import { createContext, useContext } from "solid-js";

/**
 * Context handed to descendants of `<ScrollArea.Viewport>`. Currently only
 * `<ScrollArea.Content>` uses this — it calls `computeThumbPosition()` when
 * its ResizeObserver fires.
 */
export interface ScrollAreaViewportContextValue {
	computeThumbPosition: () => void;
}

/**
 * `createContext<T | null>(null)` + `== null` sentinel —
 * Solid 2's `useContext` throws `ContextNotFoundError` when the default is
 * `undefined`, which would shadow the intended Base UI error message below.
 */
export const ScrollAreaViewportContext =
	createContext<ScrollAreaViewportContextValue | null>(null);

export function useScrollAreaViewportContext(): ScrollAreaViewportContextValue {
	const context = useContext(ScrollAreaViewportContext);
	if (context == null) {
		throw new Error(
			"Base UI: ScrollAreaViewportContext missing. ScrollAreaViewport parts must be placed within <ScrollArea.Viewport>.",
		);
	}
	return context;
}