import { getSettings } from '../SettingsHandler.ipc'

interface EventCallback {
	'waitProgress': (remainingSeconds: number, totalSeconds: number) => void
	'complete': () => void
}
type Callbacks = { [E in keyof EventCallback]?: EventCallback[E] }

class GoogleTimer {

	private rateLimitCounter = Infinity
	private callbacks: Callbacks = {}

	/**
	 * Initializes the timer to call the callbacks if they are defined.
	 */
	constructor() {
		setInterval(() => {
			this.rateLimitCounter++
			this.updateCallbacks()
		}, 1000)
	}

	/**
	 * Calls `callback` when `event` fires. (no events will be fired after `this.cancelTimer()` is called)
	 */
	on<E extends keyof EventCallback>(event: E, callback: EventCallback[E]) {
		this.callbacks[event] = callback
		this.updateCallbacks() // Fire events immediately after the listeners have been added
	}

	/**
	 * Check the state of the callbacks and call them if necessary.
	 */
	private updateCallbacks() {
		if (this.hasTimerEnded() && this.callbacks.complete != undefined) {
			this.endTimer()
		} else if (this.callbacks.waitProgress != undefined) {
			const delay = getSettings().rateLimitDelay
			this.callbacks.waitProgress(delay - this.rateLimitCounter, delay)
		}
	}

	/**
	 * Prevents the callbacks from activating when the timer ends.
	 */
	cancelTimer() {
		this.callbacks = {}
	}

	/**
	 * Checks if enough time has elapsed since the last timer activation.
	 */
	private hasTimerEnded() {
		return this.rateLimitCounter > getSettings().rateLimitDelay
	}

	/**
	 * Activates the completion callback and resets the timer.
	 */
	private endTimer() {
		this.rateLimitCounter = 0
		const completeCallback = this.callbacks.complete
		this.callbacks = {}
		completeCallback()
	}
}

/**
 * Important: this instance cannot be used by more than one file download at a time.
 */
export const googleTimer = new GoogleTimer()