export class MessageBus {
	constructor() {
		this.bus = new EventTarget()
		this.counter = 0
		this.fnmap = new Map()
	}

	subscribe(eventName, fn) {
		this.counter++
		this.bus.addEventListener(eventName, fn)
		this.fnmap.set(this.counter, { eventName, fn })
		return this.counter
	}

	unsubscribe(mappedID) {
		const mapped = this.fnmap.get(mappedID)
		if (mapped === undefined) {
			console.warn('unsubscribe, no such mapped ID', mappedID)
			return
		}
		this.fnmap.delete(mappedID)
		this.bus.removeEventListener(mapped.eventName, mapped.fn)
	}

	dispatch(eventName, data) {
		console.debug('mbus', eventName, data)
		this.bus.dispatchEvent(new CustomEvent(eventName, { detail: data }))
	}
}