import { Injectable } from '@angular/core';
import {
  PushDevice,
  PushDeviceSubscription,
} from '@task-stream/web/tracker/domain';

/** The service worker that shows the notifications (apps/web/public). */
const WORKER = '/push-sw.js';

/** Push through this browser's service worker and PushManager. */
@Injectable()
export class BrowserPushDevice extends PushDevice {
  get supported(): boolean {
    return (
      typeof window !== 'undefined' &&
      'serviceWorker' in navigator &&
      'PushManager' in window &&
      'Notification' in window
    );
  }

  async current(): Promise<PushDeviceSubscription | null> {
    if (!this.supported) return null;
    const registration = await navigator.serviceWorker.getRegistration(WORKER);
    const subscription = await registration?.pushManager.getSubscription();
    return subscription ? toDevice(subscription) : null;
  }

  async subscribe(publicKey: string): Promise<PushDeviceSubscription> {
    if (!this.supported) throw new Error('Este navegador no admite avisos');
    if ((await Notification.requestPermission()) !== 'granted')
      throw new Error(
        'El navegador no tiene permiso para mostrar avisos: dáselo en los ajustes del sitio.',
      );
    const registration = await navigator.serviceWorker.register(WORKER);
    await navigator.serviceWorker.ready;
    try {
      const subscription =
        (await registration.pushManager.getSubscription()) ??
        (await registration.pushManager.subscribe({
          userVisibleOnly: true,
          applicationServerKey: fromBase64Url(publicKey),
        }));
      return toDevice(subscription);
    } catch {
      // The browser's own message is in English and says little.
      throw new Error(
        'Este navegador no ha dejado activar los avisos. En iPhone, añade antes TaskStream a la pantalla de inicio.',
      );
    }
  }

  async unsubscribe(): Promise<string | null> {
    if (!this.supported) return null;
    const registration = await navigator.serviceWorker.getRegistration(WORKER);
    const subscription = await registration?.pushManager.getSubscription();
    if (!subscription) return null;
    await subscription.unsubscribe();
    return subscription.endpoint;
  }
}

function toDevice(subscription: PushSubscription): PushDeviceSubscription {
  const json = subscription.toJSON();
  return {
    endpoint: subscription.endpoint,
    p256dh: json.keys?.['p256dh'] ?? '',
    auth: json.keys?.['auth'] ?? '',
  };
}

/** VAPID keys travel as base64url; PushManager wants the bytes. */
function fromBase64Url(text: string): Uint8Array<ArrayBuffer> {
  const base64 = (text + '='.repeat((4 - (text.length % 4)) % 4))
    .replace(/-/g, '+')
    .replace(/_/g, '/');
  const raw = atob(base64);
  const bytes = new Uint8Array(new ArrayBuffer(raw.length));
  for (let i = 0; i < raw.length; i++) bytes[i] = raw.charCodeAt(i);
  return bytes;
}