export const usePush = () => {
  const isSupported = ref(false)
  const subscription = ref<PushSubscription | null>(null)

  const checkSupport = () => {
    isSupported.value = 'serviceWorker' in navigator && 'PushManager' in window
  }

  const getRegistration = async (): Promise<ServiceWorkerRegistration | null> => {
    if (!('serviceWorker' in navigator)) return null
    return navigator.serviceWorker.ready
  }

  const subscribe = async (): Promise<boolean> => {
    const registration = await getRegistration()
    if (!registration) return false

    try {
      const existing = await registration.pushManager.getSubscription()
      if (existing) {
        subscription.value = existing
        await sendSubscriptionToServer(existing)
        return true
      }

      // In production, get VAPID public key from server
      const vapidKey = await $fetch<string>('/api/push/vapid-public-key').catch(() => null)
      const applicationServerKey = vapidKey
        ? (urlBase64ToUint8Array(vapidKey) as unknown as ArrayBuffer)
        : undefined

      const sub = await registration.pushManager.subscribe({
        userVisibleOnly: true,
        applicationServerKey
      })

      subscription.value = sub
      await sendSubscriptionToServer(sub)
      return true
    } catch (err) {
      console.error('Push subscription failed:', err)
      return false
    }
  }

  const sendSubscriptionToServer = async (sub: PushSubscription) => {
    await $fetch('/api/push/subscribe', {
      method: 'POST',
      body: { subscription: sub.toJSON() }
    })
  }

  const unsubscribe = async (): Promise<boolean> => {
    const registration = await getRegistration()
    if (!registration) return false

    const existing = await registration.pushManager.getSubscription()
    if (existing) {
      await existing.unsubscribe()
      subscription.value = null
    }
    return true
  }

  const urlBase64ToUint8Array = (base64String: string): Uint8Array => {
    const padding = '='.repeat((4 - (base64String.length % 4)) % 4)
    const base64 = (base64String + padding).replace(/-/g, '+').replace(/_/g, '/')
    const rawData = atob(base64)
    return Uint8Array.from([...rawData].map(char => char.charCodeAt(0)))
  }

  const showLocalNotification = (title: string, options?: NotificationOptions) => {
    if ('Notification' in window && Notification.permission === 'granted') {
      navigator.serviceWorker.ready.then(reg => {
        reg.showNotification(title, {
          icon: '/pwa-192x192.svg',
          badge: '/favicon.svg',
          ...options as any
        })
      })
    }
  }

  const requestPermission = async (): Promise<boolean> => {
    if (!('Notification' in window)) return false
    const permission = await Notification.requestPermission()
    return permission === 'granted'
  }

  onMounted(() => {
    checkSupport()
  })

  return {
    isSupported,
    subscription,
    subscribe,
    unsubscribe,
    requestPermission,
    showLocalNotification
  }
}