/*
Open Asset Import Library (assimp)
----------------------------------------------------------------------

Copyright (c) 2006-2017, assimp team

All rights reserved.

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  copyright notice, this list of conditions and the
  following disclaimer.

* Redistributions in binary form must reproduce the above
  copyright notice, this list of conditions and the
  following disclaimer in the documentation and/or other
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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----------------------------------------------------------------------
*/

// TODO: refactor entire file to get rid of the "flat-copy" first approach
// to copying structures. This easily breaks in the most unintuitive way
// possible as new fields are added to assimp structures.

// ----------------------------------------------------------------------------
/** 
  * @file Implements Assimp::SceneCombiner. This is a smart utility
  *       class that combines multiple scenes, meshes, ... into one. Currently
  *       these utilities are used by the IRR and LWS loaders and the
  *       OptimizeGraph step.
  */
// ----------------------------------------------------------------------------
#include <assimp/SceneCombiner.h>
#include "StringUtils.h"
#include "fast_atof.h"
#include "Hash.h"
#include "time.h"
#include <assimp/DefaultLogger.hpp>
#include <assimp/scene.h>
#include <assimp/mesh.h>
#include <stdio.h>
#include "ScenePrivate.h"

namespace Assimp {

// ------------------------------------------------------------------------------------------------
// Add a prefix to a string
inline
void PrefixString(aiString& string,const char* prefix, unsigned int len) {
    // If the string is already prefixed, we won't prefix it a second time
    if (string.length >= 1 && string.data[0] == '$')
        return;

    if (len+string.length>=MAXLEN-1) {
        DefaultLogger::get()->debug("Can't add an unique prefix because the string is too long");
        ai_assert(false);
        return;
    }

    // Add the prefix
    ::memmove(string.data+len,string.data,string.length+1);
    ::memcpy (string.data, prefix, len);

    // And update the string's length
    string.length += len;
}

// ------------------------------------------------------------------------------------------------
// Add node identifiers to a hashing set
void SceneCombiner::AddNodeHashes(aiNode* node, std::set<unsigned int>& hashes) {
    // Add node name to hashing set if it is non-empty - empty nodes are allowed
    // and they can't have any anims assigned so its absolutely safe to duplicate them.
    if (node->mName.length) {
        hashes.insert( SuperFastHash(node->mName.data, static_cast<uint32_t>(node->mName.length)) );
    }

    // Process all children recursively
    for (unsigned int i = 0; i < node->mNumChildren;++i)
        AddNodeHashes(node->mChildren[i],hashes);
}

// ------------------------------------------------------------------------------------------------
// Add a name prefix to all nodes in a hierarchy
void SceneCombiner::AddNodePrefixes(aiNode* node, const char* prefix, unsigned int len) {
    ai_assert(NULL != prefix);
    PrefixString(node->mName,prefix,len);

    // Process all children recursively
    for ( unsigned int i = 0; i < node->mNumChildren; ++i ) {
        AddNodePrefixes( node->mChildren[ i ], prefix, len );
    }
}

// ------------------------------------------------------------------------------------------------
// Search for matching names
bool SceneCombiner::FindNameMatch(const aiString& name, std::vector<SceneHelper>& input, unsigned int cur) {
    const unsigned int hash = SuperFastHash(name.data, static_cast<uint32_t>(name.length));

    // Check whether we find a positive match in one of the given sets
    for (unsigned int i = 0; i < input.size(); ++i) {
        if (cur != i && input[i].hashes.find(hash) != input[i].hashes.end()) {
            return true;
        }
    }
    return false;
}

// ------------------------------------------------------------------------------------------------
// Add a name prefix to all nodes in a hierarchy if a hash match is found
void SceneCombiner::AddNodePrefixesChecked(aiNode* node, const char* prefix, unsigned int len,
        std::vector<SceneHelper>& input, unsigned int cur) {
    ai_assert(NULL != prefix);
    const unsigned int hash = SuperFastHash(node->mName.data, static_cast<uint32_t>(node->mName.length));

    // Check whether we find a positive match in one of the given sets
    for (unsigned int i = 0; i < input.size(); ++i) {
        if (cur != i && input[i].hashes.find(hash) != input[i].hashes.end()) {
            PrefixString(node->mName,prefix,len);
            break;
        }
    }

    // Process all children recursively
    for (unsigned int i = 0; i < node->mNumChildren;++i)
        AddNodePrefixesChecked(node->mChildren[i],prefix,len,input,cur);
}

// ------------------------------------------------------------------------------------------------
// Add an offset to all mesh indices in a node graph
void SceneCombiner::OffsetNodeMeshIndices (aiNode* node, unsigned int offset) {
    for (unsigned int i = 0; i < node->mNumMeshes;++i)
        node->mMeshes[i] += offset;

    for ( unsigned int i = 0; i < node->mNumChildren; ++i ) {
        OffsetNodeMeshIndices( node->mChildren[ i ], offset );
    }
}

// ------------------------------------------------------------------------------------------------
// Merges two scenes. Currently only used by the LWS loader.
void SceneCombiner::MergeScenes(aiScene** _dest,std::vector<aiScene*>& src, unsigned int flags) {
    if ( nullptr == _dest ) {
        return;
    }

    // if _dest points to NULL allocate a new scene. Otherwise clear the old and reuse it
    if (src.empty()) {
        if (*_dest) {
            (*_dest)->~aiScene();
            SceneCombiner::CopySceneFlat(_dest,src[0]);
        }
        else *_dest = src[0];
        return;
    }
    if (*_dest)(*_dest)->~aiScene();
    else *_dest = new aiScene();

    // Create a dummy scene to serve as master for the others
    aiScene* master = new aiScene();
    master->mRootNode = new aiNode();
    master->mRootNode->mName.Set("<MergeRoot>");

    std::vector<AttachmentInfo> srcList (src.size());
    for (unsigned int i = 0; i < srcList.size();++i)    {
        srcList[i] = AttachmentInfo(src[i],master->mRootNode);
    }

    // 'master' will be deleted afterwards
    MergeScenes (_dest, master, srcList, flags);
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::AttachToGraph (aiNode* attach, std::vector<NodeAttachmentInfo>& srcList) {
    unsigned int cnt;
    for ( cnt = 0; cnt < attach->mNumChildren; ++cnt ) {
        AttachToGraph( attach->mChildren[ cnt ], srcList );
    }

    cnt = 0;
    for (std::vector<NodeAttachmentInfo>::iterator it = srcList.begin();
         it != srcList.end(); ++it)
    {
        if ((*it).attachToNode == attach && !(*it).resolved)
            ++cnt;
    }

    if (cnt)    {
        aiNode** n = new aiNode*[cnt+attach->mNumChildren];
        if (attach->mNumChildren)   {
            ::memcpy(n,attach->mChildren,sizeof(void*)*attach->mNumChildren);
            delete[] attach->mChildren;
        }
        attach->mChildren = n;

        n += attach->mNumChildren;
        attach->mNumChildren += cnt;

        for (unsigned int i = 0; i < srcList.size();++i)    {
            NodeAttachmentInfo& att = srcList[i];
            if (att.attachToNode == attach && !att.resolved)    {
                *n = att.node;
                (**n).mParent = attach;
                ++n;

                // mark this attachment as resolved
                att.resolved = true;
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::AttachToGraph ( aiScene* master, std::vector<NodeAttachmentInfo>& src) {
    ai_assert(NULL != master);
    AttachToGraph(master->mRootNode,src);
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::MergeScenes(aiScene** _dest, aiScene* master, std::vector<AttachmentInfo>& srcList, unsigned int flags) {
    if ( nullptr == _dest ) {
        return;
    }

    // if _dest points to NULL allocate a new scene. Otherwise clear the old and reuse it
    if (srcList.empty())    {
        if (*_dest) {
            SceneCombiner::CopySceneFlat(_dest,master);
        }
        else *_dest = master;
        return;
    }
    if (*_dest) {
        (*_dest)->~aiScene();
        new (*_dest) aiScene();
    }
    else *_dest = new aiScene();

    aiScene* dest = *_dest;

    std::vector<SceneHelper> src (srcList.size()+1);
    src[0].scene = master;
    for (unsigned int i = 0; i < srcList.size();++i)    {
        src[i+1] = SceneHelper( srcList[i].scene );
    }

    // this helper array specifies which scenes are duplicates of others
    std::vector<unsigned int> duplicates(src.size(),UINT_MAX);

    // this helper array is used as lookup table several times
    std::vector<unsigned int> offset(src.size());

    // Find duplicate scenes
    for (unsigned int i = 0; i < src.size();++i) {
        if (duplicates[i] != i && duplicates[i] != UINT_MAX) {
            continue;
        }

        duplicates[i] = i;
        for ( unsigned int a = i+1; a < src.size(); ++a)    {
            if (src[i].scene == src[a].scene) {
                duplicates[a] = i;
            }
        }
    }

    // Generate unique names for all named stuff?
    if (flags & AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES)
    {
#if 0
        // Construct a proper random number generator
        boost::mt19937 rng(  );
        boost::uniform_int<> dist(1u,1 << 24u);
        boost::variate_generator<boost::mt19937&, boost::uniform_int<> > rndGen(rng, dist);
#endif
        for (unsigned int i = 1; i < src.size();++i)
        {
            //if (i != duplicates[i])
            //{
            //  // duplicate scenes share the same UID
            //  ::strcpy( src[i].id, src[duplicates[i]].id );
            //  src[i].idlen = src[duplicates[i]].idlen;

            //  continue;
            //}

            src[i].idlen = ai_snprintf(src[i].id, 32, "$%.6X$_",i);

            if (flags & AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES_IF_NECESSARY) {

                // Compute hashes for all identifiers in this scene and store them
                // in a sorted table (for convenience I'm using std::set). We hash
                // just the node and animation channel names, all identifiers except
                // the material names should be caught by doing this.
                AddNodeHashes(src[i]->mRootNode,src[i].hashes);

                for (unsigned int a = 0; a < src[i]->mNumAnimations;++a) {
                    aiAnimation* anim = src[i]->mAnimations[a];
                    src[i].hashes.insert(SuperFastHash(anim->mName.data,static_cast<uint32_t>(anim->mName.length)));
                }
            }
        }
    }

    unsigned int cnt;

    // First find out how large the respective output arrays must be
    for ( unsigned int n = 0; n < src.size();++n )
    {
        SceneHelper* cur = &src[n];

        if (n == duplicates[n] || flags & AI_INT_MERGE_SCENE_DUPLICATES_DEEP_CPY)   {
            dest->mNumTextures   += (*cur)->mNumTextures;
            dest->mNumMaterials  += (*cur)->mNumMaterials;
            dest->mNumMeshes     += (*cur)->mNumMeshes;
        }

        dest->mNumLights     += (*cur)->mNumLights;
        dest->mNumCameras    += (*cur)->mNumCameras;
        dest->mNumAnimations += (*cur)->mNumAnimations;

        // Combine the flags of all scenes
        // We need to process them flag-by-flag here to get correct results
        // dest->mFlags ; //|= (*cur)->mFlags;
        if ((*cur)->mFlags & AI_SCENE_FLAGS_NON_VERBOSE_FORMAT) {
            dest->mFlags |= AI_SCENE_FLAGS_NON_VERBOSE_FORMAT;
        }
    }

    // generate the output texture list + an offset table for all texture indices
    if (dest->mNumTextures)
    {
        aiTexture** pip = dest->mTextures = new aiTexture*[dest->mNumMaterials];
        cnt = 0;
        for ( unsigned int n = 0; n < src.size();++n )
        {
            SceneHelper* cur = &src[n];
            for (unsigned int i = 0; i < (*cur)->mNumTextures;++i)
            {
                if (n != duplicates[n])
                {
                    if ( flags & AI_INT_MERGE_SCENE_DUPLICATES_DEEP_CPY)
                        Copy(pip,(*cur)->mTextures[i]);

                    else continue;
                }
                else *pip = (*cur)->mTextures[i];
                ++pip;
            }

            offset[n] = cnt;
            cnt = (unsigned int)(pip - dest->mTextures);
        }
    }

    // generate the output material list + an offset table for all material indices
    if (dest->mNumMaterials)
    {
        aiMaterial** pip = dest->mMaterials = new aiMaterial*[dest->mNumMaterials];
        cnt = 0;
        for ( unsigned int n = 0; n < src.size();++n )  {
            SceneHelper* cur = &src[n];
            for (unsigned int i = 0; i < (*cur)->mNumMaterials;++i)
            {
                if (n != duplicates[n])
                {
                    if ( flags & AI_INT_MERGE_SCENE_DUPLICATES_DEEP_CPY)
                        Copy(pip,(*cur)->mMaterials[i]);

                    else continue;
                }
                else *pip = (*cur)->mMaterials[i];

                if ((*cur)->mNumTextures != dest->mNumTextures)     {
                    // We need to update all texture indices of the mesh. So we need to search for
                    // a material property called '$tex.file'

                    for (unsigned int a = 0; a < (*pip)->mNumProperties;++a)
                    {
                        aiMaterialProperty* prop = (*pip)->mProperties[a];
                        if (!strncmp(prop->mKey.data,"$tex.file",9))
                        {
                            // Check whether this texture is an embedded texture.
                            // In this case the property looks like this: *<n>,
                            // where n is the index of the texture.
                            aiString& s = *((aiString*)prop->mData);
                            if ('*' == s.data[0])   {
                                // Offset the index and write it back ..
                                const unsigned int idx = strtoul10(&s.data[1]) + offset[n];
                                ASSIMP_itoa10(&s.data[1],sizeof(s.data)-1,idx);
                            }
                        }

                        // Need to generate new, unique material names?
                        else if (!::strcmp( prop->mKey.data,"$mat.name" ) && flags & AI_INT_MERGE_SCENE_GEN_UNIQUE_MATNAMES)
                        {
                            aiString* pcSrc = (aiString*) prop->mData;
                            PrefixString(*pcSrc, (*cur).id, (*cur).idlen);
                        }
                    }
                }
                ++pip;
            }

            offset[n] = cnt;
            cnt = (unsigned int)(pip - dest->mMaterials);
        }
    }

    // generate the output mesh list + again an offset table for all mesh indices
    if (dest->mNumMeshes)
    {
        aiMesh** pip = dest->mMeshes = new aiMesh*[dest->mNumMeshes];
        cnt = 0;
        for ( unsigned int n = 0; n < src.size();++n )
        {
            SceneHelper* cur = &src[n];
            for (unsigned int i = 0; i < (*cur)->mNumMeshes;++i)
            {
                if (n != duplicates[n]) {
                    if ( flags & AI_INT_MERGE_SCENE_DUPLICATES_DEEP_CPY)
                        Copy(pip, (*cur)->mMeshes[i]);

                    else continue;
                }
                else *pip = (*cur)->mMeshes[i];

                // update the material index of the mesh
                (*pip)->mMaterialIndex +=  offset[n];
                ++pip;
            }

            // reuse the offset array - store now the mesh offset in it
            offset[n] = cnt;
            cnt = (unsigned int)(pip - dest->mMeshes);
        }
    }

    std::vector <NodeAttachmentInfo> nodes;
    nodes.reserve(srcList.size());

    // ----------------------------------------------------------------------------
    // Now generate the output node graph. We need to make those
    // names in the graph that are referenced by anims or lights
    // or cameras unique. So we add a prefix to them ... $<rand>_
    // We could also use a counter, but using a random value allows us to
    // use just one prefix if we are joining multiple scene hierarchies recursively.
    // Chances are quite good we don't collide, so we try that ...
    // ----------------------------------------------------------------------------

    // Allocate space for light sources, cameras and animations
    aiLight** ppLights = dest->mLights = (dest->mNumLights
        ? new aiLight*[dest->mNumLights] : NULL);

    aiCamera** ppCameras = dest->mCameras = (dest->mNumCameras
        ? new aiCamera*[dest->mNumCameras] : NULL);

    aiAnimation** ppAnims = dest->mAnimations = (dest->mNumAnimations
        ? new aiAnimation*[dest->mNumAnimations] : NULL);

    for ( int n = static_cast<int>(src.size()-1); n >= 0 ;--n ) /* !!! important !!! */
    {
        SceneHelper* cur = &src[n];
        aiNode* node;

        // To offset or not to offset, this is the question
        if (n != (int)duplicates[n])
        {
            // Get full scene-graph copy
            Copy( &node, (*cur)->mRootNode );
            OffsetNodeMeshIndices(node,offset[duplicates[n]]);

            if (flags & AI_INT_MERGE_SCENE_DUPLICATES_DEEP_CPY) {
                // (note:) they are already 'offseted' by offset[duplicates[n]]
                OffsetNodeMeshIndices(node,offset[n] - offset[duplicates[n]]);
            }
        }
        else // if (n == duplicates[n])
        {
            node = (*cur)->mRootNode;
            OffsetNodeMeshIndices(node,offset[n]);
        }
        if (n) // src[0] is the master node
            nodes.push_back(NodeAttachmentInfo( node,srcList[n-1].attachToNode,n ));

        // add name prefixes?
        if (flags & AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES) {

            // or the whole scenegraph
            if (flags & AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES_IF_NECESSARY) {
                AddNodePrefixesChecked(node,(*cur).id,(*cur).idlen,src,n);
            }
            else AddNodePrefixes(node,(*cur).id,(*cur).idlen);

            // meshes
            for (unsigned int i = 0; i < (*cur)->mNumMeshes;++i)    {
                aiMesh* mesh = (*cur)->mMeshes[i];

                // rename all bones
                for (unsigned int a = 0; a < mesh->mNumBones;++a)   {
                    if (flags & AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES_IF_NECESSARY) {
                        if (!FindNameMatch(mesh->mBones[a]->mName,src,n))
                            continue;
                    }
                    PrefixString(mesh->mBones[a]->mName,(*cur).id,(*cur).idlen);
                }
            }
        }

        // --------------------------------------------------------------------
        // Copy light sources
        for (unsigned int i = 0; i < (*cur)->mNumLights;++i,++ppLights)
        {
            if (n != (int)duplicates[n]) // duplicate scene?
            {
                Copy(ppLights, (*cur)->mLights[i]);
            }
            else *ppLights = (*cur)->mLights[i];


            // Add name prefixes?
            if (flags & AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES) {
                if (flags & AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES_IF_NECESSARY) {
                    if (!FindNameMatch((*ppLights)->mName,src,n))
                        continue;
                }

                PrefixString((*ppLights)->mName,(*cur).id,(*cur).idlen);
            }
        }

        // --------------------------------------------------------------------
        // Copy cameras
        for (unsigned int i = 0; i < (*cur)->mNumCameras;++i,++ppCameras)   {
            if (n != (int)duplicates[n]) // duplicate scene?
            {
                Copy(ppCameras, (*cur)->mCameras[i]);
            }
            else *ppCameras = (*cur)->mCameras[i];

            // Add name prefixes?
            if (flags & AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES) {
                if (flags & AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES_IF_NECESSARY) {
                    if (!FindNameMatch((*ppCameras)->mName,src,n))
                        continue;
                }

                PrefixString((*ppCameras)->mName,(*cur).id,(*cur).idlen);
            }
        }

        // --------------------------------------------------------------------
        // Copy animations
        for (unsigned int i = 0; i < (*cur)->mNumAnimations;++i,++ppAnims)  {
            if (n != (int)duplicates[n]) // duplicate scene?
            {
                Copy(ppAnims, (*cur)->mAnimations[i]);
            }
            else *ppAnims = (*cur)->mAnimations[i];

            // Add name prefixes?
            if (flags & AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES) {
                if (flags & AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES_IF_NECESSARY) {
                    if (!FindNameMatch((*ppAnims)->mName,src,n))
                        continue;
                }

                PrefixString((*ppAnims)->mName,(*cur).id,(*cur).idlen);

                // don't forget to update all node animation channels
                for (unsigned int a = 0; a < (*ppAnims)->mNumChannels;++a) {
                    if (flags & AI_INT_MERGE_SCENE_GEN_UNIQUE_NAMES_IF_NECESSARY) {
                        if (!FindNameMatch((*ppAnims)->mChannels[a]->mNodeName,src,n))
                            continue;
                    }

                    PrefixString((*ppAnims)->mChannels[a]->mNodeName,(*cur).id,(*cur).idlen);
                }
            }
        }
    }

    // Now build the output graph
    AttachToGraph ( master, nodes);
    dest->mRootNode = master->mRootNode;

    // Check whether we succeeded at building the output graph
    for (std::vector <NodeAttachmentInfo> ::iterator it = nodes.begin();
        it != nodes.end(); ++it)
    {
        if (!(*it).resolved) {
            if (flags & AI_INT_MERGE_SCENE_RESOLVE_CROSS_ATTACHMENTS) {
                // search for this attachment point in all other imported scenes, too.
                for ( unsigned int n = 0; n < src.size();++n ) {
                    if (n != (*it).src_idx) {
                        AttachToGraph(src[n].scene,nodes);
                        if ((*it).resolved)
                            break;
                    }
                }
            }
            if (!(*it).resolved) {
                DefaultLogger::get()->error(std::string("SceneCombiner: Failed to resolve attachment ")
                    + (*it).node->mName.data + " " + (*it).attachToNode->mName.data);
            }
        }
    }

    // now delete all input scenes. Make sure duplicate scenes aren't
    // deleted more than one time
    for ( unsigned int n = 0; n < src.size();++n )  {
        if (n != duplicates[n]) // duplicate scene?
            continue;

        aiScene* deleteMe = src[n].scene;

        // We need to delete the arrays before the destructor is called -
        // we are reusing the array members
        delete[] deleteMe->mMeshes;     deleteMe->mMeshes     = NULL;
        delete[] deleteMe->mCameras;    deleteMe->mCameras    = NULL;
        delete[] deleteMe->mLights;     deleteMe->mLights     = NULL;
        delete[] deleteMe->mMaterials;  deleteMe->mMaterials  = NULL;
        delete[] deleteMe->mAnimations; deleteMe->mAnimations = NULL;

        deleteMe->mRootNode = NULL;

        // Now we can safely delete the scene
        delete deleteMe;
    }

    // Check flags
    if (!dest->mNumMeshes || !dest->mNumMaterials) {
        dest->mFlags |= AI_SCENE_FLAGS_INCOMPLETE;
    }

    // We're finished
}

// ------------------------------------------------------------------------------------------------
// Build a list of unique bones
void SceneCombiner::BuildUniqueBoneList(std::list<BoneWithHash>& asBones,
    std::vector<aiMesh*>::const_iterator it,
    std::vector<aiMesh*>::const_iterator end)
{
    unsigned int iOffset = 0;
    for (; it != end;++it)  {
        for (unsigned int l = 0; l < (*it)->mNumBones;++l)  {
            aiBone* p = (*it)->mBones[l];
            uint32_t itml = SuperFastHash(p->mName.data,(unsigned int)p->mName.length);

            std::list<BoneWithHash>::iterator it2  = asBones.begin();
            std::list<BoneWithHash>::iterator end2 = asBones.end();

            for (;it2 != end2;++it2)    {
                if ((*it2).first == itml)   {
                    (*it2).pSrcBones.push_back(BoneSrcIndex(p,iOffset));
                    break;
                }
            }
            if (end2 == it2)    {
                // need to begin a new bone entry
                asBones.push_back(BoneWithHash());
                BoneWithHash& btz = asBones.back();

                // setup members
                btz.first = itml;
                btz.second = &p->mName;
                btz.pSrcBones.push_back(BoneSrcIndex(p,iOffset));
            }
        }
        iOffset += (*it)->mNumVertices;
    }
}

// ------------------------------------------------------------------------------------------------
// Merge a list of bones
void SceneCombiner::MergeBones(aiMesh* out,std::vector<aiMesh*>::const_iterator it,
    std::vector<aiMesh*>::const_iterator end)
{
    if ( nullptr == out || out->mNumBones == 0 ) {
        return;
    }

    // find we need to build an unique list of all bones.
    // we work with hashes to make the comparisons MUCH faster,
    // at least if we have many bones.
    std::list<BoneWithHash> asBones;
    BuildUniqueBoneList(asBones, it,end);

    // now create the output bones
    out->mNumBones = 0;
    out->mBones = new aiBone*[asBones.size()];

    for (std::list<BoneWithHash>::const_iterator it = asBones.begin(),end = asBones.end(); it != end;++it)  {
        // Allocate a bone and setup it's name
        aiBone* pc = out->mBones[out->mNumBones++] = new aiBone();
        pc->mName = aiString( *((*it).second ));

        std::vector< BoneSrcIndex >::const_iterator wend = (*it).pSrcBones.end();

        // Loop through all bones to be joined for this bone
        for (std::vector< BoneSrcIndex >::const_iterator wmit = (*it).pSrcBones.begin(); wmit != wend; ++wmit)  {
            pc->mNumWeights += (*wmit).first->mNumWeights;

            // NOTE: different offset matrices for bones with equal names
            // are - at the moment - not handled correctly.
            if (wmit != (*it).pSrcBones.begin() && pc->mOffsetMatrix != (*wmit).first->mOffsetMatrix)   {
                DefaultLogger::get()->warn("Bones with equal names but different offset matrices can't be joined at the moment");
                continue;
            }
            pc->mOffsetMatrix = (*wmit).first->mOffsetMatrix;
        }

        // Allocate the vertex weight array
        aiVertexWeight* avw = pc->mWeights = new aiVertexWeight[pc->mNumWeights];

        // And copy the final weights - adjust the vertex IDs by the
        // face index offset of the corresponding mesh.
        for (std::vector< BoneSrcIndex >::const_iterator wmit = (*it).pSrcBones.begin(); wmit != wend; ++wmit)  {
            aiBone* pip = (*wmit).first;
            for (unsigned int mp = 0; mp < pip->mNumWeights;++mp,++avw) {
                const aiVertexWeight& vfi = pip->mWeights[mp];
                avw->mWeight = vfi.mWeight;
                avw->mVertexId = vfi.mVertexId + (*wmit).second;
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Merge a list of meshes
void SceneCombiner::MergeMeshes(aiMesh** _out, unsigned int /*flags*/,
    std::vector<aiMesh*>::const_iterator begin,
    std::vector<aiMesh*>::const_iterator end)
{
    if ( nullptr == _out ) {
        return;
    }

    if (begin == end)   {
        *_out = NULL; // no meshes ...
        return;
    }

    // Allocate the output mesh
    aiMesh* out = *_out = new aiMesh();
    out->mMaterialIndex = (*begin)->mMaterialIndex;

    std::string name;
    // Find out how much output storage we'll need
    for (std::vector<aiMesh*>::const_iterator it = begin; it != end; ++it) {
        const char *meshName( (*it)->mName.C_Str() );
        name += std::string( meshName );
        if ( it != end - 1 ) {
            name += ".";
        }
        out->mNumVertices   += (*it)->mNumVertices;
        out->mNumFaces      += (*it)->mNumFaces;
        out->mNumBones      += (*it)->mNumBones;

        // combine primitive type flags
        out->mPrimitiveTypes |= (*it)->mPrimitiveTypes;
    }
    out->mName.Set( name.c_str() );

    if (out->mNumVertices) {
        aiVector3D* pv2;

        // copy vertex positions
        if ((**begin).HasPositions())   {

            pv2 = out->mVertices = new aiVector3D[out->mNumVertices];
            for (std::vector<aiMesh*>::const_iterator it = begin; it != end; ++it)  {
                if ((*it)->mVertices)   {
                    ::memcpy(pv2,(*it)->mVertices,(*it)->mNumVertices*sizeof(aiVector3D));
                }
                else DefaultLogger::get()->warn("JoinMeshes: Positions expected but input mesh contains no positions");
                pv2 += (*it)->mNumVertices;
            }
        }
        // copy normals
        if ((**begin).HasNormals()) {

            pv2 = out->mNormals = new aiVector3D[out->mNumVertices];
            for (std::vector<aiMesh*>::const_iterator it = begin; it != end;++it)   {
                if ((*it)->mNormals)    {
                    ::memcpy(pv2,(*it)->mNormals,(*it)->mNumVertices*sizeof(aiVector3D));
                }
                else DefaultLogger::get()->warn("JoinMeshes: Normals expected but input mesh contains no normals");
                pv2 += (*it)->mNumVertices;
            }
        }
        // copy tangents and bi-tangents
        if ((**begin).HasTangentsAndBitangents())   {

            pv2 = out->mTangents = new aiVector3D[out->mNumVertices];
            aiVector3D* pv2b = out->mBitangents = new aiVector3D[out->mNumVertices];

            for (std::vector<aiMesh*>::const_iterator it = begin; it != end;++it)   {
                if ((*it)->mTangents)   {
                    ::memcpy(pv2, (*it)->mTangents,  (*it)->mNumVertices*sizeof(aiVector3D));
                    ::memcpy(pv2b,(*it)->mBitangents,(*it)->mNumVertices*sizeof(aiVector3D));
                }
                else DefaultLogger::get()->warn("JoinMeshes: Tangents expected but input mesh contains no tangents");
                pv2  += (*it)->mNumVertices;
                pv2b += (*it)->mNumVertices;
            }
        }
        // copy texture coordinates
        unsigned int n = 0;
        while ((**begin).HasTextureCoords(n))   {
            out->mNumUVComponents[n] = (*begin)->mNumUVComponents[n];

            pv2 = out->mTextureCoords[n] = new aiVector3D[out->mNumVertices];
            for (std::vector<aiMesh*>::const_iterator it = begin; it != end;++it)   {

                if ((*it)->mTextureCoords[n])   {
                    ::memcpy(pv2,(*it)->mTextureCoords[n],(*it)->mNumVertices*sizeof(aiVector3D));
                }
                else DefaultLogger::get()->warn("JoinMeshes: UVs expected but input mesh contains no UVs");
                pv2 += (*it)->mNumVertices;
            }
            ++n;
        }
        // copy vertex colors
        n = 0;
        while ((**begin).HasVertexColors(n))    {
            aiColor4D* pv2 = out->mColors[n] = new aiColor4D[out->mNumVertices];
            for (std::vector<aiMesh*>::const_iterator it = begin; it != end;++it)   {

                if ((*it)->mColors[n])  {
                    ::memcpy(pv2,(*it)->mColors[n],(*it)->mNumVertices*sizeof(aiColor4D));
                }
                else DefaultLogger::get()->warn("JoinMeshes: VCs expected but input mesh contains no VCs");
                pv2 += (*it)->mNumVertices;
            }
            ++n;
        }
    }

    if (out->mNumFaces) // just for safety
    {
        // copy faces
        out->mFaces = new aiFace[out->mNumFaces];
        aiFace* pf2 = out->mFaces;

        unsigned int ofs = 0;
        for (std::vector<aiMesh*>::const_iterator it = begin; it != end;++it)   {
            for (unsigned int m = 0; m < (*it)->mNumFaces;++m,++pf2)    {
                aiFace& face = (*it)->mFaces[m];
                pf2->mNumIndices = face.mNumIndices;
                pf2->mIndices = face.mIndices;

                if (ofs)    {
                    // add the offset to the vertex
                    for (unsigned int q = 0; q < face.mNumIndices; ++q)
                        face.mIndices[q] += ofs;
                }
                face.mIndices = NULL;
            }
            ofs += (*it)->mNumVertices;
        }
    }

    // bones - as this is quite lengthy, I moved the code to a separate function
    if (out->mNumBones)
        MergeBones(out,begin,end);

    // delete all source meshes
    for (std::vector<aiMesh*>::const_iterator it = begin; it != end;++it)
        delete *it;
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::MergeMaterials(aiMaterial** dest,
        std::vector<aiMaterial*>::const_iterator begin,
        std::vector<aiMaterial*>::const_iterator end)
{
    if ( nullptr == dest ) {
        return;
    }

    if (begin == end)   {
        *dest = NULL; // no materials ...
        return;
    }

    // Allocate the output material
    aiMaterial* out = *dest = new aiMaterial();

    // Get the maximal number of properties
    unsigned int size = 0;
    for (std::vector<aiMaterial*>::const_iterator it = begin; it != end; ++it) {
        size += (*it)->mNumProperties;
    }

    out->Clear();
    delete[] out->mProperties;

    out->mNumAllocated = size;
    out->mNumProperties = 0;
    out->mProperties = new aiMaterialProperty*[out->mNumAllocated];

    for (std::vector<aiMaterial*>::const_iterator it = begin; it != end; ++it) {
        for(unsigned int i = 0; i < (*it)->mNumProperties; ++i) {
            aiMaterialProperty* sprop = (*it)->mProperties[i];

            // Test if we already have a matching property
            const aiMaterialProperty* prop_exist;
            if(aiGetMaterialProperty(out, sprop->mKey.C_Str(), sprop->mSemantic, sprop->mIndex, &prop_exist) != AI_SUCCESS) {
                // If not, we add it to the new material
                aiMaterialProperty* prop = out->mProperties[out->mNumProperties] = new aiMaterialProperty();

                prop->mDataLength = sprop->mDataLength;
                prop->mData = new char[prop->mDataLength];
                ::memcpy(prop->mData, sprop->mData, prop->mDataLength);

                prop->mIndex    = sprop->mIndex;
                prop->mSemantic = sprop->mSemantic;
                prop->mKey      = sprop->mKey;
                prop->mType     = sprop->mType;

                out->mNumProperties++;
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
template <typename Type>
inline
void CopyPtrArray (Type**& dest, const Type* const * src, ai_uint num) {
    if (!num) {
        dest = NULL;
        return;
    }
    dest = new Type*[num];
    for (ai_uint i = 0; i < num;++i) {
        SceneCombiner::Copy(&dest[i],src[i]);
    }
}

// ------------------------------------------------------------------------------------------------
template <typename Type>
inline
void GetArrayCopy(Type*& dest, ai_uint num ) {
    if ( !dest ) {
        return;
    }
    Type* old = dest;

    dest = new Type[num];
    ::memcpy(dest, old, sizeof(Type) * num);
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::CopySceneFlat(aiScene** _dest,const aiScene* src) {
    if ( nullptr == _dest || nullptr == src ) {
        return;
    }

    // reuse the old scene or allocate a new?
    if (*_dest) {
        (*_dest)->~aiScene();
        new (*_dest) aiScene();
    } else {
        *_dest = new aiScene();
    }

    ::memcpy(*_dest,src,sizeof(aiScene));
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::CopyScene(aiScene** _dest,const aiScene* src,bool allocate) {
    if ( nullptr == _dest || nullptr == src ) {
        return;
    }

    if (allocate) {
        *_dest = new aiScene();
    }
    aiScene* dest = *_dest;
    ai_assert(dest);

    // copy animations
    dest->mNumAnimations = src->mNumAnimations;
    CopyPtrArray(dest->mAnimations,src->mAnimations,
        dest->mNumAnimations);

    // copy textures
    dest->mNumTextures = src->mNumTextures;
    CopyPtrArray(dest->mTextures,src->mTextures,
        dest->mNumTextures);

    // copy materials
    dest->mNumMaterials = src->mNumMaterials;
    CopyPtrArray(dest->mMaterials,src->mMaterials,
        dest->mNumMaterials);

    // copy lights
    dest->mNumLights = src->mNumLights;
    CopyPtrArray(dest->mLights,src->mLights,
        dest->mNumLights);

    // copy cameras
    dest->mNumCameras = src->mNumCameras;
    CopyPtrArray(dest->mCameras,src->mCameras,
        dest->mNumCameras);

    // copy meshes
    dest->mNumMeshes = src->mNumMeshes;
    CopyPtrArray(dest->mMeshes,src->mMeshes,
        dest->mNumMeshes);

    // now - copy the root node of the scene (deep copy, too)
    Copy( &dest->mRootNode, src->mRootNode);

    // and keep the flags ...
    dest->mFlags = src->mFlags;

    // source private data might be NULL if the scene is user-allocated (i.e. for use with the export API)
    if (dest->mPrivate != NULL) {
        ScenePriv(dest)->mPPStepsApplied = ScenePriv(src) ? ScenePriv(src)->mPPStepsApplied : 0;
    }
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::Copy( aiMesh** _dest, const aiMesh* src ) {
    if ( nullptr == _dest || nullptr == src ) {
        return;
    }

    aiMesh* dest = *_dest = new aiMesh();

    // get a flat copy
    ::memcpy(dest,src,sizeof(aiMesh));

    // and reallocate all arrays
    GetArrayCopy( dest->mVertices,   dest->mNumVertices );
    GetArrayCopy( dest->mNormals ,   dest->mNumVertices );
    GetArrayCopy( dest->mTangents,   dest->mNumVertices );
    GetArrayCopy( dest->mBitangents, dest->mNumVertices );

    unsigned int n = 0;
    while (dest->HasTextureCoords(n))
        GetArrayCopy( dest->mTextureCoords[n++],   dest->mNumVertices );

    n = 0;
    while (dest->HasVertexColors(n))
        GetArrayCopy( dest->mColors[n++],   dest->mNumVertices );

    // make a deep copy of all bones
    CopyPtrArray(dest->mBones,dest->mBones,dest->mNumBones);

    // make a deep copy of all faces
    GetArrayCopy(dest->mFaces,dest->mNumFaces);
    for (unsigned int i = 0; i < dest->mNumFaces;++i) {
        aiFace& f = dest->mFaces[i];
        GetArrayCopy(f.mIndices,f.mNumIndices);
    }
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::Copy (aiMaterial** _dest, const aiMaterial* src) {
    if ( nullptr == _dest || nullptr == src ) {
        return;
    }

    aiMaterial* dest = (aiMaterial*) ( *_dest = new aiMaterial() );

    dest->Clear();
    delete[] dest->mProperties;

    dest->mNumAllocated  =  src->mNumAllocated;
    dest->mNumProperties =  src->mNumProperties;
    dest->mProperties    =  new aiMaterialProperty* [dest->mNumAllocated];

    for (unsigned int i = 0; i < dest->mNumProperties;++i)
    {
        aiMaterialProperty* prop  = dest->mProperties[i] = new aiMaterialProperty();
        aiMaterialProperty* sprop = src->mProperties[i];

        prop->mDataLength = sprop->mDataLength;
        prop->mData = new char[prop->mDataLength];
        ::memcpy(prop->mData,sprop->mData,prop->mDataLength);

        prop->mIndex    = sprop->mIndex;
        prop->mSemantic = sprop->mSemantic;
        prop->mKey      = sprop->mKey;
        prop->mType     = sprop->mType;
    }
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::Copy(aiTexture** _dest, const aiTexture* src) {
    if ( nullptr == _dest || nullptr == src ) {
        return;
    }

    aiTexture* dest = *_dest = new aiTexture();

    // get a flat copy
    ::memcpy(dest,src,sizeof(aiTexture));

    // and reallocate all arrays. We must do it manually here
    const char* old = (const char*)dest->pcData;
    if (old)
    {
        unsigned int cpy;
        if (!dest->mHeight)cpy = dest->mWidth;
        else cpy = dest->mHeight * dest->mWidth * sizeof(aiTexel);

        if (!cpy)
        {
            dest->pcData = NULL;
            return;
        }
        // the cast is legal, the aiTexel c'tor does nothing important
        dest->pcData = (aiTexel*) new char[cpy];
        ::memcpy(dest->pcData, old, cpy);
    }
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::Copy( aiAnimation** _dest, const aiAnimation* src ) {
    if ( nullptr == _dest || nullptr == src ) {
        return;
    }

    aiAnimation* dest = *_dest = new aiAnimation();

    // get a flat copy
    ::memcpy(dest,src,sizeof(aiAnimation));

    // and reallocate all arrays
    CopyPtrArray( dest->mChannels, src->mChannels, dest->mNumChannels );
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::Copy(aiNodeAnim** _dest, const aiNodeAnim* src) {
    if ( nullptr == _dest || nullptr == src ) {
        return;
    }

    aiNodeAnim* dest = *_dest = new aiNodeAnim();

    // get a flat copy
    ::memcpy(dest,src,sizeof(aiNodeAnim));

    // and reallocate all arrays
    GetArrayCopy( dest->mPositionKeys, dest->mNumPositionKeys );
    GetArrayCopy( dest->mScalingKeys,  dest->mNumScalingKeys );
    GetArrayCopy( dest->mRotationKeys, dest->mNumRotationKeys );
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::Copy( aiCamera** _dest,const  aiCamera* src) {
    if ( nullptr == _dest || nullptr == src ) {
        return;
    }

    aiCamera* dest = *_dest = new aiCamera();

    // get a flat copy, that's already OK
    ::memcpy(dest,src,sizeof(aiCamera));
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::Copy(aiLight** _dest, const aiLight* src) {
    if ( nullptr == _dest || nullptr == src ) {
        return;
    }

    aiLight* dest = *_dest = new aiLight();

    // get a flat copy, that's already OK
    ::memcpy(dest,src,sizeof(aiLight));
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::Copy(aiBone** _dest, const aiBone* src) {
    if ( nullptr == _dest || nullptr == src ) {
        return;
    }

    aiBone* dest = *_dest = new aiBone();

    // get a flat copy
    ::memcpy(dest,src,sizeof(aiBone));

    // and reallocate all arrays
    GetArrayCopy( dest->mWeights, dest->mNumWeights );
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::Copy     (aiNode** _dest, const aiNode* src)
{
    ai_assert(NULL != _dest && NULL != src);

    aiNode* dest = *_dest = new aiNode();

    // get a flat copy
    ::memcpy(dest,src,sizeof(aiNode));

    if (src->mMetaData) {
        Copy(&dest->mMetaData, src->mMetaData);
    }

    // and reallocate all arrays
    GetArrayCopy( dest->mMeshes, dest->mNumMeshes );
    CopyPtrArray( dest->mChildren, src->mChildren,dest->mNumChildren);

	// need to set the mParent fields to the created aiNode.
	for( unsigned int i = 0; i < dest->mNumChildren; i ++ ) {
		dest->mChildren[i]->mParent = dest;
	}
}

// ------------------------------------------------------------------------------------------------
void SceneCombiner::Copy(aiMetadata** _dest, const aiMetadata* src) {
    if ( nullptr == _dest || nullptr == src ) {
        return;
    }

    if ( 0 == src->mNumProperties ) {
        return;
    }

    aiMetadata* dest = *_dest = aiMetadata::Alloc( src->mNumProperties );
    std::copy(src->mKeys, src->mKeys + src->mNumProperties, dest->mKeys);

    dest->mValues = new aiMetadataEntry[src->mNumProperties];
    for (unsigned int i = 0; i < src->mNumProperties; ++i) {
        aiMetadataEntry& in = src->mValues[i];
        aiMetadataEntry& out = dest->mValues[i];
        out.mType = in.mType;
        switch (dest->mValues[i].mType) {
        case AI_BOOL:
            out.mData = new bool(*static_cast<bool*>(in.mData));
            break;
        case AI_INT32:
            out.mData = new int32_t(*static_cast<int32_t*>(in.mData));
            break;
        case AI_UINT64:
            out.mData = new uint64_t(*static_cast<uint64_t*>(in.mData));
            break;
        case AI_FLOAT:
            out.mData = new float(*static_cast<float*>(in.mData));
            break;
        case AI_DOUBLE:
            out.mData = new double(*static_cast<double*>(in.mData));
            break;
        case AI_AISTRING:
            out.mData = new aiString(*static_cast<aiString*>(in.mData));
            break;
        case AI_AIVECTOR3D:
            out.mData = new aiVector3D(*static_cast<aiVector3D*>(in.mData));
            break;
        default:
            ai_assert(false);
        }
    }
}

} // Namespace Assimp