/*
Open Asset Import Library (assimp)
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*/

/** @file  OptimizeMeshes.h
 *  @brief Declares a post processing step to join meshes, if possible
 */
#ifndef AI_OPTIMIZEMESHESPROCESS_H_INC
#define AI_OPTIMIZEMESHESPROCESS_H_INC

#include "Common/BaseProcess.h"

#include <assimp/types.h>

#include <vector>

struct aiMesh;
struct aiNode;
class OptimizeMeshesProcessTest;

namespace Assimp {

// ---------------------------------------------------------------------------
/** @brief Postprocessing step to optimize mesh usage
 *
 *  The implementation looks for meshes that could be joined and joins them.
 *  Usually this will reduce the number of drawcalls.
 *
 *  @note Instanced meshes are currently not processed.
 */
class OptimizeMeshesProcess : public BaseProcess {
public:
    // -------------------------------------------------------------------
    /// The default class constructor / destructor.
    OptimizeMeshesProcess();
    ~OptimizeMeshesProcess() override = default;

    /** @brief Internal utility to store additional mesh info
     */
    struct MeshInfo {
        MeshInfo() AI_NO_EXCEPT
        : instance_cnt(0)
        , vertex_format(0)
        , output_id(0xffffffff) {
            // empty
        }

        //! Number of times this mesh is referenced
        unsigned int instance_cnt;

        //! Vertex format id
        unsigned int vertex_format;

        //! Output ID
        unsigned int output_id;
    };

    // -------------------------------------------------------------------
    bool IsActive( unsigned int pFlags) const override;

    // -------------------------------------------------------------------
    void Execute( aiScene* pScene) override;

    // -------------------------------------------------------------------
    void SetupProperties(const Importer* pImp) override;

    // -------------------------------------------------------------------
    /** @brief Specify whether you want meshes with different
     *   primitive types to be merged as well.
     *
     *  IsActive() sets this property automatically to true if the
     *  aiProcess_SortByPType flag is found.
     */
    void EnablePrimitiveTypeSorting(bool enable) {
        pts = enable;
    }

    // Getter
    bool IsPrimitiveTypeSortingEnabled () const {
        return pts;
    }


    // -------------------------------------------------------------------
    /** @brief Specify a maximum size of a single output mesh.
     *
     *  If a single input mesh already exceeds this limit, it won't
     *  be split.
     *  @param verts Maximum number of vertices per mesh
     *  @param faces Maximum number of faces per mesh
     */
    void SetPreferredMeshSizeLimit (unsigned int verts, unsigned int faces)
    {
        max_verts = verts;
        max_faces = faces;
    }


protected:

    // -------------------------------------------------------------------
    /** @brief Do the actual optimization on all meshes of this node
     *  @param pNode Node we're working with
     */
    void ProcessNode( aiNode* pNode);

    // -------------------------------------------------------------------
    /** @brief Returns true if b can be joined with a
     *
     *  @param verts Number of output verts up to now
     *  @param faces Number of output faces up to now
     */
    bool CanJoin ( unsigned int a, unsigned int b,
        unsigned int verts, unsigned int faces );

    // -------------------------------------------------------------------
    /** @brief Find instanced meshes, for the moment we're excluding
     *   them from all optimizations
     */
    void FindInstancedMeshes (aiNode* pNode);

private:

    //! Scene we're working with
    aiScene* mScene;

    //! Per mesh info
    std::vector<MeshInfo> meshes;

    //! Output meshes
    std::vector<aiMesh*> output;

    //! @see EnablePrimitiveTypeSorting
    mutable bool pts;

    //! @see SetPreferredMeshSizeLimit
    mutable unsigned int max_verts,max_faces;

    //! Temporary storage
    std::vector<aiMesh*> merge_list;
};

} // end of namespace Assimp

#endif // AI_CALCTANGENTSPROCESS_H_INC
