/*
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Open Asset Import Library (assimp)
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*/

/** @file Implementation of the STL importer class */


#ifndef ASSIMP_BUILD_NO_STL_IMPORTER

// internal headers
#include "STLLoader.h"
#include <assimp/ParsingUtils.h>
#include <assimp/fast_atof.h>
#include <memory>
#include <assimp/IOSystem.hpp>
#include <assimp/scene.h>
#include <assimp/DefaultLogger.hpp>
#include <assimp/importerdesc.h>

using namespace Assimp;

namespace {
    
static const aiImporterDesc desc = {
    "Stereolithography (STL) Importer",
    "",
    "",
    "",
    aiImporterFlags_SupportTextFlavour | aiImporterFlags_SupportBinaryFlavour,
    0,
    0,
    0,
    0,
    "stl"
};

// A valid binary STL buffer should consist of the following elements, in order:
// 1) 80 byte header
// 2) 4 byte face count
// 3) 50 bytes per face
static bool IsBinarySTL(const char* buffer, unsigned int fileSize) {
    if( fileSize < 84 ) {
        return false;
    }

    const char *facecount_pos = buffer + 80;
    uint32_t faceCount( 0 );
    ::memcpy( &faceCount, facecount_pos, sizeof( uint32_t ) );
    const uint32_t expectedBinaryFileSize = faceCount * 50 + 84;

    return expectedBinaryFileSize == fileSize;
}

static const size_t BufferSize = 500;
static const char UnicodeBoundary = 127;

// An ascii STL buffer will begin with "solid NAME", where NAME is optional.
// Note: The "solid NAME" check is necessary, but not sufficient, to determine
// if the buffer is ASCII; a binary header could also begin with "solid NAME".
static bool IsAsciiSTL(const char* buffer, unsigned int fileSize) {
    if (IsBinarySTL(buffer, fileSize))
        return false;

    const char* bufferEnd = buffer + fileSize;

    if (!SkipSpaces(&buffer))
        return false;

    if (buffer + 5 >= bufferEnd)
        return false;

    bool isASCII( strncmp( buffer, "solid", 5 ) == 0 );
    if( isASCII ) {
        // A lot of importers are write solid even if the file is binary. So we have to check for ASCII-characters.
        if( fileSize >= BufferSize) {
            isASCII = true;
            for( unsigned int i = 0; i < BufferSize; i++ ) {
                if( buffer[ i ] > UnicodeBoundary) {
                    isASCII = false;
                    break;
                }
            }
        }
    }
    return isASCII;
}
} // namespace

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
STLImporter::STLImporter()
    : mBuffer(),
    fileSize(),
    pScene()
{}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
STLImporter::~STLImporter()
{}

// ------------------------------------------------------------------------------------------------
// Returns whether the class can handle the format of the given file.
bool STLImporter::CanRead( const std::string& pFile, IOSystem* pIOHandler, bool checkSig) const
{
    const std::string extension = GetExtension(pFile);

    if( extension == "stl" ) {
        return true;
    } else if (!extension.length() || checkSig)   {
        if( !pIOHandler ) {
            return true;
        }
        const char* tokens[] = {"STL","solid"};
        return SearchFileHeaderForToken(pIOHandler,pFile,tokens,2);
    }

    return false;
}

// ------------------------------------------------------------------------------------------------
const aiImporterDesc* STLImporter::GetInfo () const {
    return &desc;
}

void addFacesToMesh(aiMesh* pMesh)
{
    pMesh->mFaces = new aiFace[pMesh->mNumFaces];
    for (unsigned int i = 0, p = 0; i < pMesh->mNumFaces;++i)    {

        aiFace& face = pMesh->mFaces[i];
        face.mIndices = new unsigned int[face.mNumIndices = 3];
        for (unsigned int o = 0; o < 3;++o,++p) {
            face.mIndices[o] = p;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Imports the given file into the given scene structure.
void STLImporter::InternReadFile( const std::string& pFile, aiScene* pScene, IOSystem* pIOHandler )
{
    std::unique_ptr<IOStream> file( pIOHandler->Open( pFile, "rb"));

    // Check whether we can read from the file
    if( file.get() == nullptr) {
        throw DeadlyImportError( "Failed to open STL file " + pFile + ".");
    }

    fileSize = (unsigned int)file->FileSize();

    // allocate storage and copy the contents of the file to a memory buffer
    // (terminate it with zero)
    std::vector<char> buffer2;
    TextFileToBuffer(file.get(),buffer2);

    this->pScene = pScene;
    this->mBuffer = &buffer2[0];

    // the default vertex color is light gray.
    clrColorDefault.r = clrColorDefault.g = clrColorDefault.b = clrColorDefault.a = (ai_real) 0.6;

    // allocate a single node
    pScene->mRootNode = new aiNode();

    bool bMatClr = false;

    if (IsBinarySTL(mBuffer, fileSize)) {
        bMatClr = LoadBinaryFile();
    } else if (IsAsciiSTL(mBuffer, fileSize)) {
        LoadASCIIFile( pScene->mRootNode );
    } else {
        throw DeadlyImportError( "Failed to determine STL storage representation for " + pFile + ".");
    }

    // create a single default material, using a white diffuse color for consistency with
    // other geometric types (e.g., PLY).
    aiMaterial* pcMat = new aiMaterial();
    aiString s;
    s.Set(AI_DEFAULT_MATERIAL_NAME);
    pcMat->AddProperty(&s, AI_MATKEY_NAME);

    aiColor4D clrDiffuse(ai_real(1.0),ai_real(1.0),ai_real(1.0),ai_real(1.0));
    if (bMatClr) {
        clrDiffuse = clrColorDefault;
    }
    pcMat->AddProperty(&clrDiffuse,1,AI_MATKEY_COLOR_DIFFUSE);
    pcMat->AddProperty(&clrDiffuse,1,AI_MATKEY_COLOR_SPECULAR);
    clrDiffuse = aiColor4D( ai_real(1.0), ai_real(1.0), ai_real(1.0), ai_real(1.0));
    pcMat->AddProperty(&clrDiffuse,1,AI_MATKEY_COLOR_AMBIENT);

    pScene->mNumMaterials = 1;
    pScene->mMaterials = new aiMaterial*[1];
    pScene->mMaterials[0] = pcMat;

    mBuffer = nullptr;
}

// ------------------------------------------------------------------------------------------------
// Read an ASCII STL file
void STLImporter::LoadASCIIFile( aiNode *root ) {
    std::vector<aiMesh*> meshes;
    std::vector<aiNode*> nodes;
    const char* sz = mBuffer;
    const char* bufferEnd = mBuffer + fileSize;
    std::vector<aiVector3D> positionBuffer;
    std::vector<aiVector3D> normalBuffer;

    // try to guess how many vertices we could have
    // assume we'll need 160 bytes for each face
    size_t sizeEstimate = std::max(1u, fileSize / 160u ) * 3;
    positionBuffer.reserve(sizeEstimate);
    normalBuffer.reserve(sizeEstimate);

    while (IsAsciiSTL(sz, static_cast<unsigned int>(bufferEnd - sz))) {
        std::vector<unsigned int> meshIndices;
        aiMesh* pMesh = new aiMesh();
        pMesh->mMaterialIndex = 0;
        meshIndices.push_back((unsigned int) meshes.size() );
        meshes.push_back(pMesh);
        aiNode *node = new aiNode;
        node->mParent = root;
        nodes.push_back( node );
        SkipSpaces(&sz);
        ai_assert(!IsLineEnd(sz));

        sz += 5; // skip the "solid"
        SkipSpaces(&sz);
        const char* szMe = sz;
        while (!::IsSpaceOrNewLine(*sz)) {
            sz++;
        }

        size_t temp;
        // setup the name of the node
        if ((temp = (size_t)(sz-szMe))) {
            if (temp >= MAXLEN) {
                throw DeadlyImportError( "STL: Node name too long" );
            }
            std::string name( szMe, temp );
            node->mName.Set( name.c_str() );
            //pScene->mRootNode->mName.length = temp;
            //memcpy(pScene->mRootNode->mName.data,szMe,temp);
            //pScene->mRootNode->mName.data[temp] = '\0';
        } else {
            pScene->mRootNode->mName.Set("<STL_ASCII>");
        }

        unsigned int faceVertexCounter = 3;
        for ( ;; ) {
            // go to the next token
            if(!SkipSpacesAndLineEnd(&sz))
            {
                // seems we're finished although there was no end marker
                ASSIMP_LOG_WARN("STL: unexpected EOF. \'endsolid\' keyword was expected");
                break;
            }
            // facet normal -0.13 -0.13 -0.98
            if (!strncmp(sz,"facet",5) && IsSpaceOrNewLine(*(sz+5)) && *(sz + 5) != '\0')    {

                if (faceVertexCounter != 3) {
                    ASSIMP_LOG_WARN("STL: A new facet begins but the old is not yet complete");
                }
                faceVertexCounter = 0;
                normalBuffer.push_back(aiVector3D());
                aiVector3D* vn = &normalBuffer.back();

                sz += 6;
                SkipSpaces(&sz);
                if (strncmp(sz,"normal",6))    {
                    ASSIMP_LOG_WARN("STL: a facet normal vector was expected but not found");
                } else {
                    if (sz[6] == '\0') {
                        throw DeadlyImportError("STL: unexpected EOF while parsing facet");
                    }
                    sz += 7;
                    SkipSpaces(&sz);
                    sz = fast_atoreal_move<ai_real>(sz, (ai_real&)vn->x );
                    SkipSpaces(&sz);
                    sz = fast_atoreal_move<ai_real>(sz, (ai_real&)vn->y );
                    SkipSpaces(&sz);
                    sz = fast_atoreal_move<ai_real>(sz, (ai_real&)vn->z );
                    normalBuffer.push_back(*vn);
                    normalBuffer.push_back(*vn);
                }
            } else if (!strncmp(sz,"vertex",6) && ::IsSpaceOrNewLine(*(sz+6))) { // vertex 1.50000 1.50000 0.00000
                if (faceVertexCounter >= 3) {
                    ASSIMP_LOG_ERROR("STL: a facet with more than 3 vertices has been found");
                    ++sz;
                } else {
                    if (sz[6] == '\0') {
                        throw DeadlyImportError("STL: unexpected EOF while parsing facet");
                    }
                    sz += 7;
                    SkipSpaces(&sz);
                    positionBuffer.push_back(aiVector3D());
                    aiVector3D* vn = &positionBuffer.back();
                    sz = fast_atoreal_move<ai_real>(sz, (ai_real&)vn->x );
                    SkipSpaces(&sz);
                    sz = fast_atoreal_move<ai_real>(sz, (ai_real&)vn->y );
                    SkipSpaces(&sz);
                    sz = fast_atoreal_move<ai_real>(sz, (ai_real&)vn->z );
                    faceVertexCounter++;
                }
            } else if (!::strncmp(sz,"endsolid",8))    {
                do {
                    ++sz;
                } while (!::IsLineEnd(*sz));
                SkipSpacesAndLineEnd(&sz);
                // finished!
                break;
            } else { // else skip the whole identifier
                do {
                    ++sz;
                } while (!::IsSpaceOrNewLine(*sz));
            }
        }

        if (positionBuffer.empty())    {
            pMesh->mNumFaces = 0;
            ASSIMP_LOG_WARN("STL: mesh is empty or invalid; no data loaded");
        }
        if (positionBuffer.size() % 3 != 0)    {
            pMesh->mNumFaces = 0;
            throw DeadlyImportError("STL: Invalid number of vertices");
        }
        if (normalBuffer.size() != positionBuffer.size())    {
            pMesh->mNumFaces = 0;
            throw DeadlyImportError("Normal buffer size does not match position buffer size");
        }

        // only process positionbuffer when filled, else exception when accessing with index operator
        // see line 353: only warning is triggered
        // see line 373(now): access to empty positionbuffer with index operator forced exception
        if (!positionBuffer.empty()) {
            pMesh->mNumFaces = static_cast<unsigned int>(positionBuffer.size() / 3);
            pMesh->mNumVertices = static_cast<unsigned int>(positionBuffer.size());
            pMesh->mVertices = new aiVector3D[pMesh->mNumVertices];
            memcpy(pMesh->mVertices, &positionBuffer[0].x, pMesh->mNumVertices * sizeof(aiVector3D));
            positionBuffer.clear();
        }
        // also only process normalBuffer when filled, else exception when accessing with index operator
        if (!normalBuffer.empty()) {
            pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];
            memcpy(pMesh->mNormals, &normalBuffer[0].x, pMesh->mNumVertices * sizeof(aiVector3D));
            normalBuffer.clear();
        }

        // now copy faces
        addFacesToMesh(pMesh);

        // assign the meshes to the current node
        pushMeshesToNode( meshIndices, node );
    }

    // now add the loaded meshes
    pScene->mNumMeshes = (unsigned int)meshes.size();
    pScene->mMeshes = new aiMesh*[pScene->mNumMeshes];
    for (size_t i = 0; i < meshes.size(); i++) {
        pScene->mMeshes[ i ] = meshes[i];
    }

    root->mNumChildren = (unsigned int) nodes.size();
    root->mChildren = new aiNode*[ root->mNumChildren ];
    for ( size_t i=0; i<nodes.size(); ++i ) {
        root->mChildren[ i ] = nodes[ i ];
    }
}

// ------------------------------------------------------------------------------------------------
// Read a binary STL file
bool STLImporter::LoadBinaryFile()
{
    // allocate one mesh
    pScene->mNumMeshes = 1;
    pScene->mMeshes = new aiMesh*[1];
    aiMesh* pMesh = pScene->mMeshes[0] = new aiMesh();
    pMesh->mMaterialIndex = 0;

    // skip the first 80 bytes
    if (fileSize < 84) {
        throw DeadlyImportError("STL: file is too small for the header");
    }
    bool bIsMaterialise = false;

    // search for an occurrence of "COLOR=" in the header
    const unsigned char* sz2 = (const unsigned char*)mBuffer;
    const unsigned char* const szEnd = sz2+80;
    while (sz2 < szEnd) {

        if ('C' == *sz2++ && 'O' == *sz2++ && 'L' == *sz2++ &&
            'O' == *sz2++ && 'R' == *sz2++ && '=' == *sz2++)    {

            // read the default vertex color for facets
            bIsMaterialise = true;
            ASSIMP_LOG_INFO("STL: Taking code path for Materialise files");
            const ai_real invByte = (ai_real)1.0 / ( ai_real )255.0;
            clrColorDefault.r = (*sz2++) * invByte;
            clrColorDefault.g = (*sz2++) * invByte;
            clrColorDefault.b = (*sz2++) * invByte;
            clrColorDefault.a = (*sz2++) * invByte;
            break;
        }
    }
    const unsigned char* sz = (const unsigned char*)mBuffer + 80;

    // now read the number of facets
    pScene->mRootNode->mName.Set("<STL_BINARY>");

    pMesh->mNumFaces = *((uint32_t*)sz);
    sz += 4;

    if (fileSize < 84 + pMesh->mNumFaces*50) {
        throw DeadlyImportError("STL: file is too small to hold all facets");
    }

    if (!pMesh->mNumFaces) {
        throw DeadlyImportError("STL: file is empty. There are no facets defined");
    }

    pMesh->mNumVertices = pMesh->mNumFaces*3;

    
    aiVector3D *vp = pMesh->mVertices = new aiVector3D[pMesh->mNumVertices];
    aiVector3D *vn = pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];

    typedef aiVector3t<float> aiVector3F;
    aiVector3F* theVec;
    aiVector3F theVec3F;
    
    for ( unsigned int i = 0; i < pMesh->mNumFaces; ++i ) {
        // NOTE: Blender sometimes writes empty normals ... this is not
        // our fault ... the RemoveInvalidData helper step should fix that

        // There's one normal for the face in the STL; use it three times
        // for vertex normals
        theVec = (aiVector3F*) sz;
        ::memcpy( &theVec3F, theVec, sizeof(aiVector3F) );
        vn->x = theVec3F.x; vn->y = theVec3F.y; vn->z = theVec3F.z;
        *(vn+1) = *vn;
        *(vn+2) = *vn;
        ++theVec;
        vn += 3;

        // vertex 1
        ::memcpy( &theVec3F, theVec, sizeof(aiVector3F) );
        vp->x = theVec3F.x; vp->y = theVec3F.y; vp->z = theVec3F.z;
        ++theVec;
        ++vp;

        // vertex 2
        ::memcpy( &theVec3F, theVec, sizeof(aiVector3F) );
        vp->x = theVec3F.x; vp->y = theVec3F.y; vp->z = theVec3F.z;
        ++theVec;
        ++vp;

        // vertex 3
        ::memcpy( &theVec3F, theVec, sizeof(aiVector3F) );
        vp->x = theVec3F.x; vp->y = theVec3F.y; vp->z = theVec3F.z;
        ++theVec;
        ++vp;
        
        sz = (const unsigned char*) theVec;

        uint16_t color = *((uint16_t*)sz);
        sz += 2;

        if (color & (1 << 15))
        {
            // seems we need to take the color
            if (!pMesh->mColors[0])
            {
                pMesh->mColors[0] = new aiColor4D[pMesh->mNumVertices];
                for (unsigned int i = 0; i <pMesh->mNumVertices;++i)
                    *pMesh->mColors[0]++ = this->clrColorDefault;
                pMesh->mColors[0] -= pMesh->mNumVertices;

                ASSIMP_LOG_INFO("STL: Mesh has vertex colors");
            }
            aiColor4D* clr = &pMesh->mColors[0][i*3];
            clr->a = 1.0;
            const ai_real invVal( (ai_real)1.0 / ( ai_real )31.0 );
            if (bIsMaterialise) // this is reversed
            {
                clr->r = (color & 0x31u) *invVal;
                clr->g = ((color & (0x31u<<5))>>5u) *invVal;
                clr->b = ((color & (0x31u<<10))>>10u) *invVal;
            }
            else
            {
                clr->b = (color & 0x31u) *invVal;
                clr->g = ((color & (0x31u<<5))>>5u) *invVal;
                clr->r = ((color & (0x31u<<10))>>10u) *invVal;
            }
            // assign the color to all vertices of the face
            *(clr+1) = *clr;
            *(clr+2) = *clr;
        }
    }

    // now copy faces
    addFacesToMesh(pMesh);

    aiNode* root = pScene->mRootNode;

    // allocate one node
    aiNode* node = new aiNode();
    node->mParent = root;

    root->mNumChildren = 1u;
    root->mChildren = new aiNode*[root->mNumChildren];
    root->mChildren[0] = node;

    // add all created meshes to the single node
    node->mNumMeshes = pScene->mNumMeshes;
    node->mMeshes = new unsigned int[pScene->mNumMeshes];
    for (unsigned int i = 0; i < pScene->mNumMeshes; i++)
        node->mMeshes[i] = i;

    if (bIsMaterialise && !pMesh->mColors[0])
    {
        // use the color as diffuse material color
        return true;
    }
    return false;
}

void STLImporter::pushMeshesToNode( std::vector<unsigned int> &meshIndices, aiNode *node ) {
    ai_assert( nullptr != node );
    if ( meshIndices.empty() ) {
        return;
    }

    node->mNumMeshes = static_cast<unsigned int>( meshIndices.size() );
    node->mMeshes = new unsigned int[ meshIndices.size() ];
    for ( size_t i=0; i<meshIndices.size(); ++i ) {
        node->mMeshes[ i ] = meshIndices[ i ];
    }
    meshIndices.clear();
}

#endif // !! ASSIMP_BUILD_NO_STL_IMPORTER
