The source code

    /*!
     * Ext JS Library 3.2.1
     * Copyright(c) 2006-2010 Ext JS, Inc.
     * licensing@extjs.com
     * http://www.extjs.com/license
     */
    /**
     * @class Ext.data.Tree
     * @extends Ext.util.Observable
     * Represents a tree data structure and bubbles all the events for its nodes. The nodes
     * in the tree have most standard DOM functionality.
     * @constructor
     * @param {Node} root (optional) The root node
     */
    Ext.data.Tree = function(root){
       this.nodeHash = {};
       /**
        * The root node for this tree
        * @type Node
        */
       this.root = null;
       if(root){
           this.setRootNode(root);
       }
       this.addEvents(
           /**
            * @event append
            * Fires when a new child node is appended to a node in this tree.
            * @param {Tree} tree The owner tree
            * @param {Node} parent The parent node
            * @param {Node} node The newly appended node
            * @param {Number} index The index of the newly appended node
            */
           "append",
           /**
            * @event remove
            * Fires when a child node is removed from a node in this tree.
            * @param {Tree} tree The owner tree
            * @param {Node} parent The parent node
            * @param {Node} node The child node removed
            */
           "remove",
           /**
            * @event move
            * Fires when a node is moved to a new location in the tree
            * @param {Tree} tree The owner tree
            * @param {Node} node The node moved
            * @param {Node} oldParent The old parent of this node
            * @param {Node} newParent The new parent of this node
            * @param {Number} index The index it was moved to
            */
           "move",
           /**
            * @event insert
            * Fires when a new child node is inserted in a node in this tree.
            * @param {Tree} tree The owner tree
            * @param {Node} parent The parent node
            * @param {Node} node The child node inserted
            * @param {Node} refNode The child node the node was inserted before
            */
           "insert",
           /**
            * @event beforeappend
            * Fires before a new child is appended to a node in this tree, return false to cancel the append.
            * @param {Tree} tree The owner tree
            * @param {Node} parent The parent node
            * @param {Node} node The child node to be appended
            */
           "beforeappend",
           /**
            * @event beforeremove
            * Fires before a child is removed from a node in this tree, return false to cancel the remove.
            * @param {Tree} tree The owner tree
            * @param {Node} parent The parent node
            * @param {Node} node The child node to be removed
            */
           "beforeremove",
           /**
            * @event beforemove
            * Fires before a node is moved to a new location in the tree. Return false to cancel the move.
            * @param {Tree} tree The owner tree
            * @param {Node} node The node being moved
            * @param {Node} oldParent The parent of the node
            * @param {Node} newParent The new parent the node is moving to
            * @param {Number} index The index it is being moved to
            */
           "beforemove",
           /**
            * @event beforeinsert
            * Fires before a new child is inserted in a node in this tree, return false to cancel the insert.
            * @param {Tree} tree The owner tree
            * @param {Node} parent The parent node
            * @param {Node} node The child node to be inserted
            * @param {Node} refNode The child node the node is being inserted before
            */
           "beforeinsert"
       );

        Ext.data.Tree.superclass.constructor.call(this);
    };

    Ext.extend(Ext.data.Tree, Ext.util.Observable, {
        /**
         * @cfg {String} pathSeparator
         * The token used to separate paths in node ids (defaults to '/').
         */
        pathSeparator: "/",

        // private
        proxyNodeEvent : function(){
            return this.fireEvent.apply(this, arguments);
        },

        /**
         * Returns the root node for this tree.
         * @return {Node}
         */
        getRootNode : function(){
            return this.root;
        },

        /**
         * Sets the root node for this tree.
         * @param {Node} node
         * @return {Node}
         */
        setRootNode : function(node){
            this.root = node;
            node.ownerTree = this;
            node.isRoot = true;
            this.registerNode(node);
            return node;
        },

        /**
         * Gets a node in this tree by its id.
         * @param {String} id
         * @return {Node}
         */
        getNodeById : function(id){
            return this.nodeHash[id];
        },

        // private
        registerNode : function(node){
            this.nodeHash[node.id] = node;
        },

        // private
        unregisterNode : function(node){
            delete this.nodeHash[node.id];
        },

        toString : function(){
            return "[Tree"+(this.id?" "+this.id:"")+"]";
        }
    });

    /**
     * @class Ext.data.Node
     * @extends Ext.util.Observable
     * @cfg {Boolean} leaf true if this node is a leaf and does not have children
     * @cfg {String} id The id for this node. If one is not specified, one is generated.
     * @constructor
     * @param {Object} attributes The attributes/config for the node
     */
    Ext.data.Node = function(attributes){
        /**
         * The attributes supplied for the node. You can use this property to access any custom attributes you supplied.
         * @type {Object}
         */
        this.attributes = attributes || {};
        this.leaf = this.attributes.leaf;
        /**
         * The node id. @type String
         */
        this.id = this.attributes.id;
        if(!this.id){
            this.id = Ext.id(null, "xnode-");
            this.attributes.id = this.id;
        }
        /**
         * All child nodes of this node. @type Array
         */
        this.childNodes = [];
        if(!this.childNodes.indexOf){ // indexOf is a must
            this.childNodes.indexOf = function(o){
                for(var i = 0, len = this.length; i < len; i++){
                    if(this[i] == o){
                        return i;
                    }
                }
                return -1;
            };
        }
        /**
         * The parent node for this node. @type Node
         */
        this.parentNode = null;
        /**
         * The first direct child node of this node, or null if this node has no child nodes. @type Node
         */
        this.firstChild = null;
        /**
         * The last direct child node of this node, or null if this node has no child nodes. @type Node
         */
        this.lastChild = null;
        /**
         * The node immediately preceding this node in the tree, or null if there is no sibling node. @type Node
         */
        this.previousSibling = null;
        /**
         * The node immediately following this node in the tree, or null if there is no sibling node. @type Node
         */
        this.nextSibling = null;

        this.addEvents({
           /**
            * @event append
            * Fires when a new child node is appended
            * @param {Tree} tree The owner tree
            * @param {Node} this This node
            * @param {Node} node The newly appended node
            * @param {Number} index The index of the newly appended node
            */
           "append" : true,
           /**
            * @event remove
            * Fires when a child node is removed
            * @param {Tree} tree The owner tree
            * @param {Node} this This node
            * @param {Node} node The removed node
            */
           "remove" : true,
           /**
            * @event move
            * Fires when this node is moved to a new location in the tree
            * @param {Tree} tree The owner tree
            * @param {Node} this This node
            * @param {Node} oldParent The old parent of this node
            * @param {Node} newParent The new parent of this node
            * @param {Number} index The index it was moved to
            */
           "move" : true,
           /**
            * @event insert
            * Fires when a new child node is inserted.
            * @param {Tree} tree The owner tree
            * @param {Node} this This node
            * @param {Node} node The child node inserted
            * @param {Node} refNode The child node the node was inserted before
            */
           "insert" : true,
           /**
            * @event beforeappend
            * Fires before a new child is appended, return false to cancel the append.
            * @param {Tree} tree The owner tree
            * @param {Node} this This node
            * @param {Node} node The child node to be appended
            */
           "beforeappend" : true,
           /**
            * @event beforeremove
            * Fires before a child is removed, return false to cancel the remove.
            * @param {Tree} tree The owner tree
            * @param {Node} this This node
            * @param {Node} node The child node to be removed
            */
           "beforeremove" : true,
           /**
            * @event beforemove
            * Fires before this node is moved to a new location in the tree. Return false to cancel the move.
            * @param {Tree} tree The owner tree
            * @param {Node} this This node
            * @param {Node} oldParent The parent of this node
            * @param {Node} newParent The new parent this node is moving to
            * @param {Number} index The index it is being moved to
            */
           "beforemove" : true,
           /**
            * @event beforeinsert
            * Fires before a new child is inserted, return false to cancel the insert.
            * @param {Tree} tree The owner tree
            * @param {Node} this This node
            * @param {Node} node The child node to be inserted
            * @param {Node} refNode The child node the node is being inserted before
            */
           "beforeinsert" : true
       });
        this.listeners = this.attributes.listeners;
        Ext.data.Node.superclass.constructor.call(this);
    };

    Ext.extend(Ext.data.Node, Ext.util.Observable, {
        // private
        fireEvent : function(evtName){
            // first do standard event for this node
            if(Ext.data.Node.superclass.fireEvent.apply(this, arguments) === false){
                return false;
            }
            // then bubble it up to the tree if the event wasn't cancelled
            var ot = this.getOwnerTree();
            if(ot){
                if(ot.proxyNodeEvent.apply(ot, arguments) === false){
                    return false;
                }
            }
            return true;
        },

        /**
         * Returns true if this node is a leaf
         * @return {Boolean}
         */
        isLeaf : function(){
            return this.leaf === true;
        },

        // private
        setFirstChild : function(node){
            this.firstChild = node;
        },

        //private
        setLastChild : function(node){
            this.lastChild = node;
        },

        /**
         * Returns true if this node is the last child of its parent
         * @return {Boolean}
         */
        isLast : function(){
           return (!this.parentNode ? true : this.parentNode.lastChild == this);
        },

        /**
         * Returns true if this node is the first child of its parent
         * @return {Boolean}
         */
        isFirst : function(){
           return (!this.parentNode ? true : this.parentNode.firstChild == this);
        },

        /**
         * Returns true if this node has one or more child nodes, else false.
         * @return {Boolean}
         */
        hasChildNodes : function(){
            return !this.isLeaf() && this.childNodes.length > 0;
        },

        /**
         * Returns true if this node has one or more child nodes, or if the expandable
         * node attribute is explicitly specified as true (see {@link #attributes}), otherwise returns false.
         * @return {Boolean}
         */
        isExpandable : function(){
            return this.attributes.expandable || this.hasChildNodes();
        },

        /**
         * Insert node(s) as the last child node of this node.
         * @param {Node/Array} node The node or Array of nodes to append
         * @return {Node} The appended node if single append, or null if an array was passed
         */
        appendChild : function(node){
            var multi = false;
            if(Ext.isArray(node)){
                multi = node;
            }else if(arguments.length > 1){
                multi = arguments;
            }
            // if passed an array or multiple args do them one by one
            if(multi){
                for(var i = 0, len = multi.length; i < len; i++) {
                    this.appendChild(multi[i]);
                }
            }else{
                if(this.fireEvent("beforeappend", this.ownerTree, this, node) === false){
                    return false;
                }
                var index = this.childNodes.length;
                var oldParent = node.parentNode;
                // it's a move, make sure we move it cleanly
                if(oldParent){
                    if(node.fireEvent("beforemove", node.getOwnerTree(), node, oldParent, this, index) === false){
                        return false;
                    }
                    oldParent.removeChild(node);
                }
                index = this.childNodes.length;
                if(index === 0){
                    this.setFirstChild(node);
                }
                this.childNodes.push(node);
                node.parentNode = this;
                var ps = this.childNodes[index-1];
                if(ps){
                    node.previousSibling = ps;
                    ps.nextSibling = node;
                }else{
                    node.previousSibling = null;
                }
                node.nextSibling = null;
                this.setLastChild(node);
                node.setOwnerTree(this.getOwnerTree());
                this.fireEvent("append", this.ownerTree, this, node, index);
                if(oldParent){
                    node.fireEvent("move", this.ownerTree, node, oldParent, this, index);
                }
                return node;
            }
        },

        /**
         * Removes a child node from this node.
         * @param {Node} node The node to remove
         * @param {Boolean} destroy true to destroy the node upon removal. Defaults to false.
         * @return {Node} The removed node
         */
        removeChild : function(node, destroy){
            var index = this.childNodes.indexOf(node);
            if(index == -1){
                return false;
            }
            if(this.fireEvent("beforeremove", this.ownerTree, this, node) === false){
                return false;
            }

            // remove it from childNodes collection
            this.childNodes.splice(index, 1);

            // update siblings
            if(node.previousSibling){
                node.previousSibling.nextSibling = node.nextSibling;
            }
            if(node.nextSibling){
                node.nextSibling.previousSibling = node.previousSibling;
            }

            // update child refs
            if(this.firstChild == node){
                this.setFirstChild(node.nextSibling);
            }
            if(this.lastChild == node){
                this.setLastChild(node.previousSibling);
            }

            this.fireEvent("remove", this.ownerTree, this, node);
            if(destroy){
                node.destroy(true);
            }else{
                node.clear();
            }
            return node;
        },

        // private
        clear : function(destroy){
            // clear any references from the node
            this.setOwnerTree(null, destroy);
            this.parentNode = this.previousSibling = this.nextSibling = null;
            if(destroy){
                this.firstChild = this.lastChild = null;
            }
        },

        /**
         * Destroys the node.
         */
        destroy : function(/* private */ silent){
            /*
             * Silent is to be used in a number of cases
             * 1) When setRootNode is called.
             * 2) When destroy on the tree is called
             * 3) For destroying child nodes on a node
             */
            if(silent === true){
                this.purgeListeners();
                this.clear(true);
                Ext.each(this.childNodes, function(n){
                    n.destroy(true);
                });
                this.childNodes = null;
            }else{
                this.remove(true);
            }
        },

        /**
         * Inserts the first node before the second node in this nodes childNodes collection.
         * @param {Node} node The node to insert
         * @param {Node} refNode The node to insert before (if null the node is appended)
         * @return {Node} The inserted node
         */
        insertBefore : function(node, refNode){
            if(!refNode){ // like standard Dom, refNode can be null for append
                return this.appendChild(node);
            }
            // nothing to do
            if(node == refNode){
                return false;
            }

            if(this.fireEvent("beforeinsert", this.ownerTree, this, node, refNode) === false){
                return false;
            }
            var index = this.childNodes.indexOf(refNode);
            var oldParent = node.parentNode;
            var refIndex = index;

            // when moving internally, indexes will change after remove
            if(oldParent == this && this.childNodes.indexOf(node) < index){
                refIndex--;
            }

            // it's a move, make sure we move it cleanly
            if(oldParent){
                if(node.fireEvent("beforemove", node.getOwnerTree(), node, oldParent, this, index, refNode) === false){
                    return false;
                }
                oldParent.removeChild(node);
            }
            if(refIndex === 0){
                this.setFirstChild(node);
            }
            this.childNodes.splice(refIndex, 0, node);
            node.parentNode = this;
            var ps = this.childNodes[refIndex-1];
            if(ps){
                node.previousSibling = ps;
                ps.nextSibling = node;
            }else{
                node.previousSibling = null;
            }
            node.nextSibling = refNode;
            refNode.previousSibling = node;
            node.setOwnerTree(this.getOwnerTree());
            this.fireEvent("insert", this.ownerTree, this, node, refNode);
            if(oldParent){
                node.fireEvent("move", this.ownerTree, node, oldParent, this, refIndex, refNode);
            }
            return node;
        },

        /**
         * Removes this node from its parent
         * @param {Boolean} destroy true to destroy the node upon removal. Defaults to false.
         * @return {Node} this
         */
        remove : function(destroy){
            if (this.parentNode) {
                this.parentNode.removeChild(this, destroy);
            }
            return this;
        },

        /**
         * Removes all child nodes from this node.
         * @param {Boolean} destroy true to destroy the node upon removal. Defaults to false.
         * @return {Node} this
         */
        removeAll : function(destroy){
            var cn = this.childNodes,
                n;
            while((n = cn[0])){
                this.removeChild(n, destroy);
            }
            return this;
        },

        /**
         * Returns the child node at the specified index.
         * @param {Number} index
         * @return {Node}
         */
        item : function(index){
            return this.childNodes[index];
        },

        /**
         * Replaces one child node in this node with another.
         * @param {Node} newChild The replacement node
         * @param {Node} oldChild The node to replace
         * @return {Node} The replaced node
         */
        replaceChild : function(newChild, oldChild){
            var s = oldChild ? oldChild.nextSibling : null;
            this.removeChild(oldChild);
            this.insertBefore(newChild, s);
            return oldChild;
        },

        /**
         * Returns the index of a child node
         * @param {Node} node
         * @return {Number} The index of the node or -1 if it was not found
         */
        indexOf : function(child){
            return this.childNodes.indexOf(child);
        },

        /**
         * Returns the tree this node is in.
         * @return {Tree}
         */
        getOwnerTree : function(){
            // if it doesn't have one, look for one
            if(!this.ownerTree){
                var p = this;
                while(p){
                    if(p.ownerTree){
                        this.ownerTree = p.ownerTree;
                        break;
                    }
                    p = p.parentNode;
                }
            }
            return this.ownerTree;
        },

        /**
         * Returns depth of this node (the root node has a depth of 0)
         * @return {Number}
         */
        getDepth : function(){
            var depth = 0;
            var p = this;
            while(p.parentNode){
                ++depth;
                p = p.parentNode;
            }
            return depth;
        },

        // private
        setOwnerTree : function(tree, destroy){
            // if it is a move, we need to update everyone
            if(tree != this.ownerTree){
                if(this.ownerTree){
                    this.ownerTree.unregisterNode(this);
                }
                this.ownerTree = tree;
                // If we're destroying, we don't need to recurse since it will be called on each child node
                if(destroy !== true){
                    Ext.each(this.childNodes, function(n){
                        n.setOwnerTree(tree);
                    });
                }
                if(tree){
                    tree.registerNode(this);
                }
            }
        },

        /**
         * Changes the id of this node.
         * @param {String} id The new id for the node.
         */
        setId: function(id){
            if(id !== this.id){
                var t = this.ownerTree;
                if(t){
                    t.unregisterNode(this);
                }
                this.id = this.attributes.id = id;
                if(t){
                    t.registerNode(this);
                }
                this.onIdChange(id);
            }
        },

        // private
        onIdChange: Ext.emptyFn,

        /**
         * Returns the path for this node. The path can be used to expand or select this node programmatically.
         * @param {String} attr (optional) The attr to use for the path (defaults to the node's id)
         * @return {String} The path
         */
        getPath : function(attr){
            attr = attr || "id";
            var p = this.parentNode;
            var b = [this.attributes[attr]];
            while(p){
                b.unshift(p.attributes[attr]);
                p = p.parentNode;
            }
            var sep = this.getOwnerTree().pathSeparator;
            return sep + b.join(sep);
        },

        /**
         * Bubbles up the tree from this node, calling the specified function with each node. The arguments to the function
         * will be the args provided or the current node. If the function returns false at any point,
         * the bubble is stopped.
         * @param {Function} fn The function to call
         * @param {Object} scope (optional) The scope (this reference) in which the function is executed. Defaults to the current Node.
         * @param {Array} args (optional) The args to call the function with (default to passing the current Node)
         */
        bubble : function(fn, scope, args){
            var p = this;
            while(p){
                if(fn.apply(scope || p, args || [p]) === false){
                    break;
                }
                p = p.parentNode;
            }
        },

        /**
         * Cascades down the tree from this node, calling the specified function with each node. The arguments to the function
         * will be the args provided or the current node. If the function returns false at any point,
         * the cascade is stopped on that branch.
         * @param {Function} fn The function to call
         * @param {Object} scope (optional) The scope (this reference) in which the function is executed. Defaults to the current Node.
         * @param {Array} args (optional) The args to call the function with (default to passing the current Node)
         */
        cascade : function(fn, scope, args){
            if(fn.apply(scope || this, args || [this]) !== false){
                var cs = this.childNodes;
                for(var i = 0, len = cs.length; i < len; i++) {
                    cs[i].cascade(fn, scope, args);
                }
            }
        },

        /**
         * Interates the child nodes of this node, calling the specified function with each node. The arguments to the function
         * will be the args provided or the current node. If the function returns false at any point,
         * the iteration stops.
         * @param {Function} fn The function to call
         * @param {Object} scope (optional) The scope (this reference) in which the function is executed. Defaults to the current Node in the iteration.
         * @param {Array} args (optional) The args to call the function with (default to passing the current Node)
         */
        eachChild : function(fn, scope, args){
            var cs = this.childNodes;
            for(var i = 0, len = cs.length; i < len; i++) {
                if(fn.apply(scope || this, args || [cs[i]]) === false){
                    break;
                }
            }
        },

        /**
         * Finds the first child that has the attribute with the specified value.
         * @param {String} attribute The attribute name
         * @param {Mixed} value The value to search for
         * @param {Boolean} deep (Optional) True to search through nodes deeper than the immediate children
         * @return {Node} The found child or null if none was found
         */
        findChild : function(attribute, value, deep){
            return this.findChildBy(function(){
                return this.attributes[attribute] == value;
            }, null, deep);
        },

        /**
         * Finds the first child by a custom function. The child matches if the function passed returns true.
         * @param {Function} fn A function which must return true if the passed Node is the required Node.
         * @param {Object} scope (optional) The scope (this reference) in which the function is executed. Defaults to the Node being tested.
         * @param {Boolean} deep (Optional) True to search through nodes deeper than the immediate children
         * @return {Node} The found child or null if none was found
         */
        findChildBy : function(fn, scope, deep){
            var cs = this.childNodes,
                len = cs.length,
                i = 0,
                n,
                res;
            for(; i < len; i++){
                n = cs[i];
                if(fn.call(scope || n, n) === true){
                    return n;
                }else if (deep){
                    res = n.findChildBy(fn, scope, deep);
                    if(res != null){
                        return res;
                    }
                }

            }
            return null;
        },

        /**
         * Sorts this nodes children using the supplied sort function.
         * @param {Function} fn A function which, when passed two Nodes, returns -1, 0 or 1 depending upon required sort order.
         * @param {Object} scope (optional)The scope (this reference) in which the function is executed. Defaults to the browser window.
         */
        sort : function(fn, scope){
            var cs = this.childNodes;
            var len = cs.length;
            if(len > 0){
                var sortFn = scope ? function(){fn.apply(scope, arguments);} : fn;
                cs.sort(sortFn);
                for(var i = 0; i < len; i++){
                    var n = cs[i];
                    n.previousSibling = cs[i-1];
                    n.nextSibling = cs[i+1];
                    if(i === 0){
                        this.setFirstChild(n);
                    }
                    if(i == len-1){
                        this.setLastChild(n);
                    }
                }
            }
        },

        /**
         * Returns true if this node is an ancestor (at any point) of the passed node.
         * @param {Node} node
         * @return {Boolean}
         */
        contains : function(node){
            return node.isAncestor(this);
        },

        /**
         * Returns true if the passed node is an ancestor (at any point) of this node.
         * @param {Node} node
         * @return {Boolean}
         */
        isAncestor : function(node){
            var p = this.parentNode;
            while(p){
                if(p == node){
                    return true;
                }
                p = p.parentNode;
            }
            return false;
        },

        toString : function(){
            return "[Node"+(this.id?" "+this.id:"")+"]";
        }
    });