#ifndef OSGUTIL_RENDERGRAPH
#define OSGUTIL_RENDERGRAPH 1

#include <osg/Matrix>
#include <osg/Drawable>
#include <osg/StateSet>
#include <osg/State>
#include <osg/Light>

#include <osgUtil/RenderLeaf>

#include <set>
#include <vector>

namespace osgUtil {


class OSGUTIL_EXPORT RenderGraph : public osg::Referenced
{
    public:
    

        typedef std::map< const osg::StateSet*, osg::ref_ptr<RenderGraph> >   ChildList;
        typedef std::vector< osg::ref_ptr<RenderLeaf> >                 LeafList;

        RenderGraph*                        _parent;
        osg::ref_ptr<const osg::StateSet>   _stateset;

        int                                 _depth;
        ChildList                           _children;
        LeafList                            _leaves;


        RenderGraph():
            _parent(NULL), 
            _stateset(NULL), 
            _depth(0)
        {
        }

        RenderGraph(RenderGraph* parent,const osg::StateSet* stateset):
            _parent(parent), 
            _stateset(stateset)
        {
            if (_parent) _depth = _parent->_depth + 1;
            else _depth = 0;
        }
            
        ~RenderGraph() {}
        

        /** return true if all of drawables, lights and children are empty.*/
        inline const bool empty() const
        {
            return _leaves.empty() && _children.empty();
        }
        
        inline const bool leaves_empty() const
        {
            return _leaves.empty();
        }

        /** reset the internal contents of a RenderGraph, including deleting all children.*/
        void reset();

        /** recursively clean the RenderGraph of all its drawables, lights and depths.
          * Leaves children intact, and ready to be populated again.*/
        void clean();

        /** recursively prune the RenderGraph of empty children.*/
        void prune();
        
        
        inline RenderGraph* find_or_insert(const osg::StateSet* stateset)
        {
            // search for the appropriate state group, return it if found.
            ChildList::iterator itr = _children.find(stateset);
            if (itr!=_children.end()) return itr->second.get();
            
            // create a state group and insert it into the children list
            // then return the state group.
            RenderGraph* sg = new RenderGraph(this,stateset);
            _children[stateset] = sg;
            return sg;
        }

        /** add a render leaf.*/
        inline void addLeaf(RenderLeaf* leaf)
        {
            if (leaf)
            {
                _leaves.push_back(leaf);
                leaf->_parent = this;
            }
        }

        static inline void moveRenderGraph(osg::State& state,RenderGraph* sg_curr,RenderGraph* sg_new)
        {
            if (sg_new==sg_curr || sg_new==NULL) return;

            if (sg_curr==NULL)
            {

                // use return path to trace back steps to sg_new.
                std::vector<RenderGraph*> return_path;

                // need to pop back root render graph.
                do 
                {
                    return_path.push_back(sg_new);
                    sg_new = sg_new->_parent;
                } while (sg_new);

                for(std::vector<RenderGraph*>::reverse_iterator itr=return_path.rbegin();
                    itr!=return_path.rend();
                    ++itr)
                {
                    RenderGraph* rg = (*itr);
                    if (rg->_stateset.valid()) state.pushStateSet(rg->_stateset.get());
                }
                return;
            }
        

            // first handle the typical case which is two state groups
            // are neighbours.
            if (sg_curr->_parent==sg_new->_parent)
            {
                
                // state has changed so need to pop old state.
                if (sg_curr->_stateset.valid()) state.popStateSet();
                // and push new state.
                if (sg_new->_stateset.valid()) state.pushStateSet(sg_new->_stateset.get());
                return;
            }
        

            // need to pop back up to the same depth as the new state group.
            while (sg_curr->_depth>sg_new->_depth)
            {
                if (sg_curr->_stateset.valid()) state.popStateSet();
                sg_curr = sg_curr->_parent;
            }
            
            // use return path to trace back steps to sg_new.
            std::vector<RenderGraph*> return_path;

            // need to pop back up to the same depth as the curr state group.
            while (sg_new->_depth>sg_curr->_depth)
            {
                return_path.push_back(sg_new);
                sg_new = sg_new->_parent;
            }
            
            // now pop back up both parent paths until they agree.
            while (sg_curr->_parent!=sg_new->_parent)
            {
                if (sg_curr->_stateset.valid()) state.popStateSet();
                sg_curr = sg_curr->_parent;

                return_path.push_back(sg_new);
                sg_new = sg_new->_parent;
            }
            
            for(std::vector<RenderGraph*>::reverse_iterator itr=return_path.rbegin();
                itr!=return_path.rend();
                ++itr)
            {
                RenderGraph* rg = (*itr);
                if (rg->_stateset.valid()) state.pushStateSet(rg->_stateset.get());
            }

        }

        inline static void moveToRootRenderGraph(osg::State& state,RenderGraph* sg_curr)
        {
            // need to pop back all statesets and matrices.
            while (sg_curr)
            {
                if (sg_curr->_stateset.valid()) state.popStateSet();
                sg_curr = sg_curr->_parent;
            }
            
        }
        
    private:

        /// disallow copy construction.
        RenderGraph(const RenderGraph&):osg::Referenced() {}
        /// disallow copy operator.
        RenderGraph& operator = (const RenderGraph&) { return *this; }

};

};

#endif