let interactables = new Set<HTMLElement>()
let originals = new Map<HTMLElement, { 'aria-hidden': string | null; inert: boolean }>()

function inert(element: HTMLElement) {
    element.setAttribute('aria-hidden', 'true')
    // @ts-expect-error `inert` does not exist on HTMLElement (yet!)
    element.inert = true
}

function restore(element: HTMLElement) {
    let original = originals.get(element)
    if (!original) return

    if (original['aria-hidden'] === null) element.removeAttribute('aria-hidden')
    else element.setAttribute('aria-hidden', original['aria-hidden'])
    // @ts-expect-error `inert` does not exist on HTMLElement (yet!)
    element.inert = original.inert
}

export function useInertOthers<TElement extends HTMLElement>(
    container: TElement | null,
    enabled: boolean = true
) {
    if (!enabled) return
    if (!container) return

    let element = container

    // Mark myself as an interactable element
    interactables.add(element)

    // Restore elements that now contain an interactable child
    for (let original of originals.keys()) {
        if (original.contains(element)) {
            restore(original)
            originals.delete(original)
        }
    }

    // Collect direct children of the body
    document.querySelectorAll('body > *').forEach(child => {
        if (!(child instanceof HTMLElement)) return // Skip non-HTMLElements

        // Skip the interactables, and the parents of the interactables
        for (let interactable of interactables) {
            if (child.contains(interactable)) return
        }

        // Keep track of the elements
        if (interactables.size === 1) {
            originals.set(child, {
                'aria-hidden': child.getAttribute('aria-hidden'),
                // @ts-expect-error `inert` does not exist on HTMLElement (yet!)
                inert: child.inert,
            })

            // Mutate the element
            inert(child)
        }
    })

    return () => {
        // Inert is disabled on the current element
        interactables.delete(element)

        // We still have interactable elements, therefore this one and its parent
        // will become inert as well.
        if (interactables.size > 0) {
            // Collect direct children of the body
            document.querySelectorAll('body > *').forEach(child => {
                if (!(child instanceof HTMLElement)) return // Skip non-HTMLElements

                // Skip already inert parents
                if (originals.has(child)) return

                // Skip the interactables, and the parents of the interactables
                for (let interactable of interactables) {
                    if (child.contains(interactable)) return
                }

                originals.set(child, {
                    'aria-hidden': child.getAttribute('aria-hidden'),
                    // @ts-expect-error `inert` does not exist on HTMLElement (yet!)
                    inert: child.inert,
                })

                // Mutate the element
                inert(child)
            })
        } else {
            for (let element of originals.keys()) {
                // Restore
                restore(element)

                // Cleanup
                originals.delete(element)
            }
        }
    }
}