/**
 * Shadow-DOM-safe containment check.
 *
 * `Node.contains` does not pierce shadow-root boundaries: a node inside a
 * shadow tree will report `parent.contains(child) === false` even when the
 * shadow host is itself a descendant of `parent`. This helper first tries
 * the native method (fast path) and, if the child is inside a shadow root,
 * walks back up through shadow-host boundaries to check containment.
 */
export function contains(
	parent?: Element | null,
	child?: Element | null,
): boolean {
	if (!parent || !child) {
		return false;
	}

	// First, attempt with the faster native method.
	if (parent.contains(child)) {
		return true;
	}

	// Then fall back to traversing out of shadow roots when needed.
	const rootNode = child.getRootNode?.();
	if (rootNode && rootNode instanceof ShadowRoot) {
		let next: Node | null = child;
		while (next) {
			if (parent === next) {
				return true;
			}
			next = next.parentNode ?? (next as ShadowRoot).host ?? null;
		}
	}

	return false;
}