'use client';

import { useSyncExternalStore } from 'react';

const disabledKey = 'site-push-disabled';
const preferenceEvent = 'notifications:preference';
export function sitePushDisabled() { return localStorage.getItem(disabledKey) === '1'; }
export function setSitePushDisabled(disabled: boolean) {
  if (disabled) localStorage.setItem(disabledKey, '1');
  else localStorage.removeItem(disabledKey);
  window.dispatchEvent(new Event(preferenceEvent));
}
function subscribePreference(onChange: () => void) {
  window.addEventListener(preferenceEvent, onChange);
  window.addEventListener('storage', onChange);
  return () => {
    window.removeEventListener(preferenceEvent, onChange);
    window.removeEventListener('storage', onChange);
  };
}
export function useSitePushDisabled() {
  return useSyncExternalStore(subscribePreference, sitePushDisabled, () => false);
}

// Serialize subscription changes so pausing also stops an in-flight automatic sync.
let pending: Promise<unknown> = Promise.resolve();
function updateSubscription<T>(operation: () => Promise<T>): Promise<T> {
  const result = pending.then(operation, operation);
  pending = result.catch(() => undefined);
  return result;
}

export function disableSitePush(userId?: string) {
  return updateSubscription(async () => {
    if ('serviceWorker' in navigator) {
      const registration = await navigator.serviceWorker.getRegistration('/');
      const subscription = await registration?.pushManager.getSubscription();
      if (subscription && !await subscription.unsubscribe()) throw new Error('push-unsubscribe-failed');
    }
    if (userId) sessionStorage.removeItem(`site-push-synced-${userId}`);
    setSitePushDisabled(true);
  });
}

// All notification features share one browser permission and root service worker.
export function syncSitePush(userId: string, resume = false) {
  return updateSubscription(async () => {
    if (!resume && sitePushDisabled()) return;
    const configResponse = await fetch('/api/commission/push-subscription', { cache: 'no-store' });
    if (!configResponse.ok) throw new Error('push-config-failed');
    const config = await configResponse.json() as { publicKey: string; canAdmin: boolean };
    const registration = await navigator.serviceWorker.register('/commission-push-sw.js', { scope: '/' });
    const subscription = await registration.pushManager.getSubscription() ?? await registration.pushManager.subscribe({ userVisibleOnly: true, applicationServerKey: config.publicKey });
    const data = subscription.toJSON();
    const registrations = [
      { url: '/api/comments/push-subscription', body: data },
      { url: '/api/commission/push-subscription', body: { ...data, scope: config.canAdmin ? 'admin' : 'customer' } },
    ];
    const responses = await Promise.all(registrations.map(feature => fetch(feature.url, { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify(feature.body) })));
    if (responses.some(response => !response.ok)) throw new Error('push-subscription-failed');
    sessionStorage.setItem(`site-push-synced-${userId}`, '1');
  });
}