add ordered element queries

backend/app/Element/ElementRepository.php

@@ -2,6 +2,7 @@
 
 namespace App\Element;
 
+use App\Set\Set;
 use DomainException;
 
 interface ElementRepository
@@ -12,4 +13,14 @@ interface ElementRepository
     public function create(CreateElementDto $dto): Element;
 
     public function find(int $id): ?Element;
+
+    /**
+     * @return list<Element>
+     */
+    public function findTopLevelBySet(Set $set): array;
+
+    /**
+     * @return list<Element>
+     */
+    public function findByParentElement(Element $parentElement): array;
 }

backend/app/Element/EloquentElementRepository.php

@@ -45,6 +45,48 @@ class EloquentElementRepository implements ElementRepository
         return $model === null ? null : $this->toDomain($model);
     }
 
+    public function findTopLevelBySet(Set $set): array
+    {
+        $models = ElementModel::query()
+            ->where('set_id', $set->getId())
+            ->whereNull('parent_element_id')
+            ->orderBy('position')
+            ->orderBy('id')
+            ->get();
+        $elements = [];
+
+        foreach ($models as $model) {
+            $elements[] = $this->toDomainWithRelations(
+                model: $model,
+                set: $set,
+                parentElement: null,
+            );
+        }
+
+        return $elements;
+    }
+
+    public function findByParentElement(Element $parentElement): array
+    {
+        $models = ElementModel::query()
+            ->where('set_id', $parentElement->getSet()->getId())
+            ->where('parent_element_id', $parentElement->getId())
+            ->orderBy('position')
+            ->orderBy('id')
+            ->get();
+        $elements = [];
+
+        foreach ($models as $model) {
+            $elements[] = $this->toDomainWithRelations(
+                model: $model,
+                set: $parentElement->getSet(),
+                parentElement: $parentElement,
+            );
+        }
+
+        return $elements;
+    }
+
     /**
      * @throws DomainException
      */
@@ -94,6 +136,18 @@ class EloquentElementRepository implements ElementRepository
             }
         }
 
+        return $this->toDomainWithRelations(
+            model: $model,
+            set: $set,
+            parentElement: $parentElement,
+        );
+    }
+
+    private function toDomainWithRelations(
+        ElementModel $model,
+        Set $set,
+        ?Element $parentElement,
+    ): Element {
         return new Element(
             id: $model->id,
             name: $model->name,