import { type Accessor, createContext, useContext } from "solid-js";
import type { TransitionStatus } from "../internals/use-transition-status/use-transition-status";
import type { AccordionRootState } from "./accordion-root-context.ts";

/**
 * Per-item state. Inherits the root's `{ value, disabled, orientation }`
 * projection plus item-level fields — `index` and `open` map directly to
 * `data-index` / `data-open`.
 */
export interface AccordionItemState extends AccordionRootState {
	/** Item's index within the accordion (DOM order). */
	index: number;
	/** Whether the item is currently expanded. */
	open: boolean;
	/** Enter/exit transition phase (threaded through to panel). */
	transitionStatus: TransitionStatus;
}

/**
 * Context carried by `<Accordion.Item>`. The trigger uses `triggerId` for its
 * own `id` (so the panel's `aria-labelledby` can point to it); the panel uses
 * it for `aria-labelledby`. `setTriggerId` is how the trigger registers a
 * consumer-provided id upstream.
 */
export interface AccordionItemContextValue {
	/** Live accessor for this item's open state. */
	open: Accessor<boolean>;
	/** Live accessor for this item's projected state. */
	state: Accessor<AccordionItemState>;
	/** Consumer-provided (or generated) id of the item's trigger. */
	triggerId: Accessor<string | undefined>;
	/** Called by the trigger to register its id for `aria-labelledby`. */
	setTriggerId: (id: string | undefined) => 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 AccordionItemContext =
	createContext<AccordionItemContextValue | null>(null);

export function useAccordionItemContext(): AccordionItemContextValue {
	const context = useContext(AccordionItemContext);
	if (context == null) {
		throw new Error(
			"Base UI: AccordionItemContext is missing. Accordion parts must be placed within <Accordion.Item>.",
		);
	}
	return context;
}