/**
 * Abonnement Web Push. Le front ne fait que : demander la permission, s'abonner (clé VAPID du back),
 * transmettre la subscription au back. Le back décide quand/quoi envoyer.
 */
function urlB64ToUint8Array(base64String: string): Uint8Array {
  const padding = '='.repeat((4 - (base64String.length % 4)) % 4)
  const base64 = (base64String + padding).replace(/-/g, '+').replace(/_/g, '/')
  const raw = atob(base64)
  const arr = new Uint8Array(raw.length)
  for (let i = 0; i < raw.length; i++) arr[i] = raw.charCodeAt(i)
  return arr
}

export function usePush() {
  const { api } = useApi()

  function isSupported(): boolean {
    return import.meta.client && 'serviceWorker' in navigator && 'PushManager' in window && 'Notification' in window
  }

  async function enable(vapidPublicKey: string) {
    if (!isSupported()) throw new Error('Notifications non supportées sur cet appareil.')
    const perm = await Notification.requestPermission()
    if (perm !== 'granted') throw new Error('Permission refusée.')

    const reg = await navigator.serviceWorker.ready
    const existing = await reg.pushManager.getSubscription()
    const sub = existing ?? await reg.pushManager.subscribe({
      userVisibleOnly: true,
      applicationServerKey: urlB64ToUint8Array(vapidPublicKey)
    })

    const json = sub.toJSON() as { endpoint?: string, keys?: { p256dh: string, auth: string } }
    await api('/api/push/subscribe', { method: 'POST', body: { endpoint: json.endpoint, keys: json.keys } })
  }

  async function disable() {
    if (!isSupported()) return
    const reg = await navigator.serviceWorker.ready
    const sub = await reg.pushManager.getSubscription()
    if (sub) {
      await api('/api/push/unsubscribe', { method: 'POST', body: { endpoint: sub.endpoint } }).catch(() => {})
      await sub.unsubscribe()
    }
  }

  async function sendTest() {
    await api('/api/push/test', { method: 'POST' })
  }

  return { isSupported, enable, disable, sendTest }
}