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/** @file  UnrealLoader.cpp
 *  @brief Implementation of the UNREAL (*.3D) importer class
 *
 *  Sources:
 *    http://local.wasp.uwa.edu.au/~pbourke/dataformats/unreal/
 */

#ifndef ASSIMP_BUILD_NO_3D_IMPORTER

#include "AssetLib/Unreal/UnrealLoader.h"
#include "PostProcessing/ConvertToLHProcess.h"

#include <assimp/ParsingUtils.h>
#include <assimp/StreamReader.h>
#include <assimp/fast_atof.h>
#include <assimp/importerdesc.h>
#include <assimp/scene.h>
#include <assimp/DefaultLogger.hpp>
#include <assimp/IOSystem.hpp>
#include <assimp/Importer.hpp>

#include <cstdint>
#include <memory>

using namespace Assimp;

namespace Unreal {

/*
    0 = Normal one-sided
    1 = Normal two-sided
    2 = Translucent two-sided
    3 = Masked two-sided
    4 = Modulation blended two-sided
    8 = Placeholder triangle for weapon positioning (invisible)
*/
enum MeshFlags {
    MF_NORMAL_OS = 0,
    MF_NORMAL_TS = 1,
    MF_NORMAL_TRANS_TS = 2,
    MF_NORMAL_MASKED_TS = 3,
    MF_NORMAL_MOD_TS = 4,
    MF_WEAPON_PLACEHOLDER = 8
};

// a single triangle
struct Triangle {
    uint16_t mVertex[3]; // Vertex indices
    char mType; // James' Mesh Type
    char mColor; // Color for flat and Gourand Shaded
    unsigned char mTex[3][2]; // Texture UV coordinates
    unsigned char mTextureNum; // Source texture offset
    char mFlags; // Unreal Mesh Flags (unused)
    unsigned int matIndex;
};

// temporary representation for a material
struct TempMat {
    TempMat() :
            type(MF_NORMAL_OS), tex(), numFaces(0) {}

    explicit TempMat(const Triangle &in) :
            type((Unreal::MeshFlags)in.mType), tex(in.mTextureNum), numFaces(0) {}

    // type of mesh
    Unreal::MeshFlags type;

    // index of texture
    unsigned int tex;

    // number of faces using us
    unsigned int numFaces;

    // for std::find
    bool operator==(const TempMat &o) {
        return (tex == o.tex && type == o.type);
    }
};

struct Vertex {
    int32_t X : 11;
    int32_t Y : 11;
    int32_t Z : 10;
};

// UNREAL vertex compression
inline void CompressVertex(const aiVector3D &v, uint32_t &out) {
    union {
        Vertex n;
        int32_t t;
    };
    t = 0;
    n.X = (int32_t)v.x;
    n.Y = (int32_t)v.y;
    n.Z = (int32_t)v.z;
    ::memcpy(&out, &t, sizeof(int32_t));
}

// UNREAL vertex decompression
inline void DecompressVertex(aiVector3D &v, int32_t in) {
    union {
        Vertex n;
        int32_t i;
    };
    i = in;

    v.x = (float)n.X;
    v.y = (float)n.Y;
    v.z = (float)n.Z;
}

} // end namespace Unreal

static const aiImporterDesc desc = {
    "Unreal Mesh Importer",
    "",
    "",
    "",
    aiImporterFlags_SupportTextFlavour,
    0,
    0,
    0,
    0,
    "3d uc"
};

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
UnrealImporter::UnrealImporter() :
        mConfigFrameID(0), mConfigHandleFlags(true) {
    // empty
}

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

// ------------------------------------------------------------------------------------------------
// Returns whether the class can handle the format of the given file.
bool UnrealImporter::CanRead(const std::string & filename, IOSystem * /*pIOHandler*/, bool /*checkSig*/) const {
    return SimpleExtensionCheck(filename, "3d", "uc");
}

// ------------------------------------------------------------------------------------------------
// Build a string of all file extensions supported
const aiImporterDesc *UnrealImporter::GetInfo() const {
    return &desc;
}

// ------------------------------------------------------------------------------------------------
// Setup configuration properties for the loader
void UnrealImporter::SetupProperties(const Importer *pImp) {
    // The
    // AI_CONFIG_IMPORT_UNREAL_KEYFRAME option overrides the
    // AI_CONFIG_IMPORT_GLOBAL_KEYFRAME option.
    mConfigFrameID = pImp->GetPropertyInteger(AI_CONFIG_IMPORT_UNREAL_KEYFRAME, -1);
    if (static_cast<unsigned int>(-1) == mConfigFrameID) {
        mConfigFrameID = pImp->GetPropertyInteger(AI_CONFIG_IMPORT_GLOBAL_KEYFRAME, 0);
    }

    // AI_CONFIG_IMPORT_UNREAL_HANDLE_FLAGS, default is true
    mConfigHandleFlags = (0 != pImp->GetPropertyInteger(AI_CONFIG_IMPORT_UNREAL_HANDLE_FLAGS, 1));
}

// ------------------------------------------------------------------------------------------------
// Imports the given file into the given scene structure.
void UnrealImporter::InternReadFile(const std::string &pFile,
        aiScene *pScene, IOSystem *pIOHandler) {
    // For any of the 3 files being passed get the three correct paths
    // First of all, determine file extension
    std::string::size_type pos = pFile.find_last_of('.');
    std::string extension = GetExtension(pFile);

    std::string d_path, a_path, uc_path;
    if (extension == "3d") {
        // jjjj_d.3d
        // jjjj_a.3d
        pos = pFile.find_last_of('_');
        if (std::string::npos == pos) {
            throw DeadlyImportError("UNREAL: Unexpected naming scheme");
        }
        extension = pFile.substr(0, pos);
    } else {
        extension = pFile.substr(0, pos);
    }

    // build proper paths
    d_path = extension + "_d.3d";
    a_path = extension + "_a.3d";
    uc_path = extension + ".uc";

    ASSIMP_LOG_DEBUG("UNREAL: data file is ", d_path);
    ASSIMP_LOG_DEBUG("UNREAL: aniv file is ", a_path);
    ASSIMP_LOG_DEBUG("UNREAL: uc file is ", uc_path);

    // and open the files ... we can't live without them
    std::unique_ptr<IOStream> p(pIOHandler->Open(d_path));
    if (!p)
        throw DeadlyImportError("UNREAL: Unable to open _d file");
    StreamReaderLE d_reader(pIOHandler->Open(d_path));

    const uint16_t numTris = d_reader.GetI2();
    const uint16_t numVert = d_reader.GetI2();
    d_reader.IncPtr(44);
    if (!numTris || numVert < 3)
        throw DeadlyImportError("UNREAL: Invalid number of vertices/triangles");

    // maximum texture index
    unsigned int maxTexIdx = 0;

    // collect triangles
    std::vector<Unreal::Triangle> triangles(numTris);
    for (auto &tri : triangles) {
        for (unsigned int i = 0; i < 3; ++i) {

            tri.mVertex[i] = d_reader.GetI2();
            if (tri.mVertex[i] >= numTris) {
                ASSIMP_LOG_WARN("UNREAL: vertex index out of range");
                tri.mVertex[i] = 0;
            }
        }
        tri.mType = d_reader.GetI1();

        // handle mesh flagss?
        if (mConfigHandleFlags)
            tri.mType = Unreal::MF_NORMAL_OS;
        else {
            // ignore MOD and MASKED for the moment, treat them as two-sided
            if (tri.mType == Unreal::MF_NORMAL_MOD_TS || tri.mType == Unreal::MF_NORMAL_MASKED_TS)
                tri.mType = Unreal::MF_NORMAL_TS;
        }
        d_reader.IncPtr(1);

        for (unsigned int i = 0; i < 3; ++i)
            for (unsigned int i2 = 0; i2 < 2; ++i2)
                tri.mTex[i][i2] = d_reader.GetI1();

        tri.mTextureNum = d_reader.GetI1();
        maxTexIdx = std::max(maxTexIdx, (unsigned int)tri.mTextureNum);
        d_reader.IncPtr(1);
    }

    p.reset(pIOHandler->Open(a_path));
    if (!p)
        throw DeadlyImportError("UNREAL: Unable to open _a file");
    StreamReaderLE a_reader(pIOHandler->Open(a_path));

    // read number of frames
    const uint32_t numFrames = a_reader.GetI2();
    if (mConfigFrameID >= numFrames) {
        throw DeadlyImportError("UNREAL: The requested frame does not exist");
    }

    uint32_t st = a_reader.GetI2();
    if (st != numVert * 4u)
        throw DeadlyImportError("UNREAL: Unexpected aniv file length");

    // skip to our frame
    a_reader.IncPtr(mConfigFrameID * numVert * 4);

    // collect vertices
    std::vector<aiVector3D> vertices(numVert);
    for (auto &vertex : vertices) {
        int32_t val = a_reader.GetI4();
        Unreal::DecompressVertex(vertex, val);
    }

    // list of textures.
    std::vector<std::pair<unsigned int, std::string>> textures;

    // allocate the output scene
    aiNode *nd = pScene->mRootNode = new aiNode();
    nd->mName.Set("<UnrealRoot>");

    // we can live without the uc file if necessary
    std::unique_ptr<IOStream> pb(pIOHandler->Open(uc_path));
    if (pb.get()) {

        std::vector<char> _data;
        TextFileToBuffer(pb.get(), _data);
        const char *data = &_data[0];

        std::vector<std::pair<std::string, std::string>> tempTextures;

        // do a quick search in the UC file for some known, usually texture-related, tags
        for (; *data; ++data) {
            if (TokenMatchI(data, "#exec", 5)) {
                SkipSpacesAndLineEnd(&data);

                // #exec TEXTURE IMPORT [...] NAME=jjjjj [...] FILE=jjjj.pcx [...]
                if (TokenMatchI(data, "TEXTURE", 7)) {
                    SkipSpacesAndLineEnd(&data);

                    if (TokenMatchI(data, "IMPORT", 6)) {
                        tempTextures.emplace_back();
                        std::pair<std::string, std::string> &me = tempTextures.back();
                        for (; !IsLineEnd(*data); ++data) {
                            if (!::ASSIMP_strincmp(data, "NAME=", 5)) {
                                const char *d = data += 5;
                                for (; !IsSpaceOrNewLine(*data); ++data)
                                    ;
                                me.first = std::string(d, (size_t)(data - d));
                            } else if (!::ASSIMP_strincmp(data, "FILE=", 5)) {
                                const char *d = data += 5;
                                for (; !IsSpaceOrNewLine(*data); ++data)
                                    ;
                                me.second = std::string(d, (size_t)(data - d));
                            }
                        }
                        if (!me.first.length() || !me.second.length())
                            tempTextures.pop_back();
                    }
                }
                // #exec MESHMAP SETTEXTURE MESHMAP=box NUM=1 TEXTURE=Jtex1
                // #exec MESHMAP SCALE MESHMAP=box X=0.1 Y=0.1 Z=0.2
                else if (TokenMatchI(data, "MESHMAP", 7)) {
                    SkipSpacesAndLineEnd(&data);

                    if (TokenMatchI(data, "SETTEXTURE", 10)) {

                        textures.emplace_back();
                        std::pair<unsigned int, std::string> &me = textures.back();

                        for (; !IsLineEnd(*data); ++data) {
                            if (!::ASSIMP_strincmp(data, "NUM=", 4)) {
                                data += 4;
                                me.first = strtoul10(data, &data);
                            } else if (!::ASSIMP_strincmp(data, "TEXTURE=", 8)) {
                                data += 8;
                                const char *d = data;
                                for (; !IsSpaceOrNewLine(*data); ++data)
                                    ;
                                me.second = std::string(d, (size_t)(data - d));

                                // try to find matching path names, doesn't care if we don't find them
                                for (std::vector<std::pair<std::string, std::string>>::const_iterator it = tempTextures.begin();
                                        it != tempTextures.end(); ++it) {
                                    if ((*it).first == me.second) {
                                        me.second = (*it).second;
                                        break;
                                    }
                                }
                            }
                        }
                    } else if (TokenMatchI(data, "SCALE", 5)) {

                        for (; !IsLineEnd(*data); ++data) {
                            if (data[0] == 'X' && data[1] == '=') {
                                data = fast_atoreal_move<float>(data + 2, (float &)nd->mTransformation.a1);
                            } else if (data[0] == 'Y' && data[1] == '=') {
                                data = fast_atoreal_move<float>(data + 2, (float &)nd->mTransformation.b2);
                            } else if (data[0] == 'Z' && data[1] == '=') {
                                data = fast_atoreal_move<float>(data + 2, (float &)nd->mTransformation.c3);
                            }
                        }
                    }
                }
            }
        }
    } else {
        ASSIMP_LOG_ERROR("Unable to open .uc file");
    }

    std::vector<Unreal::TempMat> materials;
    materials.reserve(textures.size() * 2 + 5);

    // find out how many output meshes and materials we'll have and build material indices
    for (Unreal::Triangle &tri : triangles) {
        Unreal::TempMat mat(tri);
        std::vector<Unreal::TempMat>::iterator nt = std::find(materials.begin(), materials.end(), mat);
        if (nt == materials.end()) {
            // add material
            tri.matIndex = static_cast<unsigned int>(materials.size());
            mat.numFaces = 1;
            materials.push_back(mat);

            ++pScene->mNumMeshes;
        } else {
            tri.matIndex = static_cast<unsigned int>(nt - materials.begin());
            ++nt->numFaces;
        }
    }

    if (!pScene->mNumMeshes) {
        throw DeadlyImportError("UNREAL: Unable to find valid mesh data");
    }

    // allocate meshes and bind them to the node graph
    pScene->mMeshes = new aiMesh *[pScene->mNumMeshes];
    pScene->mMaterials = new aiMaterial *[pScene->mNumMaterials = pScene->mNumMeshes];

    nd->mNumMeshes = pScene->mNumMeshes;
    nd->mMeshes = new unsigned int[nd->mNumMeshes];
    for (unsigned int i = 0; i < pScene->mNumMeshes; ++i) {
        aiMesh *m = pScene->mMeshes[i] = new aiMesh();
        m->mPrimitiveTypes = aiPrimitiveType_TRIANGLE;

        const unsigned int num = materials[i].numFaces;
        m->mFaces = new aiFace[num];
        m->mVertices = new aiVector3D[num * 3];
        m->mTextureCoords[0] = new aiVector3D[num * 3];

        nd->mMeshes[i] = i;

        // create materials, too
        aiMaterial *mat = new aiMaterial();
        pScene->mMaterials[i] = mat;

        // all white by default - texture rulez
        aiColor3D color(1.f, 1.f, 1.f);

        aiString s;
        ::ai_snprintf(s.data, MAXLEN, "mat%u_tx%u_", i, materials[i].tex);

        // set the two-sided flag
        if (materials[i].type == Unreal::MF_NORMAL_TS) {
            const int twosided = 1;
            mat->AddProperty(&twosided, 1, AI_MATKEY_TWOSIDED);
            ::strcat(s.data, "ts_");
        } else
            ::strcat(s.data, "os_");

        // make TRANS faces 90% opaque that RemRedundantMaterials won't catch us
        if (materials[i].type == Unreal::MF_NORMAL_TRANS_TS) {
            const float opac = 0.9f;
            mat->AddProperty(&opac, 1, AI_MATKEY_OPACITY);
            ::strcat(s.data, "tran_");
        } else
            ::strcat(s.data, "opaq_");

        // a special name for the weapon attachment point
        if (materials[i].type == Unreal::MF_WEAPON_PLACEHOLDER) {
            s.length = ::ai_snprintf(s.data, MAXLEN, "$WeaponTag$");
            color = aiColor3D(0.f, 0.f, 0.f);
        }

        // set color and name
        mat->AddProperty(&color, 1, AI_MATKEY_COLOR_DIFFUSE);
        s.length = static_cast<ai_uint32>(::strlen(s.data));
        mat->AddProperty(&s, AI_MATKEY_NAME);

        // set texture, if any
        const unsigned int tex = materials[i].tex;
        for (std::vector<std::pair<unsigned int, std::string>>::const_iterator it = textures.begin(); it != textures.end(); ++it) {
            if ((*it).first == tex) {
                s.Set((*it).second);
                mat->AddProperty(&s, AI_MATKEY_TEXTURE_DIFFUSE(0));
                break;
            }
        }
    }

    // fill them.
    for (const Unreal::Triangle &tri : triangles) {
        Unreal::TempMat mat(tri);
        std::vector<Unreal::TempMat>::iterator nt = std::find(materials.begin(), materials.end(), mat);

        aiMesh *mesh = pScene->mMeshes[nt - materials.begin()];
        aiFace &f = mesh->mFaces[mesh->mNumFaces++];
        f.mIndices = new unsigned int[f.mNumIndices = 3];

        for (unsigned int i = 0; i < 3; ++i, mesh->mNumVertices++) {
            f.mIndices[i] = mesh->mNumVertices;

            mesh->mVertices[mesh->mNumVertices] = vertices[tri.mVertex[i]];
            mesh->mTextureCoords[0][mesh->mNumVertices] = aiVector3D(tri.mTex[i][0] / 255.f, 1.f - tri.mTex[i][1] / 255.f, 0.f);
        }
    }

    // convert to RH
    MakeLeftHandedProcess hero;
    hero.Execute(pScene);

    FlipWindingOrderProcess flipper;
    flipper.Execute(pScene);
}

#endif // !! ASSIMP_BUILD_NO_3D_IMPORTER
