/*****************************************************************************************
 *                                                                                       *
 * OpenSpace                                                                             *
 *                                                                                       *
 * Copyright (c) 2014-2018                                                               *
 *                                                                                       *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this  *
 * software and associated documentation files (the "Software"), to deal in the Software *
 * without restriction, including without limitation the rights to use, copy, modify,    *
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to    *
 * permit persons to whom the Software is furnished to do so, subject to the following   *
 * conditions:                                                                           *
 *                                                                                       *
 * The above copyright notice and this permission notice shall be included in all copies *
 * or substantial portions of the Software.                                              *
 *                                                                                       *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,   *
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A         *
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT    *
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF  *
 * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE  *
 * OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                                         *
 ****************************************************************************************/

#include <modules/space/rendering/renderablestars.h>

#include <openspace/documentation/documentation.h>
#include <openspace/documentation/verifier.h>
#include <openspace/util/updatestructures.h>
#include <openspace/util/distanceconstants.h>
#include <openspace/engine/openspaceengine.h>
#include <openspace/rendering/renderengine.h>

#include <ghoul/filesystem/cachemanager.h>
#include <ghoul/filesystem/filesystem.h>
#include <ghoul/misc/templatefactory.h>
#include <ghoul/io/texture/texturereader.h>
#include <ghoul/opengl/programobject.h>
#include <ghoul/opengl/texture.h>
#include <ghoul/opengl/textureunit.h>

#include <array>
#include <fstream>
#include <stdint.h>
#include <limits>

//#define USING_STELLAR_TEST_GRID

namespace {
    constexpr const char* _loggerCat = "RenderableStars";

    constexpr const char* KeyFile = "File";

    constexpr int8_t CurrentCacheVersion = 1;

    struct ColorVBOLayout {
        std::array<float, 4> position; // (x,y,z,e)

        float bvColor; // B-V color value
        float luminance;
        float absoluteMagnitude;
    };

    struct VelocityVBOLayout {
        std::array<float, 4> position; // (x,y,z,e)

        float bvColor; // B-V color value
        float luminance;
        float absoluteMagnitude;

        float vx; // v_x
        float vy; // v_y
        float vz; // v_z
    };

    struct SpeedVBOLayout {
        std::array<float, 4> position; // (x,y,z,e)

        float bvColor; // B-V color value
        float luminance;
        float absoluteMagnitude;

        float speed;
    };

    static const openspace::properties::Property::PropertyInfo PsfTextureInfo = {
        "Texture",
        "Point Spread Function Texture",
        "The path to the texture that should be used as a point spread function for the "
        "stars."
    };

    static const openspace::properties::Property::PropertyInfo ColorTextureInfo = {
        "ColorMap",
        "ColorBV Texture",
        "The path to the texture that is used to convert from the B-V value of the star "
        "to its color. The texture is used as a one dimensional lookup function."
    };

    static const openspace::properties::Property::PropertyInfo ColorOptionInfo = {
        "ColorOption",
        "Color Option",
        "This value determines which quantity is used for determining the color of the "
        "stars."
    };

    static const openspace::properties::Property::PropertyInfo MagnitudeExponentInfo = {
        "MagnitudeExponent",
        "MagnitudeExponent",
        "Adjust star magnitude by 10^MagnitudeExponent. "
        "Stars closer than this distance are given full opacity. "
        "Farther away, stars dim proportionally to the logarithm of their distance."
    };

    static const openspace::properties::Property::PropertyInfo SharpnessInfo = {
        "Sharpness",
        "Sharpness",
        "Adjust star sharpness"
    };

    static const openspace::properties::Property::PropertyInfo BillboardSizeInfo = {
        "BillboardSize",
        "Billboard Size",
        "Set the billboard size of all stars"
    };
}  // namespace

namespace openspace {

documentation::Documentation RenderableStars::Documentation() {
    using namespace documentation;
    return {
        "RenderableStars",
        "space_renderablestars",
        {
            {
                "Type",
                new StringEqualVerifier("RenderableStars"),
                Optional::No
            },
            {
                KeyFile,
                new StringVerifier,
                Optional::No,
                "The path to the SPECK file that contains information about the stars "
                "being rendered."
            },
            {
                PsfTextureInfo.identifier,
                new StringVerifier,
                Optional::No,
                PsfTextureInfo.description
            },
            {
                ColorTextureInfo.identifier,
                new StringVerifier,
                Optional::No,
                ColorTextureInfo.description
            },
            {
                ColorOptionInfo.identifier,
                new StringInListVerifier({
                    "Color", "Velocity", "Speed"
                }),
                Optional::Yes,
                ColorOptionInfo.description
            },
            {
                MagnitudeExponentInfo.identifier,
                new DoubleVerifier,
                Optional::Yes,
                MagnitudeExponentInfo.description
            },
            {
                SharpnessInfo.identifier,
                new DoubleVerifier,
                Optional::Yes,
                SharpnessInfo.description
            },
            {
                BillboardSizeInfo.identifier,
                new DoubleVerifier,
                Optional::Yes,
                BillboardSizeInfo.description
            }
        }
    };
}

RenderableStars::RenderableStars(const ghoul::Dictionary& dictionary)
    : Renderable(dictionary)
    , _pointSpreadFunctionTexturePath(PsfTextureInfo)
    , _pointSpreadFunctionTexture(nullptr)
    , _pointSpreadFunctionTextureIsDirty(true)
    , _colorTexturePath(ColorTextureInfo)
    , _colorTexture(nullptr)
    , _colorTextureIsDirty(true)
    , _colorOption(ColorOptionInfo, properties::OptionProperty::DisplayType::Dropdown)
    , _dataIsDirty(true)
    , _magnitudeExponent(MagnitudeExponentInfo, 19.f, 0.f, 30.f)
    , _sharpness(SharpnessInfo, 1.f, 0.f, 5.f)
    , _billboardSize(BillboardSizeInfo, 30.f, 1.f, 100.f)
    , _program(nullptr)
    , _speckFile("")
    , _nValuesPerStar(0)
    , _vao(0)
    , _vbo(0)
{
    using File = ghoul::filesystem::File;

    documentation::testSpecificationAndThrow(
        Documentation(),
        dictionary,
        "RenderableStars"
    );

    _pointSpreadFunctionTexturePath = absPath(dictionary.value<std::string>(
        PsfTextureInfo.identifier
    ));
    _pointSpreadFunctionFile = std::make_unique<File>(_pointSpreadFunctionTexturePath);

    _colorTexturePath = absPath(dictionary.value<std::string>(
        ColorTextureInfo.identifier
    ));
    _colorTextureFile = std::make_unique<File>(_colorTexturePath);

    _speckFile = absPath(dictionary.value<std::string>(KeyFile));

    _colorOption.addOptions({
        { ColorOption::Color, "Color" },
        { ColorOption::Velocity, "Velocity" },
        { ColorOption::Speed, "Speed" }
    });
    if (dictionary.hasKey(ColorOptionInfo.identifier)) {
        const std::string colorOption = dictionary.value<std::string>(
            ColorOptionInfo.identifier
        );
        if (colorOption == "Color") {
            _colorOption = ColorOption::Color;
        }
        else if (colorOption == "Velocity") {
            _colorOption = ColorOption::Velocity;
        }
        else {
            _colorOption = ColorOption::Speed;
        }
    }
    _colorOption.onChange([&] { _dataIsDirty = true; });
    addProperty(_colorOption);

    _pointSpreadFunctionTexturePath.onChange(
        [&]{ _pointSpreadFunctionTextureIsDirty = true; }
    );
    _pointSpreadFunctionFile->setCallback(
        [&](const File&) { _pointSpreadFunctionTextureIsDirty = true; }
    );
    addProperty(_pointSpreadFunctionTexturePath);

    _colorTexturePath.onChange([&]{ _colorTextureIsDirty = true; });
    _colorTextureFile->setCallback(
        [&](const File&) { _colorTextureIsDirty = true; }
    );
    addProperty(_colorTexturePath);

    if (dictionary.hasKey(MagnitudeExponentInfo.identifier)) {
        _magnitudeExponent = static_cast<float>(
            dictionary.value<double>(MagnitudeExponentInfo.identifier)
        );
    }
    addProperty(_magnitudeExponent);

    if (dictionary.hasKey(SharpnessInfo.identifier)) {
        _sharpness = static_cast<float>(
            dictionary.value<double>(SharpnessInfo.identifier)
            );
    }
    addProperty(_sharpness);

    if (dictionary.hasKey(BillboardSizeInfo.identifier)) {
        _billboardSize = static_cast<float>(
            dictionary.value<double>(BillboardSizeInfo.identifier)
        );
    }
    addProperty(_billboardSize);
}

RenderableStars::~RenderableStars() {}

bool RenderableStars::isReady() const {
    return (_program != nullptr) && (!_fullData.empty());
}

void RenderableStars::initializeGL() {
    RenderEngine& renderEngine = OsEng.renderEngine();
    _program = renderEngine.buildRenderProgram("Star",
        absPath("${MODULE_SPACE}/shaders/star_vs.glsl"),
        absPath("${MODULE_SPACE}/shaders/star_fs.glsl"),
        absPath("${MODULE_SPACE}/shaders/star_ge.glsl")
    );

    _uniformCache.model = _program->uniformLocation("model");
    _uniformCache.view = _program->uniformLocation("view");
    _uniformCache.viewScaling = _program->uniformLocation("viewScaling");
    _uniformCache.projection = _program->uniformLocation("projection");
    _uniformCache.colorOption = _program->uniformLocation("colorOption");
    _uniformCache.magnitudeExponent = _program->uniformLocation("magnitudeExponent");
    _uniformCache.sharpness = _program->uniformLocation("sharpness");
    _uniformCache.billboardSize = _program->uniformLocation("billboardSize");
    _uniformCache.screenSize = _program->uniformLocation("screenSize");
    _uniformCache.psfTexture = _program->uniformLocation("psfTexture");
    _uniformCache.colorTexture = _program->uniformLocation("colorTexture");

    bool success = loadData();
    if (!success) {
        throw ghoul::RuntimeError("Error loading data");
    }
}

void RenderableStars::deinitializeGL() {
    glDeleteBuffers(1, &_vbo);
    _vbo = 0;
    glDeleteVertexArrays(1, &_vao);
    _vao = 0;

    _pointSpreadFunctionTexture = nullptr;
    _colorTexture = nullptr;

    RenderEngine& renderEngine = OsEng.renderEngine();
    if (_program) {
        renderEngine.removeRenderProgram(_program.get());
        _program = nullptr;
    }
}

void RenderableStars::render(const RenderData& data, RendererTasks&) {
    glBlendFunc(GL_SRC_ALPHA, GL_ONE);
    glDepthMask(false);

    _program->activate();

    glm::mat4 model =
        glm::translate(glm::dmat4(1.0), data.modelTransform.translation) *
        glm::dmat4(data.modelTransform.rotation) *
        glm::dmat4(glm::scale(glm::dmat4(1.0), glm::dvec3(data.modelTransform.scale)));

    glm::mat4 view = data.camera.combinedViewMatrix();
    glm::mat4 projection = data.camera.projectionMatrix();
    float viewScaling = data.camera.scaling();

    _program->setUniform(_uniformCache.model, model);
    _program->setUniform(_uniformCache.view, view);
    _program->setUniform(_uniformCache.projection, projection);
    _program->setUniform(_uniformCache.viewScaling, viewScaling);

    _program->setUniform(_uniformCache.colorOption, _colorOption);
    _program->setUniform(_uniformCache.magnitudeExponent, _magnitudeExponent);
    _program->setUniform(_uniformCache.sharpness, _sharpness);
    _program->setUniform(_uniformCache.billboardSize, _billboardSize);
    _program->setUniform(
        _uniformCache.screenSize,
        glm::vec2(OsEng.renderEngine().renderingResolution())
    );

    _program->setUniform("eyePosition", glm::vec3(data.camera.eyePositionVec3()));

    ghoul::opengl::TextureUnit psfUnit;
    psfUnit.activate();
    _pointSpreadFunctionTexture->bind();
    _program->setUniform(_uniformCache.psfTexture, psfUnit);

    ghoul::opengl::TextureUnit colorUnit;
    colorUnit.activate();
    _colorTexture->bind();
    _program->setUniform(_uniformCache.colorTexture, colorUnit);

    glBindVertexArray(_vao);
    const GLsizei nStars = static_cast<GLsizei>(_fullData.size() / _nValuesPerStar);
    glDrawArrays(GL_POINTS, 0, nStars);

    glBindVertexArray(0);
    _program->deactivate();

    glDepthMask(true);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
}

void RenderableStars::update(const UpdateData&) {
    if (_dataIsDirty) {
        const int value = _colorOption;
        LDEBUG("Regenerating data");

        createDataSlice(ColorOption(value));

        int size = static_cast<int>(_slicedData.size());

        if (_vao == 0) {
            glGenVertexArrays(1, &_vao);
        }
        if (_vbo == 0) {
            glGenBuffers(1, &_vbo);
        }
        glBindVertexArray(_vao);
        glBindBuffer(GL_ARRAY_BUFFER, _vbo);
        glBufferData(
            GL_ARRAY_BUFFER,
            size * sizeof(GLfloat),
            &_slicedData[0],
            GL_STATIC_DRAW
        );

        GLint positionAttrib = _program->attributeLocation("in_position");
        GLint brightnessDataAttrib = _program->attributeLocation("in_brightness");

        const size_t nStars = _fullData.size() / _nValuesPerStar;
        const size_t nValues = _slicedData.size() / nStars;

        GLsizei stride = static_cast<GLsizei>(sizeof(GLfloat) * nValues);

        glEnableVertexAttribArray(positionAttrib);
        glEnableVertexAttribArray(brightnessDataAttrib);
        const int colorOption = _colorOption;
        switch (colorOption) {
        case ColorOption::Color:
            glVertexAttribPointer(
                positionAttrib,
                4,
                GL_FLOAT,
                GL_FALSE,
                stride,
                nullptr // = offsetof(ColorVBOLayout, position)
            );
            glVertexAttribPointer(
                brightnessDataAttrib,
                3,
                GL_FLOAT,
                GL_FALSE,
                stride,
                reinterpret_cast<void*>(offsetof(ColorVBOLayout, bvColor))
            );

            break;
        case ColorOption::Velocity:
            {
                glVertexAttribPointer(
                    positionAttrib,
                    4,
                    GL_FLOAT,
                    GL_FALSE,
                    stride,
                    nullptr // = offsetof(VelocityVBOLayout, position)
                );
                glVertexAttribPointer(
                    brightnessDataAttrib,
                    3,
                    GL_FLOAT,
                    GL_FALSE,
                    stride,
                    reinterpret_cast<void*>(offsetof(VelocityVBOLayout, bvColor))
                );

                GLint velocityAttrib = _program->attributeLocation("in_velocity");
                glEnableVertexAttribArray(velocityAttrib);
                glVertexAttribPointer(
                    velocityAttrib,
                    3,
                    GL_FLOAT,
                    GL_TRUE,
                    stride,
                    reinterpret_cast<void*>(offsetof(VelocityVBOLayout, vx))
                );

                break;
            }
        case ColorOption::Speed:
            {
                glVertexAttribPointer(
                    positionAttrib,
                    4,
                    GL_FLOAT,
                    GL_FALSE,
                    stride,
                    nullptr // = offsetof(SpeedVBOLayout, position)
                );
                glVertexAttribPointer(
                    brightnessDataAttrib,
                    3,
                    GL_FLOAT,
                    GL_FALSE,
                    stride,
                    reinterpret_cast<void*>(offsetof(SpeedVBOLayout, bvColor))
                );

                GLint speedAttrib = _program->attributeLocation("in_speed");
                glEnableVertexAttribArray(speedAttrib);
                glVertexAttribPointer(
                    speedAttrib,
                    1,
                    GL_FLOAT,
                    GL_TRUE,
                    stride,
                    reinterpret_cast<void*>(offsetof(SpeedVBOLayout, speed))
                );
            }
        }

        glBindBuffer(GL_ARRAY_BUFFER, 0);
        glBindVertexArray(0);

        _dataIsDirty = false;
    }

    if (_pointSpreadFunctionTextureIsDirty) {
        LDEBUG("Reloading Point Spread Function texture");
        _pointSpreadFunctionTexture = nullptr;
        if (_pointSpreadFunctionTexturePath.value() != "") {
            _pointSpreadFunctionTexture = ghoul::io::TextureReader::ref().loadTexture(
                absPath(_pointSpreadFunctionTexturePath)
            );

            if (_pointSpreadFunctionTexture) {
                LDEBUG(fmt::format(
                    "Loaded texture from '{}'",
                    absPath(_pointSpreadFunctionTexturePath)
                ));
                _pointSpreadFunctionTexture->uploadTexture();
            }
            _pointSpreadFunctionTexture->setFilter(
                ghoul::opengl::Texture::FilterMode::AnisotropicMipMap
            );

            _pointSpreadFunctionFile = std::make_unique<ghoul::filesystem::File>(
                _pointSpreadFunctionTexturePath
            );
            _pointSpreadFunctionFile->setCallback(
                [&](const ghoul::filesystem::File&) {
                    _pointSpreadFunctionTextureIsDirty = true;
                }
            );
        }
        _pointSpreadFunctionTextureIsDirty = false;
    }

    if (_colorTextureIsDirty) {
        LDEBUG("Reloading Color Texture");
        _colorTexture = nullptr;
        if (_colorTexturePath.value() != "") {
            _colorTexture = ghoul::io::TextureReader::ref().loadTexture(
                absPath(_colorTexturePath)
            );
            if (_colorTexture) {
                LDEBUG(fmt::format(
                    "Loaded texture from '{}'",
                    absPath(_colorTexturePath)
                ));
                _colorTexture->uploadTexture();
            }

            _colorTextureFile = std::make_unique<ghoul::filesystem::File>(
                _colorTexturePath
            );
            _colorTextureFile->setCallback(
                [&](const ghoul::filesystem::File&) { _colorTextureIsDirty = true; }
            );
        }
        _colorTextureIsDirty = false;
    }

    if (_program->isDirty()) {
        _program->rebuildFromFile();

        _uniformCache.model = _program->uniformLocation("model");
        _uniformCache.view = _program->uniformLocation("view");
        _uniformCache.viewScaling = _program->uniformLocation("viewScaling");
        _uniformCache.projection = _program->uniformLocation("projection");
        _uniformCache.colorOption = _program->uniformLocation("colorOption");
        _uniformCache.magnitudeExponent = _program->uniformLocation("magnitudeExponent");
        _uniformCache.sharpness = _program->uniformLocation("sharpness");
        _uniformCache.billboardSize = _program->uniformLocation("billboardSize");
        _uniformCache.screenSize = _program->uniformLocation("screenSize");
        _uniformCache.psfTexture = _program->uniformLocation("psfTexture");
        _uniformCache.colorTexture = _program->uniformLocation("colorTexture");
    }
}

bool RenderableStars::loadData() {
    std::string _file = _speckFile;
    std::string cachedFile = FileSys.cacheManager()->cachedFilename(
        _file,
        ghoul::filesystem::CacheManager::Persistent::Yes
    );

    bool hasCachedFile = FileSys.fileExists(cachedFile);
    if (hasCachedFile) {
        LINFO(fmt::format(
            "Cached file '{}' used for Speck file '{}'",
            cachedFile,
            _file
        ));

        bool success = loadCachedFile(cachedFile);
        if (success) {
            return true;
        }
        else {
            FileSys.cacheManager()->removeCacheFile(_file);
            // Intentional fall-through to the 'else' computation to generate the cache
            // file for the next run
        }
    }
    else {
        LINFO(fmt::format("Cache for Speck file '{}' not found", _file));
    }
    LINFO(fmt::format("Loading Speck file '{}'", _file));

    bool success = readSpeckFile();
    if (!success) {
        return false;
    }

    LINFO("Saving cache");
    success = saveCachedFile(cachedFile);

    return success;
}

bool RenderableStars::readSpeckFile() {
    std::string _file = _speckFile;
    std::ifstream file(_file);
    if (!file.good()) {
        LERROR(fmt::format("Failed to open Speck file '{}'", _file));
        return false;
    }

    _nValuesPerStar = 0;

    // The beginning of the speck file has a header that either contains comments
    // (signaled by a preceding '#') or information about the structure of the file
    // (signaled by the keywords 'datavar', 'texturevar', and 'texture')
    std::string line = "";
    while (true) {
        std::streampos position = file.tellg();
        std::getline(file, line);

        if (line[0] == '#' || line.empty()) {
            continue;
        }

        if (line.substr(0, 7) != "datavar" &&
            line.substr(0, 10) != "texturevar" &&
            line.substr(0, 7) != "texture")
        {
            // we read a line that doesn't belong to the header, so we have to jump back
            // before the beginning of the current line
            file.seekg(position);
            break;
        }
        
        if (line.substr(0, 7) == "datavar") {
            // datavar lines are structured as follows:
            // datavar # description
            // where # is the index of the data variable; so if we repeatedly overwrite
            // the 'nValues' variable with the latest index, we will end up with the total
            // number of values (+3 since X Y Z are not counted in the Speck file index)
            std::stringstream str(line);

            std::string dummy;
            str >> dummy;
            str >> _nValuesPerStar;
            _nValuesPerStar += 1; // We want the number, but the index is 0 based
        }
    }

    _nValuesPerStar += 3; // X Y Z are not counted in the Speck file indices

    float minLumValue = std::numeric_limits<float>::max();
    float maxLumValue = std::numeric_limits<float>::min();

    do {
        std::vector<float> values(_nValuesPerStar);

        std::getline(file, line);
        std::stringstream str(line);

        for (int i = 0; i < _nValuesPerStar; ++i) {
            str >> values[i];
        }
        bool nullArray = true;
        for (size_t i = 0; i < values.size(); ++i) {
            if (values[i] != 0.0) {
                nullArray = false;
                break;
            }
        }
        minLumValue = std::min(values[4], minLumValue);
        maxLumValue = std::max(values[4], minLumValue);
        if (!nullArray) {
            _fullData.insert(_fullData.end(), values.begin(), values.end());
        }
    } while (!file.eof());

    // Normalize Luminosity:
    int luminosityVarColumnPos = 4;
    for (size_t i = 0; i < _fullData.size(); i += _nValuesPerStar) {
        _fullData[i + luminosityVarColumnPos] = 
            (_fullData[i + luminosityVarColumnPos] - minLumValue) / 
            (maxLumValue - minLumValue);
    }

    return true;
}

bool RenderableStars::loadCachedFile(const std::string& file) {
    std::ifstream fileStream(file, std::ifstream::binary);
    if (fileStream.good()) {
        int8_t version = 0;
        fileStream.read(reinterpret_cast<char*>(&version), sizeof(int8_t));
        if (version != CurrentCacheVersion) {
            LINFO("The format of the cached file has changed: deleting old cache");
            fileStream.close();
            FileSys.deleteFile(file);
            return false;
        }

        int32_t nValues = 0;
        fileStream.read(reinterpret_cast<char*>(&nValues), sizeof(int32_t));
        fileStream.read(reinterpret_cast<char*>(&_nValuesPerStar), sizeof(int32_t));

        _fullData.resize(nValues);
        fileStream.read(reinterpret_cast<char*>(&_fullData[0]),
            nValues * sizeof(_fullData[0]));

        bool success = fileStream.good();
        return success;
    }
    else {
        LERROR(fmt::format("Error opening file '{}' for loading cache file", file));
        return false;
    }
}

bool RenderableStars::saveCachedFile(const std::string& file) const {
    std::ofstream fileStream(file, std::ofstream::binary);
    if (fileStream.good()) {
        fileStream.write(reinterpret_cast<const char*>(&CurrentCacheVersion),
            sizeof(int8_t));

        int32_t nValues = static_cast<int32_t>(_fullData.size());
        if (nValues == 0) {
            LERROR("Error writing cache: No values were loaded");
            return false;
        }
        fileStream.write(reinterpret_cast<const char*>(&nValues), sizeof(int32_t));

        int32_t nValuesPerStar = static_cast<int32_t>(_nValuesPerStar);
        fileStream.write(reinterpret_cast<const char*>(&nValuesPerStar), sizeof(int32_t));

        size_t nBytes = nValues * sizeof(_fullData[0]);
        fileStream.write(reinterpret_cast<const char*>(&_fullData[0]), nBytes);

        bool success = fileStream.good();
        return success;
    }
    else {
        LERROR(fmt::format("Error opening file '{}' for save cache file", file));
        return false;
    }
}

void RenderableStars::createDataSlice(ColorOption option) {
    _slicedData.clear();

    for (size_t i = 0; i < _fullData.size(); i+=_nValuesPerStar) {
        glm::vec3 p = glm::vec3(_fullData[i + 0], _fullData[i + 1], _fullData[i + 2]);
        p *= openspace::distanceconstants::Parsec;

        switch (option) {
        case ColorOption::Color:
            {
                union {
                    ColorVBOLayout value;
                    std::array<float, sizeof(ColorVBOLayout) / sizeof(float)> data;
                } layout;

                layout.value.position = { {
                    p[0], p[1], p[2], 1.0
                } };

#ifdef USING_STELLAR_TEST_GRID
                layout.value.bvColor = 0.650;// _fullData[i + 3];
                layout.value.luminance = _fullData[i + 4];
                layout.value.absoluteMagnitude = _fullData[i + 3];
#else
                layout.value.bvColor = _fullData[i + 3];
                layout.value.luminance = _fullData[i + 4];
                layout.value.absoluteMagnitude = _fullData[i + 5];
#endif

                _slicedData.insert(_slicedData.end(),
                                   layout.data.begin(),
                                   layout.data.end());

                break;
            }
        case ColorOption::Velocity:
            {
                union {
                    VelocityVBOLayout value;
                    std::array<float, sizeof(VelocityVBOLayout) / sizeof(float)> data;
                } layout;

                layout.value.position = { {
                        p[0], p[1], p[2], 1.0
                    } };

                layout.value.bvColor = _fullData[i + 3];
                layout.value.luminance = _fullData[i + 4];
                layout.value.absoluteMagnitude = _fullData[i + 5];

                layout.value.vx = _fullData[i + 12];
                layout.value.vy = _fullData[i + 13];
                layout.value.vz = _fullData[i + 14];

                _slicedData.insert(_slicedData.end(),
                                   layout.data.begin(),
                                   layout.data.end());
                break;
            }
        case ColorOption::Speed:
            {
                union {
                    SpeedVBOLayout value;
                    std::array<float, sizeof(SpeedVBOLayout) / sizeof(float)> data;
                } layout;

                layout.value.position = { {
                        p[0], p[1], p[2], 1.0
                    } };

                layout.value.bvColor = _fullData[i + 3];
                layout.value.luminance = _fullData[i + 4];
                layout.value.absoluteMagnitude = _fullData[i + 5];

                layout.value.speed = _fullData[i + 15];

                _slicedData.insert(_slicedData.end(),
                                   layout.data.begin(),
                                   layout.data.end());
                break;
            }
        }
    }
}

} // namespace openspace