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/// @file SplitByBoneCountProcess.cpp

/// Implementation of the SplitByBoneCount postprocessing step

// internal headers of the post-processing framework

#include "SplitByBoneCountProcess.h"

#include <assimp/postprocess.h>

#include <assimp/DefaultLogger.hpp>

#include <limits>

#include <assimp/TinyFormatter.h>

#include <assimp/Exceptional.h>

#include <set>

using namespace Assimp;

using namespace Assimp::Formatter;

// ------------------------------------------------------------------------------------------------

// Constructor

SplitByBoneCountProcess::SplitByBoneCountProcess() : mMaxBoneCount(AI_SBBC_DEFAULT_MAX_BONES) {}

// ------------------------------------------------------------------------------------------------

// Returns whether the processing step is present in the given flag.

bool SplitByBoneCountProcess::IsActive( unsigned int pFlags) const {

    return !!(pFlags & aiProcess_SplitByBoneCount);

}

// ------------------------------------------------------------------------------------------------

// Updates internal properties

void SplitByBoneCountProcess::SetupProperties(const Importer* pImp) {

    mMaxBoneCount = pImp->GetPropertyInteger(AI_CONFIG_PP_SBBC_MAX_BONES,AI_SBBC_DEFAULT_MAX_BONES);

}

// ------------------------------------------------------------------------------------------------

// Executes the post processing step on the given imported data.

void SplitByBoneCountProcess::Execute( aiScene* pScene) {

    ASSIMP_LOG_DEBUG("SplitByBoneCountProcess begin");

    // early out

    bool isNecessary = false;

    for( unsigned int a = 0; a < pScene->mNumMeshes; ++a)

        if( pScene->mMeshes[a]->mNumBones > mMaxBoneCount ) {

            isNecessary = true;

            break;

        }

    if( !isNecessary ) {

        ASSIMP_LOG_DEBUG("SplitByBoneCountProcess early-out: no meshes with more than ", mMaxBoneCount, " bones." );

        return;

    }

    // we need to do something. Let's go.

    mSubMeshIndices.clear();

    mSubMeshIndices.resize( pScene->mNumMeshes);

    // build a new array of meshes for the scene

    std::vector<aiMesh*> meshes;

    for( unsigned int a = 0; a < pScene->mNumMeshes; ++a) {

        aiMesh* srcMesh = pScene->mMeshes[a];

        std::vector<aiMesh*> newMeshes;

        SplitMesh( pScene->mMeshes[a], newMeshes);

        // mesh was split

        if( !newMeshes.empty() ) {

            // store new meshes and indices of the new meshes

            for( unsigned int b = 0; b < newMeshes.size(); ++b) {

                mSubMeshIndices[a].push_back( static_cast<unsigned int>(meshes.size()));

                meshes.push_back( newMeshes[b]);

            }

            // and destroy the source mesh. It should be completely contained inside the new submeshes

            delete srcMesh;

        } else {

            // Mesh is kept unchanged - store it's new place in the mesh array

            mSubMeshIndices[a].push_back( static_cast<unsigned int>(meshes.size()));

            meshes.push_back( srcMesh);

        }

    }

    // rebuild the scene's mesh array

    pScene->mNumMeshes = static_cast<unsigned int>(meshes.size());

    delete [] pScene->mMeshes;

    pScene->mMeshes = new aiMesh*[pScene->mNumMeshes];

    std::copy( meshes.begin(), meshes.end(), pScene->mMeshes);

    // recurse through all nodes and translate the node's mesh indices to fit the new mesh array

    UpdateNode( pScene->mRootNode);

    ASSIMP_LOG_DEBUG( "SplitByBoneCountProcess end: split ", mSubMeshIndices.size(), " meshes into ", meshes.size(), " submeshes." );

}

// ------------------------------------------------------------------------------------------------

// Splits the given mesh by bone count.

void SplitByBoneCountProcess::SplitMesh( const aiMesh* pMesh, std::vector<aiMesh*>& poNewMeshes) const {

    // skip if not necessary

    if( pMesh->mNumBones <= mMaxBoneCount ) {

        return;

    }

    // necessary optimisation: build a list of all affecting bones for each vertex

    // TODO: (thom) maybe add a custom allocator here to avoid allocating tens of thousands of small arrays

    typedef std::pair<unsigned int, float> BoneWeight;

    std::vector< std::vector<BoneWeight> > vertexBones( pMesh->mNumVertices);

    for( unsigned int a = 0; a < pMesh->mNumBones; ++a) {

        const aiBone* bone = pMesh->mBones[a];

        for( unsigned int b = 0; b < bone->mNumWeights; ++b) {

            if (bone->mWeights[b].mWeight > 0.0f) {

                int vertexId = bone->mWeights[b].mVertexId;

                vertexBones[vertexId].emplace_back(a, bone->mWeights[b].mWeight);

                if (vertexBones[vertexId].size() > mMaxBoneCount) {

                    throw DeadlyImportError("SplitByBoneCountProcess: Single face requires more bones than specified max bone count!");

                }

            }

        }

    }

    unsigned int numFacesHandled = 0;

    std::vector<bool> isFaceHandled( pMesh->mNumFaces, false);

    while( numFacesHandled < pMesh->mNumFaces ) {

        // which bones are used in the current submesh

        unsigned int numBones = 0;

        std::vector<bool> isBoneUsed( pMesh->mNumBones, false);

        // indices of the faces which are going to go into this submesh

        IndexArray subMeshFaces;

        subMeshFaces.reserve( pMesh->mNumFaces);

        // accumulated vertex count of all the faces in this submesh

        unsigned int numSubMeshVertices = 0;

        // add faces to the new submesh as long as all bones affecting the faces' vertices fit in the limit

        for( unsigned int a = 0; a < pMesh->mNumFaces; ++a) {

            // skip if the face is already stored in a submesh

            if( isFaceHandled[a] ) {

                continue;

            }

            // a small local set of new bones for the current face. State of all used bones for that face

            // can only be updated AFTER the face is completely analysed. Thanks to imre for the fix.

            std::set<unsigned int> newBonesAtCurrentFace;

            const aiFace& face = pMesh->mFaces[a];

            // check every vertex if its bones would still fit into the current submesh

            for( unsigned int b = 0; b < face.mNumIndices; ++b ) {

                const std::vector<BoneWeight>& vb = vertexBones[face.mIndices[b]];

                for( unsigned int c = 0; c < vb.size(); ++c) {

                    unsigned int boneIndex = vb[c].first;

                    if( !isBoneUsed[boneIndex] ) {

                        newBonesAtCurrentFace.insert(boneIndex);

                    }

                }

            }

            // leave out the face if the new bones required for this face don't fit the bone count limit anymore

            if( numBones + newBonesAtCurrentFace.size() > mMaxBoneCount ) {

                continue;

            }

            // mark all new bones as necessary

            for (std::set<unsigned int>::iterator it = newBonesAtCurrentFace.begin(); it != newBonesAtCurrentFace.end(); ++it) {

                if (!isBoneUsed[*it]) {

                    isBoneUsed[*it] = true;

                    ++numBones;

                }

            }

            // store the face index and the vertex count

            subMeshFaces.push_back( a);

            numSubMeshVertices += face.mNumIndices;

            // remember that this face is handled

            isFaceHandled[a] = true;

            ++numFacesHandled;

        }

        // create a new mesh to hold this subset of the source mesh

        aiMesh* newMesh = new aiMesh;

        if( pMesh->mName.length > 0 ) {

            newMesh->mName.Set( format() << pMesh->mName.data << "_sub" << poNewMeshes.size());

        }

        newMesh->mMaterialIndex = pMesh->mMaterialIndex;

        newMesh->mPrimitiveTypes = pMesh->mPrimitiveTypes;

        poNewMeshes.emplace_back( newMesh);

        // create all the arrays for this mesh if the old mesh contained them

        newMesh->mNumVertices = numSubMeshVertices;

        newMesh->mNumFaces = static_cast<unsigned int>(subMeshFaces.size());

        newMesh->mVertices = new aiVector3D[newMesh->mNumVertices];

        if( pMesh->HasNormals() ) {

            newMesh->mNormals = new aiVector3D[newMesh->mNumVertices];

        }

        if( pMesh->HasTangentsAndBitangents() ) {

            newMesh->mTangents = new aiVector3D[newMesh->mNumVertices];

            newMesh->mBitangents = new aiVector3D[newMesh->mNumVertices];

        }

        for( unsigned int a = 0; a < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++a ) {

            if( pMesh->HasTextureCoords( a) ) {

                newMesh->mTextureCoords[a] = new aiVector3D[newMesh->mNumVertices];

            }

            newMesh->mNumUVComponents[a] = pMesh->mNumUVComponents[a];

        }

        for( unsigned int a = 0; a < AI_MAX_NUMBER_OF_COLOR_SETS; ++a ) {

            if( pMesh->HasVertexColors( a) ) {

                newMesh->mColors[a] = new aiColor4D[newMesh->mNumVertices];

            }

        }

        // and copy over the data, generating faces with linear indices along the way

        newMesh->mFaces = new aiFace[subMeshFaces.size()];

        unsigned int nvi = 0; // next vertex index

        IndexArray previousVertexIndices( numSubMeshVertices, std::numeric_limits<unsigned int>::max()); // per new vertex: its index in the source mesh

        for( unsigned int a = 0; a < subMeshFaces.size(); ++a ) {

            const aiFace& srcFace = pMesh->mFaces[subMeshFaces[a]];

            aiFace& dstFace = newMesh->mFaces[a];

            dstFace.mNumIndices = srcFace.mNumIndices;

            dstFace.mIndices = new unsigned int[dstFace.mNumIndices];

            // accumulate linearly all the vertices of the source face

            for( unsigned int b = 0; b < dstFace.mNumIndices; ++b ) {

                unsigned int srcIndex = srcFace.mIndices[b];

                dstFace.mIndices[b] = nvi;

                previousVertexIndices[nvi] = srcIndex;

                newMesh->mVertices[nvi] = pMesh->mVertices[srcIndex];

                if( pMesh->HasNormals() ) {

                    newMesh->mNormals[nvi] = pMesh->mNormals[srcIndex];

                }

                if( pMesh->HasTangentsAndBitangents() ) {

                    newMesh->mTangents[nvi] = pMesh->mTangents[srcIndex];

                    newMesh->mBitangents[nvi] = pMesh->mBitangents[srcIndex];

                }

                for( unsigned int c = 0; c < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++c ) {

                    if( pMesh->HasTextureCoords( c) ) {

                        newMesh->mTextureCoords[c][nvi] = pMesh->mTextureCoords[c][srcIndex];

                    }

                }

                for( unsigned int c = 0; c < AI_MAX_NUMBER_OF_COLOR_SETS; ++c ) {

                    if( pMesh->HasVertexColors( c) ) {

                        newMesh->mColors[c][nvi] = pMesh->mColors[c][srcIndex];

                    }

                }

                nvi++;

            }

        }

        ai_assert( nvi == numSubMeshVertices );

        // Create the bones for the new submesh: first create the bone array

        newMesh->mNumBones = 0;

        newMesh->mBones = new aiBone*[numBones];

        std::vector<unsigned int> mappedBoneIndex( pMesh->mNumBones, std::numeric_limits<unsigned int>::max());

        for( unsigned int a = 0; a < pMesh->mNumBones; ++a ) {

            if( !isBoneUsed[a] ) {

                continue;

            }

            // create the new bone

            const aiBone* srcBone = pMesh->mBones[a];

            aiBone* dstBone = new aiBone;

            mappedBoneIndex[a] = newMesh->mNumBones;

            newMesh->mBones[newMesh->mNumBones++] = dstBone;

            dstBone->mName = srcBone->mName;

            dstBone->mOffsetMatrix = srcBone->mOffsetMatrix;

            dstBone->mNumWeights = 0;

        }

        ai_assert( newMesh->mNumBones == numBones );

        // iterate over all new vertices and count which bones affected its old vertex in the source mesh

        for( unsigned int a = 0; a < numSubMeshVertices; ++a ) {

            unsigned int oldIndex = previousVertexIndices[a];

            const std::vector<BoneWeight>& bonesOnThisVertex = vertexBones[oldIndex];

            for( unsigned int b = 0; b < bonesOnThisVertex.size(); ++b ) {

                unsigned int newBoneIndex = mappedBoneIndex[ bonesOnThisVertex[b].first ];

                if( newBoneIndex != std::numeric_limits<unsigned int>::max() ) {

                    newMesh->mBones[newBoneIndex]->mNumWeights++;

                }

            }

        }

        // allocate all bone weight arrays accordingly

        for( unsigned int a = 0; a < newMesh->mNumBones; ++a ) {

            aiBone* bone = newMesh->mBones[a];

            ai_assert( bone->mNumWeights > 0 );

            bone->mWeights = new aiVertexWeight[bone->mNumWeights];

            bone->mNumWeights = 0; // for counting up in the next step

        }

        // now copy all the bone vertex weights for all the vertices which made it into the new submesh

        for( unsigned int a = 0; a < numSubMeshVertices; ++a) {

            // find the source vertex for it in the source mesh

            unsigned int previousIndex = previousVertexIndices[a];

            // these bones were affecting it

            const std::vector<BoneWeight>& bonesOnThisVertex = vertexBones[previousIndex];

            // all of the bones affecting it should be present in the new submesh, or else

            // the face it comprises shouldn't be present

            for( unsigned int b = 0; b < bonesOnThisVertex.size(); ++b) {

                unsigned int newBoneIndex = mappedBoneIndex[ bonesOnThisVertex[b].first ];

                ai_assert( newBoneIndex != std::numeric_limits<unsigned int>::max() );

                aiVertexWeight* dstWeight = newMesh->mBones[newBoneIndex]->mWeights + newMesh->mBones[newBoneIndex]->mNumWeights;

                newMesh->mBones[newBoneIndex]->mNumWeights++;

                dstWeight->mVertexId = a;

                dstWeight->mWeight = bonesOnThisVertex[b].second;

            }

        }

        // ... and copy all the morph targets for all the vertices which made it into the new submesh

        if (pMesh->mNumAnimMeshes > 0) {

            newMesh->mNumAnimMeshes = pMesh->mNumAnimMeshes;

            newMesh->mAnimMeshes = new aiAnimMesh*[newMesh->mNumAnimMeshes];

            for (unsigned int morphIdx = 0; morphIdx < newMesh->mNumAnimMeshes; ++morphIdx) {

                aiAnimMesh* origTarget = pMesh->mAnimMeshes[morphIdx];

                aiAnimMesh* newTarget = new aiAnimMesh;

                newTarget->mName = origTarget->mName;

                newTarget->mWeight = origTarget->mWeight;

                newTarget->mNumVertices = numSubMeshVertices;

                newTarget->mVertices = new aiVector3D[numSubMeshVertices];

                newMesh->mAnimMeshes[morphIdx] = newTarget;

                if (origTarget->HasNormals()) {

                    newTarget->mNormals = new aiVector3D[numSubMeshVertices];

                }

                if (origTarget->HasTangentsAndBitangents()) {

                    newTarget->mTangents = new aiVector3D[numSubMeshVertices];

                    newTarget->mBitangents = new aiVector3D[numSubMeshVertices];

                }

                for( unsigned int vi = 0; vi < numSubMeshVertices; ++vi) {

                    // find the source vertex for it in the source mesh

                    unsigned int previousIndex = previousVertexIndices[vi];

                    newTarget->mVertices[vi] = origTarget->mVertices[previousIndex];

                    if (newTarget->HasNormals()) {

                        newTarget->mNormals[vi] = origTarget->mNormals[previousIndex];

                    }

                    if (newTarget->HasTangentsAndBitangents()) {

                        newTarget->mTangents[vi] = origTarget->mTangents[previousIndex];

                        newTarget->mBitangents[vi] = origTarget->mBitangents[previousIndex];

                    }

                }

            }

        }

        // I have the strange feeling that this will break apart at some point in time...

    }

}

// ------------------------------------------------------------------------------------------------

// Recursively updates the node's mesh list to account for the changed mesh list

void SplitByBoneCountProcess::UpdateNode( aiNode* pNode) const {

    // rebuild the node's mesh index list

    if( pNode->mNumMeshes != 0 ) {

        IndexArray newMeshList;

        for( unsigned int a = 0; a < pNode->mNumMeshes; ++a) {

            unsigned int srcIndex = pNode->mMeshes[a];

            const IndexArray& replaceMeshes = mSubMeshIndices[srcIndex];

            newMeshList.insert( newMeshList.end(), replaceMeshes.begin(), replaceMeshes.end());

        }

        delete [] pNode->mMeshes;

        pNode->mNumMeshes = static_cast<unsigned int>(newMeshList.size());

        pNode->mMeshes = new unsigned int[pNode->mNumMeshes];

        std::copy( newMeshList.begin(), newMeshList.end(), pNode->mMeshes);

    }

    // do that also recursively for all children

    for( unsigned int a = 0; a < pNode->mNumChildren; ++a ) {

        UpdateNode( pNode->mChildren[a]);

    }

}