export default function removeDeprecatedFrontmatter (file, frontmatterVersions, releaseToDeprecate, nextOldestRelease) {
  // skip files with no Enterprise Server versions frontmatter
  if (!frontmatterVersions) return
  if (!frontmatterVersions.ghes) return

  const ghesRange = frontmatterVersions.ghes

  // skip files with versions frontmatter that already applies to all enterprise-server releases
  if (ghesRange === '*') return

  // if the release to deprecate is 2.13, and the FM is either '>=2.13', '>2.13', or '>=2.14',
  // we can safely change the FM to ghes: '*'
  const appliesToAllSupportedGhesReleases = (
    ghesRange === `>=${releaseToDeprecate}` ||
    ghesRange === `>${releaseToDeprecate}` ||
    ghesRange === `>=${nextOldestRelease}`
  )

  if (appliesToAllSupportedGhesReleases) {
    frontmatterVersions.ghes = '*'
    return
  }

  // if the release to deprecate is 2.13, and the FM is either '=2.13', '<2.13', '<=2.13', or '<2.14',
  // delete (aka deprecate) the ghes frontmatter property.
  const appliesToNoSupportedGhesReleases = (
    ghesRange === `=${releaseToDeprecate}` ||
    ghesRange === `<${releaseToDeprecate}` ||
    ghesRange === `<=${releaseToDeprecate}` ||
    ghesRange === `<${nextOldestRelease}`
  )

  if (appliesToNoSupportedGhesReleases) {    
    // Throw a warning if there are no other frontmatter versions specified.
    if (Object.keys(frontmatterVersions).length === 1) {
      console.log(`Warning! ${file} has frontmatter versioning that will make it never appear when ${releaseToDeprecate} is deprecated. The article should probably be removed.`)
      return
    }

    delete frontmatterVersions.ghes
  }
}