function isElementInViewport (el) {
    var rect = el.getBoundingClientRect();

    return (
        rect.top >= 0 &&
        rect.left >= 0 &&
        rect.bottom <= (window.innerHeight || document.documentElement.clientHeight) && /* or $(window).height() */
        rect.right <= (window.innerWidth || document.documentElement.clientWidth) /* or $(window).width() */
    );
}
//

// little addon to enhance the carousel


Array.from(document.getElementsByClassName("carousel")).forEach((carousel) => {
    let viewport = carousel.getElementsByClassName("carousel__viewport")[0];
    let slides = carousel.getElementsByClassName("carousel__slide");
    let nav_items = Array.from(carousel.getElementsByClassName("carousel__navigation-item"))
    let last_scroll_pos = null;

    viewport.onscroll = (_event) => {
        let position =  slides.length * viewport.scrollLeft / viewport.scrollWidth;
        let direction = last_scroll_pos == null || last_scroll_pos < viewport.scrollLeft;
        last_scroll_pos = viewport.scrollLeft;

        nav_items.forEach((item, index) => {
            if (
                (direction && position > index-1 && position <= index) ||
                (!direction && position >= index && position < index+1)
            ) {
                if (!item.classList.contains("enabled")) {
                    item.classList.add("enabled")
                }
                return
            }
            if (item.classList.contains("enabled")) {
                item.classList.remove("enabled")
            }
        })
    }
})