function Toggle(objTree, strNodeId) {
   // If there are any menus or children open, close them first.
   closeAll();

   var objNode = objTree[objTree.getIndexById(strNodeId)];
   var nodeChild = document.all[objTree.getId()+'_'+objNode.id+'_img'];
   if (objNode.expanded) {
      hideChildren(objTree, objNode)
      nodeChild.src='images/treeview/folder_closed.gif';
   } else {
      showChildren(objTree, objNode)
      nodeChild.src='images/treeview/folder_open.gif';
   };
   objNode.expanded = !objNode.expanded
   objTree.replaceByIndex(objTree.getIndexById(strNodeId), objNode);
};

function showChildren(objTree, objNode) {
   for (var i = 0; i < objTree.size(); i++) {
      if (objTree[i].parent == objNode.id) {
         var nodeChild = document.all[objTree.getId()+'_'+objTree[i].id];
         nodeChild.style.display = 'block';
         if (objTree[i].expanded) {
            showChildren(objTree, objTree[i]);
         }
      };
   };
};

function hideChildren(objTree, objNode) {
   for (var i = 0; i < objTree.size(); i++) {
      if (objTree[i].parent == objNode.id) {
         var nodeChild = document.all[objTree.getId()+'_'+objTree[i].id];
         nodeChild.style.display = 'none';
         hideChildren(objTree, objTree[i]);
      };
   };
};

function Tree(newId) {
   // Number of nodes in the tree:
   var lngNodeCount=0;
   var id;

   this.getId = function() {
      return id;
   };

   this.render = function(){
      renderChildren(this, -1, 0, id, true);
   };

   this.numChildren = function(lngParent) {
      return countChildren(this, lngParent);
   };

   function countChildren(objTree, lngParent) {
      var lngChildren=0;
      for (var i = 0; i < lngNodeCount; i++) {
         if (objTree[i].parent == lngParent) {
            lngChildren++;
         }
      }
      return lngChildren;
   };
   
   function renderChildren(objTree, lngParent, lngIndent, strID, bolExpanded) {
      //alert('Rendering children of: '+lngParent);
      for (var i = 0; i < lngNodeCount; i++) {
         if (objTree[i].parent == lngParent) {
            renderNode(objTree, objTree[i], lngIndent, bolExpanded)
            renderChildren(objTree, objTree[i].id, lngIndent+1, strID+'_'+objTree[i].id, objTree[i].expanded);
         };
      };
   };
   
   function repeat(strToRepeat, lngNumTimes) {
      var n='';
      for (var i = 0; i < lngNumTimes; i++) {
         n+=strToRepeat;
      };
      return n;
   };
   
   // Tree initialization function.
   this.init = function(thisId){
      //alert('Initializing as '+thisId+'.');
      lngNodeCount=0;
      id = thisId;
   };
   
   // Add a node to the tree
   this.add = function(objNode) {
      //alert('Adding node: '+objNode.id)
      lngNodeCount++;
      this[lngNodeCount - 1] = objNode;
   };
   
   // Get a node's index, given it's id
   this.getIndexById = function(id) {
      for (var i = 0; i < lngNodeCount; i++)
         if (this[i].id == id)
            return i;
   };

   // Replace a node in the tree with another one.
   this.replaceByIndex = function(objNode, lngIndex) {
      this[lngIndex] = objNode;
   };

   // Remove a node from the tree
   this.remove = function(lngIndex) {
      alert('Removing node: '+lngIndex)
      this[lngIndex] = null;
      for (var i = lngIndex; i <= lngNodeCount; i++)
         this[i] = this[i + 1];
      lngNodeCount--;
   };

   // Clears out the entire tree
   this.clear = function() {
      for (var i = 0; i < lngNodeCount; i++)
         this[i] = null;

      lngNodeCount = 0;
   };
   
   // Get the size of the tree (number of nodes)
   this.size = function() {
      return lngNodeCount;
   };
   
   // Determine if the tree is empty
   this.isEmpty = function() {
      return lngNodeCount==0;
   };

   // Call the initialization routing automatically.
   this.init(newId);
};