(function($){

  //variable for storing the menu count when no ID is present
  var menuCount = 0;
  
  //plugin code
  $.fn.mobileMenu = function(options){
    
    //plugin's default options
    var settings = {
      switchWidth: 400,
      topOptionText: 'Select a page',
      indentString: '   '
    };
    
    
    //function to check if selector matches a list
    function isList($this){
      return $this.is('ul, ol');
    }
  
  
    //function to decide if mobile or not
    function isMobile(){
      return ($(window).width() < settings.switchWidth);
    }
    
    
    //check if dropdown exists for the current element
    function menuExists($this){
      
      //if the list has an ID, use it to give the menu an ID
      if($this.attr('id')){
        return ($('#mobileMenu_'+$this.attr('id')).length > 0);
      } 
      
      //otherwise, give the list and select elements a generated ID
      else {
        menuCount++;
        $this.attr('id', 'mm'+menuCount);
        return ($('#mobileMenu_mm'+menuCount).length > 0);
      }
    }
    
    
    //change page on mobile menu selection
    function goToPage($this){
      if($this.val() !== null){document.location.href = $this.val()}
    }
    
    
    //show the mobile menu
    function showMenu($this){
      $this.css('display', 'none');
      $('#mobileMenu_'+$this.attr('id')).show();
    }
    
    
    //hide the mobile menu
    function hideMenu($this){
      $this.css('display', '');
      $('#mobileMenu_'+$this.attr('id')).hide();
    }
    
    
    //create the mobile menu
    function createMenu($this){
      if(isList($this)){
                
        //generate select element as a string to append via jQuery
        var selectString = '<select id="mobileMenu_'+$this.attr('id')+'" class="mobileMenu">';
        
        //create first option (no value)
        selectString += '<option value="">'+settings.topOptionText+'</option>';
        
        //loop through list items
        $this.find('li').each(function(){
          
          //when sub-item, indent
          var levelStr = '';
          var len = $(this).parents('ul, ol').length;
          for(i=1;i<len;i++){levelStr += settings.indentString;}
          
          //get url and text for option
          var link = $(this).find('a:first-child').attr('href');
          var text = levelStr + $(this).clone().children('ul, ol').remove().end().text();
          
          //add option
          selectString += '<option value="'+link+'">'+text+'</option>';
        });
        
        selectString += '</select>';
        
        //append select element to ul/ol's container
        $this.parent().append(selectString);
        
        //add change event handler for mobile menu
        $('#mobileMenu_'+$this.attr('id')).change(function(){
          goToPage($(this));
        });
        
        //hide current menu, show mobile menu
        showMenu($this);
      } else {
       
      }
    }
    
    
    //plugin functionality
    function run($this){
      
      //menu doesn't exist
      if(isMobile() && !menuExists($this)){
        createMenu($this);
      }
      
      //menu already exists
      else if(isMobile() && menuExists($this)){
        showMenu($this);
      }
      
      //not mobile browser
      else if(!isMobile() && menuExists($this)){
        hideMenu($this);
      }

    }
    
    //run plugin on each matched ul/ol
    //maintain chainability by returning "this"
    return this.each(function() {
      
      //override the default settings if user provides some
      if(options){$.extend(settings, options);}
      
      //cache "this"
      var $this = $(this);
    
      //bind event to browser resize
      $(window).resize(function(){run($this);});

      //run plugin
      run($this);

    });
    
  };
  
})(jQuery);