public function actionIndex($parent = null, $page = 1)
    {
        $searchModel = $this->module->model('ContentSearch');

        // list filter parameters correction
        $params = Yii::$app->request->queryParams;
        if ($parent === '-') { // to show all nodes
            $params['parent'] = $parent;
            unset($params[$searchModel->formName()]['parent_id']);
        } else {
            $params[$searchModel->formName()]['parent_id'] = $params['parent'] = intval($parent);
        }

        if (!Yii::$app->user->can('roleContentModerator') && Yii::$app->user->can('roleContentAuthor')) {
            $params[$searchModel->formName()]['owner_id'] = Yii::$app->user->id;
        }

        $dataProvider = $searchModel->search($params);

        $pager = $dataProvider->getPagination();
        $pager->pageSize = $this->pageSizeAdmin;
        $pager->totalCount = $dataProvider->getTotalCount();

        // page number correction:
        $maxPage = ceil($pager->totalCount / $pager->pageSize);
        if ($page > $maxPage) {
            $pager->page = $maxPage - 1;
        } else {
            $pager->page = $page - 1; //! from 0
        }

        return $this->render('index', compact('dataProvider', 'searchModel', 'params'));
    }