export const DEFAULT_IMAGE_CACHE = 'images-v1'

const objectUrlMap = new Map<string, string>()

export async function getCachedImageUrl(
  imageId: string,
  cacheName = DEFAULT_IMAGE_CACHE,
): Promise<string> {
  if (!imageId) throw new Error('imageId required')

  // reuse existing object URL if created in this session
  const existing = objectUrlMap.get(imageId)
  if (existing) return existing

  const requestUrl = `/api/image/request/${imageId}`

  // Try Cache Storage first
  let response: Response | undefined
  if ('caches' in window) {
    const cache = await caches.open(cacheName)
    response = await cache.match(requestUrl)
    if (!response) {
      const fetched = await fetch(requestUrl)
      if (!fetched.ok) throw new Error(`HTTP ${fetched.status}`)
      // store a clone in Cache Storage (non-blocking)
      cache.put(requestUrl, fetched.clone()).catch((e) => {
        console.warn('Cache put failed:', e)
      })
      response = fetched
    }
  } else {
    const fetched = await fetch(requestUrl)
    if (!fetched.ok) throw new Error(`HTTP ${fetched.status}`)
    response = fetched
  }

  const blob = await response.blob()
  const objectUrl = URL.createObjectURL(blob)
  objectUrlMap.set(imageId, objectUrl)
  return objectUrl
}

export function revokeImageUrl(imageId: string) {
  const url = objectUrlMap.get(imageId)
  if (url) {
    try {
      URL.revokeObjectURL(url)
    } catch (e) {
      /* ignore */
    }
    objectUrlMap.delete(imageId)
  }
}

export function revokeAllImageUrls() {
  for (const url of objectUrlMap.values()) {
    try {
      URL.revokeObjectURL(url)
    } catch (e) {
      /* ignore */
    }
  }
  objectUrlMap.clear()
}