private Stream getMatchingExtendedLanguageRanges()

in locales-common/src/main/java/com/spotify/i18n/locales/common/impl/LocalesResolverBaseImpl.java [213:266]
33 lines of code
4 McCabe index (conditional complexity)

  private Stream<LanguageRange> getMatchingExtendedLanguageRanges(
      final LanguageRange languageRange) {
    // If there are no wildcards, we just return the range. This is the most likely outcome.
    if (!languageRange.getRange().contains(LANGUAGE_RANGE_WILDCARD)) {
      return Stream.of(languageRange);
    }

    // Strip the range of any trailing -*
    String cleanedRange =
        languageRange.getRange().replaceAll("(-\\" + LANGUAGE_RANGE_WILDCARD + ")*$", "");

    // The range only contained wildcards, so we simply ignore it.
    if (LANGUAGE_RANGE_WILDCARD.equals(cleanedRange)) {
      return Stream.of();
    }

    // There were only trailing wildcards in this range, meaning we don't need to extend it for
    // locale resolution to get the best possible match.
    if (!cleanedRange.contains(LANGUAGE_RANGE_WILDCARD)) {
      return Stream.of(new LanguageRange(cleanedRange, languageRange.getWeight()));
    }

    // In order to enable parsing, we replace * by Und
    String preparedRangeForParsing =
        cleanedRange.replace(LANGUAGE_RANGE_WILDCARD, ULOCALE_UNDEFINED_CODE);

    // Parse the locale and extend all undefined locale codes accordingly
    return LanguageTagUtils.parse(preparedRangeForParsing)
        .map(
            parsedLocale ->
                // As candidate locales for extension, we include and prioritize the most likely
                // locale according to CLDR, then add all the supported locales for translations
                Stream.concat(
                        Stream.of(ULocale.addLikelySubtags(parsedLocale)),
                        supportedLocales().stream().map(SupportedLocale::localeForTranslations))
                    // We extend the parsed locale by defining undefined locale codes,
                    // using the ones from the candidate locales, and retain only the ones available
                    // in CLDR.
                    // Note: Ideally, entries corresponding to the same region/country should be
                    // ordered by decreasing % of language coverage, to prioritize languages
                    // accordingly, but we don't do it here as we do not have this data at hand.
                    .map(
                        supportedLocale ->
                            mitigateParsedLocaleUndefinedCodes(supportedLocale, parsedLocale))
                    .filter(AVAILABLE_UNICODE_LOCALES::contains)
                    // We remove potential duplicates
                    .distinct()
                    .map(
                        localeWithinRange ->
                            new LanguageRange(
                                localeWithinRange.toLanguageTag().toLowerCase(),
                                languageRange.getWeight())))
        .orElse(Stream.empty());
  }