TREK/client/src/components/Vacay/holidayRegions.ts

import apiClient from '../../api/client'
import iso31662 from 'iso-3166-2'
import { SCHOOL_HOLIDAY_COUNTRY_CONFIG } from '../../vacay/schoolHolidayCountries'

// Loads the subdivision (state/region) options for a holiday-calendar country.
//
// The subdivision list is sourced from ISO 3166-2 (proper names, complete per country)
// rather than inferred from which subdivisions happen to have a holiday this year — the
// latter silently dropped states with no state-specific holiday (e.g. US-WA, issue #1456).
// We only surface a list for countries that are actually region-partitioned, so countries
// with only nationwide holidays keep showing no region picker (and allow a country-level
// calendar, matching the server's applyHolidayCalendars behaviour).
export async function fetchRegionOptions(country: string): Promise<{ value: string; label: string }[]> {
  try {
    const year = new Date().getFullYear()
    const r = await apiClient.get(`/addons/vacay/holidays/${year}/${country}`)
    const hasRegions = r.data.some(h => h.counties && h.counties.length > 0)
    if (!hasRegions) return []

    const opts = new Map<string, string>() // ISO code -> display name
    const sub = iso31662.country(country)?.sub || {}
    for (const [code, info] of Object.entries(sub)) opts.set(code, info.name)

    // Fall back to any nager county code ISO doesn't know about, so nothing regresses.
    r.data.forEach(h => h.counties?.forEach(c => {
      if (!opts.has(c)) opts.set(c, iso31662.subdivision(c)?.name || c.split('-')[1] || c)
    }))

    return [...opts]
      .map(([value, label]) => ({ value, label }))
      .sort((a, b) => a.label.localeCompare(b.label))
  } catch {
    return []
  }
}

type LocalizedName = { language: string; text: string }
type OpenHolidayOption = {
  code: string
  shortName?: string
  name?: LocalizedName[]
  children?: OpenHolidayOption[] | null
}

function localizedName(names: LocalizedName[] | undefined, fallback: string): string {
  return names?.find(n => n.language?.toUpperCase() === 'DE')?.text
    || names?.find(n => n.language?.toUpperCase() === 'EN')?.text
    || names?.[0]?.text
    || fallback
}

function flattenOptions(items: OpenHolidayOption[] | undefined, prefix = ''): { value: string; label: string }[] {
  const result: { value: string; label: string }[] = []
  for (const item of items ?? []) {
    const label = localizedName(item.name, item.shortName || item.code)
    result.push({ value: item.code, label: prefix ? `${prefix} / ${label}` : label })
    result.push(...flattenOptions(item.children ?? undefined, prefix ? `${prefix} / ${label}` : label))
  }
  return result
}

export async function fetchSchoolHolidayRegionOptions(country: string): Promise<{ value: string; label: string }[]> {
  const config = SCHOOL_HOLIDAY_COUNTRY_CONFIG[country]
  if (!config || config.strategy === 'country') return []

  try {
    const r = await apiClient.get(`/addons/vacay/school-holidays/regions/${country}`)
    if (config.strategy === 'groups') {
      return flattenOptions(r.data.groups)
        .map(opt => ({
          value: `${country}|group:${opt.value}`,
          label: opt.label,
        }))
        .sort((a, b) => a.label.localeCompare(b.label))
    }

    return flattenOptions(r.data.subdivisions)
      .map(opt => ({ value: opt.value, label: opt.label }))
      .sort((a, b) => a.label.localeCompare(b.label))
  } catch {
    return []
  }
}