add child element ordering

backend/app/Element/UseCases/ReorderChildElements/ReorderChildElements.php

@@ -0,0 +1,154 @@
+<?php
+
+namespace App\Element\UseCases\ReorderChildElements;
+
+use App\Element\Element;
+use App\Element\ElementRepository;
+use App\Exceptions\BadRequestException;
+use App\Exceptions\NotFoundException;
+
+class ReorderChildElements
+{
+    public function __construct(private ElementRepository $elementRepository)
+    {
+    }
+
+    /**
+     * @return Element[]
+     * @throws BadRequestException
+     * @throws NotFoundException
+     */
+    public function execute(ReorderChildElementsRequest $request): array
+    {
+        if ($request->parentElementId === null) {
+            throw new BadRequestException('parentElementId is required');
+        }
+
+        if ($request->childElementIds === null) {
+            throw new BadRequestException('childElementIds is required');
+        }
+
+        $parentElement = $this->elementRepository->find(
+            $request->parentElementId,
+        );
+        if ($parentElement === null) {
+            throw new NotFoundException('Parent element not found');
+        }
+
+        $childElementIds = $this->validatedChildElementIds(
+            $request->childElementIds,
+        );
+        $directChildElementIds = $this->elementIds(
+            $this->elementRepository->findByParentElement($parentElement),
+        );
+
+        $this->validateNoDuplicateIds($childElementIds);
+        $this->validateAllIdsAreDirectChildren(
+            $childElementIds,
+            $directChildElementIds,
+        );
+        $this->validateEveryDirectChildWasSubmitted(
+            $childElementIds,
+            $directChildElementIds,
+        );
+
+        return $this->elementRepository->reorderChildren(
+            $parentElement,
+            $childElementIds,
+        );
+    }
+
+    /**
+     * @param mixed[] $childElementIds
+     * @return int[]
+     * @throws BadRequestException
+     */
+    private function validatedChildElementIds(array $childElementIds): array
+    {
+        $validatedChildElementIds = [];
+        foreach ($childElementIds as $childElementId) {
+            if (! is_int($childElementId)) {
+                throw new BadRequestException(
+                    'childElementIds must contain integers',
+                );
+            }
+
+            $validatedChildElementIds[] = $childElementId;
+        }
+
+        return $validatedChildElementIds;
+    }
+
+    /**
+     * @param int[] $childElementIds
+     * @throws BadRequestException
+     */
+    private function validateNoDuplicateIds(array $childElementIds): void
+    {
+        $seenChildElementIds = [];
+        foreach ($childElementIds as $childElementId) {
+            if (isset($seenChildElementIds[$childElementId])) {
+                throw new BadRequestException(
+                    'Child order contains duplicate ids',
+                );
+            }
+
+            $seenChildElementIds[$childElementId] = true;
+        }
+    }
+
+    /**
+     * @param int[] $childElementIds
+     * @param int[] $directChildElementIds
+     * @throws BadRequestException
+     */
+    private function validateAllIdsAreDirectChildren(
+        array $childElementIds,
+        array $directChildElementIds,
+    ): void {
+        $directChildElementIdsById = [];
+        foreach ($directChildElementIds as $directChildElementId) {
+            $directChildElementIdsById[$directChildElementId] = true;
+        }
+
+        foreach ($childElementIds as $childElementId) {
+            if (! isset($directChildElementIdsById[$childElementId])) {
+                throw new BadRequestException(
+                    'Child order contains invalid child',
+                );
+            }
+        }
+    }
+
+    /**
+     * @param int[] $childElementIds
+     * @param int[] $directChildElementIds
+     * @throws BadRequestException
+     */
+    private function validateEveryDirectChildWasSubmitted(
+        array $childElementIds,
+        array $directChildElementIds,
+    ): void {
+        if (count($childElementIds) === count($directChildElementIds)) {
+            return;
+        }
+
+        throw new BadRequestException(
+            'Child order must include every direct child',
+        );
+    }
+
+    /**
+     * @param Element[] $elements
+     * @return int[]
+     */
+    private function elementIds(array $elements): array
+    {
+        $elementIds = [];
+        foreach ($elements as $element) {
+            $elementIds[] = $element->getId();
+        }
+
+        return $elementIds;
+    }
+}