export function bundle(props) {
	const activeSubscribers = new Set();
	let activeUpdate = false;

	const accessor = function _bundle(values) {
		const result = {};
		activeUpdate = true;
		Object.keys(values)
			.filter(k => typeof props[k] === 'function')
			.forEach(k => {
				result[k] = props[k](values[k]);
			});

		const subscribers = Array.from(activeSubscribers);
		// Set them dirty but don't propagate.
		subscribers.forEach(s => s(result, true));
		// Now propagate.
		subscribers.forEach(s => s(result));
		activeSubscribers.clear();
		activeUpdate = false;
		return result;
	};

	const subscriptionFactory = obsFn => fn => {
		return obsFn(v => {
			if (activeUpdate) {
				activeSubscribers.add(fn);
			} else {
				fn(v);
			}
			return v;
		});
	};

	Object.keys(props).forEach(k => {
		const obs = props[k];

		accessor[k] = obs;
		obs._d = subscriptionFactory(obs._d);
	});

	return accessor;
}