add set layout api

backend/app/Element/ElementRepository.php

@@ -14,6 +14,11 @@ interface ElementRepository
 
     public function find(int $id): ?Element;
 
+    /**
+     * @return list<Element>
+     */
+    public function findBySet(Set $set): array;
+
     /**
      * @return list<Element>
      */

backend/app/Element/EloquentElementRepository.php

@@ -45,6 +45,37 @@ class EloquentElementRepository implements ElementRepository
         return $model === null ? null : $this->toDomain($model);
     }
 
+    public function findBySet(Set $set): array
+    {
+        $models = ElementModel::query()
+            ->where('set_id', $set->getId())
+            ->orderBy('id')
+            ->get();
+        $elements = [];
+        $elementsById = [];
+
+        foreach ($models as $model) {
+            $parentElement = null;
+            if ($model->parent_element_id !== null) {
+                $parentElement = $elementsById[$model->parent_element_id]
+                    ?? null;
+                if ($parentElement === null) {
+                    throw new RuntimeException('element parent not found');
+                }
+            }
+
+            $element = $this->toDomainWithRelations(
+                model: $model,
+                set: $set,
+                parentElement: $parentElement,
+            );
+            $elements[] = $element;
+            $elementsById[$element->getId()] = $element;
+        }
+
+        return $elements;
+    }
+
     public function findTopLevelBySet(Set $set): array
     {
         $models = ElementModel::query()
@@ -160,10 +191,9 @@ class EloquentElementRepository implements ElementRepository
 
     private function findSet(int $id): Set
     {
-        foreach ($this->setRepository->all() as $set) {
-            if ($set->getId() === $id) {
-                return $set;
-            }
+        $set = $this->setRepository->find($id);
+        if ($set !== null) {
+            return $set;
         }
 
         throw new RuntimeException('element set not found');

backend/app/Exceptions/NotFoundException.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace App\Exceptions;
+
+use DomainException;
+
+class NotFoundException extends DomainException {}

backend/app/Http/Controllers/SetController.php

@@ -2,7 +2,10 @@
 
 namespace App\Http\Controllers;
 
+use App\Exceptions\NotFoundException;
 use App\Set\Set;
+use App\Set\UseCases\GetSetLayout\ElementLayoutNode;
+use App\Set\UseCases\GetSetLayout\GetSetLayout;
 use App\Set\UseCases\ListSets\ListSets;
 use Illuminate\Http\JsonResponse;
 
@@ -10,6 +13,7 @@ class SetController extends Controller
 {
     public function __construct(
         private ListSets $listSets,
+        private GetSetLayout $getSetLayout,
     ) {}
 
     public function index(): JsonResponse
@@ -23,4 +27,52 @@ class SetController extends Controller
 
         return new JsonResponse(['sets' => $sets]);
     }
+
+    public function show(int $setId): JsonResponse
+    {
+        try {
+            $layout = $this->getSetLayout->execute($setId);
+        } catch (NotFoundException $exception) {
+            return new JsonResponse(
+                ['error' => $exception->getMessage()],
+                404,
+            );
+        }
+
+        $set = $layout->getSet();
+
+        return new JsonResponse([
+            'set' => [
+                'id' => $set->getId(),
+                'name' => $set->getName(),
+            ],
+            'elements' => array_map(
+                $this->elementPayload(...),
+                $layout->getElements(),
+            ),
+        ]);
+    }
+
+    /**
+     * @return array{
+     *     id: int,
+     *     name: string,
+     *     kind: string,
+     *     children: list<mixed>
+     * }
+     */
+    private function elementPayload(ElementLayoutNode $node): array
+    {
+        $element = $node->getElement();
+
+        return [
+            'id' => $element->getId(),
+            'name' => $element->getName(),
+            'kind' => $element->getKind(),
+            'children' => array_map(
+                $this->elementPayload(...),
+                $node->getChildren(),
+            ),
+        ];
+    }
 }

backend/app/Set/EloquentSetRepository.php

@@ -25,6 +25,13 @@ class EloquentSetRepository implements SetRepository
         );
     }
 
+    public function find(int $id): ?Set
+    {
+        $model = SetModel::find($id);
+
+        return $model === null ? null : $this->toDomain($model);
+    }
+
     public function all(): array
     {
         $models = SetModel::query()

backend/app/Set/SetRepository.php

@@ -6,6 +6,8 @@ interface SetRepository
 {
     public function create(CreateSetDto $dto): Set;
 
+    public function find(int $id): ?Set;
+
     /**
      * @return list<Set>
      */

backend/app/Set/UseCases/GetSetLayout/ElementLayoutNode.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace App\Set\UseCases\GetSetLayout;
+
+use App\Element\Element;
+
+final readonly class ElementLayoutNode
+{
+    /**
+     * @param list<ElementLayoutNode> $children
+     */
+    public function __construct(
+        private Element $element,
+        private array $children,
+    ) {}
+
+    public function getElement(): Element
+    {
+        return $this->element;
+    }
+
+    /**
+     * @return list<ElementLayoutNode>
+     */
+    public function getChildren(): array
+    {
+        return $this->children;
+    }
+}

backend/app/Set/UseCases/GetSetLayout/GetSetLayout.php

@@ -0,0 +1,77 @@
+<?php
+
+namespace App\Set\UseCases\GetSetLayout;
+
+use App\Element\Element;
+use App\Element\ElementRepository;
+use App\Exceptions\NotFoundException;
+use App\Set\SetRepository;
+
+class GetSetLayout
+{
+    public function __construct(
+        private SetRepository $setRepository,
+        private ElementRepository $elementRepository,
+    ) {}
+
+    /**
+     * @throws NotFoundException
+     */
+    public function execute(int $setId): SetLayout
+    {
+        $set = $this->setRepository->find($setId);
+        if ($set === null) {
+            throw new NotFoundException('set not found');
+        }
+
+        $elementsByParentId = [];
+        foreach ($this->elementRepository->findBySet($set) as $element) {
+            $parentId = $element->getParentElement()?->getId() ?? 0;
+            $elementsByParentId[$parentId][] = $element;
+        }
+
+        foreach ($elementsByParentId as &$siblings) {
+            usort($siblings, function (
+                Element $first,
+                Element $second,
+            ): int {
+                $positionComparison = $first->getPosition()
+                    <=> $second->getPosition();
+                if ($positionComparison !== 0) {
+                    return $positionComparison;
+                }
+
+                return $first->getId() <=> $second->getId();
+            });
+        }
+        unset($siblings);
+
+        return new SetLayout(
+            set: $set,
+            elements: $this->buildNodes(0, $elementsByParentId),
+        );
+    }
+
+    /**
+     * @param array<int, list<Element>> $elementsByParentId
+     * @return list<ElementLayoutNode>
+     */
+    private function buildNodes(
+        int $parentId,
+        array $elementsByParentId,
+    ): array {
+        $nodes = [];
+
+        foreach ($elementsByParentId[$parentId] ?? [] as $element) {
+            $nodes[] = new ElementLayoutNode(
+                element: $element,
+                children: $this->buildNodes(
+                    $element->getId(),
+                    $elementsByParentId,
+                ),
+            );
+        }
+
+        return $nodes;
+    }
+}

backend/app/Set/UseCases/GetSetLayout/SetLayout.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace App\Set\UseCases\GetSetLayout;
+
+use App\Set\Set;
+
+final readonly class SetLayout
+{
+    /**
+     * @param list<ElementLayoutNode> $elements
+     */
+    public function __construct(
+        private Set $set,
+        private array $elements,
+    ) {}
+
+    public function getSet(): Set
+    {
+        return $this->set;
+    }
+
+    /**
+     * @return list<ElementLayoutNode>
+     */
+    public function getElements(): array
+    {
+        return $this->elements;
+    }
+}