/*
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Open Asset Import Library (assimp)
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*/

/** @file mesh.h
 *  @brief Declares the data structures in which the imported geometry is
    returned by ASSIMP: aiMesh, aiFace and aiBone data structures.
 */
#pragma once
#ifndef AI_MESH_H_INC
#define AI_MESH_H_INC

#ifdef __GNUC__
#pragma GCC system_header
#endif

#ifdef _MSC_VER
#pragma warning(disable : 4351)
#endif // _MSC_VER

#include <assimp/aabb.h>
#include <assimp/types.h>

#ifdef __cplusplus
#include <unordered_set>

extern "C" {
#endif

// ---------------------------------------------------------------------------
// Limits. These values are required to match the settings Assimp was
// compiled against. Therefore, do not redefine them unless you build the
// library from source using the same definitions.
// ---------------------------------------------------------------------------

/** @def AI_MAX_FACE_INDICES
 *  Maximum number of indices per face (polygon). */

#ifndef AI_MAX_FACE_INDICES
#define AI_MAX_FACE_INDICES 0x7fff
#endif

/** @def AI_MAX_BONE_WEIGHTS
 *  Maximum number of indices per face (polygon). */

#ifndef AI_MAX_BONE_WEIGHTS
#define AI_MAX_BONE_WEIGHTS 0x7fffffff
#endif

/** @def AI_MAX_VERTICES
 *  Maximum number of vertices per mesh.  */

#ifndef AI_MAX_VERTICES
#define AI_MAX_VERTICES 0x7fffffff
#endif

/** @def AI_MAX_FACES
 *  Maximum number of faces per mesh. */

#ifndef AI_MAX_FACES
#define AI_MAX_FACES 0x7fffffff
#endif

/** @def AI_MAX_NUMBER_OF_COLOR_SETS
 *  Supported number of vertex color sets per mesh. */

#ifndef AI_MAX_NUMBER_OF_COLOR_SETS
#define AI_MAX_NUMBER_OF_COLOR_SETS 0x8
#endif // !! AI_MAX_NUMBER_OF_COLOR_SETS

/** @def AI_MAX_NUMBER_OF_TEXTURECOORDS
 *  Supported number of texture coord sets (UV(W) channels) per mesh */

#ifndef AI_MAX_NUMBER_OF_TEXTURECOORDS
#define AI_MAX_NUMBER_OF_TEXTURECOORDS 0x8
#endif // !! AI_MAX_NUMBER_OF_TEXTURECOORDS

// ---------------------------------------------------------------------------
/**
 * @brief A single face in a mesh, referring to multiple vertices.
 *
 * If mNumIndices is 3, we call the face 'triangle', for mNumIndices > 3
 * it's called 'polygon' (hey, that's just a definition!).
 * <br>
 * aiMesh::mPrimitiveTypes can be queried to quickly examine which types of
 * primitive are actually present in a mesh. The #aiProcess_SortByPType flag
 * executes a special post-processing algorithm which splits meshes with
 * *different* primitive types mixed up (e.g. lines and triangles) in several
 * 'clean' sub-meshes. Furthermore there is a configuration option (
 * #AI_CONFIG_PP_SBP_REMOVE) to force #aiProcess_SortByPType to remove
 * specific kinds of primitives from the imported scene, completely and forever.
 * In many cases you'll probably want to set this setting to
 * @code
 * aiPrimitiveType_LINE|aiPrimitiveType_POINT
 * @endcode
 * Together with the #aiProcess_Triangulate flag you can then be sure that
 * #aiFace::mNumIndices is always 3.
 * @note Take a look at the @link data Data Structures page @endlink for
 * more information on the layout and winding order of a face.
 */
struct aiFace {
    //! Number of indices defining this face.
    //! The maximum value for this member is #AI_MAX_FACE_INDICES.
    unsigned int mNumIndices;

    //! Pointer to the indices array. Size of the array is given in numIndices.
    unsigned int *mIndices;

#ifdef __cplusplus

    //! @brief Default constructor.
    aiFace() AI_NO_EXCEPT
            : mNumIndices(0),
              mIndices(nullptr) {
        // empty
    }

    //! @brief Default destructor. Delete the index array
    ~aiFace() {
        delete[] mIndices;
    }

    //! @brief Copy constructor. Copy the index array
    aiFace(const aiFace &o) :
            mNumIndices(0), mIndices(nullptr) {
        *this = o;
    }

    //! @brief Assignment operator. Copy the index array
    aiFace &operator=(const aiFace &o) {
        if (&o == this) {
            return *this;
        }

        delete[] mIndices;
        mNumIndices = o.mNumIndices;
        if (mNumIndices) {
            mIndices = new unsigned int[mNumIndices];
            ::memcpy(mIndices, o.mIndices, mNumIndices * sizeof(unsigned int));
        } else {
            mIndices = nullptr;
        }

        return *this;
    }

    //! @brief Comparison operator. Checks whether the index array of two faces is identical.
    bool operator==(const aiFace &o) const {
        if (mIndices == o.mIndices) {
            return true;
        }

        if (nullptr != mIndices && mNumIndices != o.mNumIndices) {
            return false;
        }

        if (nullptr == mIndices) {
            return false;
        }

        for (unsigned int i = 0; i < this->mNumIndices; ++i) {
            if (mIndices[i] != o.mIndices[i]) {
                return false;
            }
        }

        return true;
    }

    //! @brief Inverse comparison operator. Checks whether the index
    //! array of two faces is NOT identical
    bool operator!=(const aiFace &o) const {
        return !(*this == o);
    }
#endif // __cplusplus
}; // struct aiFace

// ---------------------------------------------------------------------------
/** @brief A single influence of a bone on a vertex.
 */
struct aiVertexWeight {
    //! Index of the vertex which is influenced by the bone.
    unsigned int mVertexId;

    //! The strength of the influence in the range (0...1).
    //! The influence from all bones at one vertex amounts to 1.
    ai_real mWeight;

#ifdef __cplusplus

    //! @brief Default constructor
    aiVertexWeight() AI_NO_EXCEPT
            : mVertexId(0),
              mWeight(0.0f) {
        // empty
    }

    //! @brief Initialization from a given index and vertex weight factor
    //! \param pID ID
    //! \param pWeight Vertex weight factor
    aiVertexWeight(unsigned int pID, float pWeight) :
            mVertexId(pID), mWeight(pWeight) {
        // empty
    }

    bool operator==(const aiVertexWeight &rhs) const {
        return (mVertexId == rhs.mVertexId && mWeight == rhs.mWeight);
    }

    bool operator!=(const aiVertexWeight &rhs) const {
        return (*this == rhs);
    }

#endif // __cplusplus
};

// Forward declare aiNode (pointer use only)
struct aiNode;

// ---------------------------------------------------------------------------
/** @brief A single bone of a mesh.
 *
 *  A bone has a name by which it can be found in the frame hierarchy and by
 *  which it can be addressed by animations. In addition it has a number of
 *  influences on vertices, and a matrix relating the mesh position to the
 *  position of the bone at the time of binding.
 */
struct aiBone {
    /**
     * The name of the bone.
     */
    C_STRUCT aiString mName;

    /**
     * The number of vertices affected by this bone.
     * The maximum value for this member is #AI_MAX_BONE_WEIGHTS.
     */
    unsigned int mNumWeights;

#ifndef ASSIMP_BUILD_NO_ARMATUREPOPULATE_PROCESS
    /**
     * The bone armature node - used for skeleton conversion
     * you must enable aiProcess_PopulateArmatureData to populate this
     */
    C_STRUCT aiNode *mArmature;

    /**
     * The bone node in the scene - used for skeleton conversion
     * you must enable aiProcess_PopulateArmatureData to populate this
     */
    C_STRUCT aiNode *mNode;

#endif
    /**
     * The influence weights of this bone, by vertex index.
     */
    C_STRUCT aiVertexWeight *mWeights;

    /**
     * Matrix that transforms from mesh space to bone space in bind pose.
     *
     * This matrix describes the position of the mesh
     * in the local space of this bone when the skeleton was bound.
     * Thus it can be used directly to determine a desired vertex position,
     * given the world-space transform of the bone when animated,
     * and the position of the vertex in mesh space.
     *
     * It is sometimes called an inverse-bind matrix,
     * or inverse bind pose matrix.
     */
    C_STRUCT aiMatrix4x4 mOffsetMatrix;

#ifdef __cplusplus

    ///	@brief  Default constructor
    aiBone() AI_NO_EXCEPT
            : mName(),
              mNumWeights(0),
#ifndef ASSIMP_BUILD_NO_ARMATUREPOPULATE_PROCESS
              mArmature(nullptr),
              mNode(nullptr),
#endif
              mWeights(nullptr),
              mOffsetMatrix() {
        // empty
    }

    /// @brief  Copy constructor
    aiBone(const aiBone &other) :
            mName(other.mName),
            mNumWeights(other.mNumWeights),
#ifndef ASSIMP_BUILD_NO_ARMATUREPOPULATE_PROCESS
              mArmature(nullptr),
              mNode(nullptr),
#endif
            mWeights(nullptr),
            mOffsetMatrix(other.mOffsetMatrix) {
        copyVertexWeights(other);
    }

    void copyVertexWeights( const aiBone &other ) {
        if (other.mWeights == nullptr || other.mNumWeights == 0) {
            mWeights = nullptr;
            mNumWeights = 0;
            return;
        }

        mNumWeights = other.mNumWeights;
        if (mWeights) {
            delete[] mWeights;
        }

        mWeights = new aiVertexWeight[mNumWeights];
        ::memcpy(mWeights, other.mWeights, mNumWeights * sizeof(aiVertexWeight));
    }

    //! @brief Assignment operator
    aiBone &operator = (const aiBone &other) {
        if (this == &other) {
            return *this;
        }

        mName = other.mName;
        mNumWeights = other.mNumWeights;
        mOffsetMatrix = other.mOffsetMatrix;
        copyVertexWeights(other);

        return *this;
    }

    /// @brief Compare operator.
    bool operator==(const aiBone &rhs) const {
        if (mName != rhs.mName || mNumWeights != rhs.mNumWeights ) {
            return false;
        }

        for (size_t i = 0; i < mNumWeights; ++i) {
            if (mWeights[i] != rhs.mWeights[i]) {
                return false;
            }
        }

        return true;
    }
    //! @brief Destructor - deletes the array of vertex weights
    ~aiBone() {
        delete[] mWeights;
    }
#endif // __cplusplus
};

// ---------------------------------------------------------------------------
/** @brief Enumerates the types of geometric primitives supported by Assimp.
 *
 *  @see aiFace Face data structure
 *  @see aiProcess_SortByPType Per-primitive sorting of meshes
 *  @see aiProcess_Triangulate Automatic triangulation
 *  @see AI_CONFIG_PP_SBP_REMOVE Removal of specific primitive types.
 */
enum aiPrimitiveType {
    /**
     * @brief A point primitive.
     *
     * This is just a single vertex in the virtual world,
     * #aiFace contains just one index for such a primitive.
     */
    aiPrimitiveType_POINT = 0x1,

    /**
     * @brief A line primitive.
     *
     * This is a line defined through a start and an end position.
     * #aiFace contains exactly two indices for such a primitive.
     */
    aiPrimitiveType_LINE = 0x2,

    /**
     * @brief A triangular primitive.
     *
     * A triangle consists of three indices.
     */
    aiPrimitiveType_TRIANGLE = 0x4,

    /**
     * @brief A higher-level polygon with more than 3 edges.
     *
     * A triangle is a polygon, but polygon in this context means
     * "all polygons that are not triangles". The "Triangulate"-Step
     * is provided for your convenience, it splits all polygons in
     * triangles (which are much easier to handle).
     */
    aiPrimitiveType_POLYGON = 0x8,

    /**
     * @brief A flag to determine whether this triangles only mesh is NGON encoded.
     *
     * NGON encoding is a special encoding that tells whether 2 or more consecutive triangles
     * should be considered as a triangle fan. This is identified by looking at the first vertex index.
     * 2 consecutive triangles with the same 1st vertex index are part of the same
     * NGON.
     *
     * At the moment, only quads (concave or convex) are supported, meaning that polygons are 'seen' as
     * triangles, as usual after a triangulation pass.
     *
     * To get an NGON encoded mesh, please use the aiProcess_Triangulate post process.
     *
     * @see aiProcess_Triangulate
     * @link https://github.com/KhronosGroup/glTF/pull/1620
     */
    aiPrimitiveType_NGONEncodingFlag = 0x10,

    /**
     * This value is not used. It is just here to force the
     * compiler to map this enum to a 32 Bit integer.
     */
#ifndef SWIG
    _aiPrimitiveType_Force32Bit = INT_MAX
#endif
}; //! enum aiPrimitiveType

// Get the #aiPrimitiveType flag for a specific number of face indices
#define AI_PRIMITIVE_TYPE_FOR_N_INDICES(n) \
    ((n) > 3 ? aiPrimitiveType_POLYGON : (aiPrimitiveType)(1u << ((n)-1)))

// ---------------------------------------------------------------------------
/** @brief An AnimMesh is an attachment to an #aiMesh stores per-vertex
 *  animations for a particular frame.
 *
 *  You may think of an #aiAnimMesh as a `patch` for the host mesh, which
 *  replaces only certain vertex data streams at a particular time.
 *  Each mesh stores n attached attached meshes (#aiMesh::mAnimMeshes).
 *  The actual relationship between the time line and anim meshes is
 *  established by #aiMeshAnim, which references singular mesh attachments
 *  by their ID and binds them to a time offset.
*/
struct aiAnimMesh {
    /**Anim Mesh name */
    C_STRUCT aiString mName;

    /** Replacement for aiMesh::mVertices. If this array is non-nullptr,
     *  it *must* contain mNumVertices entries. The corresponding
     *  array in the host mesh must be non-nullptr as well - animation
     *  meshes may neither add or nor remove vertex components (if
     *  a replacement array is nullptr and the corresponding source
     *  array is not, the source data is taken instead)*/
    C_STRUCT aiVector3D *mVertices;

    /** Replacement for aiMesh::mNormals.  */
    C_STRUCT aiVector3D *mNormals;

    /** Replacement for aiMesh::mTangents. */
    C_STRUCT aiVector3D *mTangents;

    /** Replacement for aiMesh::mBitangents. */
    C_STRUCT aiVector3D *mBitangents;

    /** Replacement for aiMesh::mColors */
    C_STRUCT aiColor4D *mColors[AI_MAX_NUMBER_OF_COLOR_SETS];

    /** Replacement for aiMesh::mTextureCoords */
    C_STRUCT aiVector3D *mTextureCoords[AI_MAX_NUMBER_OF_TEXTURECOORDS];

    /** The number of vertices in the aiAnimMesh, and thus the length of all
     * the member arrays.
     *
     * This has always the same value as the mNumVertices property in the
     * corresponding aiMesh. It is duplicated here merely to make the length
     * of the member arrays accessible even if the aiMesh is not known, e.g.
     * from language bindings.
     */
    unsigned int mNumVertices;

    /**
     * Weight of the AnimMesh.
     */
    float mWeight;

#ifdef __cplusplus
    /// @brief  The class constructor.
    aiAnimMesh() AI_NO_EXCEPT :
            mVertices(nullptr),
            mNormals(nullptr),
            mTangents(nullptr),
            mBitangents(nullptr),
            mColors {nullptr},
            mTextureCoords{nullptr},
            mNumVertices(0),
            mWeight(0.0f) {
        // empty
    }

    /// @brief The class destructor.
    ~aiAnimMesh() {
        delete[] mVertices;
        delete[] mNormals;
        delete[] mTangents;
        delete[] mBitangents;
        for (unsigned int a = 0; a < AI_MAX_NUMBER_OF_TEXTURECOORDS; a++) {
            delete[] mTextureCoords[a];
        }
        for (unsigned int a = 0; a < AI_MAX_NUMBER_OF_COLOR_SETS; a++) {
            delete[] mColors[a];
        }
    }

    /**
     *  @brief Check whether the anim-mesh overrides the vertex positions
     *         of its host mesh.
     *  @return true if positions are stored, false if not.
     */
    bool HasPositions() const {
        return mVertices != nullptr;
    }

    /**
     *  @brief Check whether the anim-mesh overrides the vertex normals
     *         of its host mesh
     *  @return true if normals are stored, false if not.
     */
    bool HasNormals() const {
        return mNormals != nullptr;
    }

    /**
     *  @brief Check whether the anim-mesh overrides the vertex tangents
     *         and bitangents of its host mesh. As for aiMesh,
     *         tangents and bitangents always go together.
     *  @return true if tangents and bi-tangents are stored, false if not.
     */
    bool HasTangentsAndBitangents() const {
        return mTangents != nullptr;
    }

    /**
     *  @brief Check whether the anim mesh overrides a particular
     *         set of vertex colors on his host mesh.
     *  @param pIndex 0<index<AI_MAX_NUMBER_OF_COLOR_SETS
     *  @return true if vertex colors are stored, false if not.
     */

    bool HasVertexColors(unsigned int pIndex) const {
        return pIndex >= AI_MAX_NUMBER_OF_COLOR_SETS ? false : mColors[pIndex] != nullptr;
    }

    /**
     *  @brief Check whether the anim mesh overrides a particular
     *        set of texture coordinates on his host mesh.
     *  @param pIndex 0<index<AI_MAX_NUMBER_OF_TEXTURECOORDS
     *  @return true if texture coordinates are stored, false if not.
     */
    bool HasTextureCoords(unsigned int pIndex) const {
        return pIndex >= AI_MAX_NUMBER_OF_TEXTURECOORDS ? false : mTextureCoords[pIndex] != nullptr;
    }

#endif
};

// ---------------------------------------------------------------------------
/** @brief Enumerates the methods of mesh morphing supported by Assimp.
 */
enum aiMorphingMethod {
    /** Morphing method to be determined */
    aiMorphingMethod_UNKNOWN = 0x0,

    /** Interpolation between morph targets */
    aiMorphingMethod_VERTEX_BLEND = 0x1,

    /** Normalized morphing between morph targets  */
    aiMorphingMethod_MORPH_NORMALIZED = 0x2,

    /** Relative morphing between morph targets  */
    aiMorphingMethod_MORPH_RELATIVE = 0x3,

/** This value is not used. It is just here to force the
     *  compiler to map this enum to a 32 Bit integer.
     */
#ifndef SWIG
    _aiMorphingMethod_Force32Bit = INT_MAX
#endif
}; //! enum aiMorphingMethod

// ---------------------------------------------------------------------------
/** @brief A mesh represents a geometry or model with a single material.
 *
 * It usually consists of a number of vertices and a series of primitives/faces
 * referencing the vertices. In addition there might be a series of bones, each
 * of them addressing a number of vertices with a certain weight. Vertex data
 * is presented in channels with each channel containing a single per-vertex
 * information such as a set of texture coordinates or a normal vector.
 * If a data pointer is non-null, the corresponding data stream is present.
 * From C++-programs you can also use the comfort functions Has*() to
 * test for the presence of various data streams.
 *
 * A Mesh uses only a single material which is referenced by a material ID.
 * @note The mPositions member is usually not optional. However, vertex positions
 * *could* be missing if the #AI_SCENE_FLAGS_INCOMPLETE flag is set in
 * @code
 * aiScene::mFlags
 * @endcode
 */
struct aiMesh {
    /**
     * Bitwise combination of the members of the #aiPrimitiveType enum.
     * This specifies which types of primitives are present in the mesh.
     * The "SortByPrimitiveType"-Step can be used to make sure the
     * output meshes consist of one primitive type each.
     */
    unsigned int mPrimitiveTypes;

    /**
     * The number of vertices in this mesh.
     * This is also the size of all of the per-vertex data arrays.
     * The maximum value for this member is #AI_MAX_VERTICES.
     */
    unsigned int mNumVertices;

    /**
     * The number of primitives (triangles, polygons, lines) in this  mesh.
     * This is also the size of the mFaces array.
     * The maximum value for this member is #AI_MAX_FACES.
     */
    unsigned int mNumFaces;

    /**
     * @brief Vertex positions.
     * 
     * This array is always present in a mesh. The array is
     * mNumVertices in size.
     */
    C_STRUCT aiVector3D *mVertices;

    /**
     * @brief Vertex normals.
     * 
     * The array contains normalized vectors, nullptr if not present.
     * The array is mNumVertices in size. Normals are undefined for
     * point and line primitives. A mesh consisting of points and
     * lines only may not have normal vectors. Meshes with mixed
     * primitive types (i.e. lines and triangles) may have normals,
     * but the normals for vertices that are only referenced by
     * point or line primitives are undefined and set to QNaN (WARN:
     * qNaN compares to inequal to *everything*, even to qNaN itself.
     * Using code like this to check whether a field is qnan is:
     * @code
     * #define IS_QNAN(f) (f != f)
     * @endcode
     * still dangerous because even 1.f == 1.f could evaluate to false! (
     * remember the subtleties of IEEE754 artithmetics). Use stuff like
     * @c fpclassify instead.
     * @note Normal vectors computed by Assimp are always unit-length.
     * However, this needn't apply for normals that have been taken
     * directly from the model file.
     */
    C_STRUCT aiVector3D *mNormals;

    /**
     * @brief Vertex tangents.
     * 
     * The tangent of a vertex points in the direction of the positive
     * X texture axis. The array contains normalized vectors, nullptr if
     * not present. The array is mNumVertices in size. A mesh consisting
     * of points and lines only may not have normal vectors. Meshes with
     * mixed primitive types (i.e. lines and triangles) may have
     * normals, but the normals for vertices that are only referenced by
     * point or line primitives are undefined and set to qNaN.  See
     * the #mNormals member for a detailed discussion of qNaNs.
     * @note If the mesh contains tangents, it automatically also
     * contains bitangents.
     */
    C_STRUCT aiVector3D *mTangents;

    /**
     * @brief Vertex bitangents.
     * 
     * The bitangent of a vertex points in the direction of the positive
     * Y texture axis. The array contains normalized vectors, nullptr if not
     * present. The array is mNumVertices in size.
     * @note If the mesh contains tangents, it automatically also contains
     * bitangents.
     */
    C_STRUCT aiVector3D *mBitangents;

    /**
     * @brief Vertex color sets.
     * 
     * A mesh may contain 0 to #AI_MAX_NUMBER_OF_COLOR_SETS vertex
     * colors per vertex. nullptr if not present. Each array is
     * mNumVertices in size if present.
     */
    C_STRUCT aiColor4D *mColors[AI_MAX_NUMBER_OF_COLOR_SETS];

    /**
     * @brief Vertex texture coordinates, also known as UV channels.
     * 
     * A mesh may contain 0 to AI_MAX_NUMBER_OF_TEXTURECOORDS channels per
     * vertex. Used and unused (nullptr) channels may go in any order.
     * The array is mNumVertices in size.
     */
    C_STRUCT aiVector3D *mTextureCoords[AI_MAX_NUMBER_OF_TEXTURECOORDS];

    /**
     * @brief Specifies the number of components for a given UV channel.
     * 
     * Up to three channels are supported (UVW, for accessing volume
     * or cube maps). If the value is 2 for a given channel n, the
     * component p.z of mTextureCoords[n][p] is set to 0.0f.
     * If the value is 1 for a given channel, p.y is set to 0.0f, too.
     * @note 4D coordinates are not supported
     */
    unsigned int mNumUVComponents[AI_MAX_NUMBER_OF_TEXTURECOORDS];

    /**
     * @brief The faces the mesh is constructed from.
     * 
     * Each face refers to a number of vertices by their indices.
     * This array is always present in a mesh, its size is given
     *  in mNumFaces. If the #AI_SCENE_FLAGS_NON_VERBOSE_FORMAT
     * is NOT set each face references an unique set of vertices.
     */
    C_STRUCT aiFace *mFaces;

    /**
    * The number of bones this mesh contains. Can be 0, in which case the mBones array is nullptr.
    */
    unsigned int mNumBones;

    /**
     * @brief The bones of this mesh.
     * 
     * A bone consists of a name by which it can be found in the
     * frame hierarchy and a set of vertex weights.
     */
    C_STRUCT aiBone **mBones;

    /**
     * @brief The material used by this mesh.
     * 
     * A mesh uses only a single material. If an imported model uses
     * multiple materials, the import splits up the mesh. Use this value
     * as index into the scene's material list.
     */
    unsigned int mMaterialIndex;

    /**
     *  Name of the mesh. Meshes can be named, but this is not a
     *  requirement and leaving this field empty is totally fine.
     *  There are mainly three uses for mesh names:
     *   - some formats name nodes and meshes independently.
     *   - importers tend to split meshes up to meet the
     *      one-material-per-mesh requirement. Assigning
     *      the same (dummy) name to each of the result meshes
     *      aids the caller at recovering the original mesh
     *      partitioning.
     *   - Vertex animations refer to meshes by their names.
     */
    C_STRUCT aiString mName;

    /**
     * The number of attachment meshes.
     * Currently known to work with loaders:
     * - Collada
     * - gltf
     */
    unsigned int mNumAnimMeshes;

    /**
     * Attachment meshes for this mesh, for vertex-based animation.
     * Attachment meshes carry replacement data for some of the
     * mesh'es vertex components (usually positions, normals).
     * Currently known to work with loaders:
     * - Collada
     * - gltf
     */
    C_STRUCT aiAnimMesh **mAnimMeshes;

    /**
     *  Method of morphing when anim-meshes are specified.
     *  @see aiMorphingMethod to learn more about the provided morphing targets.
     */
    enum aiMorphingMethod mMethod;

    /**
     *  The bounding box.
     */
    C_STRUCT aiAABB mAABB;

    /**
     * Vertex UV stream names. Pointer to array of size AI_MAX_NUMBER_OF_TEXTURECOORDS
     */
    C_STRUCT aiString **mTextureCoordsNames;

#ifdef __cplusplus

    //! The default class constructor.
    aiMesh() AI_NO_EXCEPT
            : mPrimitiveTypes(0),
              mNumVertices(0),
              mNumFaces(0),
              mVertices(nullptr),
              mNormals(nullptr),
              mTangents(nullptr),
              mBitangents(nullptr),
              mColors{nullptr},
              mTextureCoords{nullptr},
              mNumUVComponents{0},
              mFaces(nullptr),
              mNumBones(0),
              mBones(nullptr),
              mMaterialIndex(0),
              mNumAnimMeshes(0),
              mAnimMeshes(nullptr),
              mMethod(aiMorphingMethod_UNKNOWN),
              mAABB(),
              mTextureCoordsNames(nullptr) {
        // empty
    }

    //! @brief The class destructor.
    ~aiMesh() {
        delete[] mVertices;
        delete[] mNormals;
        delete[] mTangents;
        delete[] mBitangents;
        for (unsigned int a = 0; a < AI_MAX_NUMBER_OF_TEXTURECOORDS; a++) {
            delete[] mTextureCoords[a];
        }

        if (mTextureCoordsNames) {
            for (unsigned int a = 0; a < AI_MAX_NUMBER_OF_TEXTURECOORDS; a++) {
                delete mTextureCoordsNames[a];
            }
            delete[] mTextureCoordsNames;
        }

        for (unsigned int a = 0; a < AI_MAX_NUMBER_OF_COLOR_SETS; a++) {
            delete[] mColors[a];
        }

        // DO NOT REMOVE THIS ADDITIONAL CHECK
        if (mNumBones && mBones) {
            std::unordered_set<const aiBone *> bones;
            for (unsigned int a = 0; a < mNumBones; a++) {
                if (mBones[a]) {
                    bones.insert(mBones[a]);
                }
            }
            for (const aiBone *bone: bones) {
                delete bone;
            }
            delete[] mBones;
        }

        if (mNumAnimMeshes && mAnimMeshes) {
            for (unsigned int a = 0; a < mNumAnimMeshes; a++) {
                delete mAnimMeshes[a];
            }
            delete[] mAnimMeshes;
        }

        delete[] mFaces;
    }

    //! @brief Check whether the mesh contains positions. Provided no special
    //!        scene flags are set, this will always be true
    //! @return true, if positions are stored, false if not.
    bool HasPositions() const {
        return mVertices != nullptr && mNumVertices > 0;
    }

    //! @brief Check whether the mesh contains faces. If no special scene flags
    //!        are set this should always return true
    //! @return true, if faces are stored, false if not.
    bool HasFaces() const {
        return mFaces != nullptr && mNumFaces > 0;
    }

    //! @brief Check whether the mesh contains normal vectors
    //! @return true, if normals are stored, false if not.
    bool HasNormals() const {
        return mNormals != nullptr && mNumVertices > 0;
    }

    //! @brief Check whether the mesh contains tangent and bitangent vectors.
    //! 
    //! It is not possible that it contains tangents and no bitangents
    //! (or the other way round). The existence of one of them
    //! implies that the second is there, too.
    //! @return true, if tangents and bi-tangents are stored, false if not.
    bool HasTangentsAndBitangents() const {
        return mTangents != nullptr && mBitangents != nullptr && mNumVertices > 0;
    }

    //! @brief Check whether the mesh contains a vertex color set
    //! @param index    Index of the vertex color set
    //! @return true, if vertex colors are stored, false if not.
    bool HasVertexColors(unsigned int index) const {
        if (index >= AI_MAX_NUMBER_OF_COLOR_SETS) {
            return false;
        }
        return mColors[index] != nullptr && mNumVertices > 0;        
    }

    //! @brief Check whether the mesh contains a texture coordinate set
    //! @param index    Index of the texture coordinates set
    //! @return true, if texture coordinates are stored, false if not.
    bool HasTextureCoords(unsigned int index) const {
        if (index >= AI_MAX_NUMBER_OF_TEXTURECOORDS) {
            return false;
        }
        return (mTextureCoords[index] != nullptr && mNumVertices > 0);
    }

    //! @brief Get the number of UV channels the mesh contains.
    //! @return the number of stored uv-channels.
    unsigned int GetNumUVChannels() const {
        unsigned int n(0);
        for (unsigned i = 0; i < AI_MAX_NUMBER_OF_TEXTURECOORDS; i++) {
            if (mTextureCoords[i]) {
                ++n;
            }
        }

        return n;
    }

    //! @brief Get the number of vertex color channels the mesh contains.
    //! @return The number of stored color channels.
    unsigned int GetNumColorChannels() const {
        unsigned int n(0);
        while (n < AI_MAX_NUMBER_OF_COLOR_SETS && mColors[n]) {
            ++n;
        }
        return n;
    }

    //! @brief Check whether the mesh contains bones.
    //! @return true, if bones are stored.
    bool HasBones() const {
        return mBones != nullptr && mNumBones > 0;
    }

    //! @brief  Check whether the mesh contains a texture coordinate set name
    //! @param pIndex Index of the texture coordinates set
    //! @return true, if texture coordinates for the index exists.
    bool HasTextureCoordsName(unsigned int pIndex) const {
        if (mTextureCoordsNames == nullptr || pIndex >= AI_MAX_NUMBER_OF_TEXTURECOORDS) {
            return false;
        }
        return mTextureCoordsNames[pIndex] != nullptr;
    }

    //! @brief  Set a texture coordinate set name
    //! @param pIndex Index of the texture coordinates set
    //! @param texCoordsName name of the texture coordinate set
    void SetTextureCoordsName(unsigned int pIndex, const aiString &texCoordsName) {
        if (pIndex >= AI_MAX_NUMBER_OF_TEXTURECOORDS) {
            return;
        }

        if (mTextureCoordsNames == nullptr) {
            // Construct and null-init array
            mTextureCoordsNames = new aiString *[AI_MAX_NUMBER_OF_TEXTURECOORDS];
            for (size_t i=0; i<AI_MAX_NUMBER_OF_TEXTURECOORDS; ++i) {
                mTextureCoordsNames[i] = nullptr;
            }
        }

        if (texCoordsName.length == 0) {
            delete mTextureCoordsNames[pIndex];
            mTextureCoordsNames[pIndex] = nullptr;
            return;
        }

        if (mTextureCoordsNames[pIndex] == nullptr) {
            mTextureCoordsNames[pIndex] = new aiString(texCoordsName);
            return;
        }

        *mTextureCoordsNames[pIndex] = texCoordsName;
    }

    //! @brief  Get a texture coordinate set name
    //! @param  pIndex Index of the texture coordinates set
    //! @return The texture coordinate name.
    const aiString *GetTextureCoordsName(unsigned int index) const {
        if (mTextureCoordsNames == nullptr || index >= AI_MAX_NUMBER_OF_TEXTURECOORDS) {
            return nullptr;
        }

        return mTextureCoordsNames[index];
    }

#endif // __cplusplus
};

/**
 * @brief  A skeleton bone represents a single bone is a skeleton structure.
 *
 * Skeleton-Animations can be represented via a skeleton struct, which describes
 * a hierarchical tree assembled from skeleton bones. A bone is linked to a mesh.
 * The bone knows its parent bone. If there is no parent bone the parent id is
 * marked with -1.
 * The skeleton-bone stores a pointer to its used armature. If there is no
 * armature this value if set to nullptr.
 * A skeleton bone stores its offset-matrix, which is the absolute transformation
 * for the bone. The bone stores the locale transformation to its parent as well.
 * You can compute the offset matrix by multiplying the hierarchy like:
 * Tree: s1 -> s2 -> s3
 * Offset-Matrix s3 = locale-s3 * locale-s2 * locale-s1
 */
struct aiSkeletonBone {
    /// The parent bone index, is -1 one if this bone represents the root bone.
    int mParent;


#ifndef ASSIMP_BUILD_NO_ARMATUREPOPULATE_PROCESS
    /// @brief The bone armature node - used for skeleton conversion
    /// you must enable aiProcess_PopulateArmatureData to populate this
    C_STRUCT aiNode *mArmature;

    /// @brief The bone node in the scene - used for skeleton conversion
    /// you must enable aiProcess_PopulateArmatureData to populate this
    C_STRUCT aiNode *mNode;

#endif
    /// @brief The number of weights
    unsigned int mNumnWeights;

    /// The mesh index, which will get influenced by the weight.
    C_STRUCT aiMesh *mMeshId;

    /// The influence weights of this bone, by vertex index.
    C_STRUCT aiVertexWeight *mWeights;

    /** Matrix that transforms from bone space to mesh space in bind pose.
     *
     * This matrix describes the position of the mesh
     * in the local space of this bone when the skeleton was bound.
     * Thus it can be used directly to determine a desired vertex position,
     * given the world-space transform of the bone when animated,
     * and the position of the vertex in mesh space.
     *
     * It is sometimes called an inverse-bind matrix,
     * or inverse bind pose matrix.
     */
    C_STRUCT aiMatrix4x4 mOffsetMatrix;

    /// Matrix that transforms the locale bone in bind pose.
    C_STRUCT aiMatrix4x4 mLocalMatrix;

#ifdef __cplusplus
    ///	@brief The class constructor.
    aiSkeletonBone() :
            mParent(-1),
#ifndef ASSIMP_BUILD_NO_ARMATUREPOPULATE_PROCESS
            mArmature(nullptr),
            mNode(nullptr),
#endif
            mNumnWeights(0),
            mMeshId(nullptr),
            mWeights(nullptr),
            mOffsetMatrix(),
            mLocalMatrix() {
        // empty
    }

    /// @brief The class constructor with its parent
    /// @param  parent      The parent node index.
    aiSkeletonBone(unsigned int parent) :
            mParent(parent),
#ifndef ASSIMP_BUILD_NO_ARMATUREPOPULATE_PROCESS
            mArmature(nullptr),
            mNode(nullptr),
#endif
            mNumnWeights(0),
            mMeshId(nullptr),
            mWeights(nullptr),
            mOffsetMatrix(),
            mLocalMatrix() {
        // empty
    }
    /// @brief The class destructor.
    ~aiSkeletonBone() {
        delete[] mWeights;
        mWeights = nullptr;
    }
#endif // __cplusplus
};
/**
 * @brief A skeleton represents the bone hierarchy of an animation.
 *
 * Skeleton animations can be described as a tree of bones:
 *                  root
 *                    |
 *                  node1
 *                  /   \
 *               node3  node4
 * If you want to calculate the transformation of node three you need to compute the
 * transformation hierarchy for the transformation chain of node3:
 * root->node1->node3
 * Each node is represented as a skeleton instance.
 */
struct aiSkeleton {
    /**
     *  @brief The name of the skeleton instance.
     */
    C_STRUCT aiString mName;

    /**
     *  @brief  The number of bones in the skeleton.
     */
    unsigned int mNumBones;

    /**
     *  @brief The bone instance in the skeleton.
     */
    C_STRUCT aiSkeletonBone **mBones;

#ifdef __cplusplus
    /**
     *  @brief The class constructor.
     */
    aiSkeleton() AI_NO_EXCEPT : mName(), mNumBones(0), mBones(nullptr) {
        // empty
    }

    /**
     *  @brief  The class destructor.
     */
    ~aiSkeleton() {
        delete[] mBones;
    }
#endif // __cplusplus
};
#ifdef __cplusplus
}
#endif //! extern "C"

#endif // AI_MESH_H_INC

