<?php

namespace AppBundle\Form\DataTransformer;

use AppBundle\Entity\Entity;
use AppBundle\Entity\EntityRepository;
use Symfony\Component\Form\DataTransformerInterface;
use Symfony\Component\Form\Exception\TransformationFailedException;

class EntitiesToIdsDataTransformer implements DataTransformerInterface
{
	/**
	 * @var EntityRepository
	 */
	private $entityRepository;

	public function __construct(EntityRepository $entity)
	{
		$this->entityRepository = $entity;
	}

	/**
	 * @param array|\Traversable|null $value
	 * @return array|string
	 * @throws TransformationFailedException
	 */
	public function transform($value)
	{
		if (null === $value) {
			// as the DataTransformerInterface suggests
			return '';
		}

		if (!is_array($value) && !$value instanceof \Traversable) {
			throw new TransformationFailedException(sprintf(
				'Array or Traversable expected, %s given',
				gettype($value)
			));
		}

		$ids = [];

		foreach ($value as $entity) {
			if (!$entity instanceof Entity) {
				throw new TransformationFailedException(sprintf(
					'%s expected, %s given',
					Entity::class,
					gettype($entity)
				));
			}

			$ids[] = $entity->getId();
		}

		return $ids;
	}

	/**
	 * @param array|null $value
	 * @return \AppBundle\Entity\Entity[]|null
	 * @throws TransformationFailedException
	 */
	public function reverseTransform($value)
	{
		if (empty($value)) {
			// as the DataTransformerInterface suggests
			return null;
		}

		if (!is_array($value)) {
			throw new TransformationFailedException(sprintf(
				'Array expected, %s given',
				gettype($value)
			));
		}

		return $this->entityRepository->findByIds($value);
	}
}