/**
 * Scroll-axis utilities used by the swipe-dismiss state machine.
 *
 * 1:1 port of Base UI React's `packages/react/src/utils/scrollable.ts`.
 * Identifies scrollable ancestors of a touch target so the swipe hook can
 * arbitrate between "drag to dismiss" and "scroll the container".
 */

export type ScrollAxis = "horizontal" | "vertical";

function isHtmlElement(node: unknown): node is HTMLElement {
	return (
		typeof HTMLElement !== "undefined" &&
		node != null &&
		typeof (node as { nodeType?: unknown }).nodeType === "number" &&
		(node as HTMLElement).nodeType === 1 &&
		node instanceof HTMLElement
	);
}

export function isScrollable(element: HTMLElement, axis: ScrollAxis): boolean {
	const ownerDoc = element.ownerDocument ?? document;
	const win = ownerDoc.defaultView ?? window;
	const style = win.getComputedStyle(element);

	if (axis === "vertical") {
		const overflowY = style.overflowY;
		return (
			(overflowY === "auto" || overflowY === "scroll") &&
			element.scrollHeight > element.clientHeight
		);
	}

	const overflowX = style.overflowX;
	return (
		(overflowX === "auto" || overflowX === "scroll") &&
		element.scrollWidth > element.clientWidth
	);
}

export function hasScrollableAncestor(
	target: HTMLElement,
	root: HTMLElement,
	axes: ScrollAxis[],
): boolean {
	let node: HTMLElement | null = target;
	while (node && node !== root) {
		for (const axis of axes) {
			if (isScrollable(node, axis)) return true;
		}
		node = node.parentElement;
	}
	return false;
}

export function findScrollableTouchTarget(
	target: EventTarget | null,
	root: HTMLElement,
	axis: ScrollAxis = "vertical",
): HTMLElement | null {
	let node = isHtmlElement(target) ? target : null;
	while (node && node !== root) {
		if (isScrollable(node, axis)) return node;
		node = node.parentElement;
	}
	return isScrollable(root, axis) ? root : null;
}