"use strict";

class Event {
  constructor() {
    this.handlers = new Map();
    this.count = 0;
  }

  subscribe(handler) {
    this.handlers.set(++this.count, handler);
    return this.count;
  }

  unsubscribe(idx) {
    this.handlers.delete(idx);
  }

  notify(sender, args) {
    this.handlers.forEach((func, idx) => func(sender, args));
  }
}

class DownloadManager extends Event {
  constructor() {
    super();
  }

  downloadUrl(url) {
    // Simulador de descarga
    let progress = 0;
    let intervalId = setInterval(() => {
      if (progress >= 10) {
        clearInterval(intervalId);
        this.notify(this, { success: true, progress: progress * 10, url });
      } else {
        this.notify(this, { success: false, progress: progress * 10, url });
      }
      progress++;
    }, 500);
  }
}

class DownloadFileProcess {
  update = (sender, args) => {
    console.log(
      `DownloadFileProcess: Descargando ${args.url}: ${args.progress}%`
    );
  };
}

class DownloadFileCompleted {
  update = (sender, args) => {
    if (args.success) {
      console.log(
        `DownloadFileCompleted: ${args.url} descargada correctamente`
      );
    }
  };
}

/*
Imaginemos que tenemos una servicio de descarga de datos en segundo plano, 
Entonces me gustaría saber el progreso de la descarga y cuando esté finalizado
*/
// Subject
let downloadManager = new DownloadManager();
// Observador
let downloadFileProcess = new DownloadFileProcess();
let downloadFileCompleted = new DownloadFileCompleted();

downloadManager.subscribe(downloadFileProcess.update);
downloadManager.subscribe(downloadFileCompleted.update);
downloadManager.downloadUrl("http://hola.com");
/* 
DownloadFileProcess: Descargando http://hola.com: 0%
DownloadFileProcess: Descargando http://hola.com: 10%
DownloadFileProcess: Descargando http://hola.com: 20%
DownloadFileProcess: Descargando http://hola.com: 30%
DownloadFileProcess: Descargando http://hola.com: 40%
DownloadFileProcess: Descargando http://hola.com: 50%
DownloadFileProcess: Descargando http://hola.com: 60%
DownloadFileProcess: Descargando http://hola.com: 70%
DownloadFileProcess: Descargando http://hola.com: 80%
DownloadFileProcess: Descargando http://hola.com: 90%
DownloadFileProcess: Descargando http://hola.com: 100%
DownloadFileCompleted: http://hola.com descargada correctamente
 */