Auto translate all translation keys into supported target languages for arb file in Flutter app.

translate_arb.dart

import 'dart:io';

import 'package:http/http.dart' as http;
import 'dart:convert';

const String googleTranslateUrl =
    'https://translation.googleapis.com/language/translate/v2';

Future<String> translateText(
    String text, String targetLanguage, String apiKey) async {
  final body = jsonEncode({
    'q': text,
    'target': targetLanguage,
  });
  final response = await http.post(
    Uri.parse('$googleTranslateUrl?key=$apiKey'),
    headers: {'Content-Type': 'application/json'},
    body: body,
  );
  final translation = jsonDecode(response.body);
  return translation['data']['translations'][0]['translatedText'];
}

Map<String, dynamic> arbLoadFile(String path) {
  final file = File(path);
  final content = file.readAsStringSync();
  return jsonDecode(content);
}

String getTargetLanguage(Map<String, dynamic> locale) {
  return locale['@@locale'];
}

void main(List<String> args) async {
  // Replace with your project details
  const apiKey = 'YOUR_API_KEY';

  // Replace 'lib/l10n' with your actual localization directory path
  final directory = Directory('lib/l10n');
  final englishFile = File('${directory.path}/app_en.arb');

  // Parse the English file as reference
  final englishLocale = arbLoadFile(englishFile.path);

  // Loop through other locale files (except English)
  for (var entity in directory.listSync()) {
    if (entity is File && entity.path != englishFile.path) {
      if (!entity.path.endsWith('.arb')) {
        // Skip if not an ARB file
        continue;
      }

      final localeFile = File(entity.path);
      final locale = arbLoadFile(localeFile.path);

      final targetLanguage = getTargetLanguage(locale);

      final result = {};
      print('Translating $targetLanguage...');

      for (var key in englishLocale.keys) {
        // if the key is locale use the target language
        if (key == '@@locale') {
          result[key] = targetLanguage;
          continue;
        }

        // skip if key is meta key
        if (key.startsWith('@')) {
          continue;
        }

        // Check for missing keys compared to English
        if (!locale.containsKey(key)) {
          final englishValue = englishLocale[key];
          final translatedValue =
              await translateText(englishValue, targetLanguage, apiKey);
          result[key] = translatedValue;
          print('Translated $key: $englishValue -> $translatedValue');
        } else {
          result[key] = locale[key];
        }
      }

      // Write the result to the locale file
      localeFile.writeAsStringSync(jsonEncode(result));
    }
  }

  print('Translation completed!');
}

Make sure you have created app_<locale>.arb file with at least {"@@locale": "<locale>"} for each locale you can to translate.