resolveLocalizedUnitSymbol function

String? resolveLocalizedUnitSymbol(String token, { String? locale, })

Resolve a localized token (possibly a full word or synonym) back to a canonical unit symbol. This is used by parseLocalized helpers. Returns null if no mapping is found. Resolves a localized token (full word or synonym) back to a canonical unit symbol. Returns null if no mapping is found.

Implementation

String? resolveLocalizedUnitSymbol(String token, {String? locale}) {
  if (token.isEmpty) return null;
  final t = token.toLowerCase();
  // 1) Custom synonyms take precedence
  if (locale != null && locale.isNotEmpty) {
    final key = locale.toLowerCase();
    final syn = _customLocalizedSynonyms[key];
    if (syn != null && syn.containsKey(t)) return syn[t];
  }

  // 2) Try to reverse-lookup default + custom localized names for the locale
  String? tryReverse(String loc) {
    final custom = _customLocalizedUnits[loc];
    if (custom != null) {
      for (final e in custom.entries) {
        if (e.value.toLowerCase() == t) return e.key;
      }
    }
    if (_defaultsEnabled) {
      final defaults = _defaultLocalizedUnits[loc];
      if (defaults != null) {
        for (final e in defaults.entries) {
          if (e.value.toLowerCase() == t) return e.key;
        }
      }
    }
    return null;
  }

  if (locale != null && locale.isNotEmpty) {
    final normalized = locale.toLowerCase();
    final exact = tryReverse(normalized);
    if (exact != null) return exact;
    final separatorIndex = normalized.indexOf(RegExp('[-_]'));
    if (separatorIndex != -1) {
      final base = normalized.substring(0, separatorIndex);
      final baseMatch = tryReverse(base);
      if (baseMatch != null) return baseMatch;
    }
  }

  // 3) Fallback to English reverse lookup
  final en = tryReverse('en');
  if (en != null) return en;

  // 4) Also accept raw symbols in any case
  const allSymbols = [
    'QB',
    'RB',
    'YB',
    'ZB',
    'EB',
    'PB',
    'TB',
    'GB',
    'MB',
    'KB',
    'B',
    'YiB',
    'ZiB',
    'EiB',
    'PiB',
    'TiB',
    'GiB',
    'MiB',
    'KiB',
    'qb',
    'rb',
    'yb',
    'zb',
    'eb',
    'pb',
    'tb',
    'gb',
    'mb',
    'kb',
    'b',
    'yib',
    'zib',
    'eib',
    'pib',
    'tib',
    'gib',
    'mib',
    'kib',
  ];
  final match = allSymbols.firstWhere(
    (s) => s.toLowerCase() == t,
    orElse: () => '',
  );
  return match.isEmpty ? null : match;
}