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*/

/** @file Declares a helper class, "SceneCombiner" providing various
 *  utilities to merge scenes.
 */
#pragma once
#ifndef AI_SCENE_COMBINER_H_INC
#define AI_SCENE_COMBINER_H_INC

#ifdef __GNUC__
#pragma GCC system_header
#endif

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

#include <cstddef>
#include <cstdint>
#include <list>
#include <set>
#include <vector>

struct aiScene;
struct aiNode;
struct aiMaterial;
struct aiTexture;
struct aiCamera;
struct aiLight;
struct aiMetadata;
struct aiBone;
struct aiMesh;
struct aiAnimMesh;
struct aiAnimation;
struct aiNodeAnim;
struct aiMeshMorphAnim;

namespace Assimp {

// ---------------------------------------------------------------------------
/** \brief Helper data structure for SceneCombiner.
 *
 *  Describes to which node a scene must be attached to.
 */
struct AttachmentInfo {
    AttachmentInfo() = default;
    AttachmentInfo(aiScene *_scene, aiNode *_attachToNode) : scene(_scene), attachToNode(_attachToNode) {
        // empty
    }
    ~AttachmentInfo() = default;

    aiScene *scene{nullptr};
    aiNode *attachToNode{nullptr};
};

// ---------------------------------------------------------------------------
/// @brief Helper data structure for SceneCombiner.
struct NodeAttachmentInfo {
    NodeAttachmentInfo() = default;
    ~NodeAttachmentInfo() = default;
    NodeAttachmentInfo(aiNode *_scene, aiNode *_attachToNode, size_t idx) :
            node(_scene), attachToNode(_attachToNode), src_idx(idx) {
        // empty
    }

    aiNode *node{nullptr};
    aiNode *attachToNode{nullptr};
    bool resolved{false};
    size_t src_idx{SIZE_MAX};
};

// ---------------------------------------------------------------------------
/** @def AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES
 *  Generate unique names for all named scene items
 */
#define AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES 0x1

/** @def AI_INT_MERGE_SCENE_GEN_UNIQUE_MATNAMES
 *  Generate unique names for materials, too.
 *  This is not absolutely required to pass the validation.
 */
#define AI_INT_MERGE_SCENE_GEN_UNIQUE_MATNAMES 0x2

/** @def AI_INT_MERGE_SCENE_DUPLICATES_DEEP_CPY
 * Use deep copies of duplicate scenes
 */
#define AI_INT_MERGE_SCENE_DUPLICATES_DEEP_CPY 0x4

/** @def AI_INT_MERGE_SCENE_RESOLVE_CROSS_ATTACHMENTS
 * If attachment nodes are not found in the given master scene,
 * search the other imported scenes for them in an any order.
 */
#define AI_INT_MERGE_SCENE_RESOLVE_CROSS_ATTACHMENTS 0x8

/** @def AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES_IF_NECESSARY
 * Can be combined with AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES.
 * Unique names are generated, but only if this is absolutely
 * required to avoid name conflicts.
 */
#define AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES_IF_NECESSARY 0x10

using BoneSrcIndex = std::pair<aiBone *, unsigned int> ;

// ---------------------------------------------------------------------------
/** @brief Helper data structure for SceneCombiner::MergeBones.
 */
struct BoneWithHash : public std::pair<uint32_t, aiString *> {
    std::vector<BoneSrcIndex> pSrcBones;
};

// ---------------------------------------------------------------------------
/** @brief Utility for SceneCombiner
 */
struct SceneHelper {
    SceneHelper() :
            scene(nullptr),
            idlen(0) {
        id[0] = 0;
    }

    explicit SceneHelper(aiScene *_scene) :
            scene(_scene), idlen(0) {
        id[0] = 0;
    }

    AI_FORCE_INLINE aiScene *operator->() const {
        return scene;
    }

    // scene we're working on
    aiScene *scene;

    // prefix to be added to all identifiers in the scene ...
    char id[32];

    // and its strlen()
    unsigned int idlen;

    // hash table to quickly check whether a name is contained in the scene
    std::set<unsigned int> hashes;
};

// ---------------------------------------------------------------------------
/** \brief Static helper class providing various utilities to merge two
 *    scenes. It is intended as internal utility and NOT for use by
 *    applications.
 *
 * The class is currently being used by various postprocessing steps
 * and loaders (ie. LWS).
 */
class ASSIMP_API SceneCombiner {
public:
    // class cannot be instanced
    SceneCombiner() = delete;
    ~SceneCombiner() = delete;

    // -------------------------------------------------------------------
    /** Merges two or more scenes.
     *
     *  @param dest  Receives a pointer to the destination scene. If the
     *    pointer doesn't point to nullptr when the function is called, the
     *    existing scene is cleared and refilled.
     *  @param src Non-empty list of scenes to be merged. The function
     *    deletes the input scenes afterwards. There may be duplicate scenes.
     *  @param flags Combination of the AI_INT_MERGE_SCENE flags defined above
     */
    static void MergeScenes(aiScene **dest, std::vector<aiScene *> &src,
            unsigned int flags = 0);

    // -------------------------------------------------------------------
    /** Merges two or more scenes and attaches all scenes to a specific
     *  position in the node graph of the master scene.
     *
     *  @param dest Receives a pointer to the destination scene. If the
     *    pointer doesn't point to nullptr when the function is called, the
     *    existing scene is cleared and refilled.
     *  @param master Master scene. It will be deleted afterwards. All
     *    other scenes will be inserted in its node graph.
     *  @param src Non-empty list of scenes to be merged along with their
     *    corresponding attachment points in the master scene. The function
     *    deletes the input scenes afterwards. There may be duplicate scenes.
     *  @param flags Combination of the AI_INT_MERGE_SCENE flags defined above
     */
    static void MergeScenes(aiScene **dest, aiScene *master,
            std::vector<AttachmentInfo> &src,
            unsigned int flags = 0);

    // -------------------------------------------------------------------
    /** Merges two or more meshes
     *
     *  The meshes should have equal vertex formats. Only components
     *  that are provided by ALL meshes will be present in the output mesh.
     *  An exception is made for VColors - they are set to black. The
     *  meshes should have the same material indices, too. The output
     *  material index is always the material index of the first mesh.
     *
     *  @param dest Destination mesh. Must be empty.
     *  @param flags Currently no parameters
     *  @param begin First mesh to be processed
     *  @param end Points to the mesh after the last mesh to be processed
     */
    static void MergeMeshes(aiMesh **dest, unsigned int flags,
            std::vector<aiMesh *>::const_iterator begin,
            std::vector<aiMesh *>::const_iterator end);

    // -------------------------------------------------------------------
    /** Merges two or more bones
     *
     *  @param out Mesh to receive the output bone list
     *  @param flags Currently no parameters
     *  @param begin First mesh to be processed
     *  @param end Points to the mesh after the last mesh to be processed
     */
    static void MergeBones(aiMesh *out, std::vector<aiMesh *>::const_iterator it,
            std::vector<aiMesh *>::const_iterator end);

    // -------------------------------------------------------------------
    /** Merges two or more materials
     *
     *  The materials should be complementary as much as possible. In case
     *  of a property present in different materials, the first occurrence
     *  is used.
     *
     *  @param dest Destination material. Must be empty.
     *  @param begin First material to be processed
     *  @param end Points to the material after the last material to be processed
     */
    static void MergeMaterials(aiMaterial **dest,
            std::vector<aiMaterial *>::const_iterator begin,
            std::vector<aiMaterial *>::const_iterator end);

    // -------------------------------------------------------------------
    /** Builds a list of uniquely named bones in a mesh list
     *
     *  @param asBones Receives the output list
     *  @param it      First mesh to be processed
     *  @param end     Last mesh to be processed
     */
    static void BuildUniqueBoneList(std::list<BoneWithHash> &asBones,
            std::vector<aiMesh *>::const_iterator it,
            std::vector<aiMesh *>::const_iterator end);

    // -------------------------------------------------------------------
    /** Add a name prefix to all nodes in a scene.
     *
     *  @param node   Current node. This function is called recursively.
     *  @param prefix Prefix to be added to all nodes
     *  @param len    String length
     */
    static void AddNodePrefixes(aiNode *node, const char *prefix,
            unsigned int len);

    // -------------------------------------------------------------------
    /** Add an offset to all mesh indices in a node graph
     *
     *  @param node   Current node. This function is called recursively.
     *  @param offset Offset to be added to all mesh indices
     */
    static void OffsetNodeMeshIndices(aiNode *node, unsigned int offset);

    // -------------------------------------------------------------------
    /** Attach a list of node graphs to well-defined nodes in a master
     *  graph. This is a helper for MergeScenes()
     *
     *  @param master Master scene
     *  @param srcList List of source scenes along with their attachment
     *    points. If an attachment point is nullptr (or does not exist in
     *    the master graph), a scene is attached to the root of the master
     *    graph (as an additional child node)
     *  @duplicates List of duplicates. If elem[n] == n the scene is not
     *    a duplicate. Otherwise, elem[n] links scene n to its first occurrence.
     */
    static void AttachToGraph(aiScene *master,
            std::vector<NodeAttachmentInfo> &srcList);

    static void AttachToGraph(aiNode *attach,
            std::vector<NodeAttachmentInfo> &srcList);

    // -------------------------------------------------------------------
    /** Get a deep copy of a scene
     *
     *  @param dest     Receives a pointer to the destination scene
     *  @param source   Source scene - remains unmodified.
     *  @param allocate true for allocation a new scene
     */
    static void CopyScene(aiScene **dest, const aiScene *source, bool allocate = true);

    // -------------------------------------------------------------------
    /** Get a flat copy of a scene
     *
     *  Only the first hierarchy layer is copied. All pointer members of
     *  aiScene are shared by source and destination scene.  If the
     *    pointer doesn't point to nullptr when the function is called, the
     *    existing scene is cleared and refilled.
     *  @param dest Receives a pointer to the destination scene
     *  @param src Source scene - remains unmodified.
     */
    static void CopySceneFlat(aiScene **dest, const aiScene *source);

    // -------------------------------------------------------------------
    /** Get a deep copy of a mesh
     *
     *  @param dest Receives a pointer to the destination mesh
     *  @param src Source mesh - remains unmodified.
     */
    static void Copy(aiMesh **dest, const aiMesh *src);

    // similar to Copy():
    static void Copy(aiAnimMesh **dest, const aiAnimMesh *src);
    static void Copy(aiMaterial **dest, const aiMaterial *src);
    static void Copy(aiTexture **dest, const aiTexture *src);
    static void Copy(aiAnimation **dest, const aiAnimation *src);
    static void Copy(aiCamera **dest, const aiCamera *src);
    static void Copy(aiBone **dest, const aiBone *src);
    static void Copy(aiLight **dest, const aiLight *src);
    static void Copy(aiNodeAnim **dest, const aiNodeAnim *src);
    static void Copy(aiMeshMorphAnim **dest, const aiMeshMorphAnim *src);
    static void Copy(aiMetadata **dest, const aiMetadata *src);
    static void Copy(aiString **dest, const aiString *src);

    // recursive, of course
    static void Copy(aiNode **dest, const aiNode *src);

private:
    // -------------------------------------------------------------------
    // Same as AddNodePrefixes, but with an additional check
    static void AddNodePrefixesChecked(aiNode *node, const char *prefix,
            unsigned int len,
            std::vector<SceneHelper> &input,
            unsigned int cur);

    // -------------------------------------------------------------------
    // Add node identifiers to a hashing set
    static void AddNodeHashes(aiNode *node, std::set<unsigned int> &hashes);

    // -------------------------------------------------------------------
    // Search for duplicate names
    static bool FindNameMatch(const aiString &name,
            std::vector<SceneHelper> &input, unsigned int cur);
};

} // namespace Assimp

#endif // !! AI_SCENE_COMBINER_H_INC
