class WpMainQueryFilter {
    public function __construct() {

        add_action( 'pre_get_posts', [ $this, 'filterQuery' ] );
    }

    public function filterQuery( WP_Query $query ): void {
        if ( ! $query->is_main_query() ) {
            return;
        }

        $filterBy = $_GET['select'] ?? '';

        if ( ! $filterBy ) {
            return;
        }

        switch ( $filterBy ) {
            case in_array( $filterBy, [ 'dl7', 'dl14', 'dl30' ] ):
                add_filter( 'posts_fields', [ $this, 'selectDownloads' ], 10, 2 );
                add_filter( 'posts_join', [ $this, 'joinDownloads' ], 10, 2 );
                add_filter( 'posts_orderby', [ $this, 'orderByDownloads' ], 10, 2 );
                break;
        }
    }

    public function selectDownloads( string $select, WP_Query $query ): string {

        if ( ! $query->is_main_query() ) {
            return $select;
        }

        $select .= ", dl_stats.dl as dl";

        return $select;
    }

    public function joinDownloads( string $join, WP_Query $query ): string {

        if ( ! $query->is_main_query() ) {
            return $join;
        }

        $days = ltrim( $_GET['select'], 'dl' );

        $aggregateQuery = "
                SELECT post_id, SUM(dl) as dl
                FROM wp_day_download
                WHERE date >= DATE_ADD(CURRENT_TIMESTAMP,INTERVAL -$days DAY)
                GROUP BY post_id
                ORDER BY SUM(dl) DESC";

        $join .= " INNER JOIN ($aggregateQuery) as dl_stats ON wp_posts.ID = dl_stats.post_id";

        return $join;
    }

    public function orderByDownloads( string $orderBy, WP_Query $query ): string {

        if ( ! $query->is_main_query() ) {
            return $orderBy;
        }

        return "dl DESC";
    }
}