/**
 * Bootstrap Multiselect (http://davidstutz.de/bootstrap-multiselect/)
 *
 * Apache License, Version 2.0:
 * Copyright (c) 2012 - 2021 David Stutz
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a
 * copy of the License at http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 * BSD 3-Clause License:
 * Copyright (c) 2012 - 2021 David Stutz
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *    - Redistributions of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 *    - Redistributions in binary form must reproduce the above copyright notice,
 *      this list of conditions and the following disclaimer in the documentation
 *      and/or other materials provided with the distribution.
 *    - Neither the name of David Stutz nor the names of its contributors may be
 *      used to endorse or promote products derived from this software without
 *      specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
(function (root, factory) {
    // check to see if 'knockout' AMD module is specified if using requirejs
    if (typeof define === 'function' && define.amd &&
        typeof require === 'function' && typeof require.specified === 'function' && require.specified('knockout')) {

        // AMD. Register as an anonymous module.
        define(['jquery', 'knockout'], factory);
    } else {
        // Browser globals
        factory(root.jQuery, root.ko);
    }
})(this, function ($, ko) {
    "use strict";// jshint ;_;

    if (typeof ko !== 'undefined' && ko.bindingHandlers && !ko.bindingHandlers.multiselect) {
        ko.bindingHandlers.multiselect = {
            after: ['options', 'value', 'selectedOptions', 'enable', 'disable'],

            init: function (element, valueAccessor, allBindings, viewModel, bindingContext) {
                var $element = $(element);
                var config = ko.toJS(valueAccessor());

                $element.multiselect(config);

                if (allBindings.has('options')) {
                    var options = allBindings.get('options');
                    if (ko.isObservable(options)) {
                        ko.computed({
                            read: function () {
                                options();
                                setTimeout(function () {
                                    var ms = $element.data('multiselect');
                                    if (ms)
                                        ms.updateOriginalOptions();//Not sure how beneficial this is.
                                    $element.multiselect('rebuild');
                                }, 1);
                            },
                            disposeWhenNodeIsRemoved: element
                        });
                    }
                }

                //value and selectedOptions are two-way, so these will be triggered even by our own actions.
                //It needs some way to tell if they are triggered because of us or because of outside change.
                //It doesn't loop but it's a waste of processing.
                if (allBindings.has('value')) {
                    var value = allBindings.get('value');
                    if (ko.isObservable(value)) {
                        ko.computed({
                            read: function () {
                                value();
                                setTimeout(function () {
                                    $element.multiselect('refresh');
                                }, 1);
                            },
                            disposeWhenNodeIsRemoved: element
                        }).extend({ rateLimit: 100, notifyWhenChangesStop: true });
                    }
                }

                //Switched from arrayChange subscription to general subscription using 'refresh'.
                //Not sure performance is any better using 'select' and 'deselect'.
                if (allBindings.has('selectedOptions')) {
                    var selectedOptions = allBindings.get('selectedOptions');
                    if (ko.isObservable(selectedOptions)) {
                        ko.computed({
                            read: function () {
                                selectedOptions();
                                setTimeout(function () {
                                    $element.multiselect('refresh');
                                }, 1);
                            },
                            disposeWhenNodeIsRemoved: element
                        }).extend({ rateLimit: 100, notifyWhenChangesStop: true });
                    }
                }

                var setEnabled = function (enable) {
                    setTimeout(function () {
                        if (enable)
                            $element.multiselect('enable');
                        else
                            $element.multiselect('disable');
                    });
                };

                if (allBindings.has('enable')) {
                    var enable = allBindings.get('enable');
                    if (ko.isObservable(enable)) {
                        ko.computed({
                            read: function () {
                                setEnabled(enable());
                            },
                            disposeWhenNodeIsRemoved: element
                        }).extend({ rateLimit: 100, notifyWhenChangesStop: true });
                    } else {
                        setEnabled(enable);
                    }
                }

                if (allBindings.has('disable')) {
                    var disable = allBindings.get('disable');
                    if (ko.isObservable(disable)) {
                        ko.computed({
                            read: function () {
                                setEnabled(!disable());
                            },
                            disposeWhenNodeIsRemoved: element
                        }).extend({ rateLimit: 100, notifyWhenChangesStop: true });
                    } else {
                        setEnabled(!disable);
                    }
                }

                ko.utils.domNodeDisposal.addDisposeCallback(element, function () {
                    $element.multiselect('destroy');
                });
            },

            update: function (element, valueAccessor, allBindings, viewModel, bindingContext) {
                var $element = $(element);
                var config = ko.toJS(valueAccessor());

                $element.multiselect('setOptions', config);
                $element.multiselect('rebuild');
            }
        };
    }

    function forEach(array, callback) {
        for (var index = 0; index < array.length; ++index) {
            callback(array[index], index);
        }
    }

    /**
     * Constructor to create a new multiselect using the given select.
     *
     * @param {jQuery} select
     * @param {Object} options
     * @returns {Multiselect}
     */
    function Multiselect(select, options) {

        this.$select = $(select);
        this.options = this.mergeOptions($.extend({}, options, this.$select.data()));

        // Placeholder via data attributes
        if (this.$select.attr("data-placeholder")) {
            this.options.nonSelectedText = this.$select.data("placeholder");
        }

        // Initialization.
        // We have to clone to create a new reference.
        this.originalOptions = this.$select.clone()[0].options;
        this.query = '';
        this.searchTimeout = null;
        this.lastToggledInput = null;

        this.options.multiple = this.$select.attr('multiple') === "multiple";
        this.options.onChange = $.proxy(this.options.onChange, this);
        this.options.onSelectAll = $.proxy(this.options.onSelectAll, this);
        this.options.onDeselectAll = $.proxy(this.options.onDeselectAll, this);
        this.options.onDropdownShow = $.proxy(this.options.onDropdownShow, this);
        this.options.onDropdownHide = $.proxy(this.options.onDropdownHide, this);
        this.options.onDropdownShown = $.proxy(this.options.onDropdownShown, this);
        this.options.onDropdownHidden = $.proxy(this.options.onDropdownHidden, this);
        this.options.onInitialized = $.proxy(this.options.onInitialized, this);
        this.options.onFiltering = $.proxy(this.options.onFiltering, this);

        // Build select all if enabled.
        this.buildContainer();
        this.buildButton();
        this.buildDropdown();
        this.buildReset();
        this.buildSelectAll();
        this.buildDropdownOptions();
        this.buildFilter();

        this.updateButtonText();
        this.updateSelectAll(true);

        if (this.options.enableClickableOptGroups && this.options.multiple) {
            this.updateOptGroups();
        }

        this.options.wasDisabled = this.$select.prop('disabled');
        if (this.options.disableIfEmpty && $('option', this.$select).length <= 0) {
            this.disable();
        }

        this.$select.wrap('<span class="multiselect-native-select" />').after(this.$container);

        if (this.options.widthSynchronizationMode !== 'never') {
            this.synchronizeButtonAndPopupWidth();
        }

        this.options.onInitialized(this.$select, this.$container);
    }

    Multiselect.prototype = {

        defaults: {
            /**
             * Default text function will either print 'None selected' in case no
             * option is selected or a list of the selected options up to a length
             * of 3 selected options.
             *
             * @param {jQuery} options
             * @param {jQuery} select
             * @returns {String}
             */
            buttonText: function (selectedOptions, select) {
                if (this.disabledText.length > 0 && select.prop('disabled')) {
                    return this.disabledText;
                }
                else if (selectedOptions.length === 0) {
                    return this.nonSelectedText;
                }
                else if (this.allSelectedText
                    && selectedOptions.length === $('option', $(select)).length
                    && $('option', $(select)).length !== 1
                    && this.multiple) {

                    if (this.selectAllNumber) {
                        return this.allSelectedText + ' (' + selectedOptions.length + ')';
                    }
                    else {
                        return this.allSelectedText;
                    }
                }
                else if (this.numberDisplayed != 0 && selectedOptions.length > this.numberDisplayed) {
                    return selectedOptions.length + ' ' + this.nSelectedText;
                }
                else {
                    var selected = '';
                    var delimiter = this.delimiterText;

                    selectedOptions.each(function () {
                        var label = ($(this).attr('label') !== undefined) ? $(this).attr('label') : $(this).text();
                        selected += label + delimiter;
                    });

                    return selected.substr(0, selected.length - this.delimiterText.length);
                }
            },
            /**
             * Updates the title of the button similar to the buttonText function.
             *
             * @param {jQuery} options
             * @param {jQuery} select
             * @returns {@exp;selected@call;substr}
             */
            buttonTitle: function (options, select) {
                if (options.length === 0) {
                    return this.nonSelectedText;
                }
                else {
                    var selected = '';
                    var delimiter = this.delimiterText;

                    options.each(function () {
                        var label = ($(this).attr('label') !== undefined) ? $(this).attr('label') : $(this).text();
                        selected += label + delimiter;
                    });
                    return selected.substr(0, selected.length - this.delimiterText.length);
                }
            },
            checkboxName: function (option) {
                return false; // no checkbox name
            },
            /**
             * Create a label.
             *
             * @param {jQuery} element
             * @returns {String}
             */
            optionLabel: function (element) {
                return $(element).attr('label') || $(element).text();
            },
            /**
             * Create a class.
             *
             * @param {jQuery} element
             * @returns {String}
             */
            optionClass: function (element) {
                return $(element).attr('class') || '';
            },
            /**
             * Triggered on change of the multiselect.
             *
             * Not triggered when selecting/deselecting options manually.
             *
             * @param {jQuery} option
             * @param {Boolean} checked
             */
            onChange: function (option, checked) {

            },
            /**
             * Triggered when the dropdown is shown.
             *
             * @param {jQuery} event
             */
            onDropdownShow: function (event) {

            },
            /**
             * Triggered when the dropdown is hidden.
             *
             * @param {jQuery} event
             */
            onDropdownHide: function (event) {

            },
            /**
             * Triggered after the dropdown is shown.
             *
             * @param {jQuery} event
             */
            onDropdownShown: function (event) {

            },
            /**
             * Triggered after the dropdown is hidden.
             *
             * @param {jQuery} event
             */
            onDropdownHidden: function (event) {

            },
            /**
             * Triggered on select all.
             */
            onSelectAll: function () {

            },
            /**
             * Triggered on deselect all.
             */
            onDeselectAll: function () {

            },
            /**
             * Triggered after initializing.
             *
             * @param {jQuery} $select
             * @param {jQuery} $container
             */
            onInitialized: function ($select, $container) {

            },
            /**
             * Triggered on filtering.
             *
             * @param {jQuery} $filter
             */
            onFiltering: function ($filter) {

            },
            enableHTML: false,
            buttonClass: 'custom-select',
            inheritClass: false,
            buttonWidth: 'auto',
            buttonContainer: '<div class="btn-group" />',
            dropRight: false,
            dropUp: false,
            selectedClass: 'active',
            // Maximum height of the dropdown menu.
            // If maximum height is exceeded a scrollbar will be displayed.
            maxHeight: false,
            includeSelectAllOption: false,
            includeSelectAllIfMoreThan: 0,
            selectAllText: ' Select all',
            selectAllValue: 'multiselect-all',
            selectAllName: false,
            selectAllNumber: true,
            selectAllJustVisible: true,
            enableFiltering: false,
            enableCaseInsensitiveFiltering: false,
            enableFullValueFiltering: false,
            enableClickableOptGroups: false,
            enableCollapsibleOptGroups: false,
            collapseOptGroupsByDefault: false,
            filterPlaceholder: 'Search',
            // possible options: 'text', 'value', 'both'
            filterBehavior: 'text',
            includeFilterClearBtn: true,
            preventInputChangeEvent: false,
            nonSelectedText: 'None selected',
            nSelectedText: 'selected',
            allSelectedText: 'All selected',
            numberDisplayed: 3,
            disableIfEmpty: false,
            disabledText: '',
            delimiterText: ', ',
            includeResetOption: false,
            includeResetDivider: false,
            resetText: 'Reset',
            indentGroupOptions: true,
            // possible options: 'never', 'always', 'ifPopupIsSmaller', 'ifPopupIsWider'
            widthSynchronizationMode: 'never',
            buttonTextAlignment: 'center',
            templates: {
                button: '<button type="button" class="multiselect dropdown-toggle" data-toggle="dropdown"><span class="multiselect-selected-text"></span></button>',
                popupContainer: '<div class="multiselect-container dropdown-menu"></div>',
                filter: '<div class="multiselect-filter d-flex align-items-center"><i class="fas fa-sm fa-search text-muted"></i><input type="search" class="multiselect-search form-control" /></div>',
                option: '<button type="button" class="multiselect-option dropdown-item"></button>',
                divider: '<div class="dropdown-divider"></div>',
                optionGroup: '<button type="button" class="multiselect-group dropdown-item"></button>',
                resetButton: '<div class="multiselect-reset text-center p-2"><button type="button" class="btn btn-sm btn-block btn-outline-secondary"></button></div>'
            }
        },

        constructor: Multiselect,

        /**
         * Builds the container of the multiselect.
         */
        buildContainer: function () {
            this.$container = $(this.options.buttonContainer);
            if (this.options.widthSynchronizationMode !== 'never') {
                this.$container.on('show.bs.dropdown', $.proxy(function () {
                    // the width needs to be synchronized again in case the width of the button changed in between
                    this.synchronizeButtonAndPopupWidth();
                    this.options.onDropdownShow();
                }, this));
            }
            else {
                this.$container.on('show.bs.dropdown', this.options.onDropdownShow);
            }
            this.$container.on('hide.bs.dropdown', this.options.onDropdownHide);
            this.$container.on('shown.bs.dropdown', this.options.onDropdownShown);
            this.$container.on('hidden.bs.dropdown', this.options.onDropdownHidden);
        },

        /**
         * Builds the button of the multiselect.
         */
        buildButton: function () {
            this.$button = $(this.options.templates.button).addClass(this.options.buttonClass);
            if (this.$select.attr('class') && this.options.inheritClass) {
                this.$button.addClass(this.$select.attr('class'));
            }
            // Adopt active state.
            if (this.$select.prop('disabled')) {
                this.disable();
            }
            else {
                this.enable();
            }

            // Manually add button width if set.
            if (this.options.buttonWidth && this.options.buttonWidth !== 'auto') {
                this.$button.css({
                    'width': '100%' //this.options.buttonWidth,
                });
                this.$container.css({
                    'width': this.options.buttonWidth
                });
            }

            if (this.options.buttonTextAlignment) {
                switch (this.options.buttonTextAlignment) {
                    case 'left':
                        this.$button.addClass('text-left');
                        break;
                    case 'center':
                        this.$button.addClass('text-center');
                        break;
                    case 'right':
                        this.$button.addClass('text-right');
                        break;
                }
            }

            // Keep the tab index from the select.
            var tabindex = this.$select.attr('tabindex');
            if (tabindex) {
                this.$button.attr('tabindex', tabindex);
            }

            this.$container.prepend(this.$button);
        },

        /**
         * Builds the popup container representing the dropdown menu.
         */
        buildDropdown: function () {

            // Build popup container.
            this.$popupContainer = $(this.options.templates.popupContainer);

            if (this.options.dropRight) {
                this.$container.addClass('dropright');
            }
            else if (this.options.dropUp) {
                this.$container.addClass("dropup");
            }

            // Set max height of dropdown menu to activate auto scrollbar.
            if (this.options.maxHeight) {
                // TODO: Add a class for this option to move the css declarations.
                this.$popupContainer.css({
                    'max-height': this.options.maxHeight + 'px',
                    'overflow-y': 'auto',
                    'overflow-x': 'hidden'
                });
            }

            if (this.options.widthSynchronizationMode !== 'never') {
                this.$popupContainer.css('overflow-x', 'hidden');
            }

            this.$popupContainer.on("touchstart click", function (e) {
                e.stopPropagation();
            });

            this.$container.append(this.$popupContainer);
        },

        synchronizeButtonAndPopupWidth: function () {
            if (!this.$popupContainer || this.options.widthSynchronizationMode === 'never') {
                return;
            }

            var buttonWidth = this.$button.outerWidth();
            switch (this.options.widthSynchronizationMode) {
                case 'always':
                    this.$popupContainer.css('min-width', buttonWidth);
                    this.$popupContainer.css('max-width', buttonWidth);
                    break;
                case 'ifPopupIsSmaller':
                    this.$popupContainer.css('min-width', buttonWidth);
                    break;
                case 'ifPopupIsWider':
                    this.$popupContainer.css('max-width', buttonWidth);
                    break;
            }
        },

        /**
         * Build the dropdown options and binds all necessary events.
         *
         * Uses createDivider and createOptionValue to create the necessary options.
         */
        buildDropdownOptions: function () {

            this.$select.children().each($.proxy(function (index, element) {

                var $element = $(element);
                // Support optgroups and options without a group simultaneously.
                var tag = $element.prop('tagName')
                    .toLowerCase();

                if ($element.prop('value') === this.options.selectAllValue) {
                    return;
                }

                if (tag === 'optgroup') {
                    this.createOptgroup(element);
                }
                else if (tag === 'option') {

                    if ($element.data('role') === 'divider') {
                        this.createDivider();
                    }
                    else {
                        this.createOptionValue(element, false);
                    }

                }

                // Other illegal tags will be ignored.
            }, this));

            // Bind the change event on the dropdown elements.
            $(this.$popupContainer).off('change', '> *:not(.multiselect-group) input[type="checkbox"], > *:not(.multiselect-group) input[type="radio"]');
            $(this.$popupContainer).on('change', '> *:not(.multiselect-group) input[type="checkbox"], > *:not(.multiselect-group) input[type="radio"]', $.proxy(function (event) {
                var $target = $(event.target);

                var checked = $target.prop('checked') || false;
                var isSelectAllOption = $target.val() === this.options.selectAllValue;

                // Apply or unapply the configured selected class.
                if (this.options.selectedClass) {
                    if (checked) {
                        $target.closest('.multiselect-option')
                            .addClass(this.options.selectedClass);
                    }
                    else {
                        $target.closest('.multiselect-option')
                            .removeClass(this.options.selectedClass);
                    }
                }

                // Get the corresponding option.
                var value = $target.val();
                var $option = this.getOptionByValue(value);

                var $optionsNotThis = $('option', this.$select).not($option);
                var $checkboxesNotThis = $('input', this.$container).not($target);

                if (isSelectAllOption) {

                    if (checked) {
                        this.selectAll(this.options.selectAllJustVisible, true);
                    }
                    else {
                        this.deselectAll(this.options.selectAllJustVisible, true);
                    }
                }
                else {
                    if (checked) {
                        $option.prop('selected', true);

                        if (this.options.multiple) {
                            // Simply select additional option.
                            $option.prop('selected', true);
                        }
                        else {
                            // Unselect all other options and corresponding checkboxes.
                            if (this.options.selectedClass) {
                                $($checkboxesNotThis).closest('.dropdown-item').removeClass(this.options.selectedClass);
                            }

                            $($checkboxesNotThis).prop('checked', false);
                            $optionsNotThis.prop('selected', false);

                            // It's a single selection, so close.
                            this.$button.click();
                        }

                        if (this.options.selectedClass === "active") {
                            $optionsNotThis.closest(".dropdown-item").css("outline", "");
                        }
                    }
                    else {
                        // Unselect option.
                        $option.prop('selected', false);
                    }

                    // To prevent select all from firing onChange: #575
                    this.options.onChange($option, checked);

                    // Do not update select all or optgroups on select all change!
                    this.updateSelectAll();

                    if (this.options.enableClickableOptGroups && this.options.multiple) {
                        this.updateOptGroups();
                    }
                }

                this.$select.change();
                this.updateButtonText();

                if (this.options.preventInputChangeEvent) {
                    return false;
                }
            }, this));

            $('.multiselect-option', this.$popupContainer).off('mousedown');
            $('.multiselect-option', this.$popupContainer).on('mousedown', function (e) {
                if (e.shiftKey) {
                    // Prevent selecting text by Shift+click
                    return false;
                }
            });

            $(this.$popupContainer).off('touchstart click', '.multiselect-option, .multiselect-all, .multiselect-group');
            $(this.$popupContainer).on('touchstart click', '.multiselect-option, .multiselect-all, .multiselect-group', $.proxy(function (event) {
                event.stopPropagation();

                var $target = $(event.target);

                if (event.shiftKey && this.options.multiple) {
                    if (!$target.is("input")) { // Handles checkbox selection manually (see https://github.com/davidstutz/bootstrap-multiselect/issues/431)
                        event.preventDefault();
                        $target = $target.closest(".multiselect-option").find("input");
                        $target.prop("checked", !$target.prop("checked"));
                    }
                    var checked = $target.prop('checked') || false;

                    if (this.lastToggledInput !== null && this.lastToggledInput !== $target) { // Make sure we actually have a range
                        var from = this.$popupContainer.find(".multiselect-option:visible").index($target.closest(".multiselect-option"));
                        var to = this.$popupContainer.find(".multiselect-option:visible").index(this.lastToggledInput.closest(".multiselect-option"));

                        if (from > to) { // Swap the indices
                            var tmp = to;
                            to = from;
                            from = tmp;
                        }

                        // Make sure we grab all elements since slice excludes the last index
                        ++to;

                        // Change the checkboxes and underlying options
                        var range = this.$popupContainer.find(".multiselect-option:not(.multiselect-filter-hidden)").slice(from, to).find("input");

                        range.prop('checked', checked);

                        if (this.options.selectedClass) {
                            range.closest('.multiselect-option')
                                .toggleClass(this.options.selectedClass, checked);
                        }

                        for (var i = 0, j = range.length; i < j; i++) {
                            var $checkbox = $(range[i]);

                            var $option = this.getOptionByValue($checkbox.val());

                            $option.prop('selected', checked);
                        }
                    }

                    // Trigger the select "change" event
                    $target.trigger("change");
                }
                else if (!$target.is('input')) {
                    var $checkbox = $target.closest('.multiselect-option, .multiselect-all').find('.form-check-input');
                    if ($checkbox.length > 0) {
                        $checkbox.prop('checked', !$checkbox.prop('checked'));
                        $checkbox.change();
                    }
                    else if (this.options.enableClickableOptGroups && this.options.multiple && !$target.hasClass("caret-container")) {
                        var groupItem = $target;
                        if (!groupItem.hasClass("multiselect-group")) {
                            groupItem = $target.closest('.multiselect-group');
                        }
                        $checkbox = groupItem.find(".form-check-input");
                        if ($checkbox.length > 0) {
                            $checkbox.prop('checked', !$checkbox.prop('checked'));
                            $checkbox.change();
                        }
                    }

                    event.preventDefault();
                }

                // Remembers last clicked option
                var $input = $target.closest(".multiselect-option").find("input[type='checkbox'], input[type='radio']");
                if ($input.length > 0) {
                    this.lastToggledInput = $target;
                }
                else {
                    this.lastToggledInput = null;
                }

                $target.blur();
            }, this));

            //Keyboard support.
            this.$container.off('keydown.multiselect').on('keydown.multiselect', $.proxy(function (event) {
                if ($('input.multiselect-search', this.$container).is(':focus')) {
                    return;
                }

                // keyCode 9 == Tab
                if (event.keyCode === 9 && this.$container.hasClass('show')) {
                    this.$button.click();
                }
                else {
                    var $items = $(this.$container).find(".multiselect-option:not(.disabled), .multiselect-group:not(.disabled), .multiselect-all").filter(":visible");

                    if (!$items.length) {
                        return;
                    }

                    var index = $items.index($items.filter(':focus'));

                    var $current = $items.eq(index);

                    // keyCode 32 = Space
                    if (event.keyCode === 32) {
                        var $checkbox = $current.find('input');

                        $checkbox.prop("checked", !$checkbox.prop("checked"));
                        $checkbox.change();

                        event.preventDefault();
                    }

                    // keyCode 13 = Enter
                    if (event.keyCode === 13) {
                        setTimeout(function () {
                            $current.focus();
                        }, 0);
                    }
                }
            }, this));

            if (this.options.enableClickableOptGroups && this.options.multiple) {
                $(".multiselect-group input", this.$popupContainer).off("change");
                $(".multiselect-group input", this.$popupContainer).on("change", $.proxy(function (event) {
                    event.stopPropagation();

                    var $target = $(event.target);
                    var checked = $target.prop('checked') || false;

                    var $item = $(event.target).closest('.dropdown-item');
                    var $group = $item.nextUntil(".multiselect-group")
                        .not('.multiselect-filter-hidden')
                        .not('.disabled');

                    var $inputs = $group.find("input");

                    var $options = [];

                    if (this.options.selectedClass) {
                        if (checked) {
                            $item.addClass(this.options.selectedClass);
                        }
                        else {
                            $item.removeClass(this.options.selectedClass);
                        }
                    }

                    $.each($inputs, $.proxy(function (index, input) {
                        var $input = $(input);
                        var value = $input.val();
                        var $option = this.getOptionByValue(value);

                        if (checked) {
                            $input.prop('checked', true);
                            $input.closest('.dropdown-item')
                                .addClass(this.options.selectedClass);

                            $option.prop('selected', true);
                        }
                        else {
                            $input.prop('checked', false);
                            $input.closest('.dropdown-item')
                                .removeClass(this.options.selectedClass);

                            $option.prop('selected', false);
                        }

                        $options.push(this.getOptionByValue(value));
                    }, this))

                    // Cannot use select or deselect here because it would call updateOptGroups again.

                    this.options.onChange($options, checked);

                    this.$select.change();
                    this.updateButtonText();
                    this.updateSelectAll();
                }, this));
            }

            if (this.options.enableCollapsibleOptGroups && this.options.multiple) {
                $(".multiselect-group .caret-container", this.$popupContainer).off("click");
                $(".multiselect-group .caret-container", this.$popupContainer).on("click", $.proxy(function (event) {
                    var $group = $(event.target).closest('.multiselect-group');
                    var $inputs = $group.nextUntil(".multiselect-group")
                        .not('.multiselect-filter-hidden');

                    var visible = true;
                    $inputs.each(function () {
                        visible = visible && !$(this).hasClass('multiselect-collapsible-hidden');
                    });

                    if (visible) {
                        $inputs.hide()
                            .addClass('multiselect-collapsible-hidden');
                    }
                    else {
                        $inputs.show()
                            .removeClass('multiselect-collapsible-hidden');
                    }
                }, this));
            }
        },

        /**
         * Create a checkbox container with input and label based on given values
         * @param {JQuery} $item 
         * @param {String} label 
         * @param {String} name 
         * @param {String} value 
         * @param {String} inputType 
         * @returns {JQuery}
         */
        createCheckbox: function ($item, label, name, value, title, inputType) {
            var $wrapper = $('<span />');
            $wrapper.addClass("form-check");

            if (this.options.enableHTML && $(label).length > 0) {
                $wrapper.append($(label));
            }
            else {
                var $checkboxLabel = $('<label class="form-check-label" />');
                $checkboxLabel.text(label);
                $wrapper.append($checkboxLabel);
            }

            var $checkbox = $('<input class="form-check-input"/>').attr('type', inputType);
            $checkbox.val(value);
            $wrapper.prepend($checkbox);

            if (name) {
                $checkbox.attr('name', name);
            }

            $item.prepend($wrapper);
            $item.attr("title", title || label);

            return $checkbox;
        },

        /**
         * Create an option using the given select option.
         *
         * @param {jQuery} element
         */
        createOptionValue: function (element, isGroupOption) {
            var $element = $(element);
            if ($element.is(':selected')) {
                $element.prop('selected', true);
            }

            // Support the label attribute on options.
            var label = this.options.optionLabel(element);
            var classes = this.options.optionClass(element);
            var value = $element.val();
            var inputType = this.options.multiple ? "checkbox" : "radio";
            var title = $element.attr('title');

            var $option = $(this.options.templates.option);
            $option.addClass(classes);

            if (isGroupOption && this.options.indentGroupOptions) {
                $option.addClass("multiselect-group-option-indented")
            }

            // Hide all children items when collapseOptGroupsByDefault is true
            if (this.options.collapseOptGroupsByDefault && $(element).parent().prop("tagName").toLowerCase() === "optgroup") {
                $option.addClass("multiselect-collapsible-hidden");
                $option.hide();
            }

            var name = this.options.checkboxName($element);
            var $checkbox = this.createCheckbox($option, label, name, value, title, inputType);

            var selected = $element.prop('selected') || false;

            if (value === this.options.selectAllValue) {
                $option.addClass("multiselect-all");
                $option.removeClass("multiselect-option");
                $checkbox.parent().parent()
                    .addClass('multiselect-all');
            }

            this.$popupContainer.append($option);

            if ($element.is(':disabled')) {
                $checkbox.attr('disabled', 'disabled')
                    .prop('disabled', true)
                    .closest('.dropdown-item')
                    .addClass('disabled');
            }

            $checkbox.prop('checked', selected);

            if (selected && this.options.selectedClass) {
                $checkbox.closest('.dropdown-item')
                    .addClass(this.options.selectedClass);
            }
        },

        /**
         * Creates a divider using the given select option.
         *
         * @param {jQuery} element
         */
        createDivider: function (element) {
            var $divider = $(this.options.templates.divider);
            this.$popupContainer.append($divider);
        },

        /**
         * Creates an optgroup.
         *
         * @param {jQuery} group
         */
        createOptgroup: function (group) {
            var $group = $(group);
            var label = $group.attr("label");
            var value = $group.attr("value");
            var title = $group.attr('title');

            var $groupOption = $("<span class='multiselect-group dropdown-item-text'></span>");

            if (this.options.enableClickableOptGroups && this.options.multiple) {
                $groupOption = $(this.options.templates.optionGroup);
                var $checkbox = this.createCheckbox($groupOption, label, null, value, title, "checkbox");
            }
            else {
                if (this.options.enableHTML) {
                    $groupOption.html(" " + label);
                }
                else {
                    $groupOption.text(" " + label);
                }
            }

            var classes = this.options.optionClass(group);
            $groupOption.addClass(classes);

            if (this.options.enableCollapsibleOptGroups && this.options.multiple) {
                $groupOption.find('.form-check').addClass('d-inline-block');
                $groupOption.append('<span class="caret-container dropdown-toggle pl-1"></span>');
            }

            if ($group.is(':disabled')) {
                $groupOption.addClass('disabled');
            }

            this.$popupContainer.append($groupOption);

            $("option", group).each($.proxy(function ($, group) {
                this.createOptionValue(group, true);
            }, this));
        },

        /**
         * Build the reset.
         *
         */
        buildReset: function () {
            if (this.options.includeResetOption) {

                // Check whether to add a divider after the reset.
                if (this.options.includeResetDivider) {
                    var divider = $(this.options.templates.divider);
                    divider.addClass("mt-0");
                    this.$popupContainer.prepend(divider);
                }

                var $resetButton = $(this.options.templates.resetButton);

                if (this.options.enableHTML) {
                    $('button', $resetButton).html(this.options.resetText);
                }
                else {
                    $('button', $resetButton).text(this.options.resetText);
                }

                $('button', $resetButton).click($.proxy(function () {
                    this.clearSelection();
                }, this));

                this.$popupContainer.prepend($resetButton);
            }
        },

        /**
         * Build the select all.
         *
         * Checks if a select all has already been created.
         */
        buildSelectAll: function () {
            if (typeof this.options.selectAllValue === 'number') {
                this.options.selectAllValue = this.options.selectAllValue.toString();
            }

            var alreadyHasSelectAll = this.hasSelectAll();

            if (!alreadyHasSelectAll && this.options.includeSelectAllOption && this.options.multiple
                && $('option', this.$select).length > this.options.includeSelectAllIfMoreThan) {

                // Check whether to add a divider after the select all.
                if (this.options.includeSelectAllDivider) {
                    this.$popupContainer.prepend($(this.options.templates.divider));
                }

                var $option = $(this.options.templates.li || this.options.templates.option);
                var $checkbox = this.createCheckbox($option, this.options.selectAllText, this.options.selectAllName, this.options.selectAllValue, this.options.selectAllText, "checkbox");

                $option.addClass("multiselect-all");
                $option.removeClass("multiselect-option");
                $option.find(".form-check-label").addClass("font-weight-bold");

                this.$popupContainer.prepend($option);

                $checkbox.prop('checked', false);
            }
        },

        /**
         * Builds the filter.
         */
        buildFilter: function () {

            // Build filter if filtering OR case insensitive filtering is enabled and the number of options exceeds (or equals) enableFilterLength.
            if (this.options.enableFiltering || this.options.enableCaseInsensitiveFiltering) {
                var enableFilterLength = Math.max(this.options.enableFiltering, this.options.enableCaseInsensitiveFiltering);

                if (this.$select.find('option').length >= enableFilterLength) {

                    this.$filter = $(this.options.templates.filter);
                    $('input', this.$filter).attr('placeholder', this.options.filterPlaceholder);

                    // Handles optional filter clear button                        
                    if (!this.options.includeFilterClearBtn) {
                        this.$filter.find(".multiselect-search").attr("type", "text");

                        // Remove clear button if the old design of the filter with input groups and separated clear button is used
                        this.$filter.find(".multiselect-clear-filter").remove();
                    }
                    else {
                        // Firefox does not support a clear button in search inputs right now therefore it must be added manually
                        if (this.isFirefox() && this.$filter.find(".multiselect-clear-filter").length === 0) {
                            this.$filter.append("<i class='fas fa-times text-muted multiselect-clear-filter multiselect-moz-clear-filter'></i>");
                        }

                        this.$filter.find(".multiselect-clear-filter").on('click', $.proxy(function (event) {
                            clearTimeout(this.searchTimeout);

                            this.query = '';
                            this.$filter.find('.multiselect-search').val('');
                            $('.dropdown-item', this.$popupContainer).show().removeClass('multiselect-filter-hidden');

                            this.updateSelectAll();

                            if (this.options.enableClickableOptGroups && this.options.multiple) {
                                this.updateOptGroups();
                            }

                        }, this));
                    }

                    this.$popupContainer.prepend(this.$filter);

                    this.$filter.val(this.query).on('click', function (event) {
                        event.stopPropagation();
                    }).on('input keydown', $.proxy(function (event) {
                        // Cancel enter key default behaviour
                        if (event.which === 13) {
                            event.preventDefault();
                        }

                        if (this.isFirefox() && this.options.includeFilterClearBtn) {
                            if (event.target.value) {
                                this.$filter.find(".multiselect-moz-clear-filter").show();
                            }
                            else {
                                this.$filter.find(".multiselect-moz-clear-filter").hide();
                            }
                        }

                        // This is useful to catch "keydown" events after the browser has updated the control.
                        clearTimeout(this.searchTimeout);

                        this.searchTimeout = this.asyncFunction($.proxy(function () {

                            if (this.query !== event.target.value) {
                                this.query = event.target.value;

                                var currentGroup, currentGroupVisible;
                                $.each($('.multiselect-option, .multiselect-group', this.$popupContainer), $.proxy(function (index, element) {
                                    var value = $('input', element).length > 0 ? $('input', element).val() : "";
                                    var text = $('.form-check-label', element).text();

                                    var filterCandidate = '';
                                    if ((this.options.filterBehavior === 'text')) {
                                        filterCandidate = text;
                                    }
                                    else if ((this.options.filterBehavior === 'value')) {
                                        filterCandidate = value;
                                    }
                                    else if (this.options.filterBehavior === 'both') {
                                        filterCandidate = text + '\n' + value;
                                    }

                                    if (value !== this.options.selectAllValue && text) {

                                        // By default lets assume that element is not
                                        // interesting for this search.
                                        var showElement = false;

                                        if (this.options.enableCaseInsensitiveFiltering) {
                                            filterCandidate = filterCandidate.toLowerCase();
                                            this.query = this.query.toLowerCase();
                                        }

                                        if (this.options.enableFullValueFiltering && this.options.filterBehavior !== 'both') {
                                            var valueToMatch = filterCandidate.trim().substring(0, this.query.length);
                                            if (this.query.indexOf(valueToMatch) > -1) {
                                                showElement = true;
                                            }
                                        }
                                        else if (filterCandidate.indexOf(this.query) > -1) {
                                            showElement = true;
                                        }

                                        // Toggle current element (group or group item) according to showElement boolean.
                                        if (!showElement) {
                                            $(element).css('display', 'none');
                                            $(element).addClass('multiselect-filter-hidden');
                                        }
                                        if (showElement) {
                                            $(element).css('display', 'block');
                                            $(element).removeClass('multiselect-filter-hidden');
                                        }

                                        // Differentiate groups and group items.
                                        if ($(element).hasClass('multiselect-group')) {
                                            // Remember group status.
                                            currentGroup = element;
                                            currentGroupVisible = showElement;
                                        }
                                        else {
                                            // Show group name when at least one of its items is visible.
                                            if (showElement) {
                                                $(currentGroup).show()
                                                    .removeClass('multiselect-filter-hidden');
                                            }

                                            // Show all group items when group name satisfies filter.
                                            if (!showElement && currentGroupVisible) {
                                                $(element).show()
                                                    .removeClass('multiselect-filter-hidden');
                                            }
                                        }
                                    }
                                }, this));
                            }

                            this.updateSelectAll();

                            if (this.options.enableClickableOptGroups && this.options.multiple) {
                                this.updateOptGroups();
                            }

                            this.options.onFiltering(event.target);

                        }, this), 300, this);
                    }, this));
                }
            }
        },

        /**
         * Unbinds the whole plugin.
         */
        destroy: function () {
            this.$container.remove();
            this.$select.show();

            // reset original state
            this.$select.prop('disabled', this.options.wasDisabled);

            this.$select.data('multiselect', null);
        },

        /**
         * Refreshs the multiselect based on the selected options of the select.
         */
        refresh: function () {
            var inputs = {};
            $('.multiselect-option input', this.$popupContainer).each(function () {
                inputs[$(this).val()] = $(this);
            });

            $('option', this.$select).each($.proxy(function (index, element) {
                var $elem = $(element);
                var $input = inputs[$(element).val()];

                if ($elem.is(':selected')) {
                    $input.prop('checked', true);

                    if (this.options.selectedClass) {
                        $input.closest('.multiselect-option')
                            .addClass(this.options.selectedClass);
                    }
                }
                else {
                    $input.prop('checked', false);

                    if (this.options.selectedClass) {
                        $input.closest('.multiselect-option')
                            .removeClass(this.options.selectedClass);
                    }
                }

                if ($elem.is(":disabled")) {
                    $input.attr('disabled', 'disabled')
                        .prop('disabled', true)
                        .closest('.multiselect-option')
                        .addClass('disabled');
                }
                else {
                    $input.prop('disabled', false)
                        .closest('.multiselect-option')
                        .removeClass('disabled');
                }
            }, this));

            this.updateButtonText();
            this.updateSelectAll();

            if (this.options.enableClickableOptGroups && this.options.multiple) {
                this.updateOptGroups();
            }
        },

        /**
         * Select all options of the given values.
         *
         * If triggerOnChange is set to true, the on change event is triggered if
         * and only if one value is passed.
         *
         * @param {Array} selectValues
         * @param {Boolean} triggerOnChange
         */
        select: function (selectValues, triggerOnChange) {
            if (!$.isArray(selectValues)) {
                selectValues = [selectValues];
            }

            for (var i = 0; i < selectValues.length; i++) {
                var value = selectValues[i];

                if (value === null || value === undefined) {
                    continue;
                }

                var $option = this.getOptionByValue(value);
                var $checkbox = this.getInputByValue(value);

                if ($option === undefined || $checkbox === undefined) {
                    continue;
                }

                if (!this.options.multiple) {
                    this.deselectAll(false);
                }

                if (this.options.selectedClass) {
                    $checkbox.closest('.dropdown-item')
                        .addClass(this.options.selectedClass);
                }

                $checkbox.prop('checked', true);
                $option.prop('selected', true);

                if (triggerOnChange) {
                    this.options.onChange($option, true);
                }
            }

            this.updateButtonText();
            this.updateSelectAll();

            if (this.options.enableClickableOptGroups && this.options.multiple) {
                this.updateOptGroups();
            }
        },

        /**
         * Clears all selected items.
         */
        clearSelection: function () {
            this.deselectAll(false);
            this.updateButtonText();
            this.updateSelectAll();

            if (this.options.enableClickableOptGroups && this.options.multiple) {
                this.updateOptGroups();
            }
        },

        /**
         * Deselects all options of the given values.
         *
         * If triggerOnChange is set to true, the on change event is triggered, if
         * and only if one value is passed.
         *
         * @param {Array} deselectValues
         * @param {Boolean} triggerOnChange
         */
        deselect: function (deselectValues, triggerOnChange) {
            if (!$.isArray(deselectValues)) {
                deselectValues = [deselectValues];
            }

            for (var i = 0; i < deselectValues.length; i++) {
                var value = deselectValues[i];

                if (value === null || value === undefined) {
                    continue;
                }

                var $option = this.getOptionByValue(value);
                var $checkbox = this.getInputByValue(value);

                if ($option === undefined || $checkbox === undefined) {
                    continue;
                }

                if (this.options.selectedClass) {
                    $checkbox.closest('.dropdown-item')
                        .removeClass(this.options.selectedClass);
                }

                $checkbox.prop('checked', false);
                $option.prop('selected', false);

                if (triggerOnChange) {
                    this.options.onChange($option, false);
                }
            }

            this.updateButtonText();
            this.updateSelectAll();

            if (this.options.enableClickableOptGroups && this.options.multiple) {
                this.updateOptGroups();
            }
        },

        /**
         * Selects all enabled & visible options.
         *
         * If justVisible is true or not specified, only visible options are selected.
         *
         * @param {Boolean} justVisible
         * @param {Boolean} triggerOnSelectAll
         */
        selectAll: function (justVisible, triggerOnSelectAll) {

            var justVisible = typeof justVisible === 'undefined' ? true : justVisible;

            if (justVisible) {
                var visibleOptions = $(".multiselect-option:not(.disabled):not(.multiselect-filter-hidden)", this.$popupContainer);
                $('input:enabled', visibleOptions).prop('checked', true);
                visibleOptions.addClass(this.options.selectedClass);

                $('input:enabled', visibleOptions).each($.proxy(function (index, element) {
                    var value = $(element).val();
                    var option = this.getOptionByValue(value);
                    $(option).prop('selected', true);
                }, this));
            }
            else {
                var allOptions = $(".multiselect-option:not(.disabled)", this.$popupContainer);
                $('input:enabled', allOptions).prop('checked', true);
                allOptions.addClass(this.options.selectedClass);

                $('input:enabled', allOptions).each($.proxy(function (index, element) {
                    var value = $(element).val();
                    var option = this.getOptionByValue(value);
                    $(option).prop('selected', true);
                }, this));
            }

            $('.multiselect-option input[value="' + this.options.selectAllValue + '"]', this.$popupContainer).prop('checked', true);

            if (this.options.enableClickableOptGroups && this.options.multiple) {
                this.updateOptGroups();
            }

            this.updateButtonText();
            this.updateSelectAll();

            if (triggerOnSelectAll) {
                this.options.onSelectAll();
            }
        },

        /**
         * Deselects all options.
         *
         * If justVisible is true or not specified, only visible options are deselected.
         *
         * @param {Boolean} justVisible
         */
        deselectAll: function (justVisible, triggerOnDeselectAll) {

            var justVisible = typeof justVisible === 'undefined' ? true : justVisible;

            if (justVisible) {
                var visibleOptions = $(".multiselect-option:not(.disabled):not(.multiselect-filter-hidden)", this.$popupContainer);
                $('input[type="checkbox"]:enabled', visibleOptions).prop('checked', false);
                visibleOptions.removeClass(this.options.selectedClass);

                $('input[type="checkbox"]:enabled', visibleOptions).each($.proxy(function (index, element) {
                    var value = $(element).val();
                    var option = this.getOptionByValue(value);
                    $(option).prop('selected', false);
                }, this));
            }
            else {
                var allOptions = $(".multiselect-option:not(.disabled):not(.multiselect-group)", this.$popupContainer);
                $('input[type="checkbox"]:enabled', allOptions).prop('checked', false);
                allOptions.removeClass(this.options.selectedClass);

                $('input[type="checkbox"]:enabled', allOptions).each($.proxy(function (index, element) {
                    var value = $(element).val();
                    var option = this.getOptionByValue(value);
                    $(option).prop('selected', false);
                }, this));
            }

            $('.multiselect-all input[value="' + this.options.selectAllValue + '"]', this.$popupContainer).prop('checked', false);

            if (this.options.enableClickableOptGroups && this.options.multiple) {
                this.updateOptGroups();
            }

            this.updateButtonText();
            this.updateSelectAll();

            if (triggerOnDeselectAll) {
                this.options.onDeselectAll();
            }
        },

        /**
         * Rebuild the plugin.
         *
         * Rebuilds the dropdown, the filter and the select all option.
         */
        rebuild: function () {
            this.$popupContainer.html('');

            // Important to distinguish between radios and checkboxes.
            this.options.multiple = this.$select.attr('multiple') === "multiple";

            this.buildSelectAll();
            this.buildDropdownOptions();
            this.buildFilter();

            this.updateButtonText();
            this.updateSelectAll(true);

            if (this.options.enableClickableOptGroups && this.options.multiple) {
                this.updateOptGroups();
            }

            if (this.options.disableIfEmpty && $('option', this.$select).length <= 0) {
                this.disable();
            }
            else {
                this.enable();
            }

            if (this.options.dropRight) {
                this.$container.addClass('dropright');
            }
            else if (this.options.dropUp) {
                this.$container.addClass('dropup');
            }

            if (this.options.widthSynchronizationMode !== 'never') {
                this.synchronizeButtonAndPopupWidth();
            }
        },

        /**
         * The provided data will be used to build the dropdown.
         */
        dataprovider: function (dataprovider) {

            var groupCounter = 0;
            var $select = this.$select.empty();

            $.each(dataprovider, function (index, option) {
                var $tag;

                if ($.isArray(option.children)) { // create optiongroup tag
                    groupCounter++;

                    $tag = $('<optgroup/>').attr({
                        label: option.label || 'Group ' + groupCounter,
                        disabled: !!option.disabled,
                        value: option.value
                    });

                    forEach(option.children, function (subOption) { // add children option tags
                        var attributes = {
                            value: subOption.value,
                            label: subOption.label || subOption.value,
                            title: subOption.title,
                            selected: !!subOption.selected,
                            disabled: !!subOption.disabled
                        };

                        //Loop through attributes object and add key-value for each attribute
                        for (var key in subOption.attributes) {
                            attributes['data-' + key] = subOption.attributes[key];
                        }
                        //Append original attributes + new data attributes to option
                        $tag.append($('<option/>').attr(attributes));
                    });
                }
                else {

                    var attributes = {
                        'value': option.value,
                        'label': option.label || option.value,
                        'title': option.title,
                        'class': option['class'],
                        'selected': !!option['selected'],
                        'disabled': !!option['disabled']
                    };
                    //Loop through attributes object and add key-value for each attribute
                    for (var key in option.attributes) {
                        attributes['data-' + key] = option.attributes[key];
                    }
                    //Append original attributes + new data attributes to option
                    $tag = $('<option/>').attr(attributes);

                    $tag.text(option.label || option.value);
                }

                $select.append($tag);
            });

            this.rebuild();
        },

        /**
         * Enable the multiselect.
         */
        enable: function () {
            this.$select.prop('disabled', false);
            this.$button.prop('disabled', false)
                .removeClass('disabled');

            this.updateButtonText();
        },

        /**
         * Disable the multiselect.
         */
        disable: function () {
            this.$select.prop('disabled', true);
            this.$button.prop('disabled', true)
                .addClass('disabled');

            this.updateButtonText();
        },

        /**
         * Set the options.
         *
         * @param {Array} options
         */
        setOptions: function (options) {
            this.options = this.mergeOptions(options);
        },

        /**
         * Merges the given options with the default options.
         *
         * @param {Array} options
         * @returns {Array}
         */
        mergeOptions: function (options) {
            return $.extend(true, {}, this.defaults, this.options, options);
        },

        /**
         * Checks whether a select all checkbox is present.
         *
         * @returns {Boolean}
         */
        hasSelectAll: function () {
            return $('.multiselect-all', this.$popupContainer).length > 0;
        },

        /**
         * Update opt groups.
         */
        updateOptGroups: function () {
            var $groups = $('.multiselect-group', this.$popupContainer)
            var selectedClass = this.options.selectedClass;

            $groups.each(function () {
                var $options = $(this).nextUntil('.multiselect-group')
                    .not('.multiselect-filter-hidden')
                    .not('.disabled');

                var checked = true;
                $options.each(function () {
                    var $input = $('input', this);

                    if (!$input.prop('checked')) {
                        checked = false;
                    }
                });

                if (selectedClass) {
                    if (checked) {
                        $(this).addClass(selectedClass);
                    }
                    else {
                        $(this).removeClass(selectedClass);
                    }
                }

                $('input', this).prop('checked', checked);
            });
        },

        /**
         * Updates the select all checkbox based on the currently displayed and selected checkboxes.
         */
        updateSelectAll: function (notTriggerOnSelectAll) {
            if (this.hasSelectAll()) {
                var allBoxes = $(".multiselect-option:not(.multiselect-filter-hidden):not(.multiselect-group):not(.disabled) input:enabled", this.$popupContainer);
                var allBoxesLength = allBoxes.length;
                var checkedBoxesLength = allBoxes.filter(":checked").length;
                var selectAllItem = $(".multiselect-all", this.$popupContainer);
                var selectAllInput = selectAllItem.find("input");

                if (checkedBoxesLength > 0 && checkedBoxesLength === allBoxesLength) {
                    selectAllInput.prop("checked", true);
                    selectAllItem.addClass(this.options.selectedClass);
                }
                else {
                    selectAllInput.prop("checked", false);
                    selectAllItem.removeClass(this.options.selectedClass);
                }
            }
        },

        /**
         * Update the button text and its title based on the currently selected options.
         */
        updateButtonText: function () {
            var options = this.getSelected();

            // First update the displayed button text.
            if (this.options.enableHTML) {
                $('.multiselect .multiselect-selected-text', this.$container).html(this.options.buttonText(options, this.$select));
            }
            else {
                $('.multiselect .multiselect-selected-text', this.$container).text(this.options.buttonText(options, this.$select));
            }

            // Now update the title attribute of the button.
            $('.multiselect', this.$container).attr('title', this.options.buttonTitle(options, this.$select));
            this.$button.trigger('change');
        },

        /**
         * Get all selected options.
         *
         * @returns {jQUery}
         */
        getSelected: function () {
            return $('option', this.$select).filter(":selected");
        },

        /**
         * Gets a select option by its value.
         *
         * @param {String} value
         * @returns {jQuery}
         */
        getOptionByValue: function (value) {

            var options = $('option', this.$select);
            var valueToCompare = value.toString();

            for (var i = 0; i < options.length; i = i + 1) {
                var option = options[i];
                if (option.value === valueToCompare) {
                    return $(option);
                }
            }
        },

        /**
         * Get the input (radio/checkbox) by its value.
         *
         * @param {String} value
         * @returns {jQuery}
         */
        getInputByValue: function (value) {

            var checkboxes = $('.multiselect-option input:not(.multiselect-search)', this.$popupContainer);
            var valueToCompare = value.toString();

            for (var i = 0; i < checkboxes.length; i = i + 1) {
                var checkbox = checkboxes[i];
                if (checkbox.value === valueToCompare) {
                    return $(checkbox);
                }
            }
        },

        /**
         * Used for knockout integration.
         */
        updateOriginalOptions: function () {
            this.originalOptions = this.$select.clone()[0].options;
        },

        asyncFunction: function (callback, timeout, self) {
            var args = Array.prototype.slice.call(arguments, 3);
            return setTimeout(function () {
                callback.apply(self || window, args);
            }, timeout);
        },

        setAllSelectedText: function (allSelectedText) {
            this.options.allSelectedText = allSelectedText;
            this.updateButtonText();
        },

        isFirefox: function () {
            var firefoxIdentifier = 'firefox';
            var valueNotFoundIndex = -1;

            if (navigator && navigator.userAgent) {
                return navigator.userAgent.toLocaleLowerCase().indexOf(firefoxIdentifier) > valueNotFoundIndex;
            }

            return false;
        }
    };

    $.fn.multiselect = function (option, parameter, extraOptions) {
        return this.each(function () {
            var data = $(this).data('multiselect');
            var options = typeof option === 'object' && option;

            // Initialize the multiselect.
            if (!data) {
                data = new Multiselect(this, options);
                $(this).data('multiselect', data);
            }

            // Call multiselect method.
            if (typeof option === 'string') {
                data[option](parameter, extraOptions);

                if (option === 'destroy') {
                    $(this).data('multiselect', false);
                }
            }
        });
    };

    $.fn.multiselect.Constructor = Multiselect;

    $(function () {
        $("select[data-role=multiselect]").multiselect();
    });

});
