Inventory/src/EventSubscriber/PieceProductSyncSubscriber.php

<?php

declare(strict_types=1);

namespace App\EventSubscriber;

use App\Entity\Piece;
use App\Repository\ProductRepository;
use Doctrine\Common\EventSubscriber;
use Doctrine\ORM\Event\LifecycleEventArgs;
use Doctrine\ORM\Event\PreUpdateEventArgs;
use Doctrine\ORM\Events;

/**
 * Keep the legacy single product relation in sync with the ManyToMany products collection.
 */
final class PieceProductSyncSubscriber implements EventSubscriber
{
    public function __construct(private readonly ProductRepository $productRepository) {}

    public function getSubscribedEvents(): array
    {
        return [
            Events::prePersist,
            Events::preUpdate,
        ];
    }

    public function prePersist(LifecycleEventArgs $args): void
    {
        $entity = $args->getObject();
        if (!$entity instanceof Piece) {
            return;
        }

        $this->syncPrimaryProduct($entity);
    }

    public function preUpdate(PreUpdateEventArgs $args): void
    {
        $entity = $args->getObject();
        if (!$entity instanceof Piece) {
            return;
        }

        $this->syncPrimaryProduct($entity);

        $em   = $args->getObjectManager();
        $meta = $em->getClassMetadata(Piece::class);
        $em->getUnitOfWork()->recomputeSingleEntityChangeSet($meta, $entity);
    }

    private function syncPrimaryProduct(Piece $piece): void
    {
        $productIds = $piece->getProductIds();

        if ([] === $productIds) {
            // If no explicit list is provided, keep the legacy relation as-is.
            return;
        }

        $primaryId = $productIds[0] ?? null;
        if (!$primaryId) {
            $piece->setProduct(null);

            return;
        }

        $currentProductId = $piece->getProduct()?->getId();
        if ($currentProductId === $primaryId) {
            return;
        }

        $primaryProduct = $this->productRepository->find($primaryId);
        $piece->setProduct($primaryProduct);
    }
}