add explicit set levels

backend/app/Set/EloquentSetLevelRepository.php

@@ -0,0 +1,88 @@
+<?php
+
+namespace App\Set;
+
+use DomainException;
+use RuntimeException;
+
+class EloquentSetLevelRepository implements SetLevelRepository
+{
+    public function __construct(
+        private SetRepository $setRepository,
+    ) {}
+
+    public function create(CreateSetLevelDto $dto): SetLevel
+    {
+        $kindExists = SetLevelModel::query()
+            ->where('set_id', $dto->set->getId())
+            ->where('kind', $dto->kind)
+            ->exists();
+        if ($kindExists) {
+            throw new DomainException(
+                'level kind must be unique within set',
+            );
+        }
+
+        $currentMaximum = SetLevelModel::query()
+            ->where('set_id', $dto->set->getId())
+            ->max('depth');
+        $depth = $currentMaximum === null
+            ? 0
+            : (int) $currentMaximum + 1;
+        $model = SetLevelModel::create([
+            'set_id' => $dto->set->getId(),
+            'kind' => $dto->kind,
+            'depth' => $depth,
+        ]);
+
+        return new SetLevel(
+            id: $model->id,
+            set: $dto->set,
+            kind: $model->kind,
+            depth: $model->depth,
+        );
+    }
+
+    public function find(int $id): ?SetLevel
+    {
+        $model = SetLevelModel::find($id);
+
+        return $model === null ? null : $this->toDomain($model);
+    }
+
+    public function findBySet(Set $set): array
+    {
+        $models = SetLevelModel::query()
+            ->where('set_id', $set->getId())
+            ->orderBy('depth')
+            ->orderBy('id')
+            ->get();
+        $levels = [];
+
+        foreach ($models as $model) {
+            $levels[] = new SetLevel(
+                id: $model->id,
+                set: $set,
+                kind: $model->kind,
+                depth: $model->depth,
+            );
+        }
+
+        return $levels;
+    }
+
+    private function toDomain(SetLevelModel $model): SetLevel
+    {
+        $set = $this->setRepository->find($model->set_id);
+        if ($set === null) {
+            throw new RuntimeException('set level set not found');
+        }
+
+        return new SetLevel(
+            id: $model->id,
+            set: $set,
+            kind: $model->kind,
+            depth: $model->depth,
+        );
+    }
+}