const UNITS: [Intl.RelativeTimeFormatUnit, number][] = [
  ['year', 365 * 24 * 60 * 60],
  ['month', 30 * 24 * 60 * 60],
  ['week', 7 * 24 * 60 * 60],
  ['day', 24 * 60 * 60],
  ['hour', 60 * 60],
  ['minute', 60],
  ['second', 1],
]

export function formatRelativeTime(dateTime: string, now: Date = new Date()): string {
  const target = new Date(dateTime)
  const diffSeconds = Math.round((target.getTime() - now.getTime()) / 1000)

  for (const [unit, secondsInUnit] of UNITS) {
    if (Math.abs(diffSeconds) >= secondsInUnit) {
      const value = Math.round(diffSeconds / secondsInUnit)
      return new Intl.RelativeTimeFormat(undefined, { numeric: 'auto' }).format(value, unit)
    }
  }

  return new Intl.RelativeTimeFormat(undefined, { numeric: 'auto' }).format(0, 'second')
}