Event Emitter

/* eslint-disable @typescript-eslint/no-explicit-any */
type Callback = (...args: any[]) => any;
type Subscription = {
  unsubscribe: () => void;
};
 
export class EventEmitter {
  private readonly events: Map<string, Set<Callback>>;
 
  constructor() {
    this.events = new Map();
  }
 
  private addEvent(eventName: string, callback: Callback): void {
    const callbacks = this.events.get(eventName);
    if (callbacks === undefined) {
      this.events.set(eventName, new Set([callback]));
      return;
    }
    callbacks.add(callback);
  }
 
  private removeEvent(eventName: string, callback: Callback): void {
    const callbacks = this.events.get(eventName);
    if (callbacks === undefined) {
      return;
    }
    callbacks.delete(callback);
  }
 
  subscribe(eventName: string, callback: Callback): Subscription {
    this.addEvent(eventName, callback);
 
    return {
      unsubscribe: () => {
        this.removeEvent(eventName, callback);
      },
    };
  }
 
  emit(eventName: string, args: any[] = []): any {
    const callbacks = this.events.get(eventName);
    if (!callbacks) {
      return [];
    }
    const results: any[] = [];
    callbacks.forEach((callback) => results.push(callback(...args)));
    return results;
  }
}