2 files changed, 104 insertions, 6 deletions

diff --git a/packages/main/src/i18n/loadLocalization.ts b/packages/main/src/i18n/loadLocalization.ts
index ec3cf84..0413373 100644
--- a/packages/main/src/i18n/loadLocalization.ts
+++ b/packages/main/src/i18n/loadLocalization.ts
@@ -18,33 +18,31 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import { fallbackLng } from '@sophie/shared';
+import { FALLBACK_LOCALE } from '@sophie/shared';
 import i18next from 'i18next';
 import { autorun } from 'mobx';
 import { addDisposer } from 'mobx-state-tree';
 
-import type Resources from '../infrastructure/resources/Resources';
 import type MainStore from '../stores/MainStore';
 import { getLogger } from '../utils/log';
 
 import I18nStore from './I18nStore';
+import LocatlizationRepository from './LocalizationRepository';
 import RepositoryBasedI18nBackend from './RepositoryBasedI18nBackend';
 import i18nLog from './i18nLog';
-import LocalizationFiles from './impl/LocaltizationFiles';
 
 const log = getLogger('loadLocationzation');
 
 export default async function loadLocalization(
   store: MainStore,
-  resources: Resources,
+  repository: LocatlizationRepository,
   devMode: boolean,
 ): Promise<void> {
-  const repository = new LocalizationFiles(resources);
   const backend = new RepositoryBasedI18nBackend(repository, devMode);
   const i18n = i18next
     .createInstance({
       lng: store.shared.language,
-      fallbackLng,
+      fallbackLng: [FALLBACK_LOCALE],
       debug: devMode,
       saveMissing: devMode,
     })
@@ -58,6 +56,7 @@ export default async function loadLocalization(
       shared: { language },
     } = store;
     if (i18n.language !== language) {
+      log.debug('Setting language', language);
       i18n.changeLanguage(language).catch((error) => {
         log.error('Failed to change language', error);
       });
diff --git a/packages/main/src/i18n/synchronizeLocalizationSettings.ts b/packages/main/src/i18n/synchronizeLocalizationSettings.ts
new file mode 100644
index 0000000..971a593
--- /dev/null
+++ b/packages/main/src/i18n/synchronizeLocalizationSettings.ts
@@ -0,0 +1,99 @@
+/*
+ * Copyright (C)  2022 Kristóf Marussy <kristof@marussy.com>
+ *
+ * This file is part of Sophie.
+ *
+ * Sophie is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { FALLBACK_LOCALE, SYSTEM_LOCALE } from '@sophie/shared';
+import { reaction } from 'mobx';
+import { addDisposer } from 'mobx-state-tree';
+
+import type MainStore from '../stores/MainStore';
+import { getLogger } from '../utils/log';
+
+const log = getLogger('synchronizeLocalizationSettings');
+
+export const TEST_LOCALE = 'cimode';
+
+/**
+ * Finds the closes requested supported language for the requested one.
+ *
+ * If `language` is supported, this function will return it.
+ * Otherwise, it returns a supported language with the same ISO639 code but
+ * no country code (e.g., `en` for `en-GB`) if it exists.
+ * If no supported language matches, `FALLBACK_LOCALE` will be returned.
+ *
+ * @param language The requested language.
+ * @param supportedLanguages  The set of supported languages.
+ * @returns The language to load.
+ */
+function getMatchingLocale(
+  language: string,
+  supportedLanguages: Set<string>,
+): string {
+  // Also let the test locale (i.e., show localization keys directly) through.
+  if (language === TEST_LOCALE || supportedLanguages.has(language)) {
+    return language;
+  }
+  const separatorIndex = language.indexOf('-');
+  if (separatorIndex < 0) {
+    return FALLBACK_LOCALE;
+  }
+  const iso639 = language.slice(0, Math.max(0, separatorIndex));
+  if (supportedLanguages.has(iso639)) {
+    return iso639;
+  }
+  return FALLBACK_LOCALE;
+}
+
+export async function synchronizeLocalizationSettings(
+  store: MainStore,
+  supportedLanguages: string[],
+  osLocale: () => Promise<string>,
+): Promise<void> {
+  const { settings, shared } = store;
+  const supportedLangaugesSet = new Set(supportedLanguages);
+  const setLanguageAsync = async (languageSetting: string) => {
+    const requestedLanguage =
+      languageSetting === SYSTEM_LOCALE ? await osLocale() : languageSetting;
+    const matchingLanguage = getMatchingLocale(
+      requestedLanguage,
+      supportedLangaugesSet,
+    );
+    log.debug(
+      'Setting language',
+      matchingLanguage,
+      'for requested language',
+      requestedLanguage,
+    );
+    shared.setLanguage(matchingLanguage);
+  };
+  const disposer = reaction(
+    () => settings.language,
+    (languageSetting) => {
+      setLanguageAsync(languageSetting).catch((error) => {
+        log.error('Failed to update language', error);
+      });
+    },
+    {
+      fireImmediately: false,
+    },
+  );
+  addDisposer(store, disposer);
+  // Make sure that the language is already set when we resolve.
+  await setLanguageAsync(settings.language);
+}