add language middleware that sets the system's language from a given...

Closes #1568

Merge request studip/studip!993

composer.json

@@ -52,6 +52,7 @@
         "symfony/console": "~5.3.16",
         "symfony/process": "^5.4",
         "jumbojett/openid-connect-php": "^0.9.2",
-        "league/oauth2-server": "^8.3"
+        "league/oauth2-server": "^8.3",
+        "willdurand/negotiation": "^3.1"
     }
 }

lib/classes/JsonApi/Middlewares/Language.php

+<?php
+namespace JsonApi\Middlewares;
+
+use Negotiation\LanguageNegotiator;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface as Request;
+use Psr\Http\Server\RequestHandlerInterface as RequestHandler;
+
+/**
+ * This class defines a middleware that tries to set the language for Stud.IP
+ * by analyzing the HTTP header "Accept-Language".
+ *
+ * @author Jan-Hendrik Willms <tleilax+studip@gmail.com>
+ */
+class Language
+{
+    /**
+     * @param Request        $request das Request-Objekt
+     * @param RequestHandler $handler der PSR-15 Request Handler
+     *
+     * @return ResponseInterface das neue Response-Objekt
+     */
+    public function __invoke(Request $request, RequestHandler $handler)
+    {
+        $language = $this->detectValidLanguageFromRequest($request);
+
+        // Set language if detected
+        if ($language) {
+            $_SESSION['_language'] = $language;
+            setTempLanguage(false, $language);
+        }
+
+        return $handler->handle($request);
+    }
+
+    /**
+     * Tries to detect a valid installed language from the request.
+     *
+     * @param Request $request
+     * @return string|null The detected language (if any)
+     */
+    private function detectValidLanguageFromRequest(Request $request): ?string
+    {
+        if (!$request->hasHeader('Accept-Language')) {
+            return null;
+        }
+
+        $negotiator = new LanguageNegotiator();
+        $best_language = $negotiator->getBest(
+            $request->getHeaderLine('Accept-Language'),
+            $this->getStudIPLanguagePriorities()
+        );
+
+        if (!$best_language) {
+            return null;
+        }
+
+        return $this->normalizeLanguageForStudIP($best_language->getType());
+    }
+
+    /**
+     * Returns a list of the normalized installed languages for the Stud.IP
+     * system.
+     *
+     * @return array
+     */
+    private function getStudIPLanguagePriorities(): array
+    {
+        return array_map(
+            function ($language) {
+                return str_replace('_', '-', $language);
+            },
+            array_keys($GLOBALS['INSTALLED_LANGUAGES'])
+        );
+    }
+
+    /**
+     * Normalizes the given language string (<language>-<variety>, e.g. de-de)
+     * for Stud.IP (e.g. de_DE).
+     *
+     * @param string $language
+     * @return string
+     */
+    private function normalizeLanguageForStudIP(string $language): string
+    {
+        $tags = explode('-', $language);
+        return $tags[0] . '_' . strtoupper($tags[1]);
+    }
+}

lib/classes/JsonApi/middleware.php

@@ -26,6 +26,9 @@ return function (App $app) {
     // Add Routing Middleware
     $app->addRoutingMiddleware();
 
+    // Add language middleware
+    $app->add(new Middlewares\Language());
+
     /** @var array|null */
     $corsOrigin = \Config::get()->getValue('JSONAPI_CORS_ORIGIN');
     if (is_array($corsOrigin) && count($corsOrigin)) {