feat: basic themes for event sites

src/Service/BookingService.php

@@ -20,6 +20,8 @@ class BookingService
     public const BOOKING_EDIT_KEY = 'booking_edit';
     public const RETURN_URL_KEY = 'booking_return_url';
     public const DEFAULT_RETURN_URL = 'https://www.ep-reisen.de';
+    public const THEME_KEY = 'booking_theme';
+    public const DEFAULT_THEME = 'base';
 
     public function __construct(
         private readonly TravelDataService $travelDataService,
@@ -188,6 +190,33 @@ class BookingService
         return $request->getSession()->get(self::RETURN_URL_KEY, self::DEFAULT_RETURN_URL);
     }
 
+    /**
+     * Stores the theme identifier in the session.
+     *
+     * Sanitizes the theme value to allow only alphanumeric characters and hyphens.
+     * Falls back to the default theme if empty or invalid.
+     */
+    public function storeTheme(Request $request, string $theme): void
+    {
+        $sanitized = preg_replace('/[^a-zA-Z0-9-]/', '', $theme);
+
+        if ('' === $sanitized) {
+            $sanitized = self::DEFAULT_THEME;
+        }
+
+        $request->getSession()->set(self::THEME_KEY, $sanitized);
+    }
+
+    /**
+     * Retrieves the theme identifier from the session.
+     *
+     * Returns the default theme if not set in session.
+     */
+    public function getTheme(Request $request): string
+    {
+        return $request->getSession()->get(self::THEME_KEY, self::DEFAULT_THEME);
+    }
+
     /**
      * Creates a fresh booking session with the provided travel parameters.
      *