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typo3/sysext/backend/Classes/Middleware/SiteResolver.php

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+<?php
+declare(strict_types = 1);
+namespace TYPO3\CMS\Backend\Middleware;
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\MiddlewareInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use TYPO3\CMS\Backend\Utility\BackendUtility;
+use TYPO3\CMS\Core\Routing\SiteMatcher;
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+use TYPO3\CMS\Core\Utility\MathUtility;
+
+/**
+ * Usually called after the route object is resolved, however, this is not possible yet as this happens
+ * within the RequestHandler/RouteDispatcher right now and should go away.
+ *
+ * This middleware checks for a "id" parameter. If present, it adds a site information to this page ID.
+ *
+ * Very useful for all "Web" related modules to resolve all available languages for a site.
+ */
+class SiteResolver implements MiddlewareInterface
+{
+    /**
+     * Resolve the site information by checking the page ID ("id" parameter) which is typically used in BE modules
+     * of type "web".
+     *
+     * @param ServerRequestInterface $request
+     * @param RequestHandlerInterface $handler
+     * @return ResponseInterface
+     */
+    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
+    {
+        $pageId = ($request->getQueryParams()['id'] ?? $request->getParsedBody()['id'] ?? 0);
+        // Check if we have a numeric _GET/_POST parameter for "id", then a site information can be resolved based.
+        if (MathUtility::canBeInterpretedAsInteger($pageId)) {
+            $pageId = (int)$pageId;
+            $rootLine = null;
+            if ($pageId > 0) {
+                $rootLine = BackendUtility::BEgetRootLine($pageId);
+            }
+            $site = GeneralUtility::makeInstance(SiteMatcher::class)->matchByPageId($pageId, $rootLine);
+            $request = $request->withAttribute('site', $site);
+            $GLOBALS['TYPO3_REQUEST'] = $request;
+        }
+        return $handler->handle($request);
+    }
+}