export type Listener<X> = (x: X) => void

export type Pub<X> = {
	(listener: Listener<X>): () => void
	once(listener: Listener<X>): () => void
	publish(x: X): void
	clear(): void
}

/** @deprecated use `pubsub` instead */
export function pub<X>(): Pub<X> {
	const listeners = new Set<Listener<X>>()

	function subscribe(listener: Listener<X>) {
		listeners.add(listener)
		return () => void listeners.delete(listener)
	}

	subscribe.publish = (x: X) => {
		for (const listener of listeners)
			listener(x)
	}

	subscribe.clear = () => listeners.clear()

	subscribe.once = (listener: Listener<X>) => {
		const actual_listener = (x: X) => {
			listener(x)
			listeners.delete(actual_listener)
		}
		listeners.add(actual_listener)
		return () => void listeners.delete(actual_listener)
	}

	return subscribe
}