'use client'

import { useState, useEffect, useCallback } from 'react'
import { RefreshCw, Download } from 'lucide-react'

const CHECK_INTERVAL = 60_000 // check every 60s

export function UpdateBanner() {
  const [updateAvailable, setUpdateAvailable] = useState(false)
  const [initialVersion, setInitialVersion] = useState<string | null>(null)
  const [updating, setUpdating] = useState(false)

  const checkVersion = useCallback(async () => {
    try {
      const res = await fetch('/api/version', { cache: 'no-store' })
      const { version } = await res.json()
      if (!version) return

      if (initialVersion === null) {
        setInitialVersion(version)
      } else if (version !== initialVersion) {
        setUpdateAvailable(true)
      }
    } catch {
      // network error, skip
    }
  }, [initialVersion])

  useEffect(() => {
    checkVersion()
    const id = setInterval(checkVersion, CHECK_INTERVAL)
    return () => clearInterval(id)
  }, [checkVersion])

  // Also check on visibility change (user returns to tab)
  useEffect(() => {
    const onVisible = () => {
      if (document.visibilityState === 'visible') checkVersion()
    }
    document.addEventListener('visibilitychange', onVisible)
    return () => document.removeEventListener('visibilitychange', onVisible)
  }, [checkVersion])

  if (!updateAvailable) return null

  const handleUpdate = async () => {
    setUpdating(true)
    try {
      // 1. Clear all service worker caches
      const keys = await caches.keys()
      await Promise.all(keys.map((k) => caches.delete(k)))

      // 2. If a new service worker is waiting, activate it
      const reg = await navigator.serviceWorker?.getRegistration()
      if (reg?.waiting) {
        // Listen for the new SW to take control, then reload
        navigator.serviceWorker.addEventListener('controllerchange', () => {
          window.location.reload()
        }, { once: true })
        reg.waiting.postMessage({ type: 'SKIP_WAITING' })
        // Fallback reload if controllerchange doesn't fire within 3s
        setTimeout(() => window.location.reload(), 3000)
        return
      }

      // 3. If there's an active SW but no waiting one, unregister and reload
      if (reg) {
        await reg.unregister()
      }
    } catch {
      // If anything fails, just reload
    }
    window.location.reload()
  }

  return (
    <div className="fixed inset-x-0 top-0 z-[100] bg-gradient-to-r from-purple-700 via-purple-600 to-indigo-600 text-white shadow-2xl animate-in slide-in-from-top duration-300">
      <div className="mx-auto max-w-2xl px-4 py-4 flex flex-col items-center gap-3 sm:flex-row sm:justify-between">
        <div className="flex items-center gap-3 text-center sm:text-left">
          <div className="rounded-full bg-white/20 p-2 animate-pulse">
            <Download className="h-5 w-5" />
          </div>
          <div>
            <h2 className="text-base font-bold tracking-tight sm:text-lg">
              Update Available
            </h2>
            <p className="text-xs text-purple-100 sm:text-sm">
              A new version of Jefflix has been deployed
            </p>
          </div>
        </div>

        <button
          onClick={handleUpdate}
          disabled={updating}
          className="flex items-center gap-2 rounded-full bg-white text-purple-700 font-bold px-6 py-2.5 text-sm shadow-lg hover:bg-purple-50 active:scale-95 transition-all cursor-pointer disabled:opacity-70 whitespace-nowrap"
        >
          <RefreshCw className={`h-4 w-4 ${updating ? 'animate-spin' : ''}`} />
          {updating ? 'Updating…' : 'Update Now'}
        </button>
      </div>
    </div>
  )
}