/*
Open Asset Import Library (assimp)
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*/

/** @file  MakeLeftHandedProcess.h
 *  @brief Defines a bunch of post-processing steps to handle
 *    coordinate system conversions.
 *
 *  - LH to RH
 *  - UV origin upper-left to lower-left
 *  - face order cw to ccw
 */
#ifndef AI_CONVERTTOLHPROCESS_H_INC
#define AI_CONVERTTOLHPROCESS_H_INC

#include <assimp/types.h>

#include "Common/BaseProcess.h"

struct aiMesh;
struct aiNodeAnim;
struct aiNode;
struct aiMaterial;
struct aiCamera;

namespace Assimp    {

// -----------------------------------------------------------------------------------
/** @brief The MakeLeftHandedProcess converts all imported data to a left-handed
 *   coordinate system.
 *
 * This implies a mirroring of the Z axis of the coordinate system. But to keep
 * transformation matrices free from reflections we shift the reflection to other
 * places. We mirror the meshes and adapt the rotations.
 *
 * @note RH-LH and LH-RH is the same, so this class can be used for both
 */
class MakeLeftHandedProcess : public BaseProcess {
public:
    MakeLeftHandedProcess() = default;
    ~MakeLeftHandedProcess() override = default;

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

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

protected:
    // -------------------------------------------------------------------
    /** Recursively converts a node and all of its children
     */
    void ProcessNode( aiNode* pNode, const aiMatrix4x4& pParentGlobalRotation);

    // -------------------------------------------------------------------
    /** Converts a single mesh to left handed coordinates.
     * This means that positions, normals and tangents are mirrored at
     * the local Z axis and the order of all faces are inverted.
     * @param pMesh The mesh to convert.
     */
    void ProcessMesh( aiMesh* pMesh);

    // -------------------------------------------------------------------
    /** Converts a single material to left-handed coordinates
     * @param pMat Material to convert
     */
    void ProcessMaterial( aiMaterial* pMat);

    // -------------------------------------------------------------------
    /** Converts the given animation to LH coordinates.
     * The rotation and translation keys are transformed, the scale keys
     * work in local space and can therefore be left untouched.
     * @param pAnim The bone animation to transform
     */
    void ProcessAnimation( aiNodeAnim* pAnim);

    // -------------------------------------------------------------------
    /** Converts a single camera to left handed coordinates.
     * The camera viewing direction is inverted by reflecting mLookAt
     * across mPosition.
     * @param pCam The camera to convert
     */
    void ProcessCamera( aiCamera* pCam);
};


// ---------------------------------------------------------------------------
/** Postprocessing step to flip the face order of the imported data
 */
class FlipWindingOrderProcess : public BaseProcess {
    friend class Importer;

public:
    /** Constructor to be privately used by Importer */
    FlipWindingOrderProcess() = default;

    /** Destructor, private as well */
    ~FlipWindingOrderProcess() override = default;

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

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

    /** Some other types of post-processing require winding order flips */
    static void ProcessMesh( aiMesh* pMesh);
};

// ---------------------------------------------------------------------------
/** Postprocessing step to flip the UV coordinate system of the import data
 */
class FlipUVsProcess : public BaseProcess
{
    friend class Importer;

public:
    /** Constructor to be privately used by Importer */
    FlipUVsProcess();

    /** Destructor, private as well */
    ~FlipUVsProcess();

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

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

protected:
    void ProcessMesh( aiMesh* pMesh);
    void ProcessMaterial( aiMaterial* mat);
};

} // end of namespace Assimp

#endif // AI_CONVERTTOLHPROCESS_H_INC
