import { DateTime, Duration } from 'luxon'

const DURATION_PLACEHOLDER = '-- h -- min'

// Luxon ships no types in Pimp (see src/types/luxon.d.ts) — this is the slice of
// DateTime/Duration's shape CpTripDetails actually relies on.
export interface TripDuration {
  shiftTo(...units: string[]): TripDuration
  toHuman(opts: { maximumFractionDigits?: number; unitDisplay?: string }): string
  toISO(): string | null
  toObject(): Record<string, number>
}

export interface TripDateTime {
  diff(other: TripDateTime, units: string[]): TripDuration
  toFormat(format: string): string
  toISO(): string | null
}

export const fromGMTToLocal = (date: string, zone: string, locale = 'en'): TripDateTime => {
  return DateTime.fromISO(date, { zone: 'utc' }).setZone(zone).setLocale(locale)
}

export const getDuration = (end: TripDateTime, start: TripDateTime): TripDuration => {
  return end.diff(start, ['hours', 'minutes'])
}

export const getFormattedDuration = (duration?: TripDuration | null, locale = 'en'): string => {
  if (!duration) return DURATION_PLACEHOLDER

  // Concatenates values to make toHuman more readable (ex: 26h becomes 1d, 2hr)
  const shiftedDuration = duration.shiftTo('hours', 'minutes').toObject()
  const entries = Object.entries(shiftedDuration).filter(([, amount]) => amount)
  const formattedDuration = Duration.fromObject(Object.fromEntries(entries), { locale })

  return (
    formattedDuration.toHuman({
      unitDisplay: 'short',
      maximumFractionDigits: 0,
    }) || DURATION_PLACEHOLDER
  )
}

export const getDayCountBetweenDates = ({
  departureDate,
  arrivalDate,
  isArrival = false,
}: {
  arrivalDate: TripDateTime
  departureDate: TripDateTime
  isArrival?: boolean
}): number => {
  const departureDay = departureDate.toFormat('yyyy-LL-dd')
  const arrivalDay = arrivalDate.toFormat('yyyy-LL-dd')

  if (isArrival) {
    return DateTime.fromISO(departureDay).diff(DateTime.fromISO(arrivalDay), 'days').days
  }

  return DateTime.fromISO(arrivalDay).diff(DateTime.fromISO(departureDay), 'days').days
}