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

/**
 * Context value published by `<Fieldset.Root>`.
 *
 * `<Fieldset.Root>` exposes:
 *
 *   - `disabled` — reactive bit that descendant control parts merge with
 *     their own `disabled` prop (matches React Base UI).
 *   - `legendId` / `setLegendId` — the `<Fieldset.Legend>` id registration
 *     pair, so the root can wire `aria-labelledby`. These mirror the
 *     `useRegisteredLabelId` pattern used across other tier-1 roots
 *     (progress / meter) and are `undefined` on the NOOP context value.
 *
 * Mirrors Base UI React's
 * `packages/react/src/fieldset/root/FieldsetRootContext.ts`.
 */
export interface FieldsetContextValue {
	disabled: Accessor<boolean>;
	/** Marker — `true` when this context was provided by a real `<Fieldset.Root>`. */
	readonly present: boolean;
	/**
	 * Current registered legend id (if any). Only meaningful when `present`
	 * is `true`; the NOOP context leaves this unset.
	 */
	legendId?: Accessor<string | undefined>;
	/**
	 * Register the legend id so the root can wire `aria-labelledby`. Called
	 * by `<Fieldset.Legend>` on mount (with the id) and on cleanup (with
	 * `undefined`). Safe to invoke from within owned scope — the underlying
	 * signal in the root opts into `ownedWrite` (pure internal plumbing).
	 * Only provided when `present` is `true`.
	 */
	setLegendId?: (id: string | undefined) => void;
}

export const NOOP_FIELDSET_CONTEXT: FieldsetContextValue = {
	disabled: () => false,
	present: false,
};

/**
 * Context carrying `<Fieldset.Root>` state. Provided via
 * `<FieldsetContext value={...}>` (Solid 2's context-as-provider pattern).
 */
export const FieldsetContext = createContext<FieldsetContextValue>(
	NOOP_FIELDSET_CONTEXT,
);

/**
 * Read the current `<Fieldset.Root>` context. Returns {@link NOOP_FIELDSET_CONTEXT}
 * when no fieldset is present — callers can branch on `.present` if they
 * need to know whether a real fieldset wraps them.
 */
export function useFieldsetContext(): FieldsetContextValue {
	return useContext(FieldsetContext);
}