fitness_hut.js

// ==UserScript==
// @name         Verify fitness hut class availability
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://www.myhut.pt/myhut/aulas/*
// @grant        none
// @require http://code.jquery.com/jquery-latest.js
// ==/UserScript==

(function() {
    'use strict';

    const class_id = '#aula-heading323069';
    const classIsAvailable = (class_id) => {
        const classNode = $(class_id).parent(".panel-off, .panel-red");
        return classNode.length === 0;
    };
    const todayClassIsAvailable = () => { return classIsAvailable(class_id); };

    const notifyMe = () => {
        return new Notification('Yey!', {
            icon: 'https://image.freepik.com/free-icon/dumbbell-exercise_318-35207.png',
            body: "Go a aula esta livre :)",
        });
    };

    // Verify if class isnt red, otherwise refresh the page (the script will run again).
    const run_until_success = (run, onSuccess) => {
        if (run()){
            return onSuccess();
        }else{
            console.log("Not available... Refreshing in a minute...");
            setTimeout(function(){ location.reload(); }, 60000);
        }
    };

    // Wait a little bit for the page to load.
    setTimeout(() => run_until_success(todayClassIsAvailable, notifyMe), 5000);
})();