/**
 * Strip the trailing `_YYYY-MM(-DD).zim` date suffix from a Kiwix-style ZIM
 * filename so different release dates of the same variant share a stem
 * (e.g., `wikipedia_en_all_nopic`) while distinct corpora keep distinct stems
 * (`wikipedia_en_simple_all_nopic`, `wikipedia_en_medicine_nopic`, etc.).
 */
export function zimFilenameStem(name: string): string {
  return name.replace(/_\d{4}-\d{2}(?:-\d{2})?\.zim$/i, '')
}

/**
 * Of the existing files, return only those that are prior-version replacements
 * of `currentFilename` — same Wikipedia variant stem, different release. Used
 * by the post-download cleanup to avoid deleting unrelated Wikipedia corpora
 * the user has installed independently (issue #884).
 */
export function findReplacedWikipediaFiles(
  currentFilename: string,
  existingNames: string[]
): string[] {
  const currentStem = zimFilenameStem(currentFilename)
  return existingNames.filter(
    (n) =>
      n.startsWith('wikipedia_en_') && n !== currentFilename && zimFilenameStem(n) === currentStem
  )
}