const showHideLensUtils = {

    // showHideLensUtils
    //  lensDivsVisibleCount
    //  showDivForLens
    //  hideLensByLensId

    lensesToShowCount: function lensesToShowCount() {
        // unlike lensDivsVisibleCount, which queries div's on the page,
        // this method queries storage utilities to determine how many lenses
        // would be shown on the page.
        // for this reason, this method will return a useful value
        // even before lenses have been added to the page

        const logHeader = 'showHideLensUtils.lensesToShowCount: ';
        log(logHeader + 'enter');

        const toFindCount = lensesToFindStorageUtils.count();

        log(logHeader + 'toFindCount=' + toFindCount);

        if (toFindCount > 0) {
            // if the user has explicitly found any lenses

            log(logHeader + 'we will return this count as the number to show');
            log(logHeader + 'leave');
            return toFindCount;
        }

        const allLensIds = lensUtils.getLensIds();
        // get the ids of all lenses

        log(logHeader + 'allLensIds.length=' + allLensIds.length);

        const findAll = findWhichGroupStateUtils.getFindAll();
        // did we find all lenses?
        //  true => find all
        //  false => find bookmarked

        log(logHeader + 'findAll=' + findAll + '(true => all, false => bookmarked)');

        const lensIdsToHide = lensesToHideStorageUtils.getLensIds();
        // get the ids of the lenses to hide

        log(logHeader + 'lensIdsToHide.length=' + lensIdsToHide.length);

        const lensIdsToHideHS = arrayUtils.arrayToHashObject(lensIdsToHide);
        // create a hash set object of ids of lenses to hide

        var foundIds = [];

        if (findAll) {
            // if we are finding all lenses, not only bookmarked lenses

            log(logHeader + 'finding ids of ALL lenses minus ids of lenses to hide');

            foundIds = allLensIds.filter(i => !lensIdsToHideHS[i]);
            // get all lens ids minus the ids of the lenses to hide
        }
        else {
            // if we are finding bookmarked lenses

            log(logHeader + 'finding ids of BOOKMARKED lenses minus ids of lenses to hide');

            const bkLensIds = bookmarkStorageUtils.getLensIds();
            // get the ids of the bookmarked lenses

            foundIds = bkLensIds.filter(i => !lensIdsToHideHS[i]);
            // get the bookmarked lens ids minus the ids of the lenses to hide
        }

        const toShowCount = foundIds.length;

        log(logHeader + 'toShowCount=' + toShowCount);
        log(logHeader + 'leave');

        return toShowCount;
    },

    lensDivsVisibleCount: function lensDivsVisibleCount() {
        // return the number of lens div elements currently visible (not hidden) on the page

        const logHeader = 'showHideLensUtils.lensDivsVisibleCount: ';
        log(logHeader + 'enter');

        const lensCount = $('.card').filter(':visible').length;
        // count the visible lens divs

        log(logHeader + 'lensCount=' + lensCount);
        log(logHeader + 'leave');

        return lensCount;
    },

    showDivForLens: function showDivForLens(lensId) {
        log('showDivForLens: enter');
        log('showDivForLens: lensId=' + lensId);

        var divName = 'lens' + lensId;
        // get the name of the parent div for the lens

        $('#' + divName).show();
        // show the div for the lens

        log('showDivForLens: leave');
    },

    hideLensByLensIdAsync: async function hideLensByLensIdAsync(lensId) {
        log('hideLensByLensIdAsync: enter');

        displayCurrentLensesCache.clear();
        // clear the entire lens cache

        noTabsCardExpStorageUtils.removeFromLensIds(lensId);
        tabsCardExpStorageUtils.removeFromLensIds(lensId);
        // remove the id from the lists of expanded cards

        cardWidthUtils.clearCardWidth(lensId);
        // clear the lens from the list of stored card widths

        lensUIUtils.clearLensDivWidth(lensId);
        // remove the width item from the style attribute in the lens div

        lensesToHideStorageUtils.addToLensIds(lensId);
        // add the lens to the list of lenses to hide

        const parentDivId = elemIdUtils.getElemId(lensId, elemIdUtils.CARD_PREFIX, undefined);
        // get the name of the parent div for the lens

        log('hideLensByLensIdAsync: parentDivId=' + parentDivId);

        $('#' + parentDivId).hide();
        // hide the div for the lens

        const byAlpha = displayByStateUtils.getDisplayAlpha();
        // are we displaying lenses alphabetically, as opposed to grouped?

        log('hideLensByLensIdAsync: byAlpha=' + byAlpha);

        if (!byAlpha) {
            // if we are displaying grouped lenses

            const lensesToDisplay = lensUtils.getLensDTOsToDisplay();
            // get the DTOs of the lenses to display
            // start with either all or bookmarked (depending on the current setting)
            // and remove lenses to hide

            const lensCount = lensesToDisplay.length;
            // how many lenses are displayed?

            const lensDTO = lensUtils.getLensById(lensId);

            if (lensDTO !== null) {
                const catId = lensDTO.CategoryId;

                const findResult = lensesToDisplay.find(x => { return x.CategoryId === catId });
                // find the first lens in the set of lenses to display with the same category as the lens we just hid
                // or undefined if not found

                if (typeof findResult === "undefined") {
                    // if the lens we hid was the last of its category displayed

                    const catDivId = 'divCategory' + catId;
                    // get the id of the parent div

                    $('#' + catDivId).remove();
                    // remove the div from the page
                    // it's a bootstrap div, so hiding it won't works

                    const catCaptionId = 'catName' + catId;
                    // get the name of the category name element

                    $('#' + catCaptionId).hide();
                    // hide the category name

                    const hrId = 'hrCategory' + catId;
                    // get the name of the <hr> below the category

                    $('#' + hrId).hide();
                    // hide the horizontal rule

                    if (lensCount < 1) {
                        $('#hrAboveFirstCat').hide();
                        // hide the top horizontal rule
                    }
                }
            }
        }

        await uiUtils.handleLensCountChangedAsync();

        expandCollapseBtnUtils.showHideExpandCollapseBtnsAndCol();
        // the last expanded or collapsed card may have been hidden
        // so we may need to hide one or both of the expand/collapse buttons

        log('hideLensByLensIdAsync: leave');
    }
};