'use client'

import { useEffect, useRef } from 'react'
import { toast } from 'sonner'

// Capture the build ID when this module first loads (from the current deployment's JS bundle).
// On subsequent fetches of /build-id.json, if the value differs, a new deploy happened.
let initialBuildId: string | null = null

export function VersionGuard() {
  const notified = useRef(false)

  useEffect(() => {
    async function checkVersion() {
      if (notified.current) return
      try {
        const res = await fetch('/build-id.json?t=' + Date.now())
        if (!res.ok) return
        const { buildId } = await res.json()
        if (!buildId) return

        // First load — capture the build ID
        if (initialBuildId === null) {
          initialBuildId = buildId
          return
        }

        // Subsequent checks — compare
        if (buildId !== initialBuildId) {
          notified.current = true
          toast('A new version is available', {
            description: 'Refresh to get the latest updates.',
            duration: Infinity,
            action: {
              label: 'Refresh',
              onClick: () => window.location.reload(),
            },
          })
        }
      } catch {
        // Network error — ignore
      }
    }

    // Initial check (captures build ID)
    checkVersion()

    // Check on tab focus (covers users returning to stale tabs)
    window.addEventListener('focus', checkVersion)

    // Also check every 5 minutes for long-lived tabs
    const interval = setInterval(checkVersion, 5 * 60 * 1000)

    return () => {
      window.removeEventListener('focus', checkVersion)
      clearInterval(interval)
    }
  }, [])

  return null
}