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/* -*-c++-*- */
/* osgEarth - Dynamic map generation toolkit for OpenSceneGraph
 * Copyright 2008-2010 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_TEXTURE_COMPOSITOR_H
#define OSGEARTH_TEXTURE_COMPOSITOR_H 1

#include <osgEarth/Common>
#include <osgEarth/GeoData>
#include <osgEarth/Map>
#include <osgEarth/ThreadingUtils>
#include <osgEarth/TerrainOptions>
#include <osg/StateSet>
#include <osg/Program>

namespace osgEarth
{
    class OSGEARTH_EXPORT TextureLayout
    {        
    public:
        // vector of texture slots, each slot containing the UID of the image layer in that slot
        // or -1 if the slot is empty.
        typedef std::vector<UID> TextureSlotVector;

        // rendering order of texture slots- each element is an index into the TextureSlotVector.
        typedef std::vector<int> RenderOrderVector;

    public:
        TextureLayout();

        int getSlot( UID layerUID, unsigned which =0, unsigned maxSlotsToSearch =~0 ) const;

        int getOrder( UID layerUID ) const;

        int getMaxUsedSlot() const;

        bool isSlotAvailable( int slot ) const;

        const TextureSlotVector& getTextureSlots() const { return _slots; }

        const RenderOrderVector& getRenderOrder() const { return _order; }

        bool containsSecondarySlots( unsigned maxSlotsToSearch = ~0) const;

        bool isBlendingEnabled( UID layerUID ) const;

    protected:
        friend class TextureCompositor;

        void applyMapModelChange( const MapModelChange& change, bool reserveSeconarySlotIfNecessary );

        void setReservedSlots( const std::set<int>& reservedSlots );

    protected:
        TextureSlotVector  _slots;
        RenderOrderVector  _order;
        bool               _textureImageUnitPerSlot;
        std::set<int>      _reservedSlots;
        std::map<UID,bool> _lodBlending;

        void assignPrimarySlot( ImageLayer* layer, int index );
        void assignSecondarySlot( ImageLayer* layer );
    };

    //-----------------------------------------------------------------------

    class OSGEARTH_EXPORT TextureCompositorTechnique : public osg::Referenced
    {
    public:
        virtual bool requiresUnitTextureSpace() const =0;

        virtual bool usesShaderComposition() const =0;

        virtual bool blendingRequiresSecondarySlot() const { return false; }

        virtual bool supportsLayerUpdate() const { return false; }

        virtual void updateMasterStateSet( osg::StateSet* stateSet, const TextureLayout& layout ) const { }

        virtual GeoImage prepareImage( const GeoImage& image, const GeoExtent& tileExtent ) const { return image; }

        virtual GeoImage prepareSecondaryImage( const GeoImage& image, const GeoExtent& tileExtent ) const { return image; }

        virtual void applyLayerUpdate( osg::StateSet* stateSet, UID layerUID, const GeoImage& preparedImage, const TileKey& tileKey, const TextureLayout& layout, osg::StateSet* parentStateSet ) const { }

        virtual void applyLayerRemoval( osg::StateSet* stateSet, UID layerUID ) const { }

        virtual osg::Shader* createSamplerFunction( 
            UID layerUID, 
            const std::string& functionName, 
            osg::Shader::Type type, 
            const TextureLayout& layout ) const { return 0L; }
    };

    //-----------------------------------------------------------------------

    class OSGEARTH_EXPORT TextureCompositor : public osg::Referenced
    {
    public:
        TextureCompositor( const TerrainOptions& options );

        const TerrainOptions::CompositingTechnique& getTechnique() const { return _tech; }

        void applyMapModelChange( const MapModelChange& change );

        bool supportsLayerUpdate() const;

        GeoImage prepareImage( const GeoImage& image, const GeoExtent& tileExtent ) const;

        GeoImage prepareSecondaryImage( const GeoImage& image, const GeoExtent& tileExtent ) const;

        void applyLayerUpdate(
            osg::StateSet*  stateSet,
            UID             layerUID,
            const GeoImage& preparedImage,
            const TileKey&  tileKey,
            osg::StateSet*  parentStateSet ) const;

        void applyLayerRemoval( osg::StateSet* stateSet, UID layerUID ) const;

        void assignTexCoordArray(
            osg::Geometry*  geom,
            UID             layerUID,
            osg::Vec2Array* texCoords ) const;

        bool requiresUnitTextureSpace() const;

        bool usesShaderComposition() const;

        void updateMasterStateSet( osg::StateSet* stateSet ) const;

        bool reserveTextureImageUnit( int& out_unit );

        void releaseTextureImageUnit( int unit );

        int getRenderOrder( UID layerUID ) const;

        osg::Shader* createSamplerFunction( UID layerUID, const std::string& functionName, osg::Shader::Type type ) const;

        TerrainOptions& getOptions() { return _options;}

    private:
        void init();

        OpenThreads::Mutex                       _initMutex;
        TerrainOptions::CompositingTechnique     _tech;
        TerrainOptions                           _options;
        bool                                     _forceTech;
        osg::ref_ptr<osg::Program>               _program;
        osg::ref_ptr<TextureCompositorTechnique> _impl;

        TextureLayout _layout;
        Threading::ReadWriteMutex _layoutMutex;

        std::set<int> _reservedUnits;
    };
}

#endif // OSGEARTH_TEXTURE_COMPOSITOR_H