function Tree(options) {
  var self = this;

  var template = options.template;

  var data = options.data;

  this.getElement = function() {
  	if (!this.elem) render();
  	return this.elem;
  }

  function onTogglerClick(e) { 
  	self.toggle( $(e.currentTarget.parentNode) );
  }

  function onCheckboxChange(e) { 
    var checked = e.target.checked;
    var id = e.target.value;
    var node = $(e.currentTarget.parentNode);

    if (checked) {
      self.open(node);
    }

    node.find('input').prop('checked', checked);
  }

  this.toggle = function(node) { 
  	ensureChildrenRendered(node);
  	node.toggleClass("tree-open tree-closed");
  };

  this.open = function(node) {
    ensureChildrenRendered(node);
    node.addClass("tree-open").removeClass("tree-closed");
  }

  this.close = function(node) {
    ensureChildrenRendered(node);
    node.addClass("tree-closed").removeClass("tree-open");
  }

  function ensureChildrenRendered(node) {
    var ul = node.children('ul');

  	if (!ul.length) {
  		renderChildren( node.data('id') ).appendTo(node);

      if (node.children('input').is(':checked')) {
        node.find('input').prop('checked', true);
      }
  	}
  }

  function renderChildren(id) {
  	return $(template({
  		children: data[id].children,
  		data: data
  	}));
  }

  function render() {
  	
  	self.elem = renderChildren(0)
  	 .addClass('tree');

  	self.elem.on('click', '.tree-toggler', onTogglerClick);

    self.elem.on('change', 'input', onCheckboxChange);
  }

}