@nodecg/types/src/shared/typed-emitter.ts

Dynamic broadcast graphics rendered in a browser

import { EventEmitter } from "events";

export interface Builtins {
	newListener(event: string, listener: EventReceiver<unknown>): void;
}

export type EventMap = Record<string, any>;
export type EventKey<T extends EventMap> = string & keyof T;
export type EventReceiver<T> = (params: T) => void;

export class TypedEmitter<T extends EventMap> {
	readonly _emitter = new EventEmitter();

	addListener<K extends EventKey<T & Builtins>>(
		eventName: K,
		fn: (T & Builtins)[K],
	): void {
		this._emitter.addListener(eventName, fn);
	}

	on<K extends EventKey<T & Builtins>>(
		eventName: K,
		fn: (T & Builtins)[K],
	): void {
		this._emitter.on(eventName, fn);
	}

	off<K extends EventKey<T & Builtins>>(
		eventName: K,
		fn: (T & Builtins)[K],
	): void {
		this._emitter.off(eventName, fn);
	}

	removeListener<K extends EventKey<T & Builtins>>(
		eventName: K,
		fn: (T & Builtins)[K],
	): void {
		this._emitter.removeListener(eventName, fn);
	}

	emit<K extends EventKey<T & Builtins>>(
		eventName: K,
		...params: Parameters<(T & Builtins)[K]>
	): void {
		this._emitter.emit(eventName, ...params);
	}

	once<K extends EventKey<T & Builtins>>(
		eventName: K,
		fn: (T & Builtins)[K],
	): void {
		this._emitter.once(eventName, fn);
	}

	setMaxListeners(max: number): void {
		this._emitter.setMaxListeners(max);
	}

	listenerCount(eventName: string): number {
		return this._emitter.listenerCount(eventName);
	}

	listeners<K extends EventKey<T & Builtins>>(
		eventName: K,
	): (T & Builtins)[K][] {
		return this._emitter.listeners(eventName) as any;
	}

	// We intentionally don't expose removeAllListeners because it would break Replicants when used.
}