From 4e049bccb63e26b072f710921211904b56e0b3d9 Mon Sep 17 00:00:00 2001
From: Elizabeth Danzberger <elizabeth@elzody.dev>
Date: Fri, 4 Sep 2026 18:27:28 -0400
Subject: [PATCH] refactor(l10n): move language tag logic to backend

Moving the Nextcloud language + locale to BCP 47 language tag logic to
the backend makes sense because it exists in two places when it should
really exist in one. This keeps it maintainable. The backend is the
natural place because requests to Collabora happen there, and the logic
can be injected into the frontend via initial state.

Assisted-by: ClaudeCode:claude-sonnet-5
Signed-off-by: Elizabeth Danzberger <elizabeth@elzody.dev>
---
 lib/Conversion/ConversionProvider.php         | 11 +---
 lib/Service/InitialStateService.php           |  2 +
 lib/Service/LanguageService.php               | 58 ++++++++++++++++++
 src/components/CoolFrame.vue                  |  4 +-
 src/helpers/index.js                          | 47 --------------
 src/helpers/url.js                            |  3 +-
 src/services/config.tsx                       |  1 +
 .../lib/Conversion/ConversionProviderTest.php | 12 ++--
 tests/lib/Service/LanguageServiceTest.php     | 61 +++++++++++++++++++
 9 files changed, 136 insertions(+), 63 deletions(-)
 create mode 100644 lib/Service/LanguageService.php
 create mode 100644 tests/lib/Service/LanguageServiceTest.php

diff --git a/lib/Conversion/ConversionProvider.php b/lib/Conversion/ConversionProvider.php
index 75c38bb423..195e2ff38b 100644
--- a/lib/Conversion/ConversionProvider.php
+++ b/lib/Conversion/ConversionProvider.php
@@ -9,6 +9,7 @@
 
 namespace OCA\Richdocuments\Conversion;
 
+use OCA\Richdocuments\Service\LanguageService;
 use OCA\Richdocuments\Service\RemoteService;
 use OCA\Richdocuments\Service\SecureViewService;
 use OCP\Files\Conversion\ConversionMimeProvider;
@@ -56,6 +57,7 @@ public function __construct(
 		private LoggerInterface $logger,
 		IFactory $l10nFactory,
 		private SecureViewService $secureViewService,
+		private LanguageService $languageService,
 	) {
 		$this->l10n = $l10nFactory->get('richdocuments');
 	}
@@ -168,17 +170,10 @@ public function convertFile(File $file, string $targetMimeType): mixed {
 		return $this->remoteService->convertFileTo(
 			$file,
 			$targetFileExtension,
-			conversionOptions: ['lang' => $this->getConversionLanguage()]
+			conversionOptions: ['lang' => $this->languageService->getBCP47LanguageTag()]
 		);
 	}
 
-	private function getConversionLanguage(): string {
-		$locale = $this->l10n->getLocaleCode();
-		$language = $locale !== '' ? $locale : $this->l10n->getLanguageCode();
-
-		return str_replace('_', '-', $language);
-	}
-
 	private function getMimeProvidersFor(array $inputMimeTypes, string $outputMimeType): array {
 		$outputMimeInfo = $this->getMimeInfoFor($outputMimeType);
 		if ($outputMimeInfo === null) {
diff --git a/lib/Service/InitialStateService.php b/lib/Service/InitialStateService.php
index 7eef2b47ae..00826ff041 100644
--- a/lib/Service/InitialStateService.php
+++ b/lib/Service/InitialStateService.php
@@ -28,6 +28,7 @@ public function __construct(
 		private TemplateManager $templateManager,
 		private CapabilitiesService $capabilitiesService,
 		private IConfig $config,
+		private LanguageService $languageService,
 		private ?string $userId,
 	) {
 	}
@@ -42,6 +43,7 @@ public function provideCapabilities(): void {
 		$this->initialState->provideInitialState('hasNextcloudBranding', $this->capabilitiesService->hasNextcloudBranding());
 		$this->initialState->provideInitialState('instanceId', $this->config->getSystemValue('instanceid'));
 		$this->initialState->provideInitialState('wopi_callback_url', $this->appConfig->getNextcloudUrl());
+		$this->initialState->provideInitialState('bcp47Language', $this->languageService->getBCP47LanguageTag());
 		$this->provideOptions();
 
 		$this->hasProvidedCapabilities = true;
diff --git a/lib/Service/LanguageService.php b/lib/Service/LanguageService.php
new file mode 100644
index 0000000000..8b00aaad04
--- /dev/null
+++ b/lib/Service/LanguageService.php
@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\Richdocuments\Service;
+
+use OCA\Richdocuments\AppInfo\Application;
+use OCP\L10N\IFactory;
+
+class LanguageService {
+	private const LOCALE_OVERRIDES = [
+		'de' => [
+			'de_CH' => 'de-CH',
+			'gsw' => 'de-CH',
+			'gsw_CH' => 'de-CH',
+		],
+		'fr' => [
+			'fr_CH' => 'fr-CH',
+		],
+		'it' => [
+			'it_CH' => 'it-CH',
+		],
+	];
+
+	public function __construct(
+		private IFactory $l10nFactory,
+	) {
+	}
+
+	/**
+	 * Converts the current user's Nextcloud language/locale settings into the
+	 * BCP 47 language tag Collabora Online expects.
+	 */
+	public function getBCP47LanguageTag(): string {
+		$l10n = $this->l10nFactory->get(Application::APPNAME);
+
+		// getLanguageCode()/getLocaleCode() mirror @nextcloud/l10n's getLanguage()/getLocale()
+		$language = str_replace('_', '-', $l10n->getLanguageCode());
+		$locale = $l10n->getLocaleCode();
+
+		$language = match ($language) {
+			'de-DE' => 'de', // German formal should just be treated as 'de'
+			'es-419' => 'es-MX', // not a valid locale string in COOL
+			default => $language,
+		};
+
+		if ($language === 'en-GB' && $locale === 'en_AU') {
+			$language = 'en-AU';
+		}
+
+		return self::LOCALE_OVERRIDES[$language][$locale] ?? $language;
+	}
+}
diff --git a/src/components/CoolFrame.vue b/src/components/CoolFrame.vue
index 579a153030..81b0f49c23 100644
--- a/src/components/CoolFrame.vue
+++ b/src/components/CoolFrame.vue
@@ -28,7 +28,7 @@
 <script>
 
 import { generateCSSVarTokens, getCollaboraTheme, getUITheme } from '../helpers/coolParameters.js'
-import { languageToBCP47 } from '../helpers/index.js'
+import { loadState } from '@nextcloud/initial-state'
 import PostMessageService from '../services/postMessage.tsx'
 
 export default {
@@ -74,7 +74,7 @@ export default {
 		window.addEventListener('message', this.handlePostMessage)
 
 		if (this.iframeUrl.length > 0) {
-			this.formAction = this.iframeUrl + '?lang=' + languageToBCP47()
+			this.formAction = this.iframeUrl + '?lang=' + loadState('richdocuments', 'bcp47Language', '')
 			this.isIframeLoaded = true
 		} else {
 			return
diff --git a/src/helpers/index.js b/src/helpers/index.js
index 7545a9133f..4933c0d41c 100644
--- a/src/helpers/index.js
+++ b/src/helpers/index.js
@@ -3,52 +3,6 @@
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
 
-import { getLanguage, getLocale } from '@nextcloud/l10n'
-
-const languageToBCP47 = () => {
-	let language = getLanguage().replace(/_/g, '-')
-	const locale = getLocale()
-
-	// German formal should just be treated as 'de'
-	if (language === 'de-DE') {
-		language = 'de'
-	}
-
-	// es-419 should be mapped as this is not considered a valid locale string in COOL
-	if (language === 'es-419') {
-		language = 'es-MX'
-	}
-
-	// Australia
-	if (language === 'en-GB' && locale === 'en_AU') {
-		language = 'en-AU'
-	}
-
-	// special case where setting the bc47 region depending on the locale setting makes sense
-	const whitelist = {
-		de: {
-			de_CH: 'de-CH',
-			gsw: 'de-CH',
-			gsw_CH: 'de-CH',
-		},
-		fr: {
-			fr_CH: 'fr-CH',
-		},
-		it: {
-			it_CH: 'it-CH',
-		},
-	}
-	const matchingWhitelist = whitelist[language]
-	if (typeof matchingWhitelist !== 'undefined' && typeof matchingWhitelist[locale] !== 'undefined') {
-		return matchingWhitelist[locale]
-	}
-
-	// Collabora Online expects BCP47 language tag syntax.
-	// When the Nextcloud language consists of two parts, we send both,
-	// as the region is then provided by the language setting.
-	return language
-}
-
 const getNextcloudVersion = () => {
 	return parseInt(OC.config.version.split('.')[0])
 }
@@ -68,7 +22,6 @@ const getRandomId = (length = 5) => {
 }
 
 export {
-	languageToBCP47,
 	getNextcloudVersion,
 	splitPath,
 	getRandomId,
diff --git a/src/helpers/url.js b/src/helpers/url.js
index 85090bbf7a..c6d66d591d 100644
--- a/src/helpers/url.js
+++ b/src/helpers/url.js
@@ -5,7 +5,6 @@
 
 import { getRootUrl, generateUrl } from '@nextcloud/router'
 import { getSharingToken } from '@nextcloud/sharing/public'
-import { languageToBCP47 } from './index.js'
 import Config from './../services/config.tsx'
 
 const getSearchParam = (name) => {
@@ -39,7 +38,7 @@ const getWopiUrl = ({ fileId, readOnly, closeButton, revisionHistory, target = u
 	//   https://<loolwsd-server>:9980/hosting/discovery
 	return Config.get('urlsrc')
 		+ 'WOPISrc=' + encodeURIComponent(getWopiSrc(fileId))
-		+ '&lang=' + languageToBCP47()
+		+ '&lang=' + Config.get('bcp47Language')
 		+ (closeButton ? '&closebutton=1' : '')
 		+ (revisionHistory ? '&revisionhistory=1' : '')
 		+ (readOnly ? '&permission=readonly' : '')
diff --git a/src/services/config.tsx b/src/services/config.tsx
index 759b69e051..eb1cf46a19 100644
--- a/src/services/config.tsx
+++ b/src/services/config.tsx
@@ -11,6 +11,7 @@ class ConfigService {
 	constructor() {
 		this.values = {
 			wopi_callback_url: loadState('richdocuments', 'wopi_callback_url', ''),
+			bcp47Language: loadState('richdocuments', 'bcp47Language', ''),
 			...loadState('richdocuments', 'document', {}),
 		}
 	}
diff --git a/tests/lib/Conversion/ConversionProviderTest.php b/tests/lib/Conversion/ConversionProviderTest.php
index ddf87b29d8..6f498f7165 100644
--- a/tests/lib/Conversion/ConversionProviderTest.php
+++ b/tests/lib/Conversion/ConversionProviderTest.php
@@ -10,6 +10,7 @@
 namespace Tests\Richdocuments\Conversion;
 
 use OCA\Richdocuments\Conversion\ConversionProvider;
+use OCA\Richdocuments\Service\LanguageService;
 use OCA\Richdocuments\Service\RemoteOptionsService;
 use OCA\Richdocuments\Service\RemoteService;
 use OCA\Richdocuments\Service\SecureViewService;
@@ -26,6 +27,7 @@ class ConversionProviderTest extends TestCase {
 	private IFactory&MockObject $l10nFactory;
 	private IL10N&MockObject $l10n;
 	private SecureViewService&MockObject $secureViewService;
+	private LanguageService&MockObject $languageService;
 	private ConversionProvider $provider;
 
 	protected function setUp(): void {
@@ -36,6 +38,7 @@ protected function setUp(): void {
 		$this->l10nFactory = $this->createMock(IFactory::class);
 		$this->l10n = $this->createMock(IL10N::class);
 		$this->secureViewService = $this->createMock(SecureViewService::class);
+		$this->languageService = $this->createMock(LanguageService::class);
 
 		$this->l10n->method('t')->willReturnCallback(static fn (string $text): string => $text);
 		$this->l10nFactory->method('get')
@@ -47,20 +50,21 @@ protected function setUp(): void {
 			$this->logger,
 			$this->l10nFactory,
 			$this->secureViewService,
+			$this->languageService,
 		);
 	}
 
 	public function testConvertFilePassesCurrentLocaleToCollabora(): void {
 		$file = $this->createMock(File::class);
 
-		$this->l10n->expects($this->once())
-			->method('getLocaleCode')
-			->willReturn('de_DE');
+		$this->languageService->expects($this->once())
+			->method('getBCP47LanguageTag')
+			->willReturn('de');
 		$this->secureViewService->method('isEnabled')
 			->willReturn(false);
 		$this->remoteService->expects($this->once())
 			->method('convertFileTo')
-			->with($file, 'pdf', RemoteOptionsService::REMOTE_TIMEOUT_DEFAULT, ['lang' => 'de-DE'])
+			->with($file, 'pdf', RemoteOptionsService::REMOTE_TIMEOUT_DEFAULT, ['lang' => 'de'])
 			->willReturn('pdf-content');
 
 		$result = $this->provider->convertFile($file, 'application/pdf');
diff --git a/tests/lib/Service/LanguageServiceTest.php b/tests/lib/Service/LanguageServiceTest.php
new file mode 100644
index 0000000000..e11a32f789
--- /dev/null
+++ b/tests/lib/Service/LanguageServiceTest.php
@@ -0,0 +1,61 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace Tests\Richdocuments\Service;
+
+use OCA\Richdocuments\AppInfo\Application;
+use OCA\Richdocuments\Service\LanguageService;
+use OCP\IL10N;
+use OCP\L10N\IFactory;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+
+class LanguageServiceTest extends TestCase {
+	private IFactory&MockObject $l10nFactory;
+	private IL10N&MockObject $l10n;
+	private LanguageService $service;
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		$this->l10nFactory = $this->createMock(IFactory::class);
+		$this->l10n = $this->createMock(IL10N::class);
+		$this->l10nFactory->method('get')
+			->with(Application::APPNAME)
+			->willReturn($this->l10n);
+
+		$this->service = new LanguageService($this->l10nFactory);
+	}
+
+	public static function languageProvider(): array {
+		return [
+			'plain pass-through' => ['en', 'en_US', 'en'],
+			'German formal is treated as plain German' => ['de_DE', 'de_DE', 'de'],
+			'es-419 is mapped to es-MX for COOL' => ['es_419', 'es_419', 'es-MX'],
+			'Australian English' => ['en_GB', 'en_AU', 'en-AU'],
+			'British English without Australian locale stays en-GB' => ['en_GB', 'en_GB', 'en-GB'],
+			'Swiss German locale' => ['de', 'de_CH', 'de-CH'],
+			'Swiss German (gsw locale)' => ['de', 'gsw', 'de-CH'],
+			'Swiss German (gsw_CH locale)' => ['de', 'gsw_CH', 'de-CH'],
+			'Swiss French locale' => ['fr', 'fr_CH', 'fr-CH'],
+			'Swiss Italian locale' => ['it', 'it_CH', 'it-CH'],
+			'German without Swiss locale stays de' => ['de', 'de_DE', 'de'],
+		];
+	}
+
+	/**
+	 * @dataProvider languageProvider
+	 */
+	public function testGetBCP47LanguageTag(string $languageCode, string $localeCode, string $expected): void {
+		$this->l10n->method('getLanguageCode')->willReturn($languageCode);
+		$this->l10n->method('getLocaleCode')->willReturn($localeCode);
+
+		$this->assertSame($expected, $this->service->getBCP47LanguageTag());
+	}
+}