function parse(iso: string): Date {
  return new Date(`${iso}T00:00:00`)
}

/** "Apr 2025 – Oct 2026", or "Oct 2024 – today" when there is no end date */
export function cvPeriod(from: string, to: string | null, lang: CvLang, t: CvText): string {
  const locale = lang === 'de' ? 'de-DE' : 'en-GB'
  const month = (iso: string) => parse(iso).toLocaleDateString(locale, { month: 'short', year: 'numeric' })
  return `${month(from)} – ${to ? month(to) : t.today}`
}

/** "1 year 6 months", counted until today when there is no end date */
export function cvDuration(from: string, to: string | null, t: CvText): string {
  const start = parse(from)
  // The end day counts, so 1 Apr – 31 Oct is 7 months, not 6
  const end = to ? parse(to) : new Date()
  end.setDate(end.getDate() + 1)
  let total = (end.getFullYear() - start.getFullYear()) * 12 + end.getMonth() - start.getMonth()
  if (end.getDate() < start.getDate()) total--
  total = Math.max(1, total)
  const years = Math.floor(total / 12)
  const months = total % 12
  return [
    years && `${years} ${t.year[years === 1 ? 0 : 1]}`,
    months && `${months} ${t.month[months === 1 ? 0 : 1]}`
  ].filter(Boolean).join(' ')
}