Simple rest-y osx text-to-speech service returning mp3's

node-tts-mp3.js

var restify = require('restify');
var crypto = require('crypto');
var spawn = require('child_process').spawn;
var fs = require('fs');

function voiceRespond(req, res, next) {
  var voice = req.params.voice;
	var text = req.query.text;
	var key = voice+'___'+text;
	var hash = crypto.createHash('md5').update(key).digest("hex");
	var fileprefix = '/tmp/voice_'+hash;
	var aiff = fileprefix+'.aiff';
	var mp3 = fileprefix+'.mp3';
	var applescript = 'say "' + text +'" using "'+voice+'" saving to "'+aiff+'"';

	// if file exists, don't transcode, just return mp3
	if (fs.existsSync(mp3)) {
		// res.send('cached voice.');
	    fs.readFile(mp3, function (err, data) {
	        res.setHeader('Content-Type', 'audio/mp3');
	        res.writeHead(200);
	        res.end(data);
		});
		return;
	}

	// speak
	var proc  = spawn('osascript', ['-e', applescript]);
	proc.on('exit', function (code, signal) {
	  console.log('child process terminated due to receipt of signal '+signal);
		// transcode
		var proc2  = spawn('lame', [aiff, mp3]);
		proc2.on('exit', function (code, signal) {
		  console.log('child process terminated due to receipt of signal '+signal);
			// res.send('voice ' + voice + ';; text ' + text+';; script '+applescript);
		    fs.readFile(mp3, function (err, data) {
		        res.setHeader('Content-Type', 'audio/mp3');
		        res.writeHead(200);
		        res.end(data);
			});
		});
	});
}

function indexRespond(req, res, next) {
    res.setHeader('Content-Type', 'text/html');
    res.writeHead(200);
	res.end('try <a href=\"/v/fred/audio.mp3?text=hello%20world\">/v/fred/audio.mp3?text=hello%20world</a>');
}

var server = restify.createServer();

server.use(restify.queryParser());

server.get('/', indexRespond);
server.head('/', indexRespond);

server.get('/v/:voice/audio.mp3', voiceRespond);
server.head('/v/:voice/audio.mp3', voiceRespond);

server.listen(8080, function() {
  console.log('%s listening at %s', server.name, server.url);
});