dev/tools/localization/gen_l10n_types.dart - external/github.com/flutter/flutter - Git at Google

 // Copyright 2014 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 import 'dart:convert';
 import 'dart:io';

 import 'package:intl/locale.dart';
 import 'package:path/path.dart' as path;

 import 'localizations_utils.dart';

 // The set of date formats that can be automatically localized.
 //
 // The localizations generation tool makes use of the intl library's
 // DateFormat class to properly format dates based on the locale, the
 // desired format, as well as the passed in [DateTime]. For example, using
 // DateFormat.yMMMMd("en_US").format(DateTime.utc(1996, 7, 10)) results
 // in the string "July 10, 1996".
 //
 // Since the tool generates code that uses DateFormat's constructor, it is
 // necessary to verify that the constructor exists, or the
 // tool will generate code that may cause a compile-time error.
 //
 // See also:
 //
 // * <https://pub.dev/packages/intl>
 // * <https://pub.dev/documentation/intl/latest/intl/DateFormat-class.html>
 // * <https://api.dartlang.org/stable/2.7.0/dart-core/DateTime-class.html>
 const Set<String> _validDateFormats = <String>{
   'd',
   'E',
   'EEEE',
   'LLL',
   'LLLL',
   'M',
   'Md',
   'MEd',
   'MMM',
   'MMMd',
   'MMMEd',
   'MMMM',
   'MMMMd',
   'MMMMEEEEd',
   'QQQ',
   'QQQQ',
   'y',
   'yM',
   'yMd',
   'yMEd',
   'yMMM',
   'yMMMd',
   'yMMMEd',
   'yMMMM',
   'yMMMMd',
   'yMMMMEEEEd',
   'yQQQ',
   'yQQQQ',
   'H',
   'Hm',
   'Hms',
   'j',
   'jm',
   'jms',
   'jmv',
   'jmz',
   'jv',
   'jz',
   'm',
   'ms',
   's',
 };

 // The set of number formats that can be automatically localized.
 //
 // The localizations generation tool makes use of the intl library's
 // NumberFormat class to properly format numbers based on the locale and
 // the desired format. For example, using
 // NumberFormat.compactLong("en_US").format(1200000) results
 // in the string "1.2 million".
 //
 // Since the tool generates code that uses NumberFormat's constructor, it is
 // necessary to verify that the constructor exists, or the
 // tool will generate code that may cause a compile-time error.
 //
 // See also:
 //
 // * <https://pub.dev/packages/intl>
 // * <https://pub.dev/documentation/intl/latest/intl/NumberFormat-class.html>
 const Set<String> _validNumberFormats = <String>{
   'compact',
   'compactCurrency',
   'compactSimpleCurrency',
   'compactLong',
   'currency',
   'decimalPattern',
   'decimalPercentPattern',
   'percentPattern',
   'scientificPattern',
   'simpleCurrency',
 };

 // The names of the NumberFormat factory constructors which have named
 // parameters rather than positional parameters.
 //
 // This helps the tool correctly generate number formmatting code correctly.
 //
 // Example of code that uses named parameters:
 // final NumberFormat format = NumberFormat.compact(
 //   locale: localeName,
 // );
 //
 // Example of code that uses positional parameters:
 // final NumberFormat format = NumberFormat.scientificPattern(localeName);
 const Set<String> _numberFormatsWithNamedParameters = <String>{
   'compact',
   'compactCurrency',
   'compactSimpleCurrency',
   'compactLong',
   'currency',
   'decimalPercentPattern',
   'simpleCurrency',
 };

 class L10nException implements Exception {
   L10nException(this.message);

   final String message;
 }

 // One optional named parameter to be used by a NumberFormat.
 //
 // Some of the NumberFormat factory constructors have optional named parameters.
 // For example NumberFormat.compactCurrency has a decimalDigits parameter that
 // specifies the number of decimal places to use when formatting.
 //
 // Optional parameters for NumberFormat placeholders are specified as a
 // JSON map value for optionalParameters in a resource's "@" ARB file entry:
 //
 // "@myResourceId": {
 //   "placeholders": {
 //     "myNumberPlaceholder": {
 //       "type": "double",
 //       "format": "compactCurrency",
 //       "optionalParameters": {
 //         "decimalDigits": 2
 //       }
 //     }
 //   }
 // }
 class OptionalParameter {
   const OptionalParameter(this.name, this.value) : assert(name != null), assert(value != null);

   final String name;
   final Object value;
 }

 // One message parameter: one placeholder from an @foo entry in the template ARB file.
 //
 // Placeholders are specified as a JSON map with one entry for each placeholder.
 // One placeholder must be specified for each message "{parameter}".
 // Each placeholder entry is also a JSON map. If the map is empty, the placeholder
 // is assumed to be an Object value whose toString() value will be displayed.
 // For example:
 //
 // "greeting": "{hello} {world}",
 // "@greeting": {
 //   "description": "A message with a two parameters",
 //   "placeholders": {
 //     "hello": {},
 //     "world": {}
 //   }
 // }
 //
 // Each placeholder can optionally specify a valid Dart type. If the type
 // is NumberFormat or DateFormat then a format which matches one of the
 // type's factory constructors can also be specified. In this example the
 // date placeholder is to be formated with DateFormat.yMMMMd:
 //
 // "helloWorldOn": "Hello World on {date}",
 // "@helloWorldOn": {
 //   "description": "A message with a date parameter",
 //   "placeholders": {
 //     "date": {
 //       "type": "DateTime",
 //       "format": "yMMMMd"
 //     }
 //   }
 // }
 //
 class Placeholder {
   Placeholder(this.resourceId, this.name, Map<String, dynamic> attributes)
     : assert(resourceId != null),
       assert(name != null),
       example = _stringAttribute(resourceId, name, attributes, 'example'),
       type = _stringAttribute(resourceId, name, attributes, 'type') ?? 'Object',
       format = _stringAttribute(resourceId, name, attributes, 'format'),
       optionalParameters = _optionalParameters(resourceId, name, attributes);

   final String resourceId;
   final String name;
   final String example;
   final String type;
   final String format;
   final List<OptionalParameter> optionalParameters;

   bool get requiresFormatting => <String>['DateTime', 'double', 'int', 'num'].contains(type);
   bool get isNumber => <String>['double', 'int', 'num'].contains(type);
   bool get hasValidNumberFormat => _validNumberFormats.contains(format);
   bool get hasNumberFormatWithParameters => _numberFormatsWithNamedParameters.contains(format);
   bool get isDate => 'DateTime' == type;
   bool get hasValidDateFormat => _validDateFormats.contains(format);

   static String _stringAttribute(
     String resourceId,
     String name,
     Map<String, dynamic> attributes,
     String attributeName,
   ) {
     final dynamic value = attributes[attributeName];
     if (value == null)
       return null;
     if (value is! String || (value as String).isEmpty) {
       throw L10nException(
         'The "$attributeName" value of the "$name" placeholder in message $resourceId '
         'must be a non-empty string.',
       );
     }
     return value as String;
   }

   static List<OptionalParameter> _optionalParameters(
     String resourceId,
     String name,
     Map<String, dynamic> attributes
   ) {
     final dynamic value = attributes['optionalParameters'];
     if (value == null)
       return <OptionalParameter>[];
     if (value is! Map<String, Object>) {
       throw L10nException(
         'The "optionalParameters" value of the "$name" placeholder in message '
         '$resourceId is not a properly formatted Map. Ensure that it is a map '
         'with keys that are strings.'
       );
     }
     final Map<String, dynamic> optionalParameterMap = value as Map<String, dynamic>;
     return optionalParameterMap.keys.map<OptionalParameter>((String parameterName) {
       return OptionalParameter(parameterName, optionalParameterMap[parameterName]);
     }).toList();
   }
 }

 // One translation: one pair of foo,@foo entries from the template ARB file.
 //
 // The template ARB file must contain an entry called @myResourceId for each
 // message named myResourceId. The @ entry describes message parameters
 // called "placeholders" and can include an optional description.
 // Here's a simple example message with no parameters:
 //
 // "helloWorld": "Hello World",
 // "@helloWorld": {
 //   "description": "The conventional newborn programmer greeting"
 // }
 //
 // The value of this Message is "Hello World". The Message's value is the
 // localized string to be shown for the template ARB file's locale.
 // The docs for the Placeholder explain how placeholder entries are defined.
 class Message {
   Message(Map<String, dynamic> bundle, this.resourceId)
     : assert(bundle != null),
       assert(resourceId != null && resourceId.isNotEmpty),
       value = _value(bundle, resourceId),
       description = _description(bundle, resourceId),
       placeholders = _placeholders(bundle, resourceId),
       _pluralMatch = _pluralRE.firstMatch(_value(bundle, resourceId));

   static final RegExp _pluralRE = RegExp(r'\s*\{([\w\s,]*),\s*plural\s*,');

   final String resourceId;
   final String value;
   final String description;
   final List<Placeholder> placeholders;
   final RegExpMatch _pluralMatch;

   bool get isPlural => _pluralMatch != null && _pluralMatch.groupCount == 1;

   bool get placeholdersRequireFormatting => placeholders.any((Placeholder p) => p.requiresFormatting);

   Placeholder getCountPlaceholder() {
     assert(isPlural);
     final String countPlaceholderName = _pluralMatch[1];
     return placeholders.firstWhere(
       (Placeholder p) => p.name == countPlaceholderName,
       orElse: () {
         throw L10nException('Cannot find the $countPlaceholderName placeholder in plural message "$resourceId".');
       }
     );
   }

   static String _value(Map<String, dynamic> bundle, String resourceId) {
     final dynamic value = bundle[resourceId];
     if (value == null)
       throw L10nException('A value for resource "$resourceId" was not found.');
     if (value is! String)
       throw L10nException('The value of "$resourceId" is not a string.');
     return bundle[resourceId] as String;
   }

   static Map<String, dynamic> _attributes(Map<String, dynamic> bundle, String resourceId) {
     final dynamic attributes = bundle['@$resourceId'];
     if (attributes == null) {
       throw L10nException(
         'Resource attribute "@$resourceId" was not found. Please '
         'ensure that each resource has a corresponding @resource.'
       );
     }
     if (attributes is! Map<String, dynamic>) {
       throw L10nException(
         'The resource attribute "@$resourceId" is not a properly formatted Map. '
         'Ensure that it is a map with keys that are strings.'
       );
     }
     return attributes as Map<String, dynamic>;
   }

   static String _description(Map<String, dynamic> bundle, String resourceId) {
     final dynamic value = _attributes(bundle, resourceId)['description'];
     if (value == null)
       return null;
     if (value is! String) {
       throw L10nException(
         'The description for "@$resourceId" is not a properly formatted String.'
       );
     }
     return value as String;
   }

   static List<Placeholder> _placeholders(Map<String, dynamic> bundle, String resourceId) {
     final dynamic value = _attributes(bundle, resourceId)['placeholders'];
     if (value == null)
       return <Placeholder>[];
     if (value is! Map<String, dynamic>) {
       throw L10nException(
         'The "placeholders" attribute for message $resourceId, is not '
         'properly formatted. Ensure that it is a map with string valued keys.'
       );
     }
     final Map<String, dynamic> allPlaceholdersMap = value as Map<String, dynamic>;
     return allPlaceholdersMap.keys.map<Placeholder>((String placeholderName) {
       final dynamic value = allPlaceholdersMap[placeholderName];
       if (value is! Map<String, dynamic>) {
         throw L10nException(
           'The value of the "$placeholderName" placeholder attribute for message '
           '"$resourceId", is not properly formatted. Ensure that it is a map '
           'with string valued keys.'
         );
       }
       return Placeholder(resourceId, placeholderName, value as Map<String, dynamic>);
     }).toList();
   }
 }

 // Represents the contents of one ARB file.
 class AppResourceBundle {
   factory AppResourceBundle(File file) {
     assert(file != null);
     // Assuming that the caller has verified that the file exists and is readable.
     Map<String, dynamic> resources;
     try {
       resources = json.decode(file.readAsStringSync()) as Map<String, dynamic>;
     } on FormatException catch (e) {
       throw L10nException(
         'The arb file ${file.path} has the following formatting issue: \n'
         '${e.toString()}',
       );
     }

     String localeString = resources['@@locale'] as String;

     // Look for the first instance of an ISO 639-1 language code, matching exactly.
     final String fileName = path.basenameWithoutExtension(file.path);

     for (int index = 0; index < fileName.length; index += 1) {
       // If an underscore was found, check if locale string follows.
       if (fileName[index] == '_' && fileName[index + 1] != null) {
         // If Locale.tryParse fails, it returns null.
         final Locale parserResult = Locale.tryParse(fileName.substring(index + 1));
         // If the parserResult is not an actual locale identifier, end the loop.
         if (parserResult != null && _iso639Languages.contains(parserResult.languageCode)) {
           // The parsed result uses dashes ('-'), but we want underscores ('_').
           final String parserLocaleString = parserResult.toString().replaceAll('-', '_');


           if (localeString == null) {
             // If @@locale was not defined, use the filename locale suffix.
             localeString = parserLocaleString;
           } else {
             // If the localeString was defined in @@locale and in the filename, verify to
             // see if the parsed locale matches, throw an error if it does not. This
             // prevents developers from confusing issues when both @@locale and
             // "_{locale}" is specified in the filename.
             if (localeString != parserLocaleString) {
               throw L10nException(
                 'The locale specified in @@locale and the arb filename do not match. \n'
                 'Please make sure that they match, since this prevents any confusion \n'
                 'with which locale to use. Otherwise, specify the locale in either the \n'
                 'filename of the @@locale key only.\n'
                 'Current @@locale value: $localeString\n'
                 'Current filename extension: $parserLocaleString'
               );
             }
           }
           break;
         }
       }
     }

     if (localeString == null) {
       throw L10nException(
         "The following .arb file's locale could not be determined: \n"
         '${file.path} \n'
         "Make sure that the locale is specified in the file's '@@locale' "
         'property or as part of the filename (e.g. file_en.arb)'
       );
     }

     final Iterable<String> ids = resources.keys.where((String key) => !key.startsWith('@'));
     return AppResourceBundle._(file, LocaleInfo.fromString(localeString), resources, ids);
   }

   const AppResourceBundle._(this.file, this.locale, this.resources, this.resourceIds);

   final File file;
   final LocaleInfo locale;
   final Map<String, dynamic> resources;
   final Iterable<String> resourceIds;

   String translationFor(Message message) => resources[message.resourceId] as String;

   @override
   String toString() {
     return 'AppResourceBundle($locale, ${file.path})';
   }
 }

 // Represents all of the ARB files in [directory] as [AppResourceBundle]s.
 class AppResourceBundleCollection {
   factory AppResourceBundleCollection(Directory directory) {
     assert(directory != null);
     // Assuming that the caller has verified that the directory is readable.

     final RegExp filenameRE = RegExp(r'(\w+)\.arb$');
     final Map<LocaleInfo, AppResourceBundle> localeToBundle = <LocaleInfo, AppResourceBundle>{};
     final Map<String, List<LocaleInfo>> languageToLocales = <String, List<LocaleInfo>>{};
     final List<File> files = directory.listSync().whereType<File>().toList()..sort(sortFilesByPath);
     for (final File file in files) {
       if (filenameRE.hasMatch(file.path)) {
         final AppResourceBundle bundle = AppResourceBundle(file);
         if (localeToBundle[bundle.locale] != null) {
           throw L10nException(
             "Multiple arb files with the same '${bundle.locale}' locale detected. \n"
             'Ensure that there is exactly one arb file for each locale.'
           );
         }
         localeToBundle[bundle.locale] = bundle;
         languageToLocales[bundle.locale.languageCode] ??= <LocaleInfo>[];
         languageToLocales[bundle.locale.languageCode].add(bundle.locale);
       }
     }

     languageToLocales.forEach((String language, List<LocaleInfo> listOfCorrespondingLocales) {
       final List<String> localeStrings = listOfCorrespondingLocales.map((LocaleInfo locale) {
         return locale.toString();
       }).toList();
       if (!localeStrings.contains(language)) {
         throw L10nException(
           'Arb file for a fallback, $language, does not exist, even though \n'
           'the following locale(s) exist: $listOfCorrespondingLocales. \n'
           'When locales specify a script code or country code, a \n'
           'base locale (without the script code or country code) should \n'
           'exist as the fallback. Please create a {fileName}_$language.arb \n'
           'file.'
         );
       }
     });

     return AppResourceBundleCollection._(directory, localeToBundle, languageToLocales);
   }

   const AppResourceBundleCollection._(this._directory, this._localeToBundle, this._languageToLocales);

   final Directory _directory;
   final Map<LocaleInfo, AppResourceBundle> _localeToBundle;
   final Map<String, List<LocaleInfo>> _languageToLocales;

   Iterable<LocaleInfo> get locales => _localeToBundle.keys;
   Iterable<AppResourceBundle> get bundles => _localeToBundle.values;
   AppResourceBundle bundleFor(LocaleInfo locale) => _localeToBundle[locale];

   Iterable<String> get languages => _languageToLocales.keys;
   Iterable<LocaleInfo> localesForLanguage(String language) => _languageToLocales[language] ?? <LocaleInfo>[];

   @override
   String toString() {
     return 'AppResourceBundleCollection(${_directory.path}, ${locales.length} locales)';
   }
 }

 // A set containing all the ISO630-1 languages. This list was pulled from https://datahub.io/core/language-codes.
 final Set<String> _iso639Languages = <String>{
   'aa',
   'ab',
   'ae',
   'af',
   'ak',
   'am',
   'an',
   'ar',
   'as',
   'av',
   'ay',
   'az',
   'ba',
   'be',
   'bg',
   'bh',
   'bi',
   'bm',
   'bn',
   'bo',
   'br',
   'bs',
   'ca',
   'ce',
   'ch',
   'co',
   'cr',
   'cs',
   'cu',
   'cv',
   'cy',
   'da',
   'de',
   'dv',
   'dz',
   'ee',
   'el',
   'en',
   'eo',
   'es',
   'et',
   'eu',
   'fa',
   'ff',
   'fi',
   'fil',
   'fj',
   'fo',
   'fr',
   'fy',
   'ga',
   'gd',
   'gl',
   'gn',
   'gsw',
   'gu',
   'gv',
   'ha',
   'he',
   'hi',
   'ho',
   'hr',
   'ht',
   'hu',
   'hy',
   'hz',
   'ia',
   'id',
   'ie',
   'ig',
   'ii',
   'ik',
   'io',
   'is',
   'it',
   'iu',
   'ja',
   'jv',
   'ka',
   'kg',
   'ki',
   'kj',
   'kk',
   'kl',
   'km',
   'kn',
   'ko',
   'kr',
   'ks',
   'ku',
   'kv',
   'kw',
   'ky',
   'la',
   'lb',
   'lg',
   'li',
   'ln',
   'lo',
   'lt',
   'lu',
   'lv',
   'mg',
   'mh',
   'mi',
   'mk',
   'ml',
   'mn',
   'mr',
   'ms',
   'mt',
   'my',
   'na',
   'nb',
   'nd',
   'ne',
   'ng',
   'nl',
   'nn',
   'no',
   'nr',
   'nv',
   'ny',
   'oc',
   'oj',
   'om',
   'or',
   'os',
   'pa',
   'pi',
   'pl',
   'ps',
   'pt',
   'qu',
   'rm',
   'rn',
   'ro',
   'ru',
   'rw',
   'sa',
   'sc',
   'sd',
   'se',
   'sg',
   'si',
   'sk',
   'sl',
   'sm',
   'sn',
   'so',
   'sq',
   'sr',
   'ss',
   'st',
   'su',
   'sv',
   'sw',
   'ta',
   'te',
   'tg',
   'th',
   'ti',
   'tk',
   'tl',
   'tn',
   'to',
   'tr',
   'ts',
   'tt',
   'tw',
   'ty',
   'ug',
   'uk',
   'ur',
   'uz',
   've',
   'vi',
   'vo',
   'wa',
   'wo',
   'xh',
   'yi',
   'yo',
   'za',
   'zh',
   'zu',
 };
	// Copyright 2014 The Flutter Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	import 'dart:convert';
	import 'dart:io';

	import 'package:intl/locale.dart';
	import 'package:path/path.dart' as path;

	import 'localizations_utils.dart';

	// The set of date formats that can be automatically localized.
	//
	// The localizations generation tool makes use of the intl library's
	// DateFormat class to properly format dates based on the locale, the
	// desired format, as well as the passed in [DateTime]. For example, using
	// DateFormat.yMMMMd("en_US").format(DateTime.utc(1996, 7, 10)) results
	// in the string "July 10, 1996".
	//
	// Since the tool generates code that uses DateFormat's constructor, it is
	// necessary to verify that the constructor exists, or the
	// tool will generate code that may cause a compile-time error.
	//
	// See also:
	//
	// * <https://pub.dev/packages/intl>
	// * <https://pub.dev/documentation/intl/latest/intl/DateFormat-class.html>
	// * <https://api.dartlang.org/stable/2.7.0/dart-core/DateTime-class.html>
	const Set<String> _validDateFormats = <String>{
	'd',
	'E',
	'EEEE',
	'LLL',
	'LLLL',
	'M',
	'Md',
	'MEd',
	'MMM',
	'MMMd',
	'MMMEd',
	'MMMM',
	'MMMMd',
	'MMMMEEEEd',
	'QQQ',
	'QQQQ',
	'y',
	'yM',
	'yMd',
	'yMEd',
	'yMMM',
	'yMMMd',
	'yMMMEd',
	'yMMMM',
	'yMMMMd',
	'yMMMMEEEEd',
	'yQQQ',
	'yQQQQ',
	'H',
	'Hm',
	'Hms',
	'j',
	'jm',
	'jms',
	'jmv',
	'jmz',
	'jv',
	'jz',
	'm',
	'ms',
	's',
	};

	// The set of number formats that can be automatically localized.
	//
	// The localizations generation tool makes use of the intl library's
	// NumberFormat class to properly format numbers based on the locale and
	// the desired format. For example, using
	// NumberFormat.compactLong("en_US").format(1200000) results
	// in the string "1.2 million".
	//
	// Since the tool generates code that uses NumberFormat's constructor, it is
	// necessary to verify that the constructor exists, or the
	// tool will generate code that may cause a compile-time error.
	//
	// See also:
	//
	// * <https://pub.dev/packages/intl>
	// * <https://pub.dev/documentation/intl/latest/intl/NumberFormat-class.html>
	const Set<String> _validNumberFormats = <String>{
	'compact',
	'compactCurrency',
	'compactSimpleCurrency',
	'compactLong',
	'currency',
	'decimalPattern',
	'decimalPercentPattern',
	'percentPattern',
	'scientificPattern',
	'simpleCurrency',
	};

	// The names of the NumberFormat factory constructors which have named
	// parameters rather than positional parameters.
	//
	// This helps the tool correctly generate number formmatting code correctly.
	//
	// Example of code that uses named parameters:
	// final NumberFormat format = NumberFormat.compact(
	// locale: localeName,
	// );
	//
	// Example of code that uses positional parameters:
	// final NumberFormat format = NumberFormat.scientificPattern(localeName);
	const Set<String> _numberFormatsWithNamedParameters = <String>{
	'compact',
	'compactCurrency',
	'compactSimpleCurrency',
	'compactLong',
	'currency',
	'decimalPercentPattern',
	'simpleCurrency',
	};

	class L10nException implements Exception {
	L10nException(this.message);

	final String message;
	}

	// One optional named parameter to be used by a NumberFormat.
	//
	// Some of the NumberFormat factory constructors have optional named parameters.
	// For example NumberFormat.compactCurrency has a decimalDigits parameter that
	// specifies the number of decimal places to use when formatting.
	//
	// Optional parameters for NumberFormat placeholders are specified as a
	// JSON map value for optionalParameters in a resource's "@" ARB file entry:
	//
	// "@myResourceId": {
	// "placeholders": {
	// "myNumberPlaceholder": {
	// "type": "double",
	// "format": "compactCurrency",
	// "optionalParameters": {
	// "decimalDigits": 2
	// }
	// }
	// }
	// }
	class OptionalParameter {
	const OptionalParameter(this.name, this.value) : assert(name != null), assert(value != null);

	final String name;
	final Object value;
	}

	// One message parameter: one placeholder from an @foo entry in the template ARB file.
	//
	// Placeholders are specified as a JSON map with one entry for each placeholder.
	// One placeholder must be specified for each message "{parameter}".
	// Each placeholder entry is also a JSON map. If the map is empty, the placeholder
	// is assumed to be an Object value whose toString() value will be displayed.
	// For example:
	//
	// "greeting": "{hello} {world}",
	// "@greeting": {
	// "description": "A message with a two parameters",
	// "placeholders": {
	// "hello": {},
	// "world": {}
	// }
	// }
	//
	// Each placeholder can optionally specify a valid Dart type. If the type
	// is NumberFormat or DateFormat then a format which matches one of the
	// type's factory constructors can also be specified. In this example the
	// date placeholder is to be formated with DateFormat.yMMMMd:
	//
	// "helloWorldOn": "Hello World on {date}",
	// "@helloWorldOn": {
	// "description": "A message with a date parameter",
	// "placeholders": {
	// "date": {
	// "type": "DateTime",
	// "format": "yMMMMd"
	// }
	// }
	// }
	//
	class Placeholder {
	Placeholder(this.resourceId, this.name, Map<String, dynamic> attributes)
	: assert(resourceId != null),
	assert(name != null),
	example = _stringAttribute(resourceId, name, attributes, 'example'),
	type = _stringAttribute(resourceId, name, attributes, 'type') ?? 'Object',
	format = _stringAttribute(resourceId, name, attributes, 'format'),
	optionalParameters = _optionalParameters(resourceId, name, attributes);

	final String resourceId;
	final String name;
	final String example;
	final String type;
	final String format;
	final List<OptionalParameter> optionalParameters;

	bool get requiresFormatting => <String>['DateTime', 'double', 'int', 'num'].contains(type);
	bool get isNumber => <String>['double', 'int', 'num'].contains(type);
	bool get hasValidNumberFormat => _validNumberFormats.contains(format);
	bool get hasNumberFormatWithParameters => _numberFormatsWithNamedParameters.contains(format);
	bool get isDate => 'DateTime' == type;
	bool get hasValidDateFormat => _validDateFormats.contains(format);

	static String _stringAttribute(
	String resourceId,
	String name,
	Map<String, dynamic> attributes,
	String attributeName,
	) {
	final dynamic value = attributes[attributeName];
	if (value == null)
	return null;
	if (value is! String \|\| (value as String).isEmpty) {
	throw L10nException(
	'The "$attributeName" value of the "$name" placeholder in message $resourceId '
	'must be a non-empty string.',
	);
	}
	return value as String;
	}

	static List<OptionalParameter> _optionalParameters(
	String resourceId,
	String name,
	Map<String, dynamic> attributes
	) {
	final dynamic value = attributes['optionalParameters'];
	if (value == null)
	return <OptionalParameter>[];
	if (value is! Map<String, Object>) {
	throw L10nException(
	'The "optionalParameters" value of the "$name" placeholder in message '
	'$resourceId is not a properly formatted Map. Ensure that it is a map '
	'with keys that are strings.'
	);
	}
	final Map<String, dynamic> optionalParameterMap = value as Map<String, dynamic>;
	return optionalParameterMap.keys.map<OptionalParameter>((String parameterName) {
	return OptionalParameter(parameterName, optionalParameterMap[parameterName]);
	}).toList();
	}
	}

	// One translation: one pair of foo,@foo entries from the template ARB file.
	//
	// The template ARB file must contain an entry called @myResourceId for each
	// message named myResourceId. The @ entry describes message parameters
	// called "placeholders" and can include an optional description.
	// Here's a simple example message with no parameters:
	//
	// "helloWorld": "Hello World",
	// "@helloWorld": {
	// "description": "The conventional newborn programmer greeting"
	// }
	//
	// The value of this Message is "Hello World". The Message's value is the
	// localized string to be shown for the template ARB file's locale.
	// The docs for the Placeholder explain how placeholder entries are defined.
	class Message {
	Message(Map<String, dynamic> bundle, this.resourceId)
	: assert(bundle != null),
	assert(resourceId != null && resourceId.isNotEmpty),
	value = _value(bundle, resourceId),
	description = _description(bundle, resourceId),
	placeholders = _placeholders(bundle, resourceId),
	_pluralMatch = _pluralRE.firstMatch(_value(bundle, resourceId));

	static final RegExp _pluralRE = RegExp(r'\s\{([\w\s,]),\splural\s,');

	final String resourceId;
	final String value;
	final String description;
	final List<Placeholder> placeholders;
	final RegExpMatch _pluralMatch;

	bool get isPlural => _pluralMatch != null && _pluralMatch.groupCount == 1;

	bool get placeholdersRequireFormatting => placeholders.any((Placeholder p) => p.requiresFormatting);

	Placeholder getCountPlaceholder() {
	assert(isPlural);
	final String countPlaceholderName = _pluralMatch[1];
	return placeholders.firstWhere(
	(Placeholder p) => p.name == countPlaceholderName,
	orElse: () {
	throw L10nException('Cannot find the $countPlaceholderName placeholder in plural message "$resourceId".');
	}
	);
	}

	static String _value(Map<String, dynamic> bundle, String resourceId) {
	final dynamic value = bundle[resourceId];
	if (value == null)
	throw L10nException('A value for resource "$resourceId" was not found.');
	if (value is! String)
	throw L10nException('The value of "$resourceId" is not a string.');
	return bundle[resourceId] as String;
	}

	static Map<String, dynamic> _attributes(Map<String, dynamic> bundle, String resourceId) {
	final dynamic attributes = bundle['@$resourceId'];
	if (attributes == null) {
	throw L10nException(
	'Resource attribute "@$resourceId" was not found. Please '
	'ensure that each resource has a corresponding @resource.'
	);
	}
	if (attributes is! Map<String, dynamic>) {
	throw L10nException(
	'The resource attribute "@$resourceId" is not a properly formatted Map. '
	'Ensure that it is a map with keys that are strings.'
	);
	}
	return attributes as Map<String, dynamic>;
	}

	static String _description(Map<String, dynamic> bundle, String resourceId) {
	final dynamic value = _attributes(bundle, resourceId)['description'];
	if (value == null)
	return null;
	if (value is! String) {
	throw L10nException(
	'The description for "@$resourceId" is not a properly formatted String.'
	);
	}
	return value as String;
	}

	static List<Placeholder> _placeholders(Map<String, dynamic> bundle, String resourceId) {
	final dynamic value = _attributes(bundle, resourceId)['placeholders'];
	if (value == null)
	return <Placeholder>[];
	if (value is! Map<String, dynamic>) {
	throw L10nException(
	'The "placeholders" attribute for message $resourceId, is not '
	'properly formatted. Ensure that it is a map with string valued keys.'
	);
	}
	final Map<String, dynamic> allPlaceholdersMap = value as Map<String, dynamic>;
	return allPlaceholdersMap.keys.map<Placeholder>((String placeholderName) {
	final dynamic value = allPlaceholdersMap[placeholderName];
	if (value is! Map<String, dynamic>) {
	throw L10nException(
	'The value of the "$placeholderName" placeholder attribute for message '
	'"$resourceId", is not properly formatted. Ensure that it is a map '
	'with string valued keys.'
	);
	}
	return Placeholder(resourceId, placeholderName, value as Map<String, dynamic>);
	}).toList();
	}
	}

	// Represents the contents of one ARB file.
	class AppResourceBundle {
	factory AppResourceBundle(File file) {
	assert(file != null);
	// Assuming that the caller has verified that the file exists and is readable.
	Map<String, dynamic> resources;
	try {
	resources = json.decode(file.readAsStringSync()) as Map<String, dynamic>;
	} on FormatException catch (e) {
	throw L10nException(
	'The arb file ${file.path} has the following formatting issue: \n'
	'${e.toString()}',
	);
	}

	String localeString = resources['@@locale'] as String;

	// Look for the first instance of an ISO 639-1 language code, matching exactly.
	final String fileName = path.basenameWithoutExtension(file.path);

	for (int index = 0; index < fileName.length; index += 1) {
	// If an underscore was found, check if locale string follows.
	if (fileName[index] == '_' && fileName[index + 1] != null) {
	// If Locale.tryParse fails, it returns null.
	final Locale parserResult = Locale.tryParse(fileName.substring(index + 1));
	// If the parserResult is not an actual locale identifier, end the loop.
	if (parserResult != null && _iso639Languages.contains(parserResult.languageCode)) {
	// The parsed result uses dashes ('-'), but we want underscores ('_').
	final String parserLocaleString = parserResult.toString().replaceAll('-', '_');


	if (localeString == null) {
	// If @@locale was not defined, use the filename locale suffix.
	localeString = parserLocaleString;
	} else {
	// If the localeString was defined in @@locale and in the filename, verify to
	// see if the parsed locale matches, throw an error if it does not. This
	// prevents developers from confusing issues when both @@locale and
	// "_{locale}" is specified in the filename.
	if (localeString != parserLocaleString) {
	throw L10nException(
	'The locale specified in @@locale and the arb filename do not match. \n'
	'Please make sure that they match, since this prevents any confusion \n'
	'with which locale to use. Otherwise, specify the locale in either the \n'
	'filename of the @@locale key only.\n'
	'Current @@locale value: $localeString\n'
	'Current filename extension: $parserLocaleString'
	);
	}
	}
	break;
	}
	}
	}

	if (localeString == null) {
	throw L10nException(
	"The following .arb file's locale could not be determined: \n"
	'${file.path} \n'
	"Make sure that the locale is specified in the file's '@@locale' "
	'property or as part of the filename (e.g. file_en.arb)'
	);
	}

	final Iterable<String> ids = resources.keys.where((String key) => !key.startsWith('@'));
	return AppResourceBundle._(file, LocaleInfo.fromString(localeString), resources, ids);
	}

	const AppResourceBundle._(this.file, this.locale, this.resources, this.resourceIds);

	final File file;
	final LocaleInfo locale;
	final Map<String, dynamic> resources;
	final Iterable<String> resourceIds;

	String translationFor(Message message) => resources[message.resourceId] as String;

	@override
	String toString() {
	return 'AppResourceBundle($locale, ${file.path})';
	}
	}

	// Represents all of the ARB files in [directory] as [AppResourceBundle]s.
	class AppResourceBundleCollection {
	factory AppResourceBundleCollection(Directory directory) {
	assert(directory != null);
	// Assuming that the caller has verified that the directory is readable.

	final RegExp filenameRE = RegExp(r'(\w+)\.arb$');
	final Map<LocaleInfo, AppResourceBundle> localeToBundle = <LocaleInfo, AppResourceBundle>{};
	final Map<String, List<LocaleInfo>> languageToLocales = <String, List<LocaleInfo>>{};
	final List<File> files = directory.listSync().whereType<File>().toList()..sort(sortFilesByPath);
	for (final File file in files) {
	if (filenameRE.hasMatch(file.path)) {
	final AppResourceBundle bundle = AppResourceBundle(file);
	if (localeToBundle[bundle.locale] != null) {
	throw L10nException(
	"Multiple arb files with the same '${bundle.locale}' locale detected. \n"
	'Ensure that there is exactly one arb file for each locale.'
	);
	}
	localeToBundle[bundle.locale] = bundle;
	languageToLocales[bundle.locale.languageCode] ??= <LocaleInfo>[];
	languageToLocales[bundle.locale.languageCode].add(bundle.locale);
	}
	}

	languageToLocales.forEach((String language, List<LocaleInfo> listOfCorrespondingLocales) {
	final List<String> localeStrings = listOfCorrespondingLocales.map((LocaleInfo locale) {
	return locale.toString();
	}).toList();
	if (!localeStrings.contains(language)) {
	throw L10nException(
	'Arb file for a fallback, $language, does not exist, even though \n'
	'the following locale(s) exist: $listOfCorrespondingLocales. \n'
	'When locales specify a script code or country code, a \n'
	'base locale (without the script code or country code) should \n'
	'exist as the fallback. Please create a {fileName}_$language.arb \n'
	'file.'
	);
	}
	});

	return AppResourceBundleCollection._(directory, localeToBundle, languageToLocales);
	}

	const AppResourceBundleCollection._(this._directory, this._localeToBundle, this._languageToLocales);

	final Directory _directory;
	final Map<LocaleInfo, AppResourceBundle> _localeToBundle;
	final Map<String, List<LocaleInfo>> _languageToLocales;

	Iterable<LocaleInfo> get locales => _localeToBundle.keys;
	Iterable<AppResourceBundle> get bundles => _localeToBundle.values;
	AppResourceBundle bundleFor(LocaleInfo locale) => _localeToBundle[locale];

	Iterable<String> get languages => _languageToLocales.keys;
	Iterable<LocaleInfo> localesForLanguage(String language) => _languageToLocales[language] ?? <LocaleInfo>[];

	@override
	String toString() {
	return 'AppResourceBundleCollection(${_directory.path}, ${locales.length} locales)';
	}
	}

	// A set containing all the ISO630-1 languages. This list was pulled from https://datahub.io/core/language-codes.
	final Set<String> _iso639Languages = <String>{
	'aa',
	'ab',
	'ae',
	'af',
	'ak',
	'am',
	'an',
	'ar',
	'as',
	'av',
	'ay',
	'az',
	'ba',
	'be',
	'bg',
	'bh',
	'bi',
	'bm',
	'bn',
	'bo',
	'br',
	'bs',
	'ca',
	'ce',
	'ch',
	'co',
	'cr',
	'cs',
	'cu',
	'cv',
	'cy',
	'da',
	'de',
	'dv',
	'dz',
	'ee',
	'el',
	'en',
	'eo',
	'es',
	'et',
	'eu',
	'fa',
	'ff',
	'fi',
	'fil',
	'fj',
	'fo',
	'fr',
	'fy',
	'ga',
	'gd',
	'gl',
	'gn',
	'gsw',
	'gu',
	'gv',
	'ha',
	'he',
	'hi',
	'ho',
	'hr',
	'ht',
	'hu',
	'hy',
	'hz',
	'ia',
	'id',
	'ie',
	'ig',
	'ii',
	'ik',
	'io',
	'is',
	'it',
	'iu',
	'ja',
	'jv',
	'ka',
	'kg',
	'ki',
	'kj',
	'kk',
	'kl',
	'km',
	'kn',
	'ko',
	'kr',
	'ks',
	'ku',
	'kv',
	'kw',
	'ky',
	'la',
	'lb',
	'lg',
	'li',
	'ln',
	'lo',
	'lt',
	'lu',
	'lv',
	'mg',
	'mh',
	'mi',
	'mk',
	'ml',
	'mn',
	'mr',
	'ms',
	'mt',
	'my',
	'na',
	'nb',
	'nd',
	'ne',
	'ng',
	'nl',
	'nn',
	'no',
	'nr',
	'nv',
	'ny',
	'oc',
	'oj',
	'om',
	'or',
	'os',
	'pa',
	'pi',
	'pl',
	'ps',
	'pt',
	'qu',
	'rm',
	'rn',
	'ro',
	'ru',
	'rw',
	'sa',
	'sc',
	'sd',
	'se',
	'sg',
	'si',
	'sk',
	'sl',
	'sm',
	'sn',
	'so',
	'sq',
	'sr',
	'ss',
	'st',
	'su',
	'sv',
	'sw',
	'ta',
	'te',
	'tg',
	'th',
	'ti',
	'tk',
	'tl',
	'tn',
	'to',
	'tr',
	'ts',
	'tt',
	'tw',
	'ty',
	'ug',
	'uk',
	'ur',
	'uz',
	've',
	'vi',
	'vo',
	'wa',
	'wo',
	'xh',
	'yi',
	'yo',
	'za',
	'zh',
	'zu',
	};