1 files changed, 23 insertions, 1 deletions
diff --git a/src/locale/helpers.ts b/src/locale/helpers.ts
index 3bae45214..a7517eae9 100644
--- a/src/locale/helpers.ts
+++ b/src/locale/helpers.ts
@@ -160,8 +160,13 @@ export function sanitizeAppLanguageSetting(appLanguage: string): AppLanguage {
   return AppLanguage.en
 }
 
+/**
+ * Handles legacy migration for Java devices.
+ *
+ * {@link https://github.com/bluesky-social/social-app/pull/4461}
+ * {@link https://xml.coverpages.org/iso639a.html}
+ */
 export function fixLegacyLanguageCode(code: string | null): string | null {
-  // handle some legacy code conversions, see https://xml.coverpages.org/iso639a.html
   if (code === 'in') {
     // indonesian
     return 'id'
@@ -176,3 +181,20 @@ export function fixLegacyLanguageCode(code: string | null): string | null {
   }
   return code
 }
+
+/**
+ * Find the first language supported by our translation infra. Values should be
+ * in order of preference, and match the values of {@link AppLanguage}.
+ *
+ * If no match, returns `en`.
+ */
+export function findSupportedAppLanguage(languageTags: (string | undefined)[]) {
+  const supported = new Set(Object.values(AppLanguage))
+  for (const tag of languageTags) {
+    if (!tag) continue
+    if (supported.has(tag as AppLanguage)) {
+      return tag
+    }
+  }
+  return AppLanguage.en
+}