Fix: Auto language detection #2122 (#2148)

* Fix: Auto language detection #2122

* add LanguageService and AdditionalLanguageJsController

* hidden swagger

src/main/java/stirling/software/SPDF/controller/api/AdditionalLanguageJsController.java

@@ -0,0 +1,65 @@
+package stirling.software.SPDF.controller.api;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.util.List;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import io.swagger.v3.oas.annotations.Hidden;
+
+import jakarta.servlet.http.HttpServletResponse;
+import stirling.software.SPDF.service.LanguageService;
+
+@RestController
+@RequestMapping("/js")
+public class AdditionalLanguageJsController {
+
+    @Autowired private LanguageService languageService;
+
+    @Hidden
+    @GetMapping(value = "/additionalLanguageCode.js", produces = "application/javascript")
+    public void generateAdditionalLanguageJs(HttpServletResponse response) throws IOException {
+        List<String> supportedLanguages = languageService.getSupportedLanguages();
+
+        response.setContentType("application/javascript");
+        PrintWriter writer = response.getWriter();
+
+        // Erstelle das JavaScript dynamisch
+        writer.println("const supportedLanguages = " + toJsonArray(supportedLanguages) + ";");
+
+        // Generiere die `getDetailedLanguageCode`-Funktion
+        writer.println(
+                """
+                function getDetailedLanguageCode() {
+                    const userLanguages = navigator.languages ? navigator.languages : [navigator.language];
+                    for (let lang of userLanguages) {
+                        let matchedLang = supportedLanguages.find(supportedLang => supportedLang.startsWith(lang.replace('-', '_')));
+                        if (matchedLang) {
+                            return matchedLang;
+                        }
+                    }
+                    // Fallback
+                    return "en_GB";
+                }
+                """);
+
+        writer.flush();
+    }
+
+    // Hilfsfunktion zum Konvertieren der Liste in ein JSON-Array
+    private String toJsonArray(List<String> list) {
+        StringBuilder jsonArray = new StringBuilder("[");
+        for (int i = 0; i < list.size(); i++) {
+            jsonArray.append("\"").append(list.get(i)).append("\"");
+            if (i < list.size() - 1) {
+                jsonArray.append(",");
+            }
+        }
+        jsonArray.append("]");
+        return jsonArray.toString();
+    }
+}

src/main/java/stirling/software/SPDF/service/LanguageService.java

@@ -0,0 +1,41 @@
+package stirling.software.SPDF.service;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
+import org.springframework.stereotype.Service;
+
+@Service
+public class LanguageService {
+
+    private final PathMatchingResourcePatternResolver resourcePatternResolver =
+            new PathMatchingResourcePatternResolver();
+
+    public List<String> getSupportedLanguages() {
+        List<String> supportedLanguages = new ArrayList<>();
+
+        try {
+            Resource[] resources =
+                    resourcePatternResolver.getResources("classpath*:messages_*.properties");
+            for (Resource resource : resources) {
+                if (resource.exists() && resource.isReadable()) {
+                    String filename = resource.getFilename();
+                    if (filename != null
+                            && filename.startsWith("messages_")
+                            && filename.endsWith(".properties")) {
+                        String languageCode =
+                                filename.replace("messages_", "").replace(".properties", "");
+                        supportedLanguages.add(languageCode);
+                    }
+                }
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+
+        return supportedLanguages;
+    }
+}