const scrollToTopBtn = document.querySelector(".lw-scroll-top-btn");

if (scrollToTopBtn) {
    const totalPageHeight = document.body.scrollHeight;
    let currentPageHeight = window.scrollY;
    const rootElement = document.documentElement;

    const fadeScrollTopBtn = (total, current) => {
        if (total / 3 < current) {
            !scrollToTopBtn.classList.contains("lw-scroll-top-btn--active")
                ? scrollToTopBtn.classList.add("lw-scroll-top-btn--active")
                : null;
        } else {
            scrollToTopBtn.classList.contains("lw-scroll-top-btn--active")
                ? scrollToTopBtn.classList.remove("lw-scroll-top-btn--active")
                : null;
        }
    };

    fadeScrollTopBtn(totalPageHeight, currentPageHeight);

    const onScrollShowBtn = () => {
        fadeScrollTopBtn(totalPageHeight, window.scrollY);
    };

    window.addEventListener("scroll", onScrollShowBtn);

    function scrollToTop() {
        rootElement.scrollTo({
            top: 0,
            behavior: "smooth",
        });
    }
    scrollToTopBtn.addEventListener("click", scrollToTop);
}