumer_secret;
  TwitterKeys.access_token_key = k.access_token_key;
  TwitterKeys.access_token_secret = k.access_token_secret;
}

if ( TwitterKeys.consumer_key === undefined ||
     TwitterKeys.consumer_secret === undefined ||
     TwitterKeys.access_token_key === undefined ||
     TwitterKeys.access_token_secret === undefined ) {
  console.log('ERROR: at least one Twitter access key is not set.');
}

var app = express();

// all environments
app.set('port', process.env.PORT || 3000);
app.set('views', __dirname + '/views');
app.set('view engine', 'jade');
app.use(express.favicon());
app.use(express.logger('dev'));
app.use(express.bodyParser());
app.use(express.methodOverride());
app.use(app.router);
app.use(express.static(path.join(__dirname, 'public')));

// development only
if ('development' === app.get('env')) {
  app.use(express.errorHandler());
}

var server = http.createServer(app).listen(app.get('port'), function() {
  console.log('TOTEM server listening on port ' + app.get('port'));
});

// Create the WebSocket endpoint that does the job
//
var searchServer = new WebSocketServer( {server: server, path: '/search'});

// One connection manages one twitter search.
// To stop current search simply close this connection.
//
searchServer.on('connection', function(ws) {
  console.log('>> searchServer.on connection');

  // Create a twitter finder for the duration of the connection
  //
  var finder = new TwitterFinder(TwitterKeys);

  // Set the events handlers on the websocket
  //
  ws.on('message', function(searchstring, flags) {
    console.log('>> ws.on message');

    // Ignore the message if the search is already running
    // The client must close the connection to stop searching
    //
    if ( finder.isRunning() ) {
      console.log('Finder already running.');
      return;
    }

    finder.on('data', function(tweets) {
      console.log('Sending ' + tweets.length + ' tweets matching the query ' + searchstring);

      // Function to transform the tweet.text to a html snippet to be sent to the client
      //
      var tweetToText = function(tweet) {
        var msg = '@' + tweet.user.screen_name + ' on ' + tweet.created_at + ' said -> ' + tweet.text;
        return msg
                .replace(/((http|ftp|https):\/\/[\w-]+(\.[\w-]+)+([\w.,@?^=%&amp;:\/~+#-]*[\w@?^=%&amp;\/~+#-])?)/g, '<a href="$1">$1</a>')
                .replace(/(@([A-Za-z0-9_]+))/g, '<a href="https://twitter.com/$2">$1</a>')
                .replace(/(\#([A-Za-z0-9_]+))/g, '<a href="https://twitter.com/search?q=%23$2&src=hash">$1</a>');
      };

      // This is the format of the object that should be sent:
      //
      // {
      //   address: "user.location attribute of the tweet",
      //   text: "text attribute of the tweet formatted as html"
      // }
      //
      // Get tweets from the bottom of the array to start
      // from the oldest.
      //
      for (var i=tweets.length-1; i>=0; i--) {
        var data = { address: tweets[i].user.location,
                     text:     tweetToText(tweets[i]) };
        ws.send(JSON.stringify(data));
      }
    });

    finder.on('stop', function(reason) {
      console.log('Twitter finder stopped. Reason: ', reason);
    });

    finder.on('error', function(err) {
      console.log('Twitter finder reported an error: ', err);

      // Stop the finder and close the socket
      finder.stop(err);
      ws.close(1001, err.message);
    });

    console.log('Start a new search for: ', searchstring);
    finder.start(searchstring);
  });

  ws.on('close', function(code, reason) {
    console.log('>> ws.on close');
    console.log('Socket closed. Code: ' + code + ', reason: ' + reason);

    // Stop the finder
    //
    finder.stop(new Error('Socket closed by the client'));
  });

  ws.on('error', function(err) {
    // Just log the error. You don't need to do anything else
    // because the WebSocket triggers the close event shortly.
    //
    console.log('>> ws.on error: ', err);
  });
});