#ifndef OSG_NODEVISITOR
#define OSG_NODEVISITOR 1

#include <osg/Node>
#include <osg/FrameStamp>

namespace osg {

class Geode;
class Billboard;
class LightSource;
class Group;
class Transform;
class LOD;
class Sequence;
class Switch;
class Impostor;

/** Visitor for type safe operations on osg::Node's.
    Based on GOF's Visitor pattern.*/ 
class SG_EXPORT NodeVisitor : public Referenced
{
    public:

        enum TraversalMode {
            TRAVERSE_NONE,
            TRAVERSE_PARENTS,
            TRAVERSE_ALL_CHILDREN,
            TRAVERSE_ACTIVE_CHILDREN,
            TRAVERSE_VISITOR
        };

        NodeVisitor(TraversalMode tm=TRAVERSE_NONE);
        virtual ~NodeVisitor();

        /** Method to call to reset visitor. Useful for your visitor accumulates
            state during a traversal, and you plan to resuse the visitor. 
            To flush that state for the next traversal than call reset() prior
            to each traversal.*/
        virtual void reset() {}


        /** Set the traversal number. Typically used to denote the frame count.*/
        inline void setTraversalNumber(const int fn) { _traversalNumber = fn; }
        
        /** Get the traversal number. Typically used to denote the frame count.*/
        inline const int getTraversalNumber() const { return _traversalNumber; }

        /** Set the FrameStamp that this traversal is assoicated with.*/
        inline void setFrameStamp(FrameStamp* fs) { _frameStamp = fs; }
        
        /** Get the FrameStamp that this traversal is assoicated with.*/
        inline const FrameStamp* getFrameStamp() const { return _frameStamp.get(); }


        /** Set the TraversalMask of this NodeVisitor.
          * The TraversalMask is used by the NodeVisitor::validNodeMask() method
          * to determine whether to operate on a node and its subgraph.
          * validNodeMask() is called automaticaly in the Node::accept() method before
          * any call to NodeVisitor::apply(), apply() is only ever called if validNodeMask
          * returns true. Note, if NodeVisitor::_traversalMask is 0 then all operations
          * will be swithced off for all nodes.  Whereas setting both _traversalMask and
          * _nodeMaskOverride to 0xffffffff will allow a visitor to work on all nodes
          * regardless of their own Node::_nodeMask state.*/
        inline void setTraversalMask(const Node::NodeMask mask) { _traversalMask = mask; }

        /** Get the TraversalMask.*/
        inline const Node::NodeMask getTraversalMask() const { return _traversalMask; }

        /** Set the NodeMaskOverride mask.
          * Used in validNodeMask() to determine whether to operate on a node or its 
          * subgraph, by OR'ing NodeVisitor::_nodeMaskOverride with the Node's own Node::_nodeMask.
          * Typically used to force on nodes which may have
          * been switched off by their own Node::_nodeMask.*/
        inline void setNodeMaskOverride(const Node::NodeMask mask) { _nodeMaskOverride = mask; }

        /** Get the NodeMaskOverride mask.*/
        inline const Node::NodeMask getNodeMaskOverride() const { return _nodeMaskOverride; }
        
        /** Method to called by Node and its subclass' Node::accept() method, if the result is true
          * to be used to cull operations of nodes and their subgraphs.
          * Return true if the result of a bit wise and of the NodeVisitor::_traversalMask
          * with the bit or between NodeVistor::_nodeMaskOverride and the Node::_nodeMask.
          * default values for _traversalMask is 0xffffffff, _nodeMaskOverride is 0x0,
          * and osg::Node::_nodeMask is 0xffffffff. */
        inline const bool validNodeMask(const osg::Node& node) const
        {
            return (getTraversalMask() & (getNodeMaskOverride() | node.getNodeMask()))!=0;
        }

        /** Set the traversal mode for Node::traverse() to use when 
            deciding which children of a node to traverse. If a
            NodeVisitor has been attached via setTraverseVisitor()
            and the new mode is not TRAVERSE_VISITOR then the attached
            visitor is detached. Default mode is TRAVERSE_NONE.*/
        void setTraversalMode(const TraversalMode mode);
        
        /** Get the traversal mode.*/
        inline const TraversalMode getTraversalMode() const { return _traversalMode; }

        /** Set a visitor to handle traversal.
            Overides the traverse mode setting it to TRAVERSAL_VISITOR.*/
        void setTraversalVisitor(NodeVisitor* nv);
        
        /** Get the traversal visitor, returns NULL if none is attached.*/
        NodeVisitor* getTraversalVisitor() { return _traversalVisitor.get(); }

        /** Inline method for handling traversal of a nodes.
            If you intend to use the visitor for actively traversing 
            the scene graph then make sure the accept() methods call
            this method unless they handle traversal directly.*/
        void traverse(Node& node)
        {
            if (_traversalVisitor.valid()) node.accept(*_traversalVisitor);
            else if (_traversalMode==TRAVERSE_PARENTS) node.ascend(*this);
            else if (_traversalMode!=TRAVERSE_NONE) node.traverse(*this);
        }

        virtual void apply(Node& node)       { traverse(node);}
        
        virtual void apply(Geode& node)      { apply((Node&)node); }
        virtual void apply(Billboard& node)  { apply((Geode&)node); }
        virtual void apply(LightSource& node){ apply((Node&)node); }
        
        virtual void apply(Group& node)      { apply((Node&)node); }
        virtual void apply(Transform& node)  { apply((Group&)node); }
        virtual void apply(Switch& node)     { apply((Group&)node); }
        virtual void apply(Sequence& node)   { apply((Group&)node); }
        virtual void apply(LOD& node)        { apply((Group&)node); }
        virtual void apply(Impostor& node)   { apply((LOD&)node); }

    protected:

        int                     _traversalNumber;
        
        ref_ptr<FrameStamp>     _frameStamp;

        ref_ptr<NodeVisitor>    _traversalVisitor;
        
        TraversalMode           _traversalMode;
        Node::NodeMask          _traversalMask;
        Node::NodeMask          _nodeMaskOverride;

};


/** Convinience functor for assisting visiting of arrays of osg::Node's.*/ 
struct NodeAcceptOp
{
    NodeVisitor& _nv;
    NodeAcceptOp(NodeVisitor& nv):_nv(nv) {}
    void operator () (Node* node) { node->accept(_nv); }
    void operator () (ref_ptr<Node> node) { node->accept(_nv); }
};

};

#endif