index.js

var http = require('http')
  , os = require('os')
  , fs = require('fs')
  , glob = require('glob')
  , util = require('util')
  , exec = require('child_process').exec
  , request = require('request')
  , static = require('node-static')
  , url = require('url')
  , twilio = require('twilio')
  , uuid = require('node-uuid')
  , child;

// The directory where our animated gifs will live
var dir = new static.Server('./public');

// Twilio REST client
var client = new twilio.RestClient();

/**
 * Delete any temp files that may have been created
 */
var cleanUp = function(id) {
  console.log('Cleaning up temp files');
  glob(os.tmpdir() + "/" + id + "*", function (err, files) {
    files.forEach(function(file) {
      fs.unlink(file, function (err) {});
    });
  });
};

/**
 * Send an MMS with an animated GIF attached
 */
var sendGif = function(host, id, from, to) {
  // an assumption made here is that the protocol is HTTP
  var gifUrl = 'http://' + host + '/' + id + '.gif';
  console.log('Success! Gif URL: ', gifUrl);
  client.sendMessage({
    to: from, from: to, 
    body: 'Powered by Twilio MMS',
    mediaUrl: gifUrl}, function(err, responseData) { 
      if (err) {
        console.log('Error sending MMS: ', JSON.stringify(err));
      }
    });
};

/**
 * Download the video, convert it into a GIF, send an MMS
 */
var processVideo = function(mediaUrl, host, from, to) {
  // create a unique UUID for all of our video/gif processing
  var id = uuid.v1();

  // Save the remote movie file to the /tmp fs
  download = request(mediaUrl).pipe(fs.createWriteStream(
    util.format('%s/%s', os.tmpdir(), id)));

  download.on('finish', function() {
    // Once it's saved, it's time to spin-up a child process to
    // handle decoding the video and building the gif
    var cmd = util.format('avconv -i %s/%s -r 8 -vframes 48 -f image2 %s/%s-%03d.jpeg && convert -delay 12 -loop 0 %s/%s*.jpeg %s/public/%s.gif && convert %s/public/%s.gif -layers optimizeplus %s/public/%s.gif', os.tmpdir(), id, os.tmpdir(), id, os.tmpdir(), id, __dirname, id, __dirname, id, __dirname, id);
    child = exec(cmd, function (error, stdout, stderr) {
      if (error !== null) {
         console.log('exec error: ' + error);
         client.sendMessage({
           to: from, from: to, 
           body: 'Very sorry but an error occurred processing your video. Try a different video?'}, 
           function(err, responseData) { 
             if (err) {
               console.log('Error sending text: ' + JSON.stringify(err));
             }
           });
       }
       else {
         sendGif(host, id, from, to);
       }
       cleanUp(id);
    });
  });
};

/**
 * Handle requests for /message
 */
var handleMessage = function(req, res) {
  // Parse the request URL
  var hash = url.parse(req.url, true);
  // This is the phone number of the person who sent the video
  var from = hash.query['From'];
  // This is the phone number the video was sent to
  var to = hash.query['To'];
  // This is the URL of the file being sent
  var mediaUrl = hash.query['MediaUrl0'];
  // This is the content type of that file
  var mediaContentType = hash.query['MediaContentType0'];
  // This is the host the machine serving this Node process 
  var host = req.headers['host']; 

  console.log('Processing MMS: ', mediaUrl, mediaContentType);

  res.writeHead(200, {'Content-type': 'text/xml'});
  var twiml = new twilio.TwimlResponse();
  // if media URL looks like a valid video, send ok back to the user
  if (mediaContentType.indexOf('video') >= 0) { 
    twiml.message('Video queued for processing, hang tight!');
    res.end(twiml.toString());
    processVideo(mediaUrl, host, from, to);
  }
  else {
    twiml.message('This is not a video format that we recognize. Try again?');
    res.end(twiml.toString());
  }
};

// Spin up our HTTP server
http.createServer(function(req, res) {
  req.addListener('end', function () {
    // if the requested path is /message, process the incoming MMS content
    if (url.parse(this.url).pathname === '/message') {
      handleMessage(req, res);
    }
    // else serve static files
    else {
      dir.serve(req, res);
    }
  }).resume();
}).listen(process.env.PORT || 3000);

console.log('Listening on port ', process.env.PORT || 3000);