class TableSort

class TableSort extends SelectQueryExtender {
    
    /**
     * The array of fields that can be sorted by.
     *
     * @var array
     */
    protected $header = array();
    public function __construct(SelectQueryInterface $query, DatabaseConnection $connection) {
        parent::__construct($query, $connection);
        // Add convenience tag to mark that this is an extended query. We have to
        // do this in the constructor to ensure that it is set before preExecute()
        // gets called.
        $this->addTag('tablesort');
    }
    
    /**
     * Order the query based on a header array.
     *
     * @see theme_table()
     * @param $header
     *   Table header array.
     * @return SelectQueryInterface
     *   The called object.
     */
    public function orderByHeader(array $header) {
        $this->header = $header;
        $ts = $this->init();
        if (!empty($ts['sql'])) {
            // Based on code from db_escape_table(), but this can also contain a dot.
            $field = preg_replace('/[^A-Za-z0-9_.]+/', '', $ts['sql']);
            // orderBy() will ensure that only ASC/DESC values are accepted, so we
            // don't need to sanitize that here.
            $this->orderBy($field, $ts['sort']);
        }
        return $this;
    }
    
    /**
     * Initializes the table sort context.
     */
    protected function init() {
        $ts = $this->order();
        $ts['sort'] = $this->getSort();
        $ts['query'] = $this->getQueryParameters();
        return $ts;
    }
    
    /**
     * Determine the current sort direction.
     *
     * @param $headers
     *   An array of column headers in the format described in theme_table().
     * @return
     *   The current sort direction ("asc" or "desc").
     */
    protected function getSort() {
        return tablesort_get_sort($this->header);
    }
    
    /**
     * Compose a URL query parameter array to append to table sorting requests.
     *
     * @return
     *   A URL query parameter array that consists of all components of the current
     *   page request except for those pertaining to table sorting.
     *
     * @see tablesort_get_query_parameters()
     */
    protected function getQueryParameters() {
        return tablesort_get_query_parameters();
    }
    
    /**
     * Determine the current sort criterion.
     *
     * @param $headers
     *   An array of column headers in the format described in theme_table().
     * @return
     *   An associative array describing the criterion, containing the keys:
     *   - "name": The localized title of the table column.
     *   - "sql": The name of the database field to sort on.
     */
    protected function order() {
        return tablesort_get_order($this->header);
    }

}