import api from './api';

function urlBase64ToUint8Array(base64String: string): Uint8Array<ArrayBuffer> {
  const padding = '='.repeat((4 - (base64String.length % 4)) % 4);
  const base64 = (base64String + padding).replace(/-/g, '+').replace(/_/g, '/');
  const rawData = window.atob(base64);
  // Explicit ArrayBuffer backing so the result satisfies BufferSource.
  const outputArray = new Uint8Array(new ArrayBuffer(rawData.length));
  for (let i = 0; i < rawData.length; ++i) {
    outputArray[i] = rawData.charCodeAt(i);
  }
  return outputArray;
}

export async function subscribeToPush(): Promise<void> {
  if (!('serviceWorker' in navigator) || !('PushManager' in window)) {
    return;
  }

  const permission = await Notification.requestPermission();
  if (permission !== 'granted') {
    return;
  }

  try {
    const { data } = await api.get<{ publicKey: string }>('/notifications/vapid-public-key');
    const registration = await navigator.serviceWorker.ready;

    const existing = await registration.pushManager.getSubscription();
    if (existing) {
      await sendSubscriptionToServer(existing);
      return;
    }

    const subscription = await registration.pushManager.subscribe({
      userVisibleOnly: true,
      applicationServerKey: urlBase64ToUint8Array(data.publicKey),
    });

    await sendSubscriptionToServer(subscription);
  } catch (err) {
    console.warn('Push subscription failed:', err);
  }
}

async function sendSubscriptionToServer(subscription: PushSubscription): Promise<void> {
  const json = subscription.toJSON();
  await api.post('/notifications/subscribe', {
    endpoint: json.endpoint,
    keys: json.keys,
  });
}