const eq = (a, b) => {
	if (a === b) {
		return true;
	}

	if (a === null || b === null) {
		return false;
	}

	if (typeof a != "object" || typeof b != "object") {
		return false;
	}

	if (Array.isArray(a) !== Array.isArray(b)) {
		return false;
	}

	if (Object.keys(a).length !== Object.keys(b).length) {
		return false;
	}

	for (const k in a) {
		if (!b.hasOwnProperty(k)) {
			return false;
		}
		if (!eq(a[k], b[k])) {
			return false;
		}
	}

	return true;
};

const keys = (ks, obj) =>
	ks.reduce(
		(ret, k) =>
			obj.hasOwnProperty(k) ?  {...ret, [k]: obj[k]} : ret,
		{},
	);

const difference = (a, b) => {
	const diff = new Set(a);
	for (const el of b) {
		diff.delete(el);
	}
	return diff;
};

const log = o => console.error(JSON.stringify(o));


module.exports = {
	eq,
	keys,
	difference,
	log,
};