utils.js

var request = require('request');

module.exports = {

	// returns an integer in the [min, max) range
	// if only min is given, the [0, min) range
	random: function(min, max) {
		if (max === undefined) {
			max = min;
			min = 0;
		}

		return min + Math.floor(Math.random() * (max - min));
	},

	// replaces {0}, {1}, ..., {n}, ... etc. in str with
	// the n-th argument after str
	format: function(str) {
		var args = Array.prototype.slice.call(arguments, 1);
		return str.replace(/{(\d+)}/g, function(match, number) {
			return typeof args[number] !== 'undefined' ? args[number] : match;
		});
	},

	// a URL shortener function, using google's goo.gl service
	// see https://developers.google.com/url-shortener/v1/getting_started
	shortenURL: function (url, cb) {
		function retry(times) {
			times--;

			request.post({
				url: 'https://www.googleapis.com/urlshortener/v1/url',
				headers: { 'Content-Type': 'application/json' },
				body: JSON.stringify({ longUrl: url })
			}, function (err, resp, body) {
				if (err) {
					console.error('Couldn\'t shorten url! (' + (times || 'no') + ' more retries) Error: ' + err);

					if (times) {
						retry(times);
					} else {
						cb(err, null);
					}

					return;
				}

				if (resp.statusCode < 200 || resp.statusCode >= 300) {
					console.error('Error: Google responded with a ' + resp.statusCode + ' status code. (' + (times || 'no') + ' more retries)');

					if (times) {
						retry(times);
					} else {
						cb(new Error('Failed to shorten URL: Google responded with a ' + resp.statusCode + ' status code.'), null);
					}

					return;
				}

				cb(null, JSON.parse(body).id);
			});
		}

		retry(3);
	},

	// converts a positive integer in seconds to a HH:MM:SS format string
	// (HH: omitted if < 1 hour; leading zero in seconds and minutes (if >= 1 h))
	durationFormat: function (time) {
		var s = time % 60;
		time = Math.floor(time / 60);
		var m = time % 60;
		time = Math.floor(time / 60);
		var h = time % 60;

		var str = '';
		if (h > 0) {
			// if hours - [h]h:mm:ss
			// otherwise - just [m]m:ss
			str = h + ':';
			if (m < 10) {
				str += 0;
			}
		}

		str += m + ':';

		if (s < 10) {
			str += '0';
		}

		str += s;

		return str;
	}
};