Reliably record an HTTP Live Stream with node.js

hlsdump.js

var fs = require('fs');
var request = require('request');
var joinUrl = require('url').resolve;

if (process.argv.length != 3) {
    console.log("Please pass playlist URL");
    process.exit(1);
}
var plsUrl = process.argv[2];
var INTERVAL = 5 * 1000;

var seen = {};
function loop() {
    request.get({ url: plsUrl,
		  encoding: 'utf8'
		}, function(err, res, body) {
	if (!err && res.statusCode === 200) {
	    var lines = body.split("\n");
	    lines = lines.filter(function(line) {
		return line && !/^#/.test(line);
	    });
	    var urls = {};
	    lines.forEach(function(line) {
		url = joinUrl(plsUrl, line);
		urls[url] = true;
		if (!seen.hasOwnProperty(url)) {
		    download(url);
		} else {
		    console.log("already seen", line);
		}
	    });
	    seen = urls;

	    setTimeout(loop, INTERVAL);
	} else {
	    console.error(err || res.statusCode);
	    setTimeout(loop, INTERVAL);
	}
    });
}
loop();

function download(url) {
    var urlParts = url.split("/");
    var fn = Date.now() + "-" + urlParts[urlParts.length - 1];
    console.log("download", url);
    request.get(url).
	pipe(fs.createWriteStream(fn));
}