public function findFilterOptionsToDisplay($filter)
    {
        $options = array();

        foreach ($filter['options'] as $option) {
            // should we check if the filter option is available in
            // the current search result?

            if ($this->conf['checkFilterCondition'] != 'none') {
                // Once one filter option has been selected, don't display the
                // others anymore since this leads to a strange behaviour (options are
                // only displayed if they have BOTH tags: the selected and the other filter option.
                if ((!count($filter['selectedOptions'])
                        || in_array($option['uid'], $filter['selectedOptions'])
                    ) && $this->filters->checkIfTagMatchesRecords($option['tag'])
                ) {
                    // build link which selects this option and keeps all the other selected filters
                    unset($linkconf);
                    $linkconf['parameter'] = $GLOBALS['TSFE']->id;
                    $linkconf['additionalParams'] = '&tx_kesearch_pi1[sword]='
                        . $this->piVars['sword']
                        . '&tx_kesearch_pi1[filter]['
                        . $filter['uid']
                        . ']='
                        . $option['tag'];
                    $linkconf['useCacheHash'] = false;
                    if (is_array($this->piVars['filter']) && count($this->piVars['filter'])) {
                        foreach ($this->piVars['filter'] as $key => $value) {
                            if ($key != $filter['uid']) {
                                $linkconf['additionalParams'] .= '&tx_kesearch_pi1[filter][' . $key . ']=' . $value;
                            }
                        }
                    }
                    $optionLink = $this->cObj->typoLink_URL($linkconf);

                    $options[$option['uid']] = array(
                        'title' => $option['title'],
                        'value' => $option['tag'],
                        'results' => $this->tagsInSearchResult[$option['tag']],
                        'selected' => is_array($filter['selectedOptions'])
                            && in_array($option['uid'], $filter['selectedOptions']),
                        'link' => $optionLink
                    );
                }
            } else {
                // do not process any checks; show all filter options
                $options[$option['uid']] = array(
                    'title' => $option['title'],
                    'value' => $option['tag'],
                    'selected' =>
                        is_array($filter['selectedOptions'])
                        && !empty($filter['selectedOptions'])
                        && in_array($option['uid'], $filter['selectedOptions']),
                );
            }
        }

        return $options;
    }