IViewLocker.ts

import { isObject } from './isObject.ts';

/**
 * Interface for managing view restoration state to prevent early access to an inconsistent view
 * or concurrent restoration by another process.
 */
export interface IViewLocker {

	/**
	 * Indicates whether the view is fully restored and ready to accept new event projections.
	 */
	ready: boolean;

	/**
	 * Locks the view to prevent external read/write operations.
	 *
	 * @returns `true` if the lock is successfully acquired, `false` otherwise.
	 */
	lock(): Promise<boolean> | boolean;

	/**
	 * Unlocks the view, allowing external read/write operations to resume.
	 */
	unlock(): Promise<void> | void;

	/**
	 * Waits until the view is fully restored and ready to accept new events.
	 *
	 * @param eventType The event type to listen for (`"ready"`).
	 * @returns A promise that resolves when the view is ready.
	 */
	once(eventType: 'ready'): Promise<void>;
}

/**
 * Checks if a given object conforms to the `IViewLocker` interface.
 *
 * @param view The object to check.
 * @returns `true` if the object implements `IViewLocker`, `false` otherwise.
 */
export const isViewLocker = (view: unknown): view is IViewLocker =>
	(
		isObject(view)
		&& 'ready' in view
		&& 'lock' in view
		&& 'unlock' in view
		&& 'once' in view
	) || (
		typeof view === 'function'
		&& typeof (view as any).lock === 'function'
		&& typeof (view as any).unlock === 'function'
		&& typeof (view as any).once === 'function'
		&& (view as any).ready !== undefined
	);