eventemitter.ts

import { EventEmitter } from "events";

const eventEmitter = new EventEmitter();

const stubMailApi = (address: string, message: string) => {
  return new Promise<{ address: string; message: string; status: string }>(
    resolve => {
      resolve({ address, message, status: "ok" });
    }
  );
};

const stubPushNotificationsApi = (message: string) => {
  return new Promise<{ message: string; status: string }>(resolve => {
    resolve({ message, status: "ok" });
  });
};

class EmailService {
  send(address: string, message: string) {
    stubMailApi(address, message).then(response => {
      eventEmitter.emit("email-sent", response);
    });
  }
}

class PushNotificationsService {
  send(message: string) {
    stubPushNotificationsApi(message).then(response => {
      eventEmitter.emit("push-notification-sent", response);
    });
  }
}

class AuthService {
  private loggedIn: string | null = null;

  login(emailAddress: string) {
    this.logout();
    this.loggedIn = emailAddress;
    eventEmitter.emit("auth-logged-in", emailAddress);
  }

  logout() {
    if (this.loggedIn) {
      const emailAddress = this.loggedIn;
      this.loggedIn = null;
      eventEmitter.emit("auth-logged-out", emailAddress);
    }
  }
}

class LoggerService {
  constructor() {
    eventEmitter.on("logger-log", this.log);
  }

  log(data: any) {
    console.log(data);
  }
}

const authService = new AuthService();
const emailService = new EmailService();
const pushNotificationsService = new PushNotificationsService();
const loggerService = new LoggerService();

eventEmitter.on("auth-logged-in", emailAddress => {
  loggerService.log(`User ${emailAddress} was logged in`);
  emailService.send(emailAddress, "You were logged in");
});

eventEmitter.on("auth-logged-out", emailAddress => {
  loggerService.log(`User ${emailAddress} was logged out`);
  emailService.send(emailAddress, "You were logged out");
});

eventEmitter.on("email-sent", response => {
  loggerService.log(`Email ${JSON.stringify(response)} was sent`);
  pushNotificationsService.send(response.message);
});

eventEmitter.on("push-notification-sent", response => {
  loggerService.log(`Push Notification ${JSON.stringify(response)} was sent`);
});

authService.login("[email protected]");