// The update gate (scripts/app-version.mjs builds the other half).
//
// The bundle knows its own build number (__APP_BUILD__). Every few minutes,
// and whenever the app comes back to the foreground, it reads version.json
// from the server, bypassing every cache. A newer build there means a release
// went out: the modal lists what changed since the build this tab is running,
// and «به‌روزرسانی» drops the service worker and every Cache Storage entry,
// then reloads — so the next load is the new release, not a precached copy.
// localStorage is left alone: sign-in, cart and settings survive the update.
import { computed, onBeforeUnmount, onMounted, ref } from 'vue'

declare const __APP_BUILD__: number
declare const __APP_VERSION__: string

export interface VersionInfo {
  build: number
  version: string
  history: { build: number; date: string; notes: string[] }[]
}

const CHECK_EVERY_MS = 5 * 60 * 1000

export const runningBuild: number = typeof __APP_BUILD__ === 'number' ? __APP_BUILD__ : 0
export const runningVersion: string = typeof __APP_VERSION__ === 'string' ? __APP_VERSION__ : ''

export function useAppUpdate() {
  const available = ref<VersionInfo | null>(null)
  const updating = ref(false)

  /** What changed between the running build and the server's, newest first. */
  const changes = computed(() => {
    const info = available.value
    if (!info) return []
    return (info.history ?? []).filter((h) => h.build > runningBuild && h.build <= info.build)
  })

  async function check() {
    if (import.meta.env.DEV || !runningBuild || available.value) return
    try {
      const res = await fetch(`${import.meta.env.BASE_URL}version.json?t=${Date.now()}`, { cache: 'no-store' })
      if (!res.ok) return
      const info = (await res.json()) as VersionInfo
      if (typeof info.build === 'number' && info.build > runningBuild) available.value = info
    } catch {
      // Offline or a deploy in progress: try again on the next tick.
    }
  }

  async function applyUpdate() {
    updating.value = true
    try {
      const regs = await navigator.serviceWorker?.getRegistrations?.()
      if (regs) await Promise.all(regs.map((r) => r.unregister()))
    } catch {
      /* no service worker */
    }
    try {
      if ('caches' in window) {
        const keys = await caches.keys()
        await Promise.all(keys.map((k) => caches.delete(k)))
      }
    } catch {
      /* Cache Storage unavailable */
    }
    window.location.reload()
  }

  let timer: ReturnType<typeof setInterval> | undefined
  const onVisible = () => {
    if (document.visibilityState === 'visible') check()
  }

  onMounted(() => {
    check()
    timer = setInterval(check, CHECK_EVERY_MS)
    document.addEventListener('visibilitychange', onVisible)
  })
  onBeforeUnmount(() => {
    if (timer) clearInterval(timer)
    document.removeEventListener('visibilitychange', onVisible)
  })

  return { available, changes, updating, applyUpdate, check }
}