- catch InvalidArgumentException for confirm and create

- more userfriendly error page for malformed links

lib/Controller/CalendarController.php

@@ -6,6 +6,7 @@ namespace OCA\AToCal\Controller;
 
 use OCA\AToCal\AppInfo\Application;
 use OCP\AppFramework\Controller;
+use OCP\AppFramework\Http;
 use OCP\AppFramework\Http\Attribute\NoAdminRequired;
 use OCP\AppFramework\Http\Attribute\NoCSRFRequired;
 use OCP\AppFramework\Http\RedirectResponse;
@@ -89,6 +90,7 @@ class CalendarController extends Controller
         string $location = '',
         string $url = ''
     ): TemplateResponse {
+        try {
             $data = $this->validateEventData(
                 $summary,
                 $description,
@@ -98,6 +100,9 @@ class CalendarController extends Controller
                 $location,
                 $url
             );
+        } catch (\InvalidArgumentException $e) {
+            return $this->renderError($e);
+        }
 
         $user = $this->userSession->getUser();
 
@@ -129,6 +134,7 @@ class CalendarController extends Controller
         string $url = '',
         string $calendarId = ''
     ): RedirectResponse|TemplateResponse {
+        try {
             $data = $this->validateEventData(
                 $summary,
                 $description,
@@ -138,6 +144,9 @@ class CalendarController extends Controller
                 $location,
                 $url
             );
+        } catch (\InvalidArgumentException $e) {
+            return $this->renderError($e);
+        }
 
         $user = $this->userSession->getUser();
 
@@ -242,6 +251,25 @@ class CalendarController extends Controller
         return '';
     }
 
+    /**
+     * Friendly error page (HTTP 400) for a malformed link,
+     * instead of an uncaught exception and a 500 error page.
+     */
+    private function renderError(\InvalidArgumentException $e): TemplateResponse
+    {
+        return new TemplateResponse(
+            'core',
+            'error',
+            [
+                'errors' => [
+                    ['error' => $e->getMessage(), 'hint' => ''],
+                ],
+            ],
+            TemplateResponse::RENDER_AS_ERROR,
+            Http::STATUS_BAD_REQUEST
+        );
+    }
+
     /**
      * Render the confirmation page, optionally with an error message.
      */