(function(undefined) {
  
  /* local var and method */
  
  /* object prototype */
  var treeRef_proto = {
    id: '',
    expandCollapse : function (domObj) {
      var oc = $(domObj).attr('src').indexOf('list-')<0?'open':'close';
      var curLevel = parseInt($(domObj).attr('data-livello'));
      
      $(domObj).attr('src', $(domObj).attr('src').replace(oc=='open'?'list+':'list-', oc=='open'?'list-':'list+'));
      
      // ciclo sui sibling fino a che finiscono o ne incontro uno con livello inferiore o uguale
      $(domObj).parent().nextAll().each(function() {
        if($(this).get(0).nodeType == 1 && $(this).get(0).nodeName == 'LI') {
          if (parseInt($(this).attr('data-livello')) <= curLevel) return false;
        
          if (oc=='open' && parseInt($(this).attr('data-livello')) == (curLevel+1)) $(this).css('display', 'block');
          if (oc=='close' && parseInt($(this).attr('data-livello')) > curLevel) {
            $(this).css('display', 'none');
            $(this).find('> img').each(function() {
              $(this).attr('src', $(this).attr('src').replace('list-', 'list+'));
            });
          }
        }
      });
      
      return this;
    },
    expandAll: function() {
      $("#"+this.id).find('li').each(function() {
        $(this).find('> img').each(function() {
          $(this).attr('src', $(this).attr('src').replace('list+', 'list-'));
        });
        $(this).css('display', 'block');
      });
    },
    collapseAll: function() {
      $("#"+this.id).find('li').each(function() {
        
        $(this).find('> img').each(function() {
          $(this).attr('src', $(this).attr('src').replace('list-', 'list+'));
        });
        if($(this).attr('data-livello') != '0') $(this).css('display', 'none');
      });
    }
  }
  
  var treeRef = {};
  
  /* public method and attribute */
  
  /**
  * connect dom with tree function trought tag id
  */
  $$.tree = function(treeID, config) { // tree in $$ global namespace
    config = $.extend(config||{}, {
      
    });
    
    // creo un oggetto la prima volta, uso quello già definito nei riferimenti successivi
    if(treeRef[treeID] == undefined) {
      treeRef[treeID] = Object.create(treeRef_proto);
      treeRef[treeID].id = treeID;
    }
    
    return treeRef[treeID];
  }
  
  
  
})();