import 'dart:async';

import 'package:flutter/services.dart' show rootBundle;

final RegExp esRegExp = RegExp('^es-');

String getFallbackLang(String lang) {
  if (lang == 'ast' ||
      lang == 'gl' ||
      lang == 'eu' ||
      lang == 'es' ||
      lang == 'ca' ||
      esRegExp.allMatches(lang).isNotEmpty) {
    return 'es';
  }
  return 'en';
}

Future<String> getFileNameOfLang(
    {required String dir,
    required String fileName,
    required String ext,
    required String lang}) async {
  final String base = '$dir/$fileName';
  final String fallback = getFallbackLang(lang);
  String file = '$base-$lang.$ext';
  if (await assetNotExists(file)) {
    file = '$base-$fallback.$ext';
    if (await assetNotExists(file)) {
      file = '$base.$ext';
    }
  }
  return file;
}

// https://github.com/flutter/flutter/issues/15325
Future<bool> assetNotExists(String asset) {
  return rootBundle
      .load(asset)
      .then((_) => false)
      .catchError((Object err, StackTrace stack) {
    return true;
  });
}