First implementation

.gitignore

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+.dart_tool
+.idea
+.packages

LICENSE

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+MIT License
+
+Copyright (c) 2017 serenader
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# Dart Gettext
+
+A Dart implementation of gettext, a localization framework.
+
+Rewritten to dart of [node-gettext](https://github.com/alexanderwallin/node-gettext) package.
+
+Also works perfectly with flutter.
+
+## Features
+
+- Supports domains, contexts and plurals
+- Ships with plural forms for 136 languages
+- Change locale or domain on the fly
+- Emits events for internal errors, such as missing translations
+
+
+## Usage
+
+```dart
+import "package:gettext/gettext.dart";
+
+final gt = new Gettext(onWarning: print);
+```
+
+Load data from json:
+```dart
+new File("./en_US.json").readAsString().then(
+ (data) {
+ final json = json.decode(data["translations"]);
+ final gt = new Gettext();
+ gt.addTranslations('en_US', Translations.fromJSON(json));
+ }
+);
+```
+
+Json content:
+```json
+{
+ "charset": "utf-8",
+ "headers": {
+ "mime-version": "1.0",
+ "content-type": "text/plain; charset=utf-8",
+ "content-transfer-encoding": "8bit",
+ "language": "es-ES",
+ "plural-forms": "nplurals=2; plural=(n!=1);",
+ },
+ "translations": {
+ "": {
+ "Hello": {
+ "msgid": "Hello",
+ "comments": {
+ "translator": "Normal string"
+ },
+ "msgstr": [
+ "Hola"
+ ]
+ },
+ "An apple": {
+ "msgid": "1 apple",
+ "comments": {
+ "translator": "Plural string"
+ },
+ "msgstr": [
+ "una manzana",
+ "%d manzanas"
+ ]
+ }
+ }
+ }
+}
+```
+
+Change locale:
+```dart
+gt.locale = "en_US";
+```
+
+Change default domain:
+```dart
+gt.domain = "types";
+```
+
+Translate messages:
+```dart
+gt.gettext("Hello");
+```
+
+Translate messages with plural forms:
+```dart
+gt.ngettext("An apple", "%d apples", 3); // returns "%d apples"
+```
+
+
+## API
+
+- gettext(String msgid, {String domain, String context}) → `String`
+- ngettext(String msgid, String msgplural, int count, {String domain, String context}) → `String`
+
+## Working with Flutter
+
+```dart
+import 'package:flutter/widgets.dart';
+import 'package:sprintf/sprintf.dart';
+import 'package:gettext/gettext.dart';
+
+class GettextLocalizations {
+ final Gettext gt;
+
+ GettextLocalizations(this.gt);
+
+ static GettextLocalizations of(BuildContext context) {
+ return Localizations.of<GettextLocalizations>(
+ context, GettextLocalizations);
+ }
+
+ String __(
+ String msgid, [
+ List args = const [],
+ ]) {
+ return sprintf(gt.gettext(msgid), args);
+ }
+
+ String __n(
+ String msgid,
+ String msgidPlural,
+ int count, [
+ List arg = const [],
+ ]) {
+ return sprintf(
+ gt.ngettext(msgid, msgidPlural, count),
+ <dynamic>[count]..addAll(arg),
+ );
+ }
+}
+
+class GettextLocalizationsDelegate
+ extends LocalizationsDelegate<GettextLocalizations> {
+ final gettext = new Gettext();
+
+ @override
+ bool isSupported(Locale locale) => true;
+
+ @override
+ bool shouldReload(LocalizationsDelegate<GettextLocalizations> old) => false;
+
+ @override
+ Future<GettextLocalizations> load(Locale locale) {
+ return loadData(locale).then((data) {
+ gettext.locale = locale.toString();
+ gettext.addTranslations(locale.toString(), Translations.fromJson(data));
+ return GettextLocalizations(gettext);
+ });
+ }
+}
+```

lib/gettext.dart

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+library gettext;
+
+import 'plurals.dart';
+
+typedef OnWarning(String message);
+
+class Gettext {
+ final Map<String, Catalog> catalogs = new Map();
+ final OnWarning onWarning;
+
+ Gettext({this.onWarning});
+
+ Function _pluralsFunc = (n) => 0;
+
+ String _locale = '';
+ String _domain = 'messages';
+
+ String get locale => _locale;
+
+ set locale(String value) {
+ _locale = value ?? '';
+ _pluralsFunc = plurals[getLanguageCode(_locale)]?.pluralsFunc;
+ }
+
+ String get domain => _domain;
+
+ set domain(String value) => _locale = value ?? '';
+
+ /**
+ * Stores a set of translations in the set of gettext catalogs.
+ *
+ * @example
+ *  gt.addTranslations('sv-SE', translations, domain: 'messages')
+ *
+ * @param {String} locale A locale string
+ * @param {String} domain A domain name
+ * @param {Object} translations An object of gettext-parser JSON shape
+ */
+ void addTranslations(String locale, Translations translations,
+ {String domain: 'messages'}) {
+ if (!catalogs.containsKey(locale)) {
+ catalogs[locale] = new Catalog({});
+ }
+
+ catalogs[locale].addTranslations(domain, translations);
+
+ if (_locale.isEmpty) {
+ this.locale = locale;
+ }
+ }
+
+ /**
+ * Translates a string using the default textdomain
+ *
+ * @example
+ *  gt.gettext('Some text')
+ *
+ * @param {String} msgid String to be translated
+ * @return {String} Translation or the original string if no translation was found
+ */
+ String gettext(String msgid, {String domain, String msgctxt = ''}) {
+ final translation = this._getTranslation(
+ domain ?? this.domain,
+ msgctxt,
+ msgid,
+ );
+
+ if (translation == null || translation.msgstr[0]?.isNotEmpty != true) {
+ _warn('No translation was found for '
+ 'msgid "$msgid" in msgctxt "$msgctxt" and domain "$domain"');
+ return msgid;
+ }
+
+ return translation.msgstr[0];
+ }
+
+ /**
+ * Translates a plural string using the default textdomain
+ *
+ * @example
+ *  gt.ngettext('One thing', 'Many things', numberOfThings)
+ *
+ * @param {String} msgid String to be translated when count is not plural
+ * @param {String} msgidPlural String to be translated when count is plural
+ * @param {Number} count Number count for the plural
+ * @return {String} Translation or the original string if no translation was found
+ */
+ String ngettext(
+ String msgid,
+ String msgidPlural,
+ int count, {
+ String domain,
+ String msgctxt = '',
+ }) {
+ final translation =
+ this._getTranslation(domain ?? this.domain, msgctxt, msgid);
+
+ final index = _pluralsFunc(count);
+
+ if (translation == null ||
+ translation.msgstr.length <= index ||
+ translation.msgstr[index]?.isNotEmpty != true) {
+ _warn('No translation was found for '
+ 'msgid "$msgid" in msgctxt "$msgctxt" and domain "$domain"');
+ return (count > 1) ? msgidPlural ?? msgid : msgid;
+ }
+
+ return translation.msgstr[index];
+ }
+
+ /**
+ * Retrieves translation object from the domain and context
+ *
+ * @private
+ * @param {String} domain A gettext domain name
+ * @param {String} msgctxt Translation context
+ * @param {String} msgid String to be translated
+ * @return {Translation} Translation object or null if not found
+ */
+ Translation _getTranslation(String domain, String msgctxt, String msgid) {
+ assert(domain != null);
+ assert(msgctxt != null);
+ assert(msgid != null);
+
+ return catalogs[_locale]?.getTranslation(domain, msgctxt, msgid);
+ }
+
+ /**
+ * Returns the language code part of a locale
+ *
+ * @example
+ *  Gettext.getLanguageCode('sv-SE')
+ *  // -> "sv"
+ *
+ * @private
+ * @param {String} locale A case-insensitive locale string
+ * @returns {String} A language code
+ */
+ static String getLanguageCode(String locale) {
+ return locale.split(RegExp(r'[\-_]'))[0].toLowerCase();
+ }
+
+ _warn(String message) {
+ if (onWarning != null) {
+ onWarning(message);
+ }
+ }
+}
+
+class Catalog {
+ final Map<String, Translations> domains;
+
+ Catalog(this.domains);
+
+ Translation getTranslation(String domain, String msgctxt, String msgid) {
+ return this.domains[domain]?.getTranslation(msgctxt, msgid);
+ }
+
+ void addTranslations(String domain, Translations translations) {
+ domains[domain] = translations;
+ }
+}
+
+class Translations {
+ final Map<String, Map<String, Translation>> contexts;
+
+ Translations(this.contexts);
+
+ Translation getTranslation(String msgctxt, String msgid) {
+ if (this.contexts[msgctxt] == null) {
+ return null;
+ }
+
+ return this.contexts[msgctxt][msgid];
+ }
+
+ static Translations fromJson(Map<String, dynamic> contexts,
+ {Map<String, String> headers}) {
+ return new Translations(
+ contexts.map((key, value) {
+ final values = new Map<String, Translation>();
+
+ if (value is Map<String, Map<String, dynamic>>) {
+ values.addAll(
+ value.map(
+ (msgid, data) => MapEntry<String, Translation>(
+ msgid,
+ Translation.fromJSON(data),
+ ),
+ ),
+ );
+ }
+
+ return MapEntry<String, Map<String, Translation>>(key, values);
+ }),
+ );
+ }
+}
+
+class Translation {
+ final List<String> msgstr;
+ final Map<String, String> comments;
+
+ Translation(this.msgstr, {this.comments}) : assert(msgstr != null);
+
+ static Translation fromJSON(Map<String, dynamic> json) {
+ return new Translation(json["msgstr"], comments: json["comments"]);
+ }
+}