FolderTable::prepareChange

static function prepareChange(EntityEvent $event, string $actionType): EntityEventResult
{
	$result = new EntityEventResult();
	$primary = $event->getParameter('primary');
	$fields = $event->getParameter('fields');
	$modifyFields = [];

	// check that index landing is exists in folder's site
	/*if ($fields['INDEX_ID'] ?? 0)
	{
		if (!array_key_exists('SITE_ID', $fields))
		{
			$fields['SITE_ID'] = self::getList([
				'select' => [
					'SITE_ID'
				],
				'filter' => [
					'ID' => $primary['ID'] ?? 0
				]
			])->fetch()['SITE_ID'] ?? 0;
		}
		$res = LandingTable::getList([
			'select' => [
				'ID'
			],
			'filter' => [
				'SITE_ID' => $fields['SITE_ID'],
				'ID' => $fields['INDEX_ID'],
				'FOLDER_ID' => $primary['ID'] ?? 0
			]
		]);
		if (!$res->fetch())
		{
			$result->setErrors([
				new EntityEntityError(
					Loc::getMessage('LANDING_TABLE_ERROR_FOLDER_INDEX_OUT_OF_SITE'),
					'FOLDER_INDEX_OUT_OF_SITE'
				)
			]);
			return $result;
		}
	}*/

	// translit the code from title
	if (
		$actionType == self::ACTION_TYPE_ADD && array_key_exists('TITLE', $fields) &&
		(!array_key_exists('CODE', $fields) || trim($fields['CODE']) == '')
	)
	{
		$fields['CODE'] = CUtil::translit(
			trim($fields['TITLE']),
			LANGUAGE_ID,
			[
				'replace_space' => '',
				'replace_other' => ''
			]
		);
		if (!$fields['CODE'])
		{
			$fields['CODE'] = Manager::getRandomString(12);
		}
		$modifyFields['CODE'] = $fields['CODE'];
	}

	// for update always we need the code
	if (isset($primary['ID']) && !array_key_exists('CODE', $fields))
	{
		$res = self::getList([
			'select' => [
				'CODE'
			],
			'filter' => [
				'ID' => $primary['ID']
			]
		]);
		if ($row = $res->fetch())
		{
			$fields['CODE'] = $row['CODE'];
		}
	}

	// check unique folder
	if (
		array_key_exists('CODE', $fields) &&
		array_key_exists('SITE_ID', $fields) &&
		BitrixLandingLanding::isCheckUniqueAddress()
	)
	{
		$filter = [
			'=CODE' => $fields['CODE'],
			'SITE_ID' => $fields['SITE_ID'],
			'PARENT_ID' => $fields['PARENT_ID'] ?? null
		];
		if (isset($primary['ID']))
		{
			$filter['!ID'] = $primary['ID'];
		}
		$res = self::getList([
			'select' => [
				'ID'
			],
			'filter' => $filter
		]);
		if ($res->fetch())
		{
			$result->setErrors([
				new EntityEntityError(
					Loc::getMessage('LANDING_TABLE_ERROR_FOLDER_IS_NOT_UNIQUE'),
					'FOLDER_IS_NOT_UNIQUE'
				)
			]);
			return $result;
		}
	}

	// check correct folder path
	if (array_key_exists('CODE', $fields))
	{
		if (mb_strpos($fields['CODE'], '/') !== false)
		{
			$result->setErrors([
				new EntityEntityError(
					Loc::getMessage('LANDING_TABLE_ERROR_FOLDER_SLASH_IS_NOT_ALLOWED'),
					'SLASH_IS_NOT_ALLOWED'
                   )
			]);
			return $result;
		}
	}

	$result->modifyFields($modifyFields);

	return $result;
}