let io = null

if (window.IntersectionObserver) {
	io = new IntersectionObserver((entries) =>
		entries
			.filter(({ isIntersecting }) => isIntersecting)
			.map(({ target }) => target)
			.filter((el) => (el.dataset.reveal || '').indexOf('no') > -1)
			.map((el, index) => {
				let hasBottom = (el.dataset.reveal || '').indexOf('bottom') > -1

				if (hasBottom) {
					el.dataset.reveal = `yes:${index + 1}`
				} else {
					el.dataset.reveal = `yes`
				}
			})
	)
}

export const watchLayoutContainerForReveal = (layoutEl) => {
	if (!window.IntersectionObserver) {
		return
	}

	let items = layoutEl.querySelectorAll('[data-reveal*="no"]')

	if (items.length === 0) return
	if (!items[0].dataset.reveal) return
	;[...items].map((el) => io.observe(el))
}