const RELOAD_FLAG_KEY = '__chunk_reload_at'
const RELOAD_COOLDOWN_MS = 10_000

function shouldReload(): boolean {
  try {
    const raw = sessionStorage.getItem(RELOAD_FLAG_KEY)
    if (!raw) return true
    const at = Number(raw)
    if (!Number.isFinite(at)) return true
    return Date.now() - at > RELOAD_COOLDOWN_MS
  } catch {
    return true
  }
}

function markReload(): void {
  try {
    sessionStorage.setItem(RELOAD_FLAG_KEY, String(Date.now()))
  } catch {
    // ignore storage failures (private mode, quota)
  }
}

export function reloadForStaleChunk(): boolean {
  if (!shouldReload()) return false
  markReload()
  location.reload()
  return true
}

const CHUNK_ERROR_PATTERNS = [
  /Failed to fetch dynamically imported module/i,
  /error loading dynamically imported module/i,
  /Importing a module script failed/i,
  /Unable to preload CSS/i,
]

export function isChunkLoadError(err: unknown): boolean {
  const msg =
    err instanceof Error
      ? err.message
      : typeof err === 'string'
        ? err
        : ''
  return CHUNK_ERROR_PATTERNS.some((re) => re.test(msg))
}

export function registerChunkReloadHandlers(): void {
  window.addEventListener('vite:preloadError', (event) => {
    if (reloadForStaleChunk()) {
      event.preventDefault()
    }
  })
}