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

#ifndef ASSIMP_BUILD_NO_STL_IMPORTER

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

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, size_t 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, size_t 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(),
        mFileSize(0),
        mScene() {
   // empty
}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
STLImporter::~STLImporter() = default;

// ------------------------------------------------------------------------------------------------
// Returns whether the class can handle the format of the given file.
bool STLImporter::CanRead(const std::string &pFile, IOSystem *pIOHandler, bool /*checkSig*/) const {
    static const char *tokens[] = { "STL", "solid" };
    return SearchFileHeaderForToken(pIOHandler, pFile, tokens, AI_COUNT_OF(tokens));
}

// ------------------------------------------------------------------------------------------------
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 == nullptr) {
        throw DeadlyImportError("Failed to open STL file ", pFile, ".");
    }

    mFileSize = 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);

    mScene = pScene;
    mBuffer = &buffer2[0];

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

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

    bool bMatClr = false;

    if (IsBinarySTL(mBuffer, mFileSize)) {
        bMatClr = LoadBinaryFile();
    } else if (IsAsciiSTL(mBuffer, mFileSize)) {
        LoadASCIIFile(mScene->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 = mClrColorDefault;
    }
    pcMat->AddProperty(&clrDiffuse, 1, AI_MATKEY_COLOR_DIFFUSE);
    pcMat->AddProperty(&clrDiffuse, 1, AI_MATKEY_COLOR_SPECULAR);
    clrDiffuse = aiColor4D(ai_real(0.05), ai_real(0.05), ai_real(0.05), ai_real(1.0));
    pcMat->AddProperty(&clrDiffuse, 1, AI_MATKEY_COLOR_AMBIENT);

    mScene->mNumMaterials = 1;
    mScene->mMaterials = new aiMaterial *[1];
    mScene->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 + mFileSize;
    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(1ull, mFileSize / 160ull) * 3ull;
    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 = (size_t)(sz - szMe);
        // setup the name of the node
        if ( temp ) {
            if (temp >= MAXLEN) {
                throw DeadlyImportError("STL: Node name too long");
            }
            std::string name(szMe, temp);
            node->mName.Set(name.c_str());
            pMesh->mName.Set(name.c_str());
        } else {
            mScene->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;

                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");
                    }
                    aiVector3D vn;
                    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.emplace_back(vn);
                    normalBuffer.emplace_back(vn);
                    normalBuffer.emplace_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.emplace_back();
                    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];
            for (size_t i=0; i<pMesh->mNumVertices; ++i ) {
                pMesh->mVertices[i].x = positionBuffer[i].x;
                pMesh->mVertices[i].y = positionBuffer[i].y;
                pMesh->mVertices[i].z = positionBuffer[i].z;
            }
            positionBuffer.clear();
        }
        // also only process normalBuffer when filled, else exception when accessing with index operator
        if (!normalBuffer.empty()) {
            pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];
            for (size_t i=0; i<pMesh->mNumVertices; ++i ) {
                pMesh->mNormals[i].x = normalBuffer[i].x;
                pMesh->mNormals[i].y = normalBuffer[i].y;
                pMesh->mNormals[i].z = normalBuffer[i].z;
            }
            normalBuffer.clear();
        }

        // now copy faces
        addFacesToMesh(pMesh);

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

    // now add the loaded meshes
    mScene->mNumMeshes = (unsigned int)meshes.size();
    mScene->mMeshes = new aiMesh *[mScene->mNumMeshes];
    for (size_t i = 0; i < meshes.size(); i++) {
        mScene->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
    mScene->mNumMeshes = 1;
    mScene->mMeshes = new aiMesh *[1];
    aiMesh *pMesh = mScene->mMeshes[0] = new aiMesh();
    pMesh->mMaterialIndex = 0;

    // skip the first 80 bytes
    if (mFileSize < 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;
            mClrColorDefault.r = (*sz2++) * invByte;
            mClrColorDefault.g = (*sz2++) * invByte;
            mClrColorDefault.b = (*sz2++) * invByte;
            mClrColorDefault.a = (*sz2++) * invByte;
            break;
        }
    }
    const unsigned char *sz = (const unsigned char *)mBuffer + 80;

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

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

    if (mFileSize < 84ull + pMesh->mNumFaces * 50ull) {
        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 j = 0; j < pMesh->mNumVertices; ++j) {
                    *pMesh->mColors[0]++ = mClrColorDefault;
                }
                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 & 0x1fu) * invVal;
                clr->g = ((color & (0x1fu << 5)) >> 5u) * invVal;
                clr->b = ((color & (0x1fu << 10)) >> 10u) * invVal;
            } else {
                clr->b = (color & 0x1fu) * invVal;
                clr->g = ((color & (0x1fu << 5)) >> 5u) * invVal;
                clr->r = ((color & (0x1fu << 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 = mScene->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 = mScene->mNumMeshes;
    node->mMeshes = new unsigned int[mScene->mNumMeshes];
    for (unsigned int i = 0; i < mScene->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
