Queue.configure(require('vow').Promise);

Queue.configure(function (handler) {
    var dfd = $.Deferred();
    try {
        handler(dfd.resolve, dfd.reject, dfd.notify);
    } catch (e) {
        dfd.reject(e);
    }
    return dfd.promise();
});

var maxConcurrent = 1;
var maxQueue = Infinity;
var queue = new Queue(maxConcurrent, maxQueue);

app.get('/version/:user/:repo', function (req, res, next) {
    queue.add(function () {
        // Assume that this action is a way too expensive
        // Call of this function will be delayed on second request
        return downloadTarballFromGithub(req.params);
    })
    .then(parseJson('package.json'))
    .then(function (package) {
        res.send(package.version);
    })
    .catch(next);
});

var maxConcurrent = 1;
var maxQueue = 1;
var queue = new Queue(maxConcurrent, maxQueue);

queue.add(function () {
    queue.getQueueLength() === 0;
    queue.getPendingLength() === 1;
    return somePromise();
});

queue.add(function () {
    queue.getQueueLength() === 0;
    queue.getPendingLength() === 0;
    return somePromise();
});

queue.getQueueLength() === 1;
queue.getPendingLength() === 1;