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<?php
/**
 * @link https://craftcms.com/
 * @copyright Copyright (c) Pixel & Tonic, Inc.
 * @license https://craftcms.github.io/license/
 */

namespace craft\validators;

use Craft;
use yii\validators\Validator;

/**
 * Will validate that the given attribute is a valid site ID.
 *
 * @author Pixel & Tonic, Inc. <support@pixelandtonic.com>
 * @since 3.0.0
 */
class SiteIdValidator extends Validator
{
    /**
     * @var bool|null $allowDisabled Whether to allow disabled sites.
     * @since 3.7.32
     */
    public ?bool $allowDisabled = null;

/**
     * @inheritdoc
     */
    public function validateAttribute($model, $attribute): void
    {
        $siteId = $model->$attribute;

if ($siteId && !in_array($siteId, Craft::$app->getSites()->getAllSiteIds($this->allowDisabled), false)) {
            $message = Craft::t('app', 'Your system isn’t set up to save content for the site “{site}”.', ['site' => $siteId]);
            $this->addError($model, $attribute, $message);
        }
    }
}

/srv/users/craft4/apps/craft4-newsite-space/vendor/craftcms/cms/src/validators/SiteIdValidator.php