eventBus.ts

type BusEvents = Record<string, (...args: any[]) => void>;

export class EventBus<T extends { [K in keyof T]: (...args: any[]) => void } = BusEvents> {
  private events: { [K in keyof T]?: Array<T[K]> } = {};

  on<K extends keyof T>(event: K, listener: T[K]): Function {
    (this.events[event] ||= []).push(listener);
    return () => this.off(event, listener);
  }

  emit<K extends keyof T>(event: K, ...args: Parameters<T[K]>) {
    (this.events[event] || []).forEach((fn) => fn(...args));
  }

  off<K extends keyof T>(event: K, listener?: T[K]) {
    if (!listener) {
      delete this.events[event];
      return;
    }
    this.events[event] = (this.events[event] || []).filter((l) => l !== listener);
  }

  once<K extends keyof T>(event: K, listener: T[K]): void {
    const onceListener = (...args: Parameters<T[K]>) => {
      listener(...args);
      this.off(event, onceListener as T[K]);
    };
    this.on(event, onceListener as T[K]);
  }

  removeAllListener() {
    this.events = {};
  }
}

export default EventBus;