JavaScript TwiML generator

example.js

Twilio = Object.create({})
Twilio.TwiML = {
  build: function(fn) {
    var prolog = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n";
    var Buffer = function(level) {
      var buffer = "";
      var indent = function(i) { return new Array((i * 2) + 1).join(" ") }
      var level  = level || 1;
      var append = function(str) {
        buffer += indent(++level) + str + "\n";
        level--;
      }

      var toAttributes = function(obj) {
        var string = "";
        for (key in obj) { string += " " + key + "=" + "\"" + obj[key] + "\"" }
        return string;
      }

      var commonElement = function(verb) {
        return function(str, attributes) {
          append("<" + verb + toAttributes(attributes) + ">" + str + "</" + verb + ">")
        }
      }

      var emptyElement = function(verb) {
        return function(attributes) { append("<" + verb + toAttributes(attributes) + " />") }
      }

      var containerElement = function(verb) {
        return function(fn, attributes) {
          var buffer = new Buffer(level + 2);
          append('<'+ verb + toAttributes(attributes) + '>');
          fn(buffer);
          level -= 2;
          append(buffer.emit().replace(/\n$/, ''));
          level += 2;
          append('</' + verb + '>');
        }
      }

      this.dial = function(arg, attributes) {
        switch(typeof arg) {
          case 'function':
            return containerElement('Dial')(arg, attributes);
            break;
          case 'string':
            return commonElement('Dial')(arg, attributes);
            break;
        }
      }

      this.say        = commonElement('Say');
      this.play       = commonElement('Play');
      this.redirect   = commonElement('Redirect');
      this.number     = commonElement('Number');
      this.client     = commonElement('Client');
      this.conference = commonElement('Conference');

      this.hangup     = emptyElement('Hangup');
      this.reject     = emptyElement('Reject');
      this.record     = emptyElement('Record');
      this.pause      = emptyElement('Pause');

      this.gather     = containerElement('Gather');

      this.emit       = function() { return buffer }
    }

    var buffer = new Buffer;

    fn(buffer);

    return prolog + "<Response>\n" + buffer.emit() + "</Response>";
  }
}

output.xml

<?xml version="1.0" encoding="UTF-8"?>
<Response>
    <Play loop="14">/welcome.mp3</Play>
    <Say loop="10" voice="woman" language="en-gb">Holy shit, batman!</Say>
    <Dial action="/bar" method="GET" timeout="60" hangupOnStar="true" timeLimit="600" callerId="+2125550000" record="true">
        <Number sendDigits="1234#" url="/pre_roll">+12125551234</Number>
    </Dial>
    <Dial>
        <Client>johnny</Client>
        <Number>+12123450000</Number>
    </Dial>
    <Dial>
        <Conference muted="true" beep="false" startConferenceOnEnter="false" endConferenceOnExit="false" waitUrl="/hold_music" waitMethod="GET" maxParticipants="10">devangels</Conference>
    </Dial>
    <Dial action="/foo">+16465551234</Dial>
    <Gather action="/dtmf" method="POST" timeout="60" finishOnKey="*" numDigits="16">
        <Say>please choose an option</Say>
        <Play>/decision_music.mp3</Play>
        <Pause />
    </Gather>
    <Record action="/callback" method="POST" timeout="5" finishOnKey="#" maxLength="30" transcribe="true" transcribeCallback="/transcribe" />
    <Reject reason="busy" />
    <Pause length="1" />
    <Redirect>http://example.com/foo</Redirect>
    <Hangup />
</Response>

twiml_generator.js

Twilio.TwiML.build(function(res) {
    res.play("/welcome.mp3", { loop: 14 });

    res.say("Holy shit, batman!", { loop: 10, voice: 'woman', language: 'en-gb' });

    res.dial(function(res) { res.number("+12125551234", { sendDigits: '1234#', url: '/pre_roll' }) },
      { action: '/bar', method: 'GET', timeout: 60, hangupOnStar: true,
        timeLimit: 600, callerId: '+2125550000', record: true });

    res.dial(function(res) {
      res.client("johnny");
      res.number("+12123450000");
    });

    res.dial(function(res) { res.conference("devangels", { muted: true, beep: false,
      startConferenceOnEnter: false, endConferenceOnExit: false,
      waitUrl: '/hold_music', waitMethod: 'GET', maxParticipants: 10 }) });

    res.dial("+16465551234", { action: '/foo' } );

    res.gather(function(res) {
      res.say('please choose an option');
      res.play('/decision_music.mp3');
      res.pause();
    }, { action: '/dtmf', method: 'POST', timeout: 60, finishOnKey: '*', numDigits: 16 })

    res.record({ action: '/callback', method: 'POST',
                 timeout: 5, finishOnKey: "#", maxLength: 30,
                 transcribe: true, transcribeCallback: '/transcribe' })

    res.reject({ reason: 'busy' });
    res.pause({length: 1});
    res.redirect('http://example.com/foo');
    res.hangup();
})