add set root ids

backend/app/Controllers/SetController.php

@@ -2,14 +2,17 @@
 
 namespace App\Controllers;
 
+use App\Element\ElementRepository;
 use App\Set\Set as DomainSet;
 use App\Set\SetRepository;
 use Illuminate\Http\JsonResponse;
 
 class SetController
 {
-    public function __construct(private SetRepository $setRepository)
+    public function __construct(
-    {
+        private SetRepository $setRepository,
+        private ElementRepository $elementRepository,
+    ) {
     }
 
     public function index(): JsonResponse
@@ -29,16 +32,20 @@ class SetController
      *     id: int,
      *     name: string,
      *     description: string,
-     *     iconImageUrl: string
+     *     iconImageUrl: string,
+     *     rootElementId: int|null
      * }
      */
     private function buildSetPayload(DomainSet $set): array
     {
+        $rootElement = $this->elementRepository->findRootBySet($set);
+
         return [
             'id' => $set->getId(),
             'name' => $set->getName(),
             'description' => $set->getDescription(),
             'iconImageUrl' => $set->getIconImageUrl(),
+            'rootElementId' => $rootElement?->getId(),
         ];
     }
 }

backend/app/Element/ElementRepository.php

@@ -10,6 +10,8 @@ interface ElementRepository
 
     public function find(int $id): ?Element;
 
+    public function findRootBySet(DomainSet $set): ?Element;
+
     /**
      * @return Element[]
      */

backend/app/Element/EloquentElementRepository.php

@@ -35,6 +35,16 @@ class EloquentElementRepository implements ElementRepository
         return $model === null ? null : $this->toDomain($model);
     }
 
+    public function findRootBySet(DomainSet $set): ?Element
+    {
+        $model = ElementModel::where('set_id', $set->getId())
+            ->whereNull('parent_element_id')
+            ->orderBy('id')
+            ->first();
+
+        return $model === null ? null : $this->toDomain($model);
+    }
+
     /**
      * @return Element[]
      */

backend/tests/Fakes/FakeElementRepository.php

@@ -37,6 +37,20 @@ class FakeElementRepository implements ElementRepository
         return $this->cloneElement($this->elementsById[$id]);
     }
 
+    public function findRootBySet(DomainSet $set): ?Element
+    {
+        foreach ($this->elementsById as $element) {
+            if (
+                $element->getSet()->getId() === $set->getId()
+                && $element->getParentElement() === null
+            ) {
+                return $this->cloneElement($element);
+            }
+        }
+
+        return null;
+    }
+
     /**
      * @return Element[]
      */