/* -*-c++-*- */
/* osgEarth - Dynamic map generation toolkit for OpenSceneGraph
* Copyright 2008-2013 Pelican Mapping
* http://osgearth.org
*
* osgEarth is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program.  If not, see <http://www.gnu.org/licenses/>
*/
#ifndef OSGEARTH_STATE_SET_CACHE_H
#define OSGEARTH_STATE_SET_CACHE_H 1

#include <osgEarth/Common>
#include <osgEarth/ThreadingUtils>
#include <osg/StateSet>
#include <set>

namespace osgEarth
{
    /**
     * Cache for optimizing state set sharing.
     */
    class OSGEARTH_EXPORT StateSetCache : public osg::Referenced
    {
    public:
        /**
         * Constructs a new cache.
         */
        StateSetCache();


        /**
         * Check whether a StateSet is eligible for sharing.
         */
        bool eligible( osg::StateSet* stateSet ) const;

        /**
         * Check whether a StateAttribute is eligible for sharing.
         */
        bool eligible( osg::StateAttribute* attr ) const;

        /**
         * Traverse the node and consolidate equivalent state sets, updating
         * the cache along the way.
         */
        void optimize( osg::Node* node );

        /**
         * Looks in the cache for a stateset matching the input. If found,
         * returns the cached one in output. If not found, stores the input 
         * in the cache and returns the same one in output.
         *
         * Must use ref_ptrs for thread safely
         */
        bool share( 
            osg::ref_ptr<osg::StateSet>& input, 
            osg::ref_ptr<osg::StateSet>& output,
            bool                         checkEligible =true );

        /**
         * Looks in the attribute cache for an attribute matching the input.
         * If found, returns the cached one in output. If not found, stores
         * the input in the cache and returns the same one in output.
         *
         * Must use ref_ptrs for thread safely
         */
        bool share(
            osg::ref_ptr<osg::StateAttribute>& input,
            osg::ref_ptr<osg::StateAttribute>& output,
            bool                               checkEligible =true );

        /**
         * Number of statesets in the cache.
         */
        unsigned size() const { return _stateSetCache.size(); }

        /**
         * Clears out the cache.
         */
        void clear();

    protected: 

        virtual ~StateSetCache();

        struct CompareStateSets {
            bool operator()(
                const osg::ref_ptr<osg::StateSet>& lhs,
                const osg::ref_ptr<osg::StateSet>& rhs) const {
                    return lhs->compare(*(rhs.get()), true) < 0;
            }
        };
        typedef std::set< osg::ref_ptr<osg::StateSet>, CompareStateSets> StateSetSet;
        StateSetSet _stateSetCache;

        struct CompareStateAttributes {
            bool operator()(
                const osg::ref_ptr<osg::StateAttribute>& lhs,
                const osg::ref_ptr<osg::StateAttribute>& rhs) const {
                    return lhs->compare(*rhs.get()) < 0;
            }
        };
        typedef std::set< osg::ref_ptr<osg::StateAttribute>, CompareStateAttributes> StateAttributeSet;
        StateAttributeSet _stateAttributeCache;

        mutable Threading::Mutex _mutex;

        void prune();
        void pruneIfNecessary();
        unsigned _pruneCount;
    };
}

#endif // OSGEARTH_STATE_SET_CACHE_H
