// ==UserScript==
// @name         Scroll to top button visible when Videos paused
// @namespace    http://tampermonkey.net/
// @version      1
// @include      *
// @grant        none
// @run-at       document-idle
// ==/UserScript==

(function() {
    function playback_checker() {
        var videos_active = false

        Array.from(document.querySelectorAll('video')).forEach(video => {
            if(!video.paused) {
                videos_active = true;
            }
        });

        return videos_active;
    }

    function create_button() {

        var button = document.getElementById('userScriptBtn');
        if(button) {
            button.parentNode.removeChild(button);
        }

        button = document.createElement("BUTTON");
        button.innerHTML = "Top";
        button.onclick = function () {
            window.scrollTo(0, 0);
            try {
                $(window).scrollTop(0);
            } catch {
            }
        };
        button.style.position = "absolute";
        button.style.width = '100px'
        button.style.right = '10px'
        button.style.zIndex= 2147483647;
        button.style.top   = ((window.screen.height - document.body.getBoundingClientRect().top - 50) + "px");
        button.style.visibility = playback_checker() ? "hidden" : "";
        button.setAttribute("id", "userScriptBtn");
        document.body.appendChild(button);
    }

    function button_visibility() {
        var button = document.getElementById('userScriptBtn');
        if(button) {
            button.style.visibility = playback_checker() ? "hidden" : "";
        }
    }

    create_button();
    document.body.onscroll = create_button;
    setInterval(button_visibility, 100);

})();