Conditional require fields on Apigility

FailedValidation.php

<?php

namespace Application\Problem;

use ZF\ApiProblem\ApiProblem;

/**
 * Represent a Failed Validation API Problem.
 *
 * This Problem must be used only when the failure is specific to one or many fields.
 */
class FailedValidation extends ApiProblem
{
    /**
     * @param array $additional
     */
    public function __construct(array $additional)
    {
        $additional = array_map(
            function ($item) {
                return (is_string($item) ? [$item] : $item);
            },
            $additional
        );

        $additional = [
            'validation_messages' => $additional,
        ];

        parent::__construct(422, 'Failed Validation', null, null, $additional);
    }
}

FooResource.php

<?php

namespace Application\V1\Rest\Foo;

use Application\Problem\FailedValidation;
use ZF\Rest\AbstractResourceListener;

/**
 * This assume the input filter has the following fields
 * 
 * - type: Required. Possible values are Baz or Foo
 * - baz_name: Optional. Required only if type is Baz
 * - foo_name: Optional. Required only if type is Foo
 * - foo_surnames: Optional. Required only if type is Foo
 * - foo_email: Optional. Required only if type is Foo
 */
class FooResource extends AbstractResourceListener
{
    /**
     * {@inheritdoc}
     */
    public function create($data)
    {
        // Revalidate using conditional rules.
        $failedValidation = $this->validateInputs($data);
        if ($failedValidation) {
            // If not empty then return API validation failed response.
            return $failedValidation;
        }
        
        // Perform resource creation logic.
        // return $something;
    }

    /**
     * @param \stdClass $data
     *
     * @return null|FailedValidation
     */
    private function validateInputs($data)
    {
        $inputFilter = $this->getInputFilter();
        $inputFilter->setData((array) $data);

        $requireField = function ($fieldName) use ($inputFilter) {
            $pcdName = $inputFilter->get($fieldName);
            $pcdName->setAllowEmpty(false);
            $pcdName->setRequired(true);
        };

        switch ($data->type) {
            case 'Baz':
                $requireField('baz_name');
                break;
            case 'Foo':
                $requireField('foo_name');
                $requireField('foo_surnames');
                $requireField('foo_email');
                break;
            default:
                $inputFilter->get('type')
                            ->setErrorMessage('type invalid');
                break;
        }

        if ($inputFilter->isValid()) {
            return null;
        }

        return new FailedValidation($inputFilter->getMessages());
    }
}