class TableSort

class TableSort {
    const ASC = 'asc';
    const DESC = 'desc';
    
    /**
     * Initializes the table sort context.
     *
     * @param array $headers
     *   An array of column headers in the format described in '#type' => 'table'.
     * @param \Symfony\Component\HttpFoundation\Request $request
     *   A current request.
     *
     * @return array
     *   The current table sort context.
     */
    public static function getContextFromRequest(array $headers, Request $request) {
        $context = static::getOrder($headers, $request);
        $context['sort'] = static::getSort($headers, $request);
        $context['query'] = static::getQueryParameters($request);
        return $context;
    }
    
    /**
     * Formats a column header.
     *
     * If the cell in question is the column header for the current sort
     * criterion, it gets special formatting. All possible sort criteria become
     * links.
     *
     * @param string $cell_content
     *   The cell content to format. Passed by reference.
     * @param array $cell_attributes
     *   The cell attributes. Passed by reference.
     * @param array $header
     *   An array of column headers in the format described in '#type' => 'table'.
     * @param array $context
     *   The current table sort context as returned from
     *   TableSort::getContextFromRequest() method.
     *
     * @throws \Exception
     *
     * @see getContextFromRequest()
     */
    public static function header(&$cell_content, array &$cell_attributes, array $header, array $context) {
        // Special formatting for the currently sorted column header.
        if (isset($cell_attributes['field'])) {
            $title = new TranslatableMarkup('sort by @s', [
                '@s' => $cell_content,
            ]);
            if ($cell_content == $context['name']) {
                // aria-sort is a WAI-ARIA property that indicates if items in a table
                // or grid are sorted in ascending or descending order. See
                // http://www.w3.org/TR/wai-aria/states_and_properties#aria-sort
                $cell_attributes['aria-sort'] = $context['sort'] == self::ASC ? 'ascending' : 'descending';
                $context['sort'] = $context['sort'] == self::ASC ? self::DESC : self::ASC;
                $cell_attributes['class'][] = 'is-active';
                $tablesort_indicator = [
                    '#theme' => 'tablesort_indicator',
                    '#style' => $context['sort'],
                ];
                $image = \Drupal::service('renderer')->render($tablesort_indicator);
            }
            else {
                // This determines the sort order when the column gets first clicked by
                // the user. It is "asc" by default but the sort can be changed if
                // $cell['initial_click_sort'] is defined. The possible values are "asc"
                // or "desc".
                $context['sort'] = $cell_attributes['initial_click_sort'] ?? self::ASC;
                $image = '';
            }
            $cell_content = Link::createFromRoute(new FormattableMarkup('@cell_content@image', [
                '@cell_content' => $cell_content,
                '@image' => $image,
            ]), '<current>', [], [
                'attributes' => [
                    'title' => $title,
                    'rel' => 'nofollow',
                ],
                'query' => array_merge($context['query'], [
                    'sort' => $context['sort'],
                    'order' => $cell_content,
                ]),
            ]);
            unset($cell_attributes['field'], $cell_attributes['sort'], $cell_attributes['initial_click_sort']);
        }
    }
    
    /**
     * Determines the current sort criterion.
     *
     * @param array $headers
     *   An array of column headers in the format described in '#type' => 'table'.
     * @param \Symfony\Component\HttpFoundation\Request $request
     *   A current request.
     *
     * @return array
     *   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.
     */
    public static function getOrder(array $headers, Request $request) {
        $order = $request->query
            ->get('order', '');
        foreach ($headers as $header) {
            if (is_array($header)) {
                if (isset($header['data']) && $order == $header['data']) {
                    $default = $header;
                    break;
                }
                if (empty($default) && isset($header['sort']) && in_array($header['sort'], [
                    self::ASC,
                    self::DESC,
                ])) {
                    $default = $header;
                }
            }
        }
        if (!isset($default)) {
            $default = reset($headers);
            if (!is_array($default)) {
                $default = [
                    'data' => $default,
                ];
            }
        }
        $default += [
            'data' => NULL,
            'field' => NULL,
        ];
        return [
            'name' => $default['data'],
            'sql' => $default['field'],
        ];
    }
    
    /**
     * Determines the current sort direction.
     *
     * @param array $headers
     *   An array of column headers in the format described in '#type' => 'table'.
     * @param \Symfony\Component\HttpFoundation\Request|null $request
     *   A current request.
     *
     * @return string
     *   The current sort direction ("asc" or "desc").
     */
    public static function getSort(array $headers, Request $request) {
        $query = $request->query;
        if ($query->has('sort')) {
            return strtolower($query->get('sort')) == self::DESC ? self::DESC : self::ASC;
        }
        // The user has not specified a sort. Use the default for the currently
        // sorted header if specified; otherwise use "asc".
        // Find out which header is currently being sorted.
        $order = static::getOrder($headers, $request);
        foreach ($headers as $header) {
            if (is_array($header) && isset($header['data']) && $header['data'] == $order['name']) {
                if (isset($header['sort'])) {
                    return $header['sort'];
                }
                if (isset($header['initial_click_sort'])) {
                    return $header['initial_click_sort'];
                }
            }
        }
        return self::ASC;
    }
    
    /**
     * Composes a URL query parameter array for table sorting links.
     *
     * @param \Symfony\Component\HttpFoundation\Request|null $request
     *   A current request.
     *
     * @return array
     *   A URL query parameter array that consists of all components of the
     *   current page request except for those pertaining to table sorting.
     *
     * @internal
     */
    public static function getQueryParameters(Request $request) {
        return UrlHelper::filterQueryParameters($request->query
            ->all(), [
            'sort',
            'order',
        ]);
    }

}