import type { Router } from 'vue-router'

const RECOVERY_KEY = 'client-static-asset-recovery'
const RECOVERY_COOLDOWN_MS = 60_000
const RECOVERY_STABLE_MS = 15_000

interface RecoveryRecord {
  href: string
  refreshedAt: number
}

function errorMessage(error: unknown) {
  if (error instanceof Error) return `${error.name}: ${error.message}`
  return typeof error === 'string' ? error : ''
}

export function isStaticAssetLoadError(error: unknown) {
  return /ChunkLoadError|Loading chunk [\w-]+ failed|Failed to fetch dynamically imported module|Importing a module script failed|error loading dynamically imported module|Unable to preload CSS/i.test(errorMessage(error))
}

function readRecoveryRecord(): RecoveryRecord | null {
  try {
    const raw = window.sessionStorage.getItem(RECOVERY_KEY)
    if (!raw) return null
    const value = JSON.parse(raw) as Partial<RecoveryRecord>
    return typeof value.href === 'string' && typeof value.refreshedAt === 'number'
      ? { href: value.href, refreshedAt: value.refreshedAt }
      : null
  } catch {
    return null
  }
}

function writeRecoveryRecord(record: RecoveryRecord) {
  try {
    window.sessionStorage.setItem(RECOVERY_KEY, JSON.stringify(record))
    return true
  } catch {
    // Without a persistent guard, reloading could loop while the deployment is still unavailable.
    return false
  }
}

function clearRecoveryRecord() {
  try {
    window.sessionStorage.removeItem(RECOVERY_KEY)
  } catch {
    // Storage availability must not affect application startup.
  }
}

function recoverFromStaticAssetFailure(error: unknown, confirmedAssetFailure = false) {
  if (!confirmedAssetFailure && !isStaticAssetLoadError(error)) return false
  const now = Date.now()
  const previous = readRecoveryRecord()
  if (previous?.href === window.location.href && now - previous.refreshedAt < RECOVERY_COOLDOWN_MS) return false
  if (!writeRecoveryRecord({ href: window.location.href, refreshedAt: now })) return false
  window.location.reload()
  return true
}

function failedApplicationAsset(event: Event) {
  const target = event.target
  if (target instanceof HTMLScriptElement) return target.src
  if (target instanceof HTMLLinkElement && ['stylesheet', 'modulepreload', 'preload'].includes(target.rel)) return target.href
  return ''
}

export function installStaticAssetRecovery(router: Router) {
  window.addEventListener('vite:preloadError', (event) => {
    const preloadEvent = event as Event & { payload?: unknown }
    if (recoverFromStaticAssetFailure(preloadEvent.payload, true)) preloadEvent.preventDefault()
  })

  window.addEventListener('error', (event) => {
    const assetUrl = failedApplicationAsset(event)
    if (!assetUrl) return
    try {
      if (new URL(assetUrl, window.location.href).origin !== window.location.origin) return
    } catch {
      return
    }
    recoverFromStaticAssetFailure(assetUrl, true)
  }, true)

  router.onError((error) => {
    recoverFromStaticAssetFailure(error)
  })

  window.setTimeout(clearRecoveryRecord, RECOVERY_STABLE_MS)
}