export function isLikeSelector(selector) {
	return selector !== null
		&& typeof selector === 'object'
		&& Reflect.getPrototypeOf(selector) === Object.prototype
		&& Reflect.ownKeys(selector).length > 0;
}

export const CIRCULAR_SELECTOR = new Error('Encountered a circular selector');

export function selectComparable(lhs, selector, circular = new Set()) {
	if (circular.has(selector)) {
		throw CIRCULAR_SELECTOR;
	}

	circular.add(selector);

	if (lhs === null || typeof lhs !== 'object') {
		return lhs;
	}

	const comparable = {};
	for (const [key, rhs] of Object.entries(selector)) {
		if (isLikeSelector(rhs)) {
			comparable[key] = selectComparable(Reflect.get(lhs, key), rhs, circular);
		} else {
			comparable[key] = Reflect.get(lhs, key);
		}
	}

	return comparable;
}