+function ($) {
  'use strict';

  // DROPDOWN CLASS DEFINITION
  // =========================

  var backdrop = '.dropdown-backdrop';
  var toggle = '[data-toggle="dropdown"]';
  var Dropdown = function (element) {
    $(element).on('click.bs.dropdown', this.toggle);
  };

  Dropdown.VERSION = '1.0.0';

  Dropdown.prototype.constructor = Dropdown;

  Dropdown.prototype.toggle = function (e) {
    var $this = $(this);

    if ($this.is('.disabled, :disabled')) return;

    var $parent = getParent($this);
    var isActive = $parent.hasClass('open');

    clearMenus();

    if (!isActive) {
      if ('ontouchstart' in document.documentElement && !$parent.closest('.navbar-nav').length) {
        $(document.createElement('div'))
          .addClass('dropdown-backdrop')
          .insertAfter($(this))
          .on('click', clearMenus);
      }

      var relatedTarget = { relatedTarget: this };

      $parent.trigger(e = $.Event('show.bs.dropdown', relatedTarget));

      if (e.isDefaultPrevented()) return;

      $this.trigger('focus')
        .attr('aria-expanded', 'true');
      $parent.toggleClass('open')
        .trigger($.Event('shown.bs.dropdown', relatedTarget));
    }

    return false;
  };

  Dropdown.prototype.keydown = function (e) {
    if (!/(38|40|27|32)/.test(e.which) || /input|textarea/i.test(e.target.tagName)) return;

    var $this = $(this);

    e.preventDefault();
    e.stopPropagation();

    if ($this.is('.disabled, :disabled')) return;

    var $parent = getParent($this);
    var isActive = $parent.hasClass('open');

    if (!isActive && e.which != 27 || isActive && e.which === 27) {
      if (e.which === 27) $parent.find(toggle).trigger('focus');
      return $this.trigger('click');
    }

    var desc = ' li:not(.disabled):visible a';
    var $items = $parent.find('.dropdown-menu' + desc);

    if (!$items.length) return;

    var index = $items.index(e.target);

    if (e.which === 38 && index > 0) index--;
    if (e.which === 40 && index < $items.length - 1) index++;
    if (!~index) index = 0;

    $items.eq(index).trigger('focus');
  };

  function getParent($this) {
    var selector = $this.attr('data-target');

    if (!selector) {
      selector = $this.attr('href');
      selector = selector && /#[A-Za-z]/.test(selector) && selector.replace(/.*(?=#[^\s]*$)/, '');
    }

    var $parent = selector && $(selector);

    return $parent && $parent.length ? $parent : $this.parent();
  }

  function clearMenus(e) {
    if (e && e.which === 3) return;

    $(backdrop).remove();
    $(toggle).each(function () {
      var $this = $(this);
      var $parent = getParent($this);
      var relatedTarget = { relatedTarget: this };

      if (!$parent.hasClass('open')) return;
      if (e && e.type === 'click' && /input|textarea/i.test(e.target.tagName) && $.contains($parent[0], e.target)) return;

      $parent.trigger(e = $.Event('hide.bs.dropdown', relatedTarget));

      if (e.isDefaultPrevented()) return;

      $this.attr('aria-expanded', 'false');
      $parent
        .removeClass('open')
        .trigger($.Event('hidden.bs.dropdown', relatedTarget));
    });
  }

  // DROPDOWN PLUGIN DEFINITION
  // ==========================

  function Plugin(option) {
    return this.each(function () {
      var $this = $(this);
      var data = $this.data('bs.dropdown');

      if (!data) $this.data('bs.dropdown', (data = new Dropdown(this)));
      if (typeof option === 'string') data[option]();
    });
  }

  var old = $.fn.dropdown;

  $.fn.dropdown = Plugin;
  $.fn.dropdown.Constructor = Dropdown;

  // DROPDOWN NO CONFLICT
  // ====================

  $.fn.dropdown.noConflict = function () {
    $.fn.dropdown = old;
    return this;
  };

  // APPLY TO STANDARD DROPDOWN ELEMENTS
  // ===================================

  $(document)
    .on('click.bs.dropdown.data-api', clearMenus)
    .on('click.bs.dropdown.data-api', '.dropdown form', function (e) { e.stopPropagation(); })
    .on('click.bs.dropdown.data-api', toggle, Dropdown.prototype.toggle)
    .on('keydown.bs.dropdown.data-api', toggle, Dropdown.prototype.keydown)
    .on('keydown.bs.dropdown.data-api', '.dropmenu', Dropdown.prototype.keydown);

}(jQuery);