load supported languages on app start

src/main/java/org/cryptomator/launcher/SupportedLanguages.java

@@ -7,17 +7,48 @@ import org.slf4j.LoggerFactory;
 
 import javax.inject.Inject;
 import javax.inject.Singleton;
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
+import java.util.Optional;
+import java.util.stream.StreamSupport;
 
 @Singleton
 public class SupportedLanguages {
 
 	private static final Logger LOG = LoggerFactory.getLogger(SupportedLanguages.class);
 	// these are BCP 47 language codes, not ISO. Note the "-" instead of the "_":
-	public static final List<String> LANGUAGAE_TAGS = List.of("en", "ar", "be", "bn", "bs", "ca", "cs", "da", "de", "el", "es", "fil", "fa", "fr", "gl", "he", //
-			"hi", "hr", "hu", "id", "it", "ja", "ko", "lv", "mk", "nb", "nl", "nn", "no", "pa", "pl", "pt", "pt-BR", "ro", "ru", "si", "sk", "sr", "sr-Latn", "sv", "sw", //
-			"ta", "te", "th", "tr", "uk", "vi", "zh", "zh-HK", "zh-TW");
+	public static final List<String> LANGUAGE_TAGS;
+
+	static {
+		List<String> supportedLanguages = new ArrayList<>();
+		supportedLanguages.add("en");
+		try {
+			var i18Dir = getI18Dir();
+			try (var dirStream = Files.newDirectoryStream(i18Dir, "strings_*.properties")) {
+				StreamSupport.stream(dirStream.spliterator(), false) //
+						.map(SupportedLanguages::getBCP47CodeFromFileName) //
+						.forEach(supportedLanguages::add);
+			}
+		} catch (URISyntaxException | IOException e) {
+			LOG.warn("Unable to determine additional supported languages.", e);
+		}
+		LANGUAGE_TAGS = supportedLanguages;
+	}
+
+	private static Path getI18Dir() throws URISyntaxException {
+		var i18nUri = Optional.of(SupportedLanguages.class.getResource("/i18n")).orElseThrow().toURI();
+		return Path.of(i18nUri);
+	}
+
+	private static String getBCP47CodeFromFileName(Path p) {
+		var fileName = p.getFileName().toString();
+		return fileName.substring("strings_".length(), fileName.indexOf(".properties")).replace('_', '-');
+	}
 
 	@Nullable
 	private final String preferredLanguage;

src/main/java/org/cryptomator/ui/preferences/InterfacePreferencesController.java

@@ -67,7 +67,7 @@ public class InterfacePreferencesController implements FxController {
 		showTrayIconCheckbox.selectedProperty().bindBidirectional(settings.showTrayIcon());
 
 		preferredLanguageChoiceBox.getItems().add(null);
-		preferredLanguageChoiceBox.getItems().addAll(SupportedLanguages.LANGUAGAE_TAGS);
+		preferredLanguageChoiceBox.getItems().addAll(SupportedLanguages.LANGUAGE_TAGS);
 		preferredLanguageChoiceBox.valueProperty().bindBidirectional(settings.languageProperty());
 		preferredLanguageChoiceBox.setConverter(new LanguageTagConverter(resourceBundle));
 

src/test/java/org/cryptomator/launcher/SupportedLanguagesTest.java

@@ -25,7 +25,7 @@ public class SupportedLanguagesTest {
 	}
 
 	public static Stream<String> languageTags() {
-		return SupportedLanguages.LANGUAGAE_TAGS.stream() //
+		return SupportedLanguages.LANGUAGE_TAGS.stream() //
 				.filter(tag -> !"en".equals(tag)); // english uses the default bundle
 	}
 }