import { useAutoRef, type AutoRef } from './auto-ref.ts'

const safeTags = new Map<string, string>()

function safeTagFor(locale: string) {
  let safeTag = safeTags.get(locale)
  if (safeTag == null) {
    safeTag = new Intl.Locale(locale).baseName
    safeTags.set(locale, safeTag)
  }
  return safeTag
}

type DisplayNamesWrapper = Intl.DisplayNames & {
  of(tag: string): string | undefined
}

const displayNamesDicts = new Map<string, DisplayNamesWrapper>()

function getWrapperKey(locale: string, options: Intl.DisplayNamesOptions) {
  return JSON.stringify({ ...options, locale })
}

export function createDisplayNames(
  locale: string,
  options: Intl.DisplayNamesOptions = { type: 'language' }
) {
  const wrapperKey = getWrapperKey(locale, options)
  let wrapper = displayNamesDicts.get(wrapperKey)

  if (wrapper == null) {
    const dict = new Intl.DisplayNames(locale, options)

    const badTags: string[] = []

    wrapper = {
      resolvedOptions() {
        return dict.resolvedOptions()
      },
      of(tag: string) {
        let attempt = 0

        // eslint-disable-next-line no-labels
        lookupLoop: do {
          let lookup: string
          switch (attempt) {
            case 0:
              lookup = tag
              break
            case 1:
              lookup = safeTagFor(tag)
              break
            default:
              // eslint-disable-next-line no-labels
              break lookupLoop
          }

          if (badTags.includes(lookup)) continue

          try {
            return dict.of(lookup)
          } catch (err) {
            console.warn(
              `Failed to get display name for ${lookup} using dictionary for ${
                this.resolvedOptions().locale
              }`
            )
            badTags.push(lookup)
            continue
          }
        } while (++attempt < 5)

        return undefined
      },
    }

    displayNamesDicts.set(wrapperKey, wrapper)
  }

  return wrapper
}

export function useDisplayNames(
  locale: AutoRef<string>,
  options?: AutoRef<Intl.DisplayNamesOptions | undefined>
) {
  const $locale = useAutoRef(locale)
  const $options = useAutoRef(options)

  return computed(() => createDisplayNames($locale.value, $options.value))
}