2.ts

interface Event {
  public isCritical(): boolean;
  public getName(): string;
  public getPayload(): object;
}

class UserProcessed implements Event {
  constructor(protected user: firestore.DocumentSnapshot) {}

  public isCritical() {
    return true;
  }

  public getName() {
    return "user.processed";
  }

  public getPayload() {
    return {
      id: this.user.id,
      name: this.user.data().name,
      email: this.user.data().email
    };
  }
}