import type { CollectionBeforeOperationHook } from 'payload'
import slugify from 'slugify'

/**
 * Normalizes a filename: slugifies the NAME part (diacritics, spaces, case)
 * while preserving the extension. Keeps uploaded media URLs clean and portable.
 *
 *   "Zdjęcie jeden nad morzem.jpg"  → "zdjecie-jeden-nad-morzem.jpg"
 *   "Faktura #12 (2024).PDF"        → "faktura-12-2024.pdf"
 *   "already-clean.webp"            → "already-clean.webp"
 *
 * Why not toSlug(): toSlug uses strict:true, which would strip the dot and
 * merge name+extension. Here we split on the LAST dot, slug the stem, lowercase
 * the extension, and rejoin.
 */
export function normalizeFilename(filename: string): string {
  const lastDot = filename.lastIndexOf('.')

  // No extension (or leading-dot dotfile) → slug the whole thing.
  if (lastDot <= 0) {
    return slugify(filename, { lower: true, strict: true, trim: true })
  }

  const stem = filename.slice(0, lastDot)
  const ext = filename.slice(lastDot + 1).toLowerCase()

  const cleanStem = slugify(stem, { lower: true, strict: true, trim: true })
  const cleanExt = slugify(ext, { lower: true, strict: true, trim: true })

  // Stem could slug to empty (e.g. filename was all symbols) — fall back so we
  // never produce a nameless file.
  const safeStem = cleanStem || 'plik'

  return cleanExt ? `${safeStem}.${cleanExt}` : safeStem
}

/**
 * beforeOperation hook for an upload collection (e.g. Media). Rewrites the
 * incoming file's name to its normalized form before Payload stores it, so both
 * the stored file and its DB filename are clean. Works with local disk and with
 * cloud storage adapters (R2/S3) — it runs before the storage layer.
 *
 * Wire into your Media collection:
 *   import { normalizeFilenameHook } from '@intecion/ipal-kit'
 *   hooks: { beforeOperation: [normalizeFilenameHook] }
 */
export const normalizeFilenameHook: CollectionBeforeOperationHook = ({ req, operation }) => {
  if (operation !== 'create' && operation !== 'update') return
  const file = req.file
  if (file?.name) {
    file.name = normalizeFilename(file.name)
  }
}