import RevealAttributes from "./RevealAttributes.js";

const reveal = new IntersectionObserver((entries) => {

    if(document.body.hasAttribute("for-preview")) {
        return;
    }

    const now = Date.now();

    for (const iterator of entries) {
        const { target } = iterator;
        if(iterator.isIntersecting) {
            RevealAttributes.add(target as HTMLElement, now);
        } else {
            RevealAttributes.remove(target as HTMLElement, now);
        }
    }
});

const revealAdded = Symbol("revealAdded");

export default class RevealObserver {
    static observe(element: HTMLElement) {
        if (element[revealAdded]) {
            return;
        }
        // carousel must observer it's own children...
        if (element.matches("carousel-slider *")) {
            return;
        }
        element[revealAdded] = true;
        reveal.observe(element);
    }

    static unobserve(element: HTMLElement) {
        delete element[revealAdded];
        reveal.unobserve(element);
    }
}