fix: generate correct referring urls

public/typo3conf/ext/ep_theme/Classes/ViewHelpers/Uri/ProductViewHelper.php

@@ -44,6 +44,7 @@ class ProductViewHelper extends AbstractViewHelper
         $this->registerArgument('forceHotelUid', 'bool', 'Whether to force link a hotel');
         $this->registerArgument('dateFrom', 'string', 'Date to limit table on detail page by (Y-m-d)');
         $this->registerArgument('dateTo', 'string', 'Date to limit table on detail page by (Y-m-d)');
+        $this->registerArgument('ref', 'string', 'Referring URL');
     }
 
     /**
@@ -81,13 +82,21 @@ class ProductViewHelper extends AbstractViewHelper
 
         $targetPageUid = is_array($product) ? (int)$product['detailPage'] : $product->getDetailPage();
 
-        return $renderingContext
+        $uri = $renderingContext
             ->getControllerContext()
             ->getUriBuilder()
             ->reset()
             ->setTargetPageUid($targetPageUid)
             ->uriFor('detail', $linkArguments, 'Product', 'epproducts', 'product_detail')
         ;
+
+        if ($arguments['ref']) {
+            $referringPageUri = urlencode($arguments['ref']);
+            $separator = false !== strpos($uri, '?') ? '&' : '?';
+            $uri .= $separator . 'ref=' . $referringPageUri;
+        }
+
+        return $uri;
     }
 
 }