/*

---------------------------------------------------------------------------

Open Asset Import Library (assimp)

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  following disclaimer.

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/** @file  SIBImporter.cpp

 *  @brief Implementation of the SIB importer class.

 *

 *  The Nevercenter Silo SIB format is undocumented.

 *  All details here have been reverse engineered from

 *  studying the binary files output by Silo.

 *

 *  Nevertheless, this implementation is reasonably complete.

 */

#ifndef ASSIMP_BUILD_NO_SIB_IMPORTER

// internal headers

#include "SIBImporter.h"

#include <assimp/ByteSwapper.h>

#include <assimp/StreamReader.h>

#include <assimp/TinyFormatter.h>

#include "utf8.h"

#include <assimp/importerdesc.h>

#include <assimp/scene.h>

#include <assimp/DefaultLogger.hpp>

#include <assimp/IOSystem.hpp>

#include <assimp/StringUtils.h>

#include <map>

namespace Assimp {

static constexpr aiImporterDesc desc = {

    "Silo SIB Importer",

    "Richard Mitton (http://www.codersnotes.com/about)",

    "",

    "Does not apply subdivision.",

    aiImporterFlags_SupportBinaryFlavour,

    0, 0,

    0, 0,

    "sib"

};

struct SIBChunk {

    uint32_t Tag;

    uint32_t Size;

};

enum {

    POS,

    NRM,

    UV,

    N

};

using SIBPair = std::pair<uint32_t, uint32_t>;

struct SIBEdge {

    uint32_t faceA, faceB;

    bool creased;

};

struct SIBMesh {

    aiMatrix4x4 axis;

    uint32_t numPts;

    std::vector<aiVector3D> pos, nrm, uv;

    std::vector<uint32_t> idx;

    std::vector<uint32_t> faceStart;

    std::vector<uint32_t> mtls;

    std::vector<SIBEdge> edges;

    std::map<SIBPair, uint32_t> edgeMap;

};

struct SIBObject {

    aiString name;

    aiMatrix4x4 axis;

    size_t meshIdx, meshCount;

};

struct SIB {

    std::vector<aiMaterial *> mtls;

    std::vector<aiMesh *> meshes;

    std::vector<aiLight *> lights;

    std::vector<SIBObject> objs, insts;

};

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

static SIBEdge &GetEdge(SIBMesh *mesh, uint32_t posA, uint32_t posB) {

    SIBPair pair = (posA < posB) ? SIBPair(posA, posB) : SIBPair(posB, posA);

    std::map<SIBPair, uint32_t>::iterator it = mesh->edgeMap.find(pair);

    if (it != mesh->edgeMap.end())

        return mesh->edges[it->second];

    SIBEdge edge;

    edge.creased = false;

    edge.faceA = edge.faceB = 0xffffffff;

    mesh->edgeMap[pair] = static_cast<uint32_t>(mesh->edges.size());

    mesh->edges.push_back(edge);

    return mesh->edges.back();

}

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

// Helpers for reading chunked data.

#define TAG(A, B, C, D) ((A << 24) | (B << 16) | (C << 8) | D)

static SIBChunk ReadChunk(StreamReaderLE *stream) {

    SIBChunk chunk;

    chunk.Tag = stream->GetU4();

    chunk.Size = stream->GetU4();

    if (chunk.Size > stream->GetRemainingSizeToLimit())

        ASSIMP_LOG_ERROR("SIB: Chunk overflow");

    ByteSwap::Swap4(&chunk.Tag);

    return chunk;

}

static aiColor3D ReadColor(StreamReaderLE *stream) {

    float r = stream->GetF4();

    float g = stream->GetF4();

    float b = stream->GetF4();

    stream->GetU4(); // Colors have an unused(?) 4th component.

    return aiColor3D(r, g, b);

}

static void UnknownChunk(StreamReaderLE * /*stream*/, const SIBChunk &chunk) {

    char temp[4] = {

        static_cast<char>((chunk.Tag >> 24) & 0xff),

        static_cast<char>((chunk.Tag >> 16) & 0xff),

        static_cast<char>((chunk.Tag >> 8) & 0xff),

        static_cast<char>(chunk.Tag & 0xff)

    };

    ASSIMP_LOG_WARN("SIB: Skipping unknown '", ai_str_toprintable(temp, 4), "' chunk.");

}

// Reads a UTF-16LE string and returns it at UTF-8.

static aiString ReadString(StreamReaderLE *stream, uint32_t numWChars) {

    if (nullptr == stream || 0 == numWChars) {

        return aiString();

    }

    // Allocate buffers (max expansion is 1 byte -> 4 bytes for UTF-8)

    std::vector<unsigned char> str;

    str.reserve(numWChars * 4 + 1);

    uint16_t *temp = new uint16_t[numWChars];

    for (uint32_t n = 0; n < numWChars; ++n) {

        temp[n] = stream->GetU2();

    }

    // Convert it and NUL-terminate.

    const uint16_t *start(temp), *end(temp + numWChars);

    utf8::utf16to8(start, end, back_inserter(str));

    str[str.size() - 1] = '\0';

    // Return the final string.

    aiString result = aiString((const char *)&str[0]);

    delete[] temp;

    return result;

}

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

// Returns whether the class can handle the format of the given file.

bool SIBImporter::CanRead(const std::string &filename, IOSystem * /*pIOHandler*/, bool /*checkSig*/) const {

    return SimpleExtensionCheck(filename, "sib");

}

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

const aiImporterDesc *SIBImporter::GetInfo() const {

    return &desc;

}

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

static void ReadVerts(SIBMesh *mesh, StreamReaderLE *stream, uint32_t count) {

    if (nullptr == mesh || nullptr == stream) {

        return;

    }

    mesh->pos.resize(count);

    for (uint32_t n = 0; n < count; ++n) {

        mesh->pos[n].x = stream->GetF4();

        mesh->pos[n].y = stream->GetF4();

        mesh->pos[n].z = stream->GetF4();

    }

}

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

static void ReadFaces(SIBMesh *mesh, StreamReaderLE *stream) {

    uint32_t ptIdx = 0;

    while (stream->GetRemainingSizeToLimit() > 0) {

        uint32_t numPoints = stream->GetU4();

        // Store room for the N index channels, plus the point count.

        size_t pos = mesh->idx.size() + 1;

        mesh->idx.resize(pos + numPoints * N);

        mesh->idx[pos - 1] = numPoints;

        uint32_t *idx = &mesh->idx[pos];

        mesh->faceStart.push_back(static_cast<uint32_t>(pos - 1));

        mesh->mtls.push_back(0);

        // Read all the position data.

        // UV/normals will be supplied later.

        // Positions are supplied indexed already, so we preserve that

        // mapping. UVs are supplied uniquely, so we allocate unique indices.

        for (uint32_t n = 0; n < numPoints; n++, idx += N, ptIdx++) {

            uint32_t p = stream->GetU4();

            if (p >= mesh->pos.size())

                throw DeadlyImportError("Vertex index is out of range.");

            idx[POS] = p;

            idx[NRM] = ptIdx;

            idx[UV] = ptIdx;

        }

    }

    // Allocate data channels for normals/UVs.

    mesh->nrm.resize(ptIdx, aiVector3D(0, 0, 0));

    mesh->uv.resize(ptIdx, aiVector3D(0, 0, 0));

    mesh->numPts = ptIdx;

}

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

static void ReadUVs(SIBMesh *mesh, StreamReaderLE *stream) {

    while (stream->GetRemainingSizeToLimit() > 0) {

        uint32_t faceIdx = stream->GetU4();

        uint32_t numPoints = stream->GetU4();

        if (faceIdx >= mesh->faceStart.size())

            throw DeadlyImportError("Invalid face index.");

        uint32_t pos = mesh->faceStart[faceIdx];

        uint32_t *idx = &mesh->idx[pos + 1];

        for (uint32_t n = 0; n < numPoints; n++, idx += N) {

            uint32_t id = idx[UV];

            mesh->uv[id].x = stream->GetF4();

            mesh->uv[id].y = stream->GetF4();

        }

    }

}

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

static void ReadMtls(SIBMesh *mesh, StreamReaderLE *stream) {

    // Material assignments are stored run-length encoded.

    // Also, we add 1 to each material so that we can use mtl #0

    // as the default material.

    uint32_t prevFace = stream->GetU4();

    uint32_t prevMtl = stream->GetU4() + 1;

    while (stream->GetRemainingSizeToLimit() > 0) {

        uint32_t face = stream->GetU4();

        uint32_t mtl = stream->GetU4() + 1;

        while (prevFace < face) {

            if (prevFace >= mesh->mtls.size())

                throw DeadlyImportError("Invalid face index.");

            mesh->mtls[prevFace++] = prevMtl;

        }

        prevFace = face;

        prevMtl = mtl;

    }

    while (prevFace < mesh->mtls.size())

        mesh->mtls[prevFace++] = prevMtl;

}

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

static void ReadAxis(aiMatrix4x4 &axis, StreamReaderLE *stream) {

    axis.a4 = stream->GetF4();

    axis.b4 = stream->GetF4();

    axis.c4 = stream->GetF4();

    axis.d4 = 1;

    axis.a1 = stream->GetF4();

    axis.b1 = stream->GetF4();

    axis.c1 = stream->GetF4();

    axis.d1 = 0;

    axis.a2 = stream->GetF4();

    axis.b2 = stream->GetF4();

    axis.c2 = stream->GetF4();

    axis.d2 = 0;

    axis.a3 = stream->GetF4();

    axis.b3 = stream->GetF4();

    axis.c3 = stream->GetF4();

    axis.d3 = 0;

}

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

static void ReadEdges(SIBMesh *mesh, StreamReaderLE *stream) {

    while (stream->GetRemainingSizeToLimit() > 0) {

        uint32_t posA = stream->GetU4();

        uint32_t posB = stream->GetU4();

        GetEdge(mesh, posA, posB);

    }

}

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

static void ReadCreases(SIBMesh *mesh, StreamReaderLE *stream) {

    while (stream->GetRemainingSizeToLimit() > 0) {

        uint32_t edge = stream->GetU4();

        if (edge >= mesh->edges.size())

            throw DeadlyImportError("SIB: Invalid edge index.");

        mesh->edges[edge].creased = true;

    }

}

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

static void ConnectFaces(SIBMesh *mesh) {

    // Find faces connected to each edge.

    size_t numFaces = mesh->faceStart.size();

    for (size_t faceIdx = 0; faceIdx < numFaces; faceIdx++) {

        uint32_t *idx = &mesh->idx[mesh->faceStart[faceIdx]];

        uint32_t numPoints = *idx++;

        uint32_t prev = idx[(numPoints - 1) * N + POS];

        for (uint32_t i = 0; i < numPoints; i++, idx += N) {

            uint32_t next = idx[POS];

            // Find this edge.

            SIBEdge &edge = GetEdge(mesh, prev, next);

            // Link this face onto it.

            // This gives potentially undesirable normals when used

            // with non-2-manifold surfaces, but then so does Silo to begin with.

            if (edge.faceA == 0xffffffff)

                edge.faceA = static_cast<uint32_t>(faceIdx);

            else if (edge.faceB == 0xffffffff)

                edge.faceB = static_cast<uint32_t>(faceIdx);

            prev = next;

        }

    }

}

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

static aiVector3D CalculateVertexNormal(SIBMesh *mesh, uint32_t faceIdx, uint32_t pos,

        const std::vector<aiVector3D> &faceNormals) {

    // Creased edges complicate this. We need to find the start/end range of the

    // ring of faces that touch this position.

    // We do this in two passes. The first pass is to find the end of the range,

    // the second is to work backwards to the start and calculate the final normal.

    aiVector3D vtxNormal;

    for (int pass = 0; pass < 2; pass++) {

        vtxNormal = aiVector3D(0, 0, 0);

        uint32_t startFaceIdx = faceIdx;

        uint32_t prevFaceIdx = faceIdx;

        // Process each connected face.

        while (true) {

            // Accumulate the face normal.

            vtxNormal += faceNormals[faceIdx];

            uint32_t nextFaceIdx = 0xffffffff;

            // Move to the next edge sharing this position.

            uint32_t *idx = &mesh->idx[mesh->faceStart[faceIdx]];

            uint32_t numPoints = *idx++;

            uint32_t posA = idx[(numPoints - 1) * N + POS];

            for (uint32_t n = 0; n < numPoints; n++, idx += N) {

                uint32_t posB = idx[POS];

                // Test if this edge shares our target position.

                if (posA == pos || posB == pos) {

                    SIBEdge &edge = GetEdge(mesh, posA, posB);

                    // Non-manifold meshes can produce faces which share

                    // positions but have no edge entry, so check it.

                    if (edge.faceA == faceIdx || edge.faceB == faceIdx) {

                        // Move to whichever side we didn't just come from.

                        if (!edge.creased) {

                            if (edge.faceA != prevFaceIdx && edge.faceA != faceIdx && edge.faceA != 0xffffffff)

                                nextFaceIdx = edge.faceA;

                            else if (edge.faceB != prevFaceIdx && edge.faceB != faceIdx && edge.faceB != 0xffffffff)

                                nextFaceIdx = edge.faceB;

                        }

                    }

                }

                posA = posB;

            }

            // Stop once we hit either an creased/unconnected edge, or we

            // wrapped around and hit our start point.

            if (nextFaceIdx == 0xffffffff || nextFaceIdx == startFaceIdx)

                break;

            prevFaceIdx = faceIdx;

            faceIdx = nextFaceIdx;

        }

    }

    // Normalize it.

    float len = vtxNormal.Length();

    if (len > 0.000000001f)

        vtxNormal /= len;

    return vtxNormal;

}

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

static void CalculateNormals(SIBMesh *mesh) {

    size_t numFaces = mesh->faceStart.size();

    // Calculate face normals.

    std::vector<aiVector3D> faceNormals(numFaces);

    for (size_t faceIdx = 0; faceIdx < numFaces; faceIdx++) {

        uint32_t *idx = &mesh->idx[mesh->faceStart[faceIdx]];

        uint32_t numPoints = *idx++;

        aiVector3D faceNormal(0, 0, 0);

        uint32_t *prev = &idx[(numPoints - 1) * N];

        for (uint32_t i = 0; i < numPoints; i++) {

            uint32_t *next = &idx[i * N];

            faceNormal += mesh->pos[prev[POS]] ^ mesh->pos[next[POS]];

            prev = next;

        }

        faceNormals[faceIdx] = faceNormal;

    }

    // Calculate vertex normals.

    for (size_t faceIdx = 0; faceIdx < numFaces; faceIdx++) {

        uint32_t *idx = &mesh->idx[mesh->faceStart[faceIdx]];

        uint32_t numPoints = *idx++;

        for (uint32_t i = 0; i < numPoints; i++) {

            uint32_t pos = idx[i * N + POS];

            uint32_t nrm = idx[i * N + NRM];

            aiVector3D vtxNorm = CalculateVertexNormal(mesh, static_cast<uint32_t>(faceIdx), pos, faceNormals);

            mesh->nrm[nrm] = vtxNorm;

        }

    }

}

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

struct TempMesh {

    std::vector<aiVector3D> vtx;

    std::vector<aiVector3D> nrm;

    std::vector<aiVector3D> uv;

    std::vector<aiFace> faces;

};

static void ReadShape(SIB *sib, StreamReaderLE *stream) {

    SIBMesh smesh;

    aiString name;

    while (stream->GetRemainingSizeToLimit() >= sizeof(SIBChunk)) {

        SIBChunk chunk = ReadChunk(stream);

        unsigned oldLimit = stream->SetReadLimit(stream->GetCurrentPos() + chunk.Size);

        switch (chunk.Tag) {

        case TAG('M', 'I', 'R', 'P'): break; // mirror plane maybe?

        case TAG('I', 'M', 'R', 'P'): break; // instance mirror? (not supported here yet)

        case TAG('D', 'I', 'N', 'F'): break; // display info, not needed

        case TAG('P', 'I', 'N', 'F'): break; // ?

        case TAG('V', 'M', 'I', 'R'): break; // ?

        case TAG('F', 'M', 'I', 'R'): break; // ?

        case TAG('T', 'X', 'S', 'M'): break; // ?

        case TAG('F', 'A', 'H', 'S'): break; // ?

        case TAG('V', 'R', 'T', 'S'): ReadVerts(&smesh, stream, chunk.Size / 12); break;

        case TAG('F', 'A', 'C', 'S'): ReadFaces(&smesh, stream); break;

        case TAG('F', 'T', 'V', 'S'): ReadUVs(&smesh, stream); break;

        case TAG('S', 'N', 'A', 'M'): name = ReadString(stream, chunk.Size / 2); break;

        case TAG('F', 'A', 'M', 'A'): ReadMtls(&smesh, stream); break;

        case TAG('A', 'X', 'I', 'S'): ReadAxis(smesh.axis, stream); break;

        case TAG('E', 'D', 'G', 'S'): ReadEdges(&smesh, stream); break;

        case TAG('E', 'C', 'R', 'S'): ReadCreases(&smesh, stream); break;

        default: UnknownChunk(stream, chunk); break;

        }

        stream->SetCurrentPos(stream->GetReadLimit());

        stream->SetReadLimit(oldLimit);

    }

    ai_assert(smesh.faceStart.size() == smesh.mtls.size()); // sanity check

    // Silo doesn't store any normals in the file - we need to compute

    // them ourselves. We can't let AssImp handle it as AssImp doesn't

    // know about our creased edges.

    ConnectFaces(&smesh);

    CalculateNormals(&smesh);

    // Construct the transforms.

    aiMatrix4x4 worldToLocal = smesh.axis;

    worldToLocal.Inverse();

    aiMatrix4x4 worldToLocalN = worldToLocal;

    worldToLocalN.a4 = worldToLocalN.b4 = worldToLocalN.c4 = 0.0f;

    worldToLocalN.Inverse().Transpose();

    // Allocate final mesh data.

    // We'll allocate one mesh for each material. (we'll strip unused ones after)

    std::vector<TempMesh> meshes(sib->mtls.size());

    // Un-index the source data and apply to each vertex.

    for (unsigned fi = 0; fi < smesh.faceStart.size(); fi++) {

        uint32_t start = smesh.faceStart[fi];

        uint32_t mtl = smesh.mtls[fi];

        uint32_t *idx = &smesh.idx[start];

        if (mtl >= meshes.size()) {

            ASSIMP_LOG_ERROR("SIB: Face material index is invalid.");

            mtl = 0;

        }

        TempMesh &dest = meshes[mtl];

        aiFace face;

        face.mNumIndices = *idx++;

        face.mIndices = new unsigned[face.mNumIndices];

        for (unsigned pt = 0; pt < face.mNumIndices; pt++, idx += N) {

            size_t vtxIdx = dest.vtx.size();

            face.mIndices[pt] = static_cast<unsigned int>(vtxIdx);

            // De-index it. We don't need to validate here as

            // we did it when creating the data.

            aiVector3D pos = smesh.pos[idx[POS]];

            aiVector3D nrm = smesh.nrm[idx[NRM]];

            aiVector3D uv = smesh.uv[idx[UV]];

            // The verts are supplied in world-space, so let's

            // transform them back into the local space of this mesh:

            pos = worldToLocal * pos;

            nrm = worldToLocalN * nrm;

            dest.vtx.push_back(pos);

            dest.nrm.push_back(nrm);

            dest.uv.push_back(uv);

        }

        dest.faces.push_back(face);

    }

    SIBObject obj;

    obj.name = name;

    obj.axis = smesh.axis;

    obj.meshIdx = sib->meshes.size();

    // Now that we know the size of everything,

    // we can build the final one-material-per-mesh data.

    for (size_t n = 0; n < meshes.size(); n++) {

        TempMesh &src = meshes[n];

        if (src.faces.empty())

            continue;

        aiMesh *mesh = new aiMesh;

        mesh->mName = name;

        mesh->mNumFaces = static_cast<unsigned int>(src.faces.size());

        mesh->mFaces = new aiFace[mesh->mNumFaces];

        mesh->mNumVertices = static_cast<unsigned int>(src.vtx.size());

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

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

        mesh->mTextureCoords[0] = new aiVector3D[mesh->mNumVertices];

        mesh->mNumUVComponents[0] = 2;

        mesh->mMaterialIndex = static_cast<unsigned int>(n);

        for (unsigned i = 0; i < mesh->mNumVertices; i++) {

            mesh->mVertices[i] = src.vtx[i];

            mesh->mNormals[i] = src.nrm[i];

            mesh->mTextureCoords[0][i] = src.uv[i];

        }

        for (unsigned i = 0; i < mesh->mNumFaces; i++) {

            mesh->mFaces[i] = src.faces[i];

        }

        sib->meshes.push_back(mesh);

    }

    obj.meshCount = sib->meshes.size() - obj.meshIdx;

    sib->objs.push_back(obj);

}

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

static void ReadMaterial(SIB *sib, StreamReaderLE *stream) {

    aiColor3D diff = ReadColor(stream);

    aiColor3D ambi = ReadColor(stream);

    aiColor3D spec = ReadColor(stream);

    aiColor3D emis = ReadColor(stream);

    float shiny = (float)stream->GetU4();

    uint32_t nameLen = stream->GetU4();

    aiString name = ReadString(stream, nameLen / 2);

    uint32_t texLen = stream->GetU4();

    aiString tex = ReadString(stream, texLen / 2);

    aiMaterial *mtl = new aiMaterial();

    mtl->AddProperty(&diff, 1, AI_MATKEY_COLOR_DIFFUSE);

    mtl->AddProperty(&ambi, 1, AI_MATKEY_COLOR_AMBIENT);

    mtl->AddProperty(&spec, 1, AI_MATKEY_COLOR_SPECULAR);

    mtl->AddProperty(&emis, 1, AI_MATKEY_COLOR_EMISSIVE);

    mtl->AddProperty(&shiny, 1, AI_MATKEY_SHININESS);

    mtl->AddProperty(&name, AI_MATKEY_NAME);

    if (tex.length > 0) {

        mtl->AddProperty(&tex, AI_MATKEY_TEXTURE_DIFFUSE(0));

        mtl->AddProperty(&tex, AI_MATKEY_TEXTURE_AMBIENT(0));

    }

    sib->mtls.push_back(mtl);

}

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

static void ReadLightInfo(aiLight *light, StreamReaderLE *stream) {

    uint32_t type = stream->GetU4();

    switch (type) {

    case 0: light->mType = aiLightSource_POINT; break;

    case 1: light->mType = aiLightSource_SPOT; break;

    case 2: light->mType = aiLightSource_DIRECTIONAL; break;

    default: light->mType = aiLightSource_UNDEFINED; break;

    }

    light->mPosition.x = stream->GetF4();

    light->mPosition.y = stream->GetF4();

    light->mPosition.z = stream->GetF4();

    light->mDirection.x = stream->GetF4();

    light->mDirection.y = stream->GetF4();

    light->mDirection.z = stream->GetF4();

    light->mColorDiffuse = ReadColor(stream);

    light->mColorAmbient = ReadColor(stream);

    light->mColorSpecular = ReadColor(stream);

    ai_real spotExponent = stream->GetF4();

    ai_real spotCutoff = stream->GetF4();

    light->mAttenuationConstant = stream->GetF4();

    light->mAttenuationLinear = stream->GetF4();

    light->mAttenuationQuadratic = stream->GetF4();

    // Silo uses the OpenGL default lighting model for it's

    // spot cutoff/exponent. AssImp unfortunately, does not.

    // Let's try and approximate it by solving for the

    // 99% and 1% percentiles.

    //    OpenGL: I = cos(angle)^E

    //   Solving: angle = acos(I^(1/E))

    ai_real E = ai_real(1.0) / std::max(spotExponent, (ai_real)0.00001);

    ai_real inner = std::acos(std::pow((ai_real)0.99, E));

    ai_real outer = std::acos(std::pow((ai_real)0.01, E));

    // Apply the cutoff.

    outer = std::min(outer, AI_DEG_TO_RAD(spotCutoff));

    light->mAngleInnerCone = std::min(inner, outer);

    light->mAngleOuterCone = outer;

}

static void ReadLight(SIB *sib, StreamReaderLE *stream) {

    aiLight *light = new aiLight();

    while (stream->GetRemainingSizeToLimit() >= sizeof(SIBChunk)) {

        SIBChunk chunk = ReadChunk(stream);

        unsigned oldLimit = stream->SetReadLimit(stream->GetCurrentPos() + chunk.Size);

        switch (chunk.Tag) {

        case TAG('L', 'N', 'F', 'O'): ReadLightInfo(light, stream); break;

        case TAG('S', 'N', 'A', 'M'): light->mName = ReadString(stream, chunk.Size / 2); break;

        default: UnknownChunk(stream, chunk); break;

        }

        stream->SetCurrentPos(stream->GetReadLimit());

        stream->SetReadLimit(oldLimit);

    }

    sib->lights.push_back(light);

}

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

static void ReadScale(aiMatrix4x4 &axis, StreamReaderLE *stream) {

    aiMatrix4x4 scale;

    scale.a1 = stream->GetF4();

    scale.b1 = stream->GetF4();

    scale.c1 = stream->GetF4();

    scale.d1 = stream->GetF4();

    scale.a2 = stream->GetF4();

    scale.b2 = stream->GetF4();

    scale.c2 = stream->GetF4();

    scale.d2 = stream->GetF4();

    scale.a3 = stream->GetF4();

    scale.b3 = stream->GetF4();

    scale.c3 = stream->GetF4();

    scale.d3 = stream->GetF4();

    scale.a4 = stream->GetF4();

    scale.b4 = stream->GetF4();

    scale.c4 = stream->GetF4();

    scale.d4 = stream->GetF4();

    axis = axis * scale;

}

static void ReadInstance(SIB *sib, StreamReaderLE *stream) {

    SIBObject inst;

    uint32_t shapeIndex = 0;

    while (stream->GetRemainingSizeToLimit() >= sizeof(SIBChunk)) {

        SIBChunk chunk = ReadChunk(stream);

        unsigned oldLimit = stream->SetReadLimit(stream->GetCurrentPos() + chunk.Size);

        switch (chunk.Tag) {

        case TAG('D', 'I', 'N', 'F'): break; // display info, not needed

        case TAG('P', 'I', 'N', 'F'): break; // ?

        case TAG('A', 'X', 'I', 'S'): ReadAxis(inst.axis, stream); break;

        case TAG('I', 'N', 'S', 'I'): shapeIndex = stream->GetU4(); break;

        case TAG('S', 'M', 'T', 'X'): ReadScale(inst.axis, stream); break;

        case TAG('S', 'N', 'A', 'M'): inst.name = ReadString(stream, chunk.Size / 2); break;

        default: UnknownChunk(stream, chunk); break;

        }

        stream->SetCurrentPos(stream->GetReadLimit());

        stream->SetReadLimit(oldLimit);

    }

    if (shapeIndex >= sib->objs.size()) {

        throw DeadlyImportError("SIB: Invalid shape index.");

    }

    const SIBObject &src = sib->objs[shapeIndex];

    inst.meshIdx = src.meshIdx;

    inst.meshCount = src.meshCount;

    sib->insts.push_back(inst);

}

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

static void CheckVersion(StreamReaderLE *stream) {

    uint32_t version = stream->GetU4();

    if (version < 1 || version > 2) {

        throw DeadlyImportError("SIB: Unsupported file version.");

    }

}

static void ReadScene(SIB *sib, StreamReaderLE *stream) {

    // Parse each chunk in turn.

    while (stream->GetRemainingSizeToLimit() >= sizeof(SIBChunk)) {

        SIBChunk chunk = ReadChunk(stream);

        unsigned oldLimit = stream->SetReadLimit(stream->GetCurrentPos() + chunk.Size);

        switch (chunk.Tag) {

        case TAG('H', 'E', 'A', 'D'): CheckVersion(stream); break;

        case TAG('S', 'H', 'A', 'P'): ReadShape(sib, stream); break;

        case TAG('G', 'R', 'P', 'S'): break; // group assignment, we don't import this

        case TAG('T', 'E', 'X', 'P'): break; // ?

        case TAG('I', 'N', 'S', 'T'): ReadInstance(sib, stream); break;

        case TAG('M', 'A', 'T', 'R'): ReadMaterial(sib, stream); break;

        case TAG('L', 'G', 'H', 'T'): ReadLight(sib, stream); break;

        default: UnknownChunk(stream, chunk); break;

        }

        stream->SetCurrentPos(stream->GetReadLimit());

        stream->SetReadLimit(oldLimit);

    }

}

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

// Imports the given file into the given scene structure.

void SIBImporter::InternReadFile(const std::string &pFile,

        aiScene *pScene, IOSystem *pIOHandler) {

    auto file = pIOHandler->Open(pFile, "rb");

    if (!file)

        throw DeadlyImportError("SIB: Could not open ", pFile);

    StreamReaderLE stream(file);

    // We should have at least one chunk

    if (stream.GetRemainingSize() < 16)

        throw DeadlyImportError("SIB file is either empty or corrupt: ", pFile);

    SIB sib;

    // Default material.

    aiMaterial *defmtl = new aiMaterial;

    aiString defname = aiString(AI_DEFAULT_MATERIAL_NAME);

    defmtl->AddProperty(&defname, AI_MATKEY_NAME);

    sib.mtls.push_back(defmtl);

    // Read it all.

    ReadScene(&sib, &stream);

    // Join the instances and objects together.

    size_t firstInst = sib.objs.size();

    sib.objs.insert(sib.objs.end(), sib.insts.begin(), sib.insts.end());

    sib.insts.clear();

    // Transfer to the aiScene.

    pScene->mNumMaterials = static_cast<unsigned int>(sib.mtls.size());

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

    pScene->mNumLights = static_cast<unsigned int>(sib.lights.size());

    pScene->mMaterials = pScene->mNumMaterials ? new aiMaterial *[pScene->mNumMaterials] : nullptr;

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

    pScene->mLights = pScene->mNumLights ? new aiLight *[pScene->mNumLights] : nullptr;

    if (pScene->mNumMaterials)

        memcpy(pScene->mMaterials, &sib.mtls[0], sizeof(aiMaterial *) * pScene->mNumMaterials);

    if (pScene->mNumMeshes)

        memcpy(pScene->mMeshes, &sib.meshes[0], sizeof(aiMesh *) * pScene->mNumMeshes);

    if (pScene->mNumLights)

        memcpy(pScene->mLights, &sib.lights[0], sizeof(aiLight *) * pScene->mNumLights);

    // Construct the root node.

    size_t childIdx = 0;

    aiNode *root = new aiNode();

    root->mName.Set("<SIBRoot>");

    root->mNumChildren = static_cast<unsigned int>(sib.objs.size() + sib.lights.size());

    root->mChildren = root->mNumChildren ? new aiNode *[root->mNumChildren] : nullptr;

    pScene->mRootNode = root;

    // Add nodes for each object.

    for (size_t n = 0; n < sib.objs.size(); n++) {

        ai_assert(root->mChildren);

        SIBObject &obj = sib.objs[n];

        aiNode *node = new aiNode;

        root->mChildren[childIdx++] = node;

        node->mName = obj.name;

        node->mParent = root;

        node->mTransformation = obj.axis;

        node->mNumMeshes = static_cast<unsigned int>(obj.meshCount);

        node->mMeshes = node->mNumMeshes ? new unsigned[node->mNumMeshes] : nullptr;

        for (unsigned i = 0; i < node->mNumMeshes; i++)

            node->mMeshes[i] = static_cast<unsigned int>(obj.meshIdx + i);

        // Mark instanced objects as being so.

        if (n >= firstInst) {

            node->mMetaData = aiMetadata::Alloc(1);

            node->mMetaData->Set(0, "IsInstance", true);

        }

    }

    // Add nodes for each light.

    // (no transformation as the light is already in world space)

    for (size_t n = 0; n < sib.lights.size(); n++) {

        ai_assert(root->mChildren);

        aiLight *light = sib.lights[n];

        if (nullptr != light) {

            aiNode *node = new aiNode;

            root->mChildren[childIdx++] = node;

            node->mName = light->mName;

            node->mParent = root;

        }

    }

}

} // namespace Assimp

#endif // !! ASSIMP_BUILD_NO_SIB_IMPORTER