const basePath = (process.env.NEXT_PUBLIC_BASE_PATH ?? '').replace(/\/+$/, '')
const SW_PATH = `${basePath}/sw.js`
const SW_SCOPE = basePath ? `${basePath}/` : '/'
const PWA_INSTALL_DISMISSED_KEY = 'pwa_install_dismissed_at'
const PWA_INSTALL_DISMISS_TTL_MS = 7 * 24 * 60 * 60 * 1000

export const PUSH_SUBSCRIPTION_ID_STORAGE_KEY = 'push_subscription_id'

export const isBrowser = () => typeof window !== 'undefined'

export const isIosDevice = () => {
  if (!isBrowser()) return false

  const ua = window.navigator.userAgent
  // iPadOS 13+ reports as "MacIntel" but, unlike a real Mac, exposes touch points.
  const isIpadOs13Plus = window.navigator.userAgent.includes('Mac') && navigator.maxTouchPoints > 1

  return /iphone|ipad|ipod/i.test(ua) || isIpadOs13Plus
}

/**
 * iOS Safari never fires `beforeinstallprompt`, so usePwa's normal
 * install-prompt flow is a permanent no-op there. Any "installed" UI on iOS
 * has to fall back to showing manual "Share → Add to Home Screen" steps.
 */
export const isIosSafari = () => {
  if (!isIosDevice()) return false

  const ua = window.navigator.userAgent
  // Chrome/Firefox/Edge on iOS all embed WebKit and match /safari/i too, so
  // they must be excluded explicitly.
  const isOtherIosBrowser = /crios|fxios|edgios|opios|duckduckgo/i.test(ua)

  return /safari/i.test(ua) && !isOtherIosBrowser
}

export const isPwaStandalone = () => {
  if (!isBrowser()) return false

  return (
    window.matchMedia('(display-mode: standalone)').matches ||
    (window.navigator as Navigator & { standalone?: boolean }).standalone === true
  )
}

export const isPushSupported = () => {
  if (!isBrowser()) return false

  return 'serviceWorker' in navigator && 'PushManager' in window && 'Notification' in window
}

export const shouldShowInstallPrompt = () => {
  if (!isBrowser() || isPwaStandalone()) return false

  const dismissedAt = Number(localStorage.getItem(PWA_INSTALL_DISMISSED_KEY) ?? 0)

  if (dismissedAt && Date.now() - dismissedAt < PWA_INSTALL_DISMISS_TTL_MS) {
    return false
  }

  return true
}

export const dismissInstallPrompt = () => {
  if (!isBrowser()) return

  localStorage.setItem(PWA_INSTALL_DISMISSED_KEY, String(Date.now()))
}

export const registerServiceWorker = async (): Promise<ServiceWorkerRegistration | null> => {
  if (process.env.NODE_ENV !== 'production' || !isBrowser() || !('serviceWorker' in navigator)) return null

  try {
    const registration = await navigator.serviceWorker.register(SW_PATH, { scope: SW_SCOPE })

    if (registration.waiting) {
      window.dispatchEvent(new CustomEvent('ghabilee:sw-update', { detail: registration }))
    }

    registration.addEventListener('updatefound', () => {
      const installing = registration.installing

      installing?.addEventListener('statechange', () => {
        if (installing.state === 'installed' && navigator.serviceWorker.controller) {
          window.dispatchEvent(new CustomEvent('ghabilee:sw-update', { detail: registration }))
        }
      })
    })

    return registration
  } catch {
    return null
  }
}

export const getServiceWorkerRegistration = async (): Promise<ServiceWorkerRegistration | null> => {
  if (!isBrowser() || !('serviceWorker' in navigator)) return null

  // `navigator.serviceWorker.ready` never rejects and may remain pending
  // forever when registration is blocked or unavailable (for example private
  // browsing or an E2E context). Logout/push cleanup must never wait on it.
  return (await navigator.serviceWorker.getRegistration(SW_SCOPE).catch(() => null)) ?? null
}

export const getStoredPushSubscriptionId = (): string | null => {
  if (!isBrowser()) return null

  return localStorage.getItem(PUSH_SUBSCRIPTION_ID_STORAGE_KEY)
}

export const setStoredPushSubscriptionId = (id: string) => {
  if (!isBrowser()) return

  localStorage.setItem(PUSH_SUBSCRIPTION_ID_STORAGE_KEY, id)
}

export const clearStoredPushSubscriptionId = () => {
  if (!isBrowser()) return

  localStorage.removeItem(PUSH_SUBSCRIPTION_ID_STORAGE_KEY)
}

/**
 * Tears down the browser-level PushSubscription for *this* device only.
 * Does not talk to the server — pair with a call that deletes the matching
 * server-side row (see services/push.ts unsubscribeCurrentDevicePush).
 */
export const unsubscribeBrowserPushManager = async (): Promise<void> => {
  const registration = await getServiceWorkerRegistration()

  if (!registration) return

  try {
    const subscription = await registration.pushManager.getSubscription()

    if (subscription) {
      await subscription.unsubscribe()
    }
  } catch {
    // Best-effort: if the browser can't tear it down, the server-side
    // delete still stops delivery, and a stale local subscription will
    // self-correct next time syncSubscription() runs.
  }
}

export const urlBase64ToUint8Array = (base64String: string) => {
  const padding = '='.repeat((4 - (base64String.length % 4)) % 4)
  const base64 = (base64String + padding).replace(/-/g, '+').replace(/_/g, '/')
  const rawData = window.atob(base64)
  const outputArray = new Uint8Array(rawData.length)

  for (let i = 0; i < rawData.length; i += 1) {
    outputArray[i] = rawData.charCodeAt(i)
  }

  return outputArray
}

export const arrayBufferToBase64Url = (buffer: ArrayBuffer) => {
  const bytes = new Uint8Array(buffer)
  let binary = ''

  for (let i = 0; i < bytes.byteLength; i += 1) {
    binary += String.fromCharCode(bytes[i])
  }

  return window.btoa(binary).replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '')
}

export const getVapidPublicKey = () => process.env.NEXT_PUBLIC_VAPID_PUBLIC_KEY?.trim() ?? ''