import { existsSync, createReadStream } from 'node:fs'
import { fileEtag, stillPath, stillThumbPath, existingStillThumbPath } from '~/server/utils/library'

export default defineEventHandler((event) => {
  const { owner } = assertLibraryOwner(event)
  const id = String(getRouterParam(event, 'id') || '')
  const still = getStill(owner, id)
  assertFolderAccess(event, still.folderId)

  const path = existingStillThumbPath(owner, id)
  const original = stillPath(owner, still.id)
  // Ready thumb → stream. Never await ffmpeg on the request path.
  if (path && existsSync(path) && path !== original) {
    const etag = fileEtag(path)
    setHeader(event, 'ETag', etag)
    setHeader(event, 'Cache-Control', 'public, max-age=86400')
    if (getHeader(event, 'if-none-match') === etag) {
      setResponseStatus(event, 304)
      return null
    }
    setHeader(event, 'Content-Type', 'image/jpeg')
    return sendStream(event, createReadStream(path))
  }

  // Missing → answer now; build .thumb.jpg in the background (job save / upload also kick this)
  void stillThumbPath(owner, id).catch(() => null)
  setHeader(event, 'Cache-Control', 'no-store')
  setResponseStatus(event, 204)
  return null
})