import { type Accessor, createContext, useContext } from "solid-js";
import type { FieldRootState } from "../internals/field-constants";

/**
 * Shape of the state surface exposed by `<Switch.Root>` to its compound parts
 * (currently just `<Switch.Thumb>`). Mirrors Base UI React's
 * `SwitchRootState` — it extends the shared `FieldRootState` (valid / touched
 * / dirty / filled / focused / disabled) with the switch-specific flags.
 */
export interface SwitchRootState extends FieldRootState {
	/** Whether the switch is currently active. */
	checked: boolean;
	/** Whether the component should ignore user interaction. */
	disabled: boolean;
	/** Whether the user should be unable to activate or deactivate the switch. */
	readOnly: boolean;
	/** Whether the user must activate the switch before submitting a form. */
	required: boolean;
}

/**
 * The value handed down by `<Switch.Root>` to its descendants.
 *
 * Solid 2 adaptations vs. React:
 *
 * - Reactive reads are exposed as `Accessor<T>` so descendants never perform a
 *   top-level reactive read on the context object itself (RFC 01).
 * - `state` is also an accessor so `<Switch.Thumb>` can drive its own
 *   `data-*` projection through `renderElement` without re-deriving.
 */
export interface SwitchRootContextValue {
	/** Current checked state. */
	checked: Accessor<boolean>;
	/** Whether the switch ignores user interaction. */
	disabled: Accessor<boolean>;
	/** Whether the switch is read-only (focusable but not activatable). */
	readOnly: Accessor<boolean>;
	/** Whether the switch is required for form submission. */
	required: Accessor<boolean>;
	/** Composite state snapshot — drives compound-part `data-*` projection. */
	state: Accessor<SwitchRootState>;
}

/**
 * Switch root context. `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 SwitchRootContext = createContext<SwitchRootContextValue | null>(
	null,
);

/**
 * Read the `<Switch.Root>` context. Throws when the caller forgot to wrap
 * the subtree in `<Switch.Root>`.
 */
export function useSwitchRootContext(): SwitchRootContextValue {
	const context = useContext(SwitchRootContext);
	if (context == null) {
		throw new Error(
			"Base UI: SwitchRootContext is missing. Switch parts must be placed within <Switch.Root>.",
		);
	}
	return context;
}