calendar/frontend/src/hooks/useVersionCheck.ts

import { useEffect, useState } from 'react'

const POLL_MS = 2 * 60 * 1000

export function useVersionCheck(healthUrl: string) {
  const [updateAvailable, setUpdateAvailable] = useState(false)

  useEffect(() => {
    let seenVersion: string | null = null

    async function check() {
      try {
        const res = await fetch(healthUrl, { cache: 'no-store' })
        if (!res.ok) return
        const data = await res.json()
        const v: string | undefined = data.version
        if (!v) return
        if (seenVersion === null) {
          seenVersion = v
        } else if (v !== seenVersion) {
          setUpdateAvailable(true)
        }
      } catch {
        // network error — skip silently
      }
    }

    check()
    const interval = setInterval(check, POLL_MS)

    function onVisible() {
      if (document.visibilityState === 'visible') check()
    }
    document.addEventListener('visibilitychange', onVisible)

    return () => {
      clearInterval(interval)
      document.removeEventListener('visibilitychange', onVisible)
    }
  }, [healthUrl])

  return updateAvailable
}