#ifndef OGRE_FROXELIZER_H

#define OGRE_FROXELIZER_H

#include "OgreLight.h"

#include "OgrePrerequisites.h"

#include "OgreVector.h"

#include <vector>

namespace Ogre

{

/** Builds a frustum-voxel ("froxel") grid for the active camera and bins

    lights into it, in the style of Filament's Froxelizer. The result feeds

    two GPU buffers (grid + records) consumed by clustered shading. */

struct Froxelizer

{

    Froxelizer() = default;

    /// Rebuild the layout

    void updateLayout(const Camera* cam, const Viewport* viewport);

    /// bin the lights into the froxel grid

    /// @return true if the light binning was updated

    bool binLights(const Camera* cam, const LightList& lights);

    // shader-facing scalars

    const Vector4f& getTileParams() const { return mTileParams; } // (countX, countY, yFix, tileSizePx)

    const Vector4f& getDepthParams() const { return mDepthParams; } // (scaleZ, biasZ, linZ, sliceCount)

    // GPU buffer data

    const std::vector<uint32>& getGrid() const { return mGrid; }      // (offset << 8) | count per froxel

    const std::vector<uint32>& getRecords() const { return mRecords; } // flat light-index list

    enum : uint32

    {

        /// 4096 froxels fit in a 16 KiB buffer, the minimum guaranteed in GLES 3.x and Vulkan 1.1

        MAX_FROXELS = 4096,

        MAX_FROXEL_SLICES = 16,

        /// 16384 light indices (uint8) fit in a 16 KiB buffer

        MAX_FROXEL_RECORDS = 16384,

        MAX_LIGHTS = 255 ///< @note stored as uint8 in the froxel records

    };

private:

    void rebuildLayout(const Viewport* viewport);

    void updateDepthParams(const Camera* cam);

    int findSliceZ(float viewSpaceZ) const;

    int mLastWidth = 0, mLastHeight = 0;

    float mZLightNear = 0.0f, mZLightFar = 0.0f;

    uint32 mLastHash = 0;

    Vector4f mTileParams = Vector4f(0);

    Vector4f mDepthParams = Vector4f(0);

    // fixed 4096 entries: (offset << 8) | count

    std::vector<uint32> mGrid;

    // one byte per light index (max 255 lights), packed into words

    std::vector<uint32> mRecords;

    // temporary per-froxel light lists

    std::vector<std::vector<uint8>> mFroxelLights;

};

} // namespace Ogre

#endif