/*
Open Asset Import Library (assimp)
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  following disclaimer.

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*/

/** @file Definition of a helper step that processes texture transformations */
#ifndef AI_TEXTURE_TRANSFORM_H_INCLUDED
#define AI_TEXTURE_TRANSFORM_H_INCLUDED

#include "Common/BaseProcess.h"

#include <assimp/BaseImporter.h>
#include <assimp/material.h>
#include <list>

struct aiNode;
struct aiMaterial;

namespace Assimp {

#define AI_TT_UV_IDX_LOCK_TBD   0xffffffff
#define AI_TT_UV_IDX_LOCK_NONE  0xeeeeeeee
#define AI_TT_ROTATION_EPSILON  ((float)AI_DEG_TO_RAD(0.5))

// ---------------------------------------------------------------------------
/** 
 * @brief Small helper structure representing a shortcut into the material list
 *        to be able to update some values quickly.
 */
struct TTUpdateInfo {
    //! Direct shortcut, if available
    unsigned int* directShortcut = nullptr;

    //! Material
    aiMaterial *mat = nullptr;

    //! Texture type
    unsigned int semantic = 0;

    //! Texture index
    unsigned int index = 0;
};

// ---------------------------------------------------------------------------
/** 
 * @brief  Helper class representing texture coordinate transformations
 */
struct STransformVecInfo : public aiUVTransform {
    //! Source texture coordinate index
    unsigned int uvIndex = 0;

    //! Texture mapping mode in the u direction
    aiTextureMapMode mapU = aiTextureMapMode_Wrap;

    //! Texture mapping mode in the v direction
    aiTextureMapMode mapV = aiTextureMapMode_Wrap;

    //! Locked destination UV index
    //! AI_TT_UV_IDX_LOCK_TBD - to be determined
    //! AI_TT_UV_IDX_LOCK_NONE - none (default)
    unsigned int lockedPos = AI_TT_UV_IDX_LOCK_NONE;

    //! Update info - shortcuts into all materials
    //! that are referencing this transform setup
    std::list<TTUpdateInfo> updateList;

    inline bool operator== (const STransformVecInfo& other) const {
        // We use a small epsilon here
        const static float epsilon = 0.05f;

        if (std::fabs( mTranslation.x - other.mTranslation.x ) > epsilon ||
                std::fabs( mTranslation.y - other.mTranslation.y ) > epsilon) {
            return false;
        }

        if (std::fabs( mScaling.x - other.mScaling.x ) > epsilon ||
                std::fabs( mScaling.y - other.mScaling.y ) > epsilon) {
            return false;
        }

        if (std::fabs( mRotation - other.mRotation) > epsilon) {
            return false;
        }
        return true;
    }

    inline bool operator!= (const STransformVecInfo& other) const {
            return !(*this == other);
    }

    // -------------------------------------------------------------------
    /** 
     * @brief Returns whether this is an untransformed texture coordinate set
     */
    inline bool IsUntransformed() const {
        return (1.0f == mScaling.x && 1.f == mScaling.y &&
            !mTranslation.x && !mTranslation.y && mRotation < AI_TT_ROTATION_EPSILON);
    }

    // -------------------------------------------------------------------
    /** 
     * @brief Build a 3x3 matrix from the transformations
     */
    inline void GetMatrix(aiMatrix3x3& mOut) {
        mOut = aiMatrix3x3();
        if (1.0f != mScaling.x || 1.0f != mScaling.y) {
            aiMatrix3x3 mScale;
            mScale.a1 = mScaling.x;
            mScale.b2 = mScaling.y;
            mOut = mScale;
        }
        if (mRotation) {
            aiMatrix3x3 mRot;
            mRot.a1 = mRot.b2 = std::cos(mRotation);
            mRot.a2 = mRot.b1 = std::sin(mRotation);
            mRot.a2 = -mRot.a2;
            mOut *= mRot;
        }
        if (mTranslation.x || mTranslation.y) {
            aiMatrix3x3 mTrans;
            mTrans.a3 = mTranslation.x;
            mTrans.b3 = mTranslation.y;
            mOut *= mTrans;
        }
    }
};

// ---------------------------------------------------------------------------
/** 
 * @brief Helper step to compute final UV coordinate sets if there are scalings
 *  or rotations in the original data read from the file.
 */
class TextureTransformStep final : public BaseProcess {
public:
    // -------------------------------------------------------------------
    /// The default class constructor. / 
    TextureTransformStep() = default;

    /// The default class destructor.
    ~TextureTransformStep() override = default;

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

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

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

protected:
    // -------------------------------------------------------------------
    /** 
     * @brief Preprocess a specific UV transformation setup
     *
     *  @param info Transformation setup to be preprocessed.
     */
    void PreProcessUVTransform(STransformVecInfo& info);

private:
    unsigned int configFlags;
};

} // namespace Assimp

#endif //! AI_TEXTURE_TRANSFORM_H_INCLUDED