/**
 * This file is part of Moodle - http://moodle.org/
 *
 * Moodle is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Moodle is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Moodle. If not, see <http://www.gnu.org/licenses/>.
 *
 * @package
 * @module    theme_snap/accessibility
 * @author    Oscar Nadjar oscar.nadjar@openlms.net
 * @copyright Copyright (c) 2019 Open LMS (https://www.openlms.net)
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

/**
 * JS code to assign attributes and expected behavior for elements in the Dom regarding accessibility.
 */
define(['jquery', 'core/str', 'core/event', 'core_form/events', 'theme_boost/bootstrap/tools/sanitizer', 'theme_boost/popover',
    'core/moremenu', 'core/log'],
    function($, str, Event, FormEvents, { DefaultWhitelist }, Popover, coreMoreMenu, log) {
        return {
            snapAxInit: function(localJouleGrader, allyReport, blockReports, localCatalogue) {
                /**
                 * Module to get the strings from Snap to add the aria-label attribute to new accessibility features.
                 */
                let stringRequests = [
                    {key: 'accessforumstringdis', component: 'theme_snap'},
                    {key: 'accessforumstringmov', component: 'theme_snap'},
                    {key: 'calendar', component: 'calendar'},
                    {key: 'accessglobalsearchstring', component: 'theme_snap'},
                    {key: 'viewcalendar', component: 'theme_snap'},
                    {key: 'viewmyfeedback', component: 'theme_snap'},
                    {key: 'viewmessaging', component: 'theme_snap'},
                    {key: 'viewforumposts', component: 'theme_snap'},
                    {key: 'editcoursesettings', component: 'theme_snap'},
                    {key: 'gradebook', component: 'local_joulegrader'},
                    {key: 'gradebook', component: 'core_grades'},
                    {key: 'numparticipants', component: 'core_message'},
                    {key: 'pld', component: 'theme_snap'},
                    {key: 'competencies', component: 'core_competency'},
                    {key: 'outcomes', component: 'core_outcome'},
                    {key: 'badges', component: 'core_badges'},
                    {key: 'coursereport', component: 'report_allylti'},
                    {key: 'pluginname', component: 'local_catalogue'},
                    {key: 'experimental', component: 'block_reports'},
                    {key: 'themesettingstitle', component: 'theme_snap'},
                ];
                str.get_strings(stringRequests).done(function(stringsjs) {
                    const stringsMap = {};
                    stringRequests.forEach((item, index) => {
                        stringsMap[item.key] = stringsjs[index];
                    });
                    module.applyPageHeadingAccessibility(stringsMap);

                    if ($("#page-mod-forum-discuss")) {
                        $("div[data-content='forum-discussion'] select.custom-select.singleselect")
                        .attr("aria-label", stringsjs[0]);
                        $("div[data-content='forum-discussion'] div.movediscussionoption " +
                            "select.custom-select.urlselect").attr("aria-label", stringsjs[1]);
                    }
                    $("i.fa-calendar").parent().attr("aria-label", stringsjs[2]);
                    $("input[name='TimeEventSelector[calendar]']").attr('aria-label', stringsjs[2]);
                    var searchbutton = $("#mr-nav .simplesearchform a.btn.btn-open");
                    $(searchbutton).attr({
                        title: stringsjs[3],
                        'aria-label': stringsjs[3],
                    });

                    // Add needed ID's for course dashboard.
                    // These ID's were added for the most used elements in the course dashboard.

                    // There is not a lang string that contains {$a} participants with capital P, and this function helps with that.
                    // Taken from https://css-tricks.com/snippets/jquery/make-jquery-contains-case-insensitive/
                    $.expr[":"].contains = $.expr.createPseudo(function(arg) {
                        return function(elem) {
                            return $(elem).text().toUpperCase().indexOf(arg.toUpperCase()) >= 0;
                        };
                    });
                    var ctparticipantsnumber = stringsjs[11].split(" ");
                    $('section#coursetools ul#coursetools-list a:contains("' + stringsjs[8] + '")')
                        .attr("id", "ct-course-settings");
                    $('section#coursetools ul#coursetools-list a:contains("' + ctparticipantsnumber[1] + '")')
                        .attr("id", "ct-participants-number");
                    $('section#coursetools ul#coursetools-list a:contains("' + stringsjs[13] + '")')
                        .attr("id", "ct-competencies");
                    $('section#coursetools ul#coursetools-list a:contains("' + stringsjs[14] + '")')
                        .attr("id", "ct-outcomes");
                    $('section#coursetools ul#coursetools-list a:contains("' + stringsjs[15] + '")')
                        .attr("id", "ct-badges");

                    // Check if the plugins are installed to pass the strings. These parameters are being passed from
                    // $initaxvars in snap/classes/output/shared.php. More validations can be added if needed.
                    if (localJouleGrader) {
                        $('section#coursetools ul#coursetools-list a:contains("' + 'Open Grader' + '")')
                            .attr("id", "ct-open-grader");
                        $('section#coursetools ul#coursetools-list a:contains("' + stringsjs[9] + '")')
                            .attr("id", "ct-course-gradebook");
                    } else {
                        $('section#coursetools ul#coursetools-list a:contains("' + stringsjs[10] + '")')
                            .attr("id", "ct-course-gradebook");
                    }
                    if (blockReports) {
                        $('section#coursetools ul#coursetools-list a:contains("' + 'Open Reports' + '")')
                            .attr("id", "ct-open-reports");
                        $('section#coursetools ul#coursetools-list a:contains("' + stringsjs[18] + '")')
                            .attr("id", "ct-open-reports-experimental");
                    }
                    if (allyReport) {
                        $('section#coursetools ul#coursetools-list a:contains("' + stringsjs[16] + '")')
                            .attr("id", "ct-ally");
                    }
                    if (localCatalogue) {
                        $('section#coursetools ul#coursetools-list a:contains("' + stringsjs[17] + '")')
                            .attr("id", "ct-open-catalogue");
                    }

                    // Add ARIA attributes.
                    $('div[role="main"] div.sitetopic ul.section.img-text').attr('role', 'presentation');
                });

                var module = this;
                $(document).ready(function() {
                    // Add necessary attributes to needed DOM elements to new accessibility features.
                    $("#page-mod-data-edit input[id*='url']").attr("type", "url").attr("autocomplete", "url");
                    str.get_string('makingaselectionpagechange', 'theme_snap').done(function(label) {
                        module.injectScreenReader(label, '#jump-to-activity');
                    });
                    $("#moodle-blocks aside#block-region-side-pre a.sr-only.sr-only-focusable").attr("tabindex", "-1");
                    // Remove tabindex="-1" set by block_settings renderer on interactive elements.
                    $(".block_settings .block_tree").find("li, a, button, p, span").removeAttr("tabindex");
                    // Ensure all links in block_settings tree are keyboard navigable.
                    $(".block_settings .block_tree a").attr({"role": "button", "tabindex": "0"});

                    // Focus first invalid input after a submit is done.
                    $('.mform').submit(function() {
                        $('input.form-control.is-invalid:first').focus();
                    });

                    // Retrieve value from the input buttons from add/remove users in a group inside a course.
                    var addtext = $('.groupmanagementtable #buttonscell p.arrow_button input[name="add"]').attr('value');
                    var removetext = $(".groupmanagementtable #buttonscell p.arrow_button input[name='remove']").attr('value');

                    // Snap tab panels.
                    new Tabpanel("snap-pm-accessible-tab");
                    new Tabpanel("modchooser-accessible-tab");

                    // Wrapping for dropdown elements in the actionable elements in an activity for PLD.
                    if( $(".dropdown-item.editing_pld").closest(".pld-dropdown").length == 0 ) {
                        $(".dropdown-item.editing_pld").wrap("<li class='pld-dropdown'></li>");
                    }
                    $(".dropdown-item.editing_pld").attr("role","button");

                    /**
                     * Store the references outside the event handler.
                     * Window reload to change the inputs value for Add and Remove buttons when adding new
                     * members to a group.
                     */
                    var $window = $(window);

                    /**
                     * Modifies attributes depending on the window size.
                     */
                    function checkWidth() {
                        var windowsize = $window.width();
                        if (windowsize < 1220) {
                            $(".groupmanagementtable #buttonscell p.arrow_button input[name='add']").attr("value", "+");
                            $(".groupmanagementtable #buttonscell p.arrow_button input[name='remove']").attr("value", "-");
                        } else if (windowsize > 1220) {
                            $(".groupmanagementtable #buttonscell p.arrow_button input[name='add']").attr("value", addtext);
                            $(".groupmanagementtable #buttonscell p.arrow_button input[name='remove']").attr("value", removetext);
                        }
                    }
                    // Execute on load
                    checkWidth();
                    // Bind event listener
                    $(window).resize(checkWidth);

                    /**
                     * Change for the active carousel slide.
                     */
                    function carouselAriaCurrentValue() {
                        var carouselindicator = $('#snap-site-carousel .carousel-indicators button');
                        carouselindicator.click(function (e) {
                            var element = $(e.target);
                            carouselindicator.attr('aria-current', false);
                            element.attr('aria-current', true);
                        });

                        /**
                         * Listener to change aria-current value dynamically.
                         */
                        var targetNode = document.getElementById('snap-carousel-container');

                        // Options for the observer (which mutations to observe)
                        var config = { attributes: true, childList: true, subtree: true };

                        // Callback function to execute when mutations are observed
                        var callback = () => {
                            $('.carousel-indicators button').attr('aria-current', false);
                            $('.carousel-indicators button.active').attr('aria-current', true);
                        };

                        // Create an observer instance linked to the callback function
                        var observer = new MutationObserver(callback);

                        if (targetNode) {
                            // Start observing the target node for configured mutations.
                            observer.observe(targetNode, config);
                        }
                    }
                    carouselAriaCurrentValue();

                    /**
                     * Creates a pause and resume cycles for Snap's carousel.
                     */
                    function carouselPausePlay() {
                        $('#snap-site-carousel').carousel({
                            interval: 6000,
                            pause: "false"
                        });

                        $('#play-button').click(function () {
                            $('#snap-site-carousel').carousel('cycle');
                        });
                        $('#pause-button').click(function () {
                            $('#snap-site-carousel').carousel('pause');
                        });
                    }
                    carouselPausePlay();

                    /**
                     * Set all the side drawers tabbing order.
                     */
                    function setDrawersTabOrder() {
                        let blocksDrawerFocus;
                        let blocksDrawerAccessed = false;

                        /**
                         * Gets both the first and the last focusable elements from a drawer.
                         *
                         * @param {object} drawer The drawer to be analyzed.
                         */
                        function getFirstAndLastOfDrawer(drawer) {
                            let focusables = '[tabindex]:not([tabindex="-1"]),' +
                                ' a[href]:not([tabindex]),' +
                                ' button:not([disabled]):not([tabindex]),' +
                                ' input:not([disabled]):not([tabindex]),' +
                                ' textarea:not([disabled]):not([tabindex]),' +
                                ' select:not([disabled]):not([tabindex]), details:not([tabindex])';

                            let first = null;
                            let last = null;
                            if (drawer) {
                                let drawerFocusables = Array.from(drawer.querySelectorAll(focusables)).filter(el => {
                                    return el.offsetParent !== null;
                                });
                                first = drawerFocusables[0];
                                last = drawerFocusables[drawerFocusables.length - 1];
                            }
                            return [first, last];
                        }

                        /**
                         * Event listener to determine keyboard navigation of the drawers.
                         *
                         * @param {object} ev event
                         */
                        function drawerTabListener(ev) {

                            // Setup for the listener.
                            let adminDrawerIcon = document.getElementById('admin-menu-trigger');
                            let adminDrawer = adminDrawerIcon ?
                                document.querySelector('section.block_settings[data-block="settings"]') : null;
                            let blocksDrawerIcon = document.querySelector('.blocks-drawer-button');
                            let blocksDrawer = blocksDrawerIcon ?
                                document.getElementById('theme_snap-drawers-blocks') : null;
                            let blocksDrawerClose = document.querySelector('#theme_snap-drawers-blocks > .drawerheader > button');
                            let snapfeedsDrawerIcon = document.getElementById('snap_feeds_side_menu_trigger');
                            let snapfeedsDrawer = snapfeedsDrawerIcon ?
                                document.querySelector('#snap_feeds_side_menu .snap-feeds') : null;
                            let snapfeedsSideMenu = document.getElementById('snap_feeds_side_menu');
                            let messageDrawerIcon = document.querySelector('a[id^=\'message-drawer-toggle-\']');
                            let messageDrawerChild = document.querySelector('div[data-region="message-drawer"]');
                            let messageDrawer = messageDrawerChild ? messageDrawerChild.parentElement : null;
                            messageDrawer = messageDrawerIcon ? messageDrawer : null;
                            let messageDrawerClose = document.querySelector('[id^="message-drawer-"] > div.closewidget > a');
                            let drawerIcons = [adminDrawerIcon, blocksDrawerIcon, snapfeedsDrawerIcon, messageDrawerIcon]
                                .filter(el => {
                                    return el !== null;
                                });
                            let drawers = [adminDrawer, blocksDrawer, snapfeedsDrawer, messageDrawer]
                                .filter(el => {
                                    return el !== null;
                                });
                            // Dynamically get the last link from the custom menu header
                            let beforeDrawers =
                              document.querySelectorAll(
                                "#snap-custom-menu-header div > ul > li:not(.d-none) > a"
                              ) ||
                              document.querySelectorAll(
                                "#snap-custom-menu-header > nav > ul > li:not(.d-none) > a"
                              );
                            beforeDrawers = beforeDrawers.length > 0 ? beforeDrawers[beforeDrawers.length - 1] : null;
                            // If custom menu header doesn't exist, get the last focusable item in snap-header
                            if (!beforeDrawers) {
                                let focusables = '[tabindex]:not([tabindex="-1"]),' +
                                    ' a[href]:not([tabindex]),' +
                                    ' button:not([disabled]):not([tabindex]),' +
                                    ' input:not([disabled]):not([tabindex]),' +
                                    ' textarea:not([disabled]):not([tabindex]),' +
                                    ' select:not([disabled]):not([tabindex]), details:not([tabindex])';
                                let snapHeader = document.getElementById('snap-header');
                                if (snapHeader) {
                                    let headerFocusables = Array.from(snapHeader.querySelectorAll(focusables)).filter(el => {
                                        return el.offsetParent !== null;
                                    });
                                    beforeDrawers = headerFocusables.length > 0 ?
                                        headerFocusables[headerFocusables.length - 1] : null;
                                }
                            }
                            let afterDrawers = document.querySelector('#snap-sidebar-menu > button.snap-sidebar-menu-trigger');

                            let adminDrawerFirst = null;
                            let adminDrawerLast = null;
                            [adminDrawerFirst, adminDrawerLast] = getFirstAndLastOfDrawer(adminDrawer);

                            let blocksDrawerFirst = null;
                            let blocksDrawerLast = null;
                            [blocksDrawerFirst, blocksDrawerLast] = getFirstAndLastOfDrawer(blocksDrawer);

                            let snapfeedsDrawerFirst = null;
                            let snapfeedsDrawerLast = null;
                            [snapfeedsDrawerFirst, snapfeedsDrawerLast] = getFirstAndLastOfDrawer(snapfeedsDrawer);

                            let messageDrawerFirst = null;
                            let messageDrawerLast = null;
                            [messageDrawerFirst, messageDrawerLast] = getFirstAndLastOfDrawer(messageDrawer);

                            let drawerFirsts = [adminDrawerFirst, blocksDrawerFirst, snapfeedsDrawerFirst, messageDrawerFirst]
                                .filter(el => {
                                    return el !== null;
                                });
                            let drawerLasts = [adminDrawerLast, blocksDrawerLast, snapfeedsDrawerLast, messageDrawerLast]
                                .filter(el => {
                                    return el !== null;
                                });

                            // Process keys (Tab, Shift+Tab, and Enter).
                            if (ev.key === 'Tab' && drawerIcons.includes(ev.target)) {
                                ev.preventDefault();
                                let idx = drawerIcons.indexOf(ev.target);
                                if ((drawers[idx].classList.contains('state-visible')
                                        && adminDrawer && drawers[idx] === adminDrawer) ||
                                    (drawers[idx].classList.contains('show') && blocksDrawer && drawers[idx] === blocksDrawer) ||
                                    (snapfeedsSideMenu && snapfeedsSideMenu.classList.contains('state-visible')
                                        && snapfeedsDrawer && drawers[idx] === snapfeedsDrawer) ||
                                    (!drawers[idx].classList.contains('hidden')
                                        && messageDrawer && drawers[idx] === messageDrawer)) {
                                    if (ev.shiftKey) {
                                        drawerLasts[idx].focus();
                                    } else {
                                        drawerFirsts[idx].focus();
                                    }
                                } else {
                                    if (ev.shiftKey) {
                                        if (idx === 0) {
                                            beforeDrawers.focus();
                                        } else {
                                            drawerIcons[idx - 1].focus();
                                        }
                                    } else {
                                        if (idx < drawers.length - 1) {
                                            drawerIcons[idx + 1].focus();
                                        } else {
                                            afterDrawers.focus();
                                        }
                                    }
                                }
                            } else if (ev.key === 'Tab' && !ev.shiftKey && drawerLasts.includes(ev.target)) {
                                ev.preventDefault();
                                let idx = drawerLasts.indexOf(ev.target);
                                drawerIcons[idx].focus();
                            } else if (ev.key === 'Tab' && ev.shiftKey && drawerFirsts.includes(ev.target)) {
                                ev.preventDefault();
                                let idx = drawerFirsts.indexOf(ev.target);
                                drawerIcons[idx].focus();
                            } else if (ev.key === 'Enter' && (drawerIcons.includes(ev.target)
                                || messageDrawerClose === ev.target)) {
                                blocksDrawerAccessed = false;
                                ev.preventDefault();
                                let idx = drawerIcons.indexOf(ev.target);
                                if (drawerIcons[idx] === messageDrawerIcon) {
                                    document.getElementById('page').classList.toggle('offcanvas');
                                } else if (drawerIcons[idx] === blocksDrawerIcon) {
                                    drawerIcons[idx].click();
                                    blocksDrawerFocus = function() {
                                        if (blocksDrawerAccessed) {
                                            return;
                                        } else {
                                            blocksDrawerAccessed = true;
                                        }
                                        blocksDrawerIcon.focus();
                                        blocksDrawerClose.removeEventListener('focus', blocksDrawerFocus);
                                    };
                                    blocksDrawerClose.addEventListener('focus', blocksDrawerFocus);
                                } else if (messageDrawerClose !== ev.target) {
                                    drawerIcons[idx].click();
                                } else {
                                    document.getElementById('page').classList.toggle('offcanvas');
                                    messageDrawerIcon.focus();
                                }
                                if (idx >= 0) {
                                    drawerIcons[idx].focus();
                                }
                            }
                        }
                        document.addEventListener('keydown', drawerTabListener);
                    }
                    setDrawersTabOrder();

                    /**
                     * Persist the active admin settings tab across page reloads.
                     */
                    function persistAdminSettingsTabs() {
                        const tabContainer = document.getElementById('snap-admin-tabs');
                        if (!tabContainer) {
                            return;
                        }
                        const section = new URLSearchParams(window.location.search).get('section') || 'default';
                        const storageKey = 'snap_admin_activetab_' + section;
                        const savedTab = sessionStorage.getItem(storageKey);

                        if (savedTab) {
                            const tabLink = tabContainer.querySelector('.nav-link[href="#' + savedTab + '"]');
                            if (tabLink) {
                                const currentActive = tabContainer.querySelector('.nav-link.active');
                                if (currentActive) {
                                    currentActive.classList.remove('active');
                                }
                                const currentPane = document.querySelector('.tab-content .tab-pane.active');
                                if (currentPane) {
                                    currentPane.classList.remove('active');
                                }
                                tabLink.classList.add('active');
                                const pane = document.getElementById(savedTab);
                                if (pane) {
                                    pane.classList.add('active');
                                }
                                tabLink.focus();
                            }
                        }

                        tabContainer.addEventListener('click', function(e) {
                            const link = e.target.closest('.nav-link');
                            if (link) {
                                const tabName = link.getAttribute('href').replace('#', '');
                                sessionStorage.setItem(storageKey, tabName);
                            }
                        });
                    }
                    persistAdminSettingsTabs();

                    // Local accessibility plugin button from Snap header
                    const accessibilityIcon = document.getElementById('local-accessibility-buttoncontainer');
                    const headerButtonsContainer = document.querySelector('#snap-header > div.float-end');
                    if (accessibilityIcon && headerButtonsContainer.querySelector('.usermenu')) {
                        const lineSeparator = document.querySelector('#snap-header div.snap_line_separator');
                        const accessibilityWrapper = document.createElement('div');
                        accessibilityWrapper.id = 'nav-local-accessibility-popover-container';
                        const accessibilityPanel = document.querySelector('div.local-accessibility-panel');
                        accessibilityPanel.classList.remove('border-primary');
                        accessibilityPanel.classList.remove('card');
                        accessibilityIcon.querySelector('button').addEventListener('focus', () => {
                            accessibilityWrapper.classList.add('focused-icon');
                        });
                        accessibilityIcon.querySelector('button').addEventListener('blur', () => {
                            accessibilityWrapper.classList.remove('focused-icon');
                        });
                        const userMenuLink = document.querySelector('.usermenu a');
                        if (userMenuLink) {
                            userMenuLink.addEventListener('click', () => {
                                accessibilityPanel.style.display = 'none';
                            });
                        }

                        if (lineSeparator) {
                            lineSeparator.parentElement.insertBefore(accessibilityWrapper, lineSeparator);
                        } else {
                            headerButtonsContainer.insertBefore(accessibilityWrapper, lineSeparator);
                        }
                        accessibilityWrapper.appendChild(accessibilityIcon);
                        accessibilityWrapper.appendChild(accessibilityPanel);

                        let animationTimeout = null;
                        let isClosingAnim = false;

                        /**
                         * Handles opening animation for accessibility panel.
                         */
                        const handlePanelOpen = () => {
                            // Clear any pending close animations
                            if (animationTimeout) {
                                clearTimeout(animationTimeout);
                                animationTimeout = null;
                            }

                            accessibilityPanel.style.display = 'block';
                            requestAnimationFrame(() => {
                                accessibilityPanel.classList.add('is-visible');
                            });
                        };

                        /**
                         * Handles closing animation for accessibility panel.
                         */
                        const handlePanelClose = () => {
                            if (isClosingAnim) {
                                return;
                            }
                            isClosingAnim = true;
                            accessibilityPanel.style.display = 'block';

                            requestAnimationFrame(() => {
                                accessibilityPanel.classList.remove('is-visible');
                                animationTimeout = setTimeout(() => {
                                    if (isClosingAnim && !accessibilityPanel.classList.contains('is-visible')) {
                                        accessibilityPanel.style.display = 'none';
                                    }
                                    isClosingAnim = false;
                                    animationTimeout = null;
                                }, 300);
                            });
                        };

                        // Required to apply the required transition in the Snap header
                        const observer = new MutationObserver(() => {
                            const isDisplayed = window.getComputedStyle(accessibilityPanel).display !== 'none';
                            const isVisible = accessibilityPanel.classList.contains('is-visible');
                            if (isDisplayed && !isVisible) {
                                handlePanelOpen();
                            }
                            if (!isDisplayed && isVisible) {
                                handlePanelClose();
                            }
                        });

                        observer.observe(accessibilityPanel, {attributes: true, attributeFilter: ['style']});
                    }

                    const snapCustomheader = document.getElementById('snap-custom-menu-header');
                    const menu = document.querySelector('.snap-navbar-content');
                    if (menu && snapCustomheader) {
                        try {
                            coreMoreMenu(menu);
                        } catch (e) {
                            menu.classList.add('flex-nowrap');
                            log.error(e);
                        } finally {
                            if (snapCustomheader.classList.contains('invisible')) {
                                snapCustomheader.classList.remove('invisible');
                            }
                        }
                    }
                });

                /**
                 * Add needed accessibility for tabs inside Snap.
                 * This makes use of Bootstrap accessible tab panel with WAI-ARIA with the arrow keys binding codes.
                 * @param {string} id
                 */
                function Tabpanel(id) {
                    this._id = id;
                    this.$tpanel = $('#' + id);
                    this.$tabs = this.$tpanel.find('.tab');
                    this.$panels = this.$tpanel.find('.tab-pane');
                    this.bindHandlers();
                    this.init();
                }

                Tabpanel.prototype.keys = {
                    left: 37,
                    up: 38,
                    right: 39,
                    down: 40
                };

                Tabpanel.prototype.init = function() {
                    var $tab;
                    this.$panels.attr('aria-hidden', 'true');
                    this.$panels.removeClass('active in');
                    $tab = this.$tabs.filter('.active');
                    if ($tab === undefined) {
                        $tab = this.$tabs.first();
                        $tab.addClass('active');
                    }
                    this.$tpanel
                        .find('#' + $tab.find('a').attr('aria-controls'))
                        .addClass('active in').attr('aria-hidden', 'false');
                };

                Tabpanel.prototype.switchTabs = function($curTab, $newTab) {
                    var $curTabLink = $curTab.find('a'),
                        $newTabLink = $newTab.find('a');
                    $curTab.removeClass('active');
                    $curTabLink.attr('tabindex', '-1').attr('aria-selected', 'false');
                    $newTab.addClass('active');
                    $newTabLink.attr('aria-selected', 'true');
                    this.$tpanel
                        .find('#' + $curTabLink.attr('aria-controls'))
                        .removeClass('active in').attr('aria-hidden', 'true');
                    this.$tpanel
                        .find('#' + $newTabLink.attr('aria-controls'))
                        .addClass('active in').attr('aria-hidden', 'false');
                    $newTabLink.attr('tabindex', '0');
                    $newTabLink.focus();
                };

                Tabpanel.prototype.bindHandlers = function() {
                    var self = this;
                    this.$tabs.keydown(function(e) {
                        return self.handleTabKeyDown($(this), e);
                    });
                    this.$tabs.click(function(e) {
                        return self.handleTabClick($(this), e);
                    });
                };

                Tabpanel.prototype.handleTabKeyDown = function($tab, e) {
                    var $newTab, tabIndex;
                    switch (e.keyCode) {
                        case this.keys.left:
                        case this.keys.up: {
                            tabIndex = this.$tabs.index($tab);
                            if (tabIndex === 0) {
                                $newTab = this.$tabs.last();
                            } else {
                                $newTab = this.$tabs.eq(tabIndex - 1);
                            }
                            this.switchTabs($tab, $newTab);
                            e.preventDefault();
                            return false;
                        }
                        case this.keys.right:
                        case this.keys.down: {
                            tabIndex = this.$tabs.index($tab);
                            if (tabIndex === this.$tabs.length - 1) {
                                $newTab = this.$tabs.first();
                            } else {
                                $newTab = this.$tabs.eq(tabIndex + 1);
                            }
                            this.switchTabs($tab, $newTab);
                            e.preventDefault();
                            return false;
                        }
                    }
                };

                Tabpanel.prototype.handleTabClick = function($tab) {
                    var $oldTab = this.$tpanel.find('.tab.active');
                    this.switchTabs($oldTab, $tab);
                };
            },

            /**
             * Override the options from theme_boost/loader::enablePopovers to enhance accesibility (VPAT).
             */
            setManualPopovers: function() {
                const btnSelector = '.iconhelp.btn';

                $('body').popover({
                    selector: '[data-toggle="popover"]',
                    trigger: 'manual',
                    container: 'body',
                    whitelist: Object.assign(DefaultWhitelist, {
                        table: [],
                        thead: [],
                        tbody: [],
                        tr: [],
                        th: [],
                        td: [],
                    }),
                });

                // Prevent Bootstrap from automatically reacting to button focus
                $(btnSelector).on('focusin', function(e) {
                    e.stopImmediatePropagation();
                });

                $(btnSelector).on('click', function(e) {
                    e.preventDefault();
                    e.stopImmediatePropagation();

                    const $el = $(this);
                    const isOpen = $el.attr('aria-expanded') === 'true';

                    if (isOpen) {
                        $el.popover('hide');
                    } else {
                        $el.popover('show');
                    }
                });

                $(btnSelector).on('keydown', function(e) {
                    const $el = $(this);

                    if (e.key === 'Enter' || e.key === ' ') {
                        e.preventDefault();
                        e.stopImmediatePropagation();

                        const isOpen = $el.attr('aria-expanded') === 'true';

                        if (isOpen) {
                            $el.popover('hide');
                        } else {
                            $el.popover('show');
                        }
                    }

                    if (e.key === 'Escape') {
                        $el.popover('hide');
                    }
                });

                $(btnSelector).on('shown.bs.popover', function () {
                    const popover = $(this).data('bs.popover').tip;
                    $(this).attr('aria-controls', popover.id);
                    $(this).attr('aria-expanded', true);
                    $(popover).insertAfter($(this));
                    $(popover).popover('update');
                });

                $(btnSelector).on('hidden.bs.popover', function () {
                    $(this).attr('aria-expanded', false);
                });
            },

            injectScreenReader: function(label, targetSelector) {
                var target = document.querySelector(targetSelector);
                if (!target) {
                    return;
                }
                var span = document.createElement('span');
                span.className = 'sr-only';
                span.textContent = label;
                target.parentNode.insertBefore(span, target);
            },

            applyPageHeadingAccessibility: function (stringsMap) {
                const bodyId = document.body.id || "";
                const pageTypeConfigs = {
                    "page-admin-setting-themesettingsnap": {
                        ariaLabel: stringsMap['themesettingstitle'],
                        ariaLevel: "1"
                    },
                };
                const configForPage = pageTypeConfigs[bodyId];
                 if (configForPage) {
                     const heading = document.querySelector("#page-header h1") || document.querySelector("h1");
                     if (heading) {
                        heading.setAttribute("aria-label", configForPage.ariaLabel);
                        heading.setAttribute("role", "heading");
                        heading.setAttribute("aria-level", configForPage.ariaLevel);
                     }
                 }
            }
        };
    }
);
