/*****************************************************************************************
 *                                                                                       *
 * OpenSpace                                                                             *
 *                                                                                       *
 * Copyright (c) 2014-2022                                                               *
 *                                                                                       *
 * 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,    *
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 * permit persons to whom the Software is furnished to do so, subject to the following   *
 * conditions:                                                                           *
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 * The above copyright notice and this permission notice shall be included in all copies *
 * or substantial portions of the Software.                                              *
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 * 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/base/rendering/renderablemodel.h>

#include <modules/base/basemodule.h>
#include <openspace/documentation/documentation.h>
#include <openspace/documentation/verifier.h>
#include <openspace/engine/globals.h>
#include <openspace/rendering/renderengine.h>
#include <openspace/util/time.h>
#include <openspace/util/timeconversion.h>
#include <openspace/util/updatestructures.h>
#include <openspace/scene/scene.h>
#include <openspace/scene/lightsource.h>
#include <ghoul/io/model/modelgeometry.h>
#include <ghoul/filesystem/filesystem.h>
#include <ghoul/logging/logmanager.h>
#include <ghoul/misc/invariants.h>
#include <ghoul/misc/profiling.h>
#include <ghoul/opengl/openglstatecache.h>
#include <ghoul/opengl/programobject.h>
#include <filesystem>
#include <optional>

namespace {
    constexpr std::string_view _loggerCat = "RenderableModel";
    constexpr std::string_view ProgramName = "ModelProgram";

    constexpr int DefaultBlending = 0;
    constexpr int AdditiveBlending = 1;
    constexpr int PointsAndLinesBlending = 2;
    constexpr int PolygonBlending = 3;
    constexpr int ColorAddingBlending = 4;

    std::map<std::string, int> BlendingMapping = {
        { "Default", DefaultBlending },
        { "Additive", AdditiveBlending },
        { "Points and Lines", PointsAndLinesBlending },
        { "Polygon", PolygonBlending },
        { "Color Adding", ColorAddingBlending }
    };

    constexpr openspace::properties::Property::PropertyInfo EnableAnimationInfo = {
        "EnableAnimation",
        "Enable Animation",
        "Enable or disable the animation for the model if it has any"
    };

    constexpr std::array<const char*, 12> UniformNames = {
        "opacity", "nLightSources", "lightDirectionsViewSpace", "lightIntensities",
        "modelViewTransform", "normalTransform", "projectionTransform",
        "performShading", "ambientIntensity", "diffuseIntensity",
        "specularIntensity", "opacityBlending"
    };

    constexpr openspace::properties::Property::PropertyInfo AmbientIntensityInfo = {
        "AmbientIntensity",
        "Ambient Intensity",
        "A multiplier for ambient lighting"
    };

    constexpr openspace::properties::Property::PropertyInfo DiffuseIntensityInfo = {
        "DiffuseIntensity",
        "Diffuse Intensity",
        "A multiplier for diffuse lighting"
    };

    constexpr openspace::properties::Property::PropertyInfo SpecularIntensityInfo = {
        "SpecularIntensity",
        "Specular Intensity",
        "A multiplier for specular lighting"
    };

    constexpr openspace::properties::Property::PropertyInfo ShadingInfo = {
        "PerformShading",
        "Perform Shading",
        "This value determines whether this model should be shaded by using the position "
        "of the Sun"
    };

    constexpr openspace::properties::Property::PropertyInfo DisableFaceCullingInfo = {
        "DisableFaceCulling",
        "Disable Face Culling",
        "Disable OpenGL automatic face culling optimization"
    };

    constexpr openspace::properties::Property::PropertyInfo ModelTransformInfo = {
        "ModelTransform",
        "Model Transform",
        "This value specifies the model transform that is applied to the model before "
        "all other transformations are applied"
    };

    constexpr openspace::properties::Property::PropertyInfo RotationVecInfo = {
        "RotationVector",
        "Rotation Vector",
        "Rotation Vector using degrees"
    };

    constexpr openspace::properties::Property::PropertyInfo LightSourcesInfo = {
        "LightSources",
        "Light Sources",
        "A list of light sources that this model should accept light from"
    };

    constexpr openspace::properties::Property::PropertyInfo DisableDepthTestInfo = {
        "DisableDepthTest",
        "Disable Depth Test",
        "Disable Depth Testing for the Model"
    };

    constexpr openspace::properties::Property::PropertyInfo BlendingOptionInfo = {
        "BlendingOption",
        "Blending Options",
        "Changes the blending function used to calculate the colors of the model with "
        "respect to the opacity"
    };

    constexpr openspace::properties::Property::PropertyInfo EnableOpacityBlendingInfo = {
        "EnableOpacityBlending",
        "Enable Opacity Blending",
        "Enable Opacity Blending"
    };

    struct [[codegen::Dictionary(RenderableModel)]] Parameters {
        // The file or files that should be loaded in this RenderableModel. The file can
        // contain filesystem tokens. This specifies the model that is rendered by
        // the Renderable.
        std::filesystem::path geometryFile;

        enum class [[codegen::map(openspace::DistanceUnit)]] ScaleUnit {
            Nanometer,
            Micrometer,
            Millimeter,
            Centimeter,
            Decimeter,
            Meter,
            Kilometer,

            // Weird units
            Thou,
            Inch,
            Foot,
            Yard,
            Chain,
            Furlong,
            Mile
        };

        // The scale of the model. For example if the model is in centimeters
        // then ModelScale = Centimeter or ModelScale = 0.01
        std::optional<std::variant<ScaleUnit, double>> modelScale;

        // By default the given ModelScale is used to scale the model down,
        // by setting this setting to true the model is instead scaled up with the
        // given ModelScale
        std::optional<bool> invertModelScale;

        // Set if invisible parts (parts with no textures or materials) of the model
        // should be forced to render or not.
        std::optional<bool> forceRenderInvisible;

        // [[codegen::verbatim(EnableAnimationInfo.description)]]
        std::optional<bool> enableAnimation;

        // The date and time that the model animation should start.
        // In format 'YYYY MM DD hh:mm:ss'.
        std::optional<std::string> animationStartTime [[codegen::datetime()]];

        enum class [[codegen::map(openspace::TimeUnit)]] AnimationTimeUnit {
            Nanosecond,
            Microsecond,
            Millisecond,
            Second,
            Minute
        };

        // The time scale for the animation relative to seconds.
        // Ex, if animation is in milliseconds then AnimationTimeScale = 0.001 or
        // AnimationTimeScale = Millisecond, default is Second
        std::optional<std::variant<AnimationTimeUnit, float>> animationTimeScale;

        enum class AnimationMode {
            Once,
            LoopFromStart,
            LoopInfinitely,
            BounceFromStart,
            BounceInfinitely
        };

        // The mode of how the animation should be played back.
        // Default is animation is played back once at the start time.
        // For a more detailed description see:
        // http://wiki.openspaceproject.com/docs/builders/model-animation
        std::optional<AnimationMode> animationMode;

        // [[codegen::verbatim(AmbientIntensityInfo.description)]]
        std::optional<float> ambientIntensity;

        // [[codegen::verbatim(DiffuseIntensityInfo.description)]]
        std::optional<float> diffuseIntensity;

        // [[codegen::verbatim(SpecularIntensityInfo.description)]]
        std::optional<float> specularIntensity;

        // [[codegen::verbatim(ShadingInfo.description)]]
        std::optional<bool> performShading;

        // [[codegen::verbatim(DisableFaceCullingInfo.description)]]
        std::optional<bool> disableFaceCulling;

        // [[codegen::verbatim(ModelTransformInfo.description)]]
        std::optional<glm::dmat3x3> modelTransform;

        // [[codegen::verbatim(RotationVecInfo.description)]]
        std::optional<glm::dvec3> rotationVector;

        // [[codegen::verbatim(LightSourcesInfo.description)]]
        std::optional<std::vector<ghoul::Dictionary>> lightSources
            [[codegen::reference("core_light_source")]];

        // [[codegen::verbatim(DisableDepthTestInfo.description)]]
        std::optional<bool> disableDepthTest;

        // [[codegen::verbatim(BlendingOptionInfo.description)]]
        std::optional<std::string> blendingOption;

        // [[codegen::verbatim(EnableOpacityBlendingInfo.description)]]
        std::optional<bool> enableOpacityBlending;

        // The path to the vertex shader program that is used instead of the default
        // shader.
        std::optional<std::filesystem::path> vertexShader;

        // The path to the fragment shader program that is used instead of the default
        // shader.
        std::optional<std::filesystem::path> fragmentShader;
    };
#include "renderablemodel_codegen.cpp"
} // namespace

namespace openspace {

documentation::Documentation RenderableModel::Documentation() {
    return codegen::doc<Parameters>("base_renderable_model");
}

RenderableModel::RenderableModel(const ghoul::Dictionary& dictionary)
    : Renderable(dictionary)
    , _enableAnimation(EnableAnimationInfo, false)
    , _ambientIntensity(AmbientIntensityInfo, 0.2f, 0.f, 1.f)
    , _diffuseIntensity(DiffuseIntensityInfo, 1.f, 0.f, 1.f)
    , _specularIntensity(SpecularIntensityInfo, 1.f, 0.f, 1.f)
    , _performShading(ShadingInfo, true)
    , _disableFaceCulling(DisableFaceCullingInfo, false)
    , _modelTransform(
        ModelTransformInfo,
        glm::dmat3(1.0),
        glm::dmat3(-1.0),
        glm::dmat3(1.0)
    )
    , _rotationVec(RotationVecInfo, glm::dvec3(0.0), glm::dvec3(0.0), glm::dvec3(360.0))
    , _disableDepthTest(DisableDepthTestInfo, false)
    , _enableOpacityBlending(EnableOpacityBlendingInfo, false)
    , _blendingFuncOption(
        BlendingOptionInfo,
        properties::OptionProperty::DisplayType::Dropdown
    )
    , _lightSourcePropertyOwner({ "LightSources", "Light Sources" })
{
    const Parameters p = codegen::bake<Parameters>(dictionary);

    addProperty(_opacity);
    registerUpdateRenderBinFromOpacity();

    if (p.forceRenderInvisible.has_value()) {
        _forceRenderInvisible = *p.forceRenderInvisible;

        if (!_forceRenderInvisible) {
            // Asset file have specifically said to not render invisible parts,
            // do not notify in the log if invisible parts are detected and dropped
            _notifyInvisibleDropped = false;
        }
    }

    std::string file = absPath(p.geometryFile.string()).string();
    _geometry = ghoul::io::ModelReader::ref().loadModel(
        file,
        ghoul::io::ModelReader::ForceRenderInvisible(_forceRenderInvisible),
        ghoul::io::ModelReader::NotifyInvisibleDropped(_notifyInvisibleDropped)
    );

    _invertModelScale = p.invertModelScale.value_or(_invertModelScale);

    if (p.modelScale.has_value()) {
        if (std::holds_alternative<Parameters::ScaleUnit>(*p.modelScale)) {
            Parameters::ScaleUnit scaleUnit =
                std::get<Parameters::ScaleUnit>(*p.modelScale);
            DistanceUnit distanceUnit = codegen::map<DistanceUnit>(scaleUnit);
            _modelScale = toMeter(distanceUnit);
        }
        else if (std::holds_alternative<double>(*p.modelScale)) {
            _modelScale = std::get<double>(*p.modelScale);
        }
        else {
            throw ghoul::MissingCaseException();
        }

        if (_invertModelScale) {
            _modelScale = 1.0 / _modelScale;
        }
    }

    if (p.animationStartTime.has_value()) {
        if (!_geometry->hasAnimation()) {
            LWARNING("Animation start time given to model without animation");
        }
        _animationStart = *p.animationStartTime;
    }

    if (p.enableAnimation.has_value()) {
        if (!_geometry->hasAnimation()) {
            LWARNING("Attempting to enable animation for a model that does not have any");
        }
        else if (*p.enableAnimation && _animationStart.empty()) {
            LWARNING("Cannot enable animation without a given start time");
        }
        else {
            _enableAnimation = *p.enableAnimation;
            _geometry->enableAnimation(_enableAnimation);
        }
    }

    if (p.animationTimeScale.has_value()) {
        if (!_geometry->hasAnimation()) {
            LWARNING("Animation time scale given to model without animation");
        }
        else if (std::holds_alternative<float>(*p.animationTimeScale)) {
            _geometry->setTimeScale(std::get<float>(*p.animationTimeScale));
        }
        else if (std::holds_alternative<Parameters::AnimationTimeUnit>(
                    *p.animationTimeScale)
                )
        {
            Parameters::AnimationTimeUnit animationTimeUnit =
                std::get<Parameters::AnimationTimeUnit>(*p.animationTimeScale);
            TimeUnit timeUnit = codegen::map<TimeUnit>(animationTimeUnit);

            _geometry->setTimeScale(static_cast<float>(
                convertTime(1.0, timeUnit, TimeUnit::Second))
            );
        }
        else {
            throw ghoul::MissingCaseException();
        }
    }

    if (p.animationMode.has_value()) {
        if (!_geometry->hasAnimation()) {
            LWARNING("Animation mode given to model without animation");
        }

        switch (*p.animationMode) {
            case Parameters::AnimationMode::LoopFromStart:
                _animationMode = AnimationMode::LoopFromStart;
                break;
            case Parameters::AnimationMode::LoopInfinitely:
                _animationMode = AnimationMode::LoopInfinitely;
                break;
            case Parameters::AnimationMode::BounceFromStart:
                _animationMode = AnimationMode::BounceFromStart;
                break;
            case Parameters::AnimationMode::BounceInfinitely:
                _animationMode = AnimationMode::BounceInfinitely;
                break;
            case Parameters::AnimationMode::Once:
                _animationMode = AnimationMode::Once;
                break;
            default:
                throw ghoul::MissingCaseException();
        }
    }

    if (p.modelTransform.has_value()) {
        _modelTransform = *p.modelTransform;
    }

    _ambientIntensity = p.ambientIntensity.value_or(_ambientIntensity);
    _diffuseIntensity = p.diffuseIntensity.value_or(_diffuseIntensity);
    _specularIntensity = p.specularIntensity.value_or(_specularIntensity);
    _performShading = p.performShading.value_or(_performShading);
    _disableDepthTest = p.disableDepthTest.value_or(_disableDepthTest);
    _disableFaceCulling = p.disableFaceCulling.value_or(_disableFaceCulling);

    if (p.vertexShader.has_value()) {
        _vertexShaderPath = p.vertexShader->string();
    }
    if (p.fragmentShader.has_value()) {
        _fragmentShaderPath = p.fragmentShader->string();
    }

    if (p.lightSources.has_value()) {
        std::vector<ghoul::Dictionary> lightsources = *p.lightSources;

        for (const ghoul::Dictionary& lsDictionary : lightsources) {
            std::unique_ptr<LightSource> lightSource =
                LightSource::createFromDictionary(lsDictionary);
            _lightSourcePropertyOwner.addPropertySubOwner(lightSource.get());
            _lightSources.push_back(std::move(lightSource));
        }
    }

    if (_geometry->hasAnimation()) {
        addProperty(_enableAnimation);
    }

    addPropertySubOwner(_lightSourcePropertyOwner);
    addProperty(_ambientIntensity);
    addProperty(_diffuseIntensity);
    addProperty(_specularIntensity);
    addProperty(_performShading);
    addProperty(_disableFaceCulling);
    addProperty(_disableDepthTest);
    addProperty(_modelTransform);
    addProperty(_rotationVec);

    _rotationVec.onChange([this]() {
        _modelTransform = glm::mat4_cast(glm::quat(glm::radians(_rotationVec.value())));
    });

    _enableAnimation.onChange([this]() {
        if (!_geometry->hasAnimation()) {
            LWARNING("Attempting to enable animation for a model that does not have any");
        }
        else if (_enableAnimation && _animationStart.empty()) {
            LWARNING("Cannot enable animation without a given start time");
            _enableAnimation = false;
        }
        else {
            _geometry->enableAnimation(_enableAnimation);
        }
    });

    if (p.rotationVector.has_value()) {
        _rotationVec = *p.rotationVector;
    }

    _blendingFuncOption.addOption(DefaultBlending, "Default");
    _blendingFuncOption.addOption(AdditiveBlending, "Additive");
    _blendingFuncOption.addOption(PointsAndLinesBlending, "Points and Lines");
    _blendingFuncOption.addOption(PolygonBlending, "Polygon");
    _blendingFuncOption.addOption(ColorAddingBlending, "Color Adding");

    addProperty(_blendingFuncOption);

    if (p.blendingOption.has_value()) {
        const std::string blendingOpt = *p.blendingOption;
        _blendingFuncOption.set(BlendingMapping[blendingOpt]);
    }

    _enableOpacityBlending = p.enableOpacityBlending.value_or(_enableOpacityBlending);

    addProperty(_enableOpacityBlending);
}

bool RenderableModel::isReady() const {
    return _program;
}

void RenderableModel::initialize() {
    ZoneScoped

    if (_geometry->hasAnimation() && _enableAnimation && _animationStart.empty()) {
        LWARNING("Model with animation not given any start time");
    }
    else if (_geometry->hasAnimation() && !_enableAnimation) {
        LINFO("Model with deactivated animation was found. "
            "The animation can be activated by entering a start time in the asset file"
        );
    }

    for (const std::unique_ptr<LightSource>& ls : _lightSources) {
        ls->initialize();
    }
}

void RenderableModel::initializeGL() {
    ZoneScoped

    std::string program = std::string(ProgramName);
    if (!_vertexShaderPath.empty()) {
        program += "|vs=" + _vertexShaderPath;
    }
    if (!_fragmentShaderPath.empty()) {
        program += "|fs=" + _fragmentShaderPath;
    }
    _program = BaseModule::ProgramObjectManager.request(
        program,
        [&]() -> std::unique_ptr<ghoul::opengl::ProgramObject> {
            std::filesystem::path vs =
                _vertexShaderPath.empty() ?
                absPath("${MODULE_BASE}/shaders/model_vs.glsl") :
                std::filesystem::path(_vertexShaderPath);
            std::filesystem::path fs =
                _fragmentShaderPath.empty() ?
                absPath("${MODULE_BASE}/shaders/model_fs.glsl") :
                std::filesystem::path(_fragmentShaderPath);

            return global::renderEngine->buildRenderProgram(program, vs, fs);
        }
    );
    // We don't really know what kind of shader the user provides us with, so we can't
    // make the assumption that we are going to use all uniforms
    _program->setIgnoreUniformLocationError(
        ghoul::opengl::ProgramObject::IgnoreError::Yes
    );

    ghoul::opengl::updateUniformLocations(*_program, _uniformCache, UniformNames);

    _geometry->initialize();
    _geometry->calculateBoundingRadius();
}

void RenderableModel::deinitializeGL() {
    _geometry->deinitialize();
    _geometry.reset();

    std::string program = std::string(ProgramName);
    if (!_vertexShaderPath.empty()) {
        program += "|vs=" + _vertexShaderPath;
    }
    if (!_fragmentShaderPath.empty()) {
        program += "|fs=" + _fragmentShaderPath;
    }
    BaseModule::ProgramObjectManager.release(
        program,
        [](ghoul::opengl::ProgramObject* p) {
            global::renderEngine->removeRenderProgram(p);
        }
    );
    _program = nullptr;
}

void RenderableModel::render(const RenderData& data, RendererTasks&) {
    const double distanceToCamera = glm::distance(
        data.camera.positionVec3(),
        data.modelTransform.translation
    );

    // This distance will be enough to render the model as one pixel if the field of
    // view is 'fov' radians and the screen resolution is 'res' pixels.
    // Formula from RenderableGlobe
    constexpr double tfov = 0.5773502691896257;
    constexpr int res = 2880;
    const double maxDistance = res * boundingSphere() / tfov;

    if (distanceToCamera < maxDistance) {
        _program->activate();

        _program->setUniform(_uniformCache.opacity, opacity());

        // Model transform and view transform needs to be in double precision
        const glm::dmat4 modelTransform =
            glm::translate(glm::dmat4(1.0), data.modelTransform.translation) *
            glm::dmat4(data.modelTransform.rotation) *
            glm::scale(glm::dmat4(1.0), glm::dvec3(data.modelTransform.scale)) *
            glm::scale(_modelTransform.value(), glm::dvec3(_modelScale));
        const glm::dmat4 modelViewTransform = data.camera.combinedViewMatrix() *
            modelTransform;

        int nLightSources = 0;
        _lightIntensitiesBuffer.resize(_lightSources.size());
        _lightDirectionsViewSpaceBuffer.resize(_lightSources.size());
        for (const std::unique_ptr<LightSource>& lightSource : _lightSources) {
            if (!lightSource->isEnabled()) {
                continue;
            }
            _lightIntensitiesBuffer[nLightSources] = lightSource->intensity();
            _lightDirectionsViewSpaceBuffer[nLightSources] =
                lightSource->directionViewSpace(data);

            ++nLightSources;
        }

        _program->setUniform(
            _uniformCache.nLightSources,
            nLightSources
        );
        _program->setUniform(
            _uniformCache.lightIntensities,
            _lightIntensitiesBuffer
        );
        _program->setUniform(
            _uniformCache.lightDirectionsViewSpace,
            _lightDirectionsViewSpaceBuffer
        );
        _program->setUniform(
            _uniformCache.modelViewTransform,
            glm::mat4(modelViewTransform)
        );

        glm::dmat4 normalTransform = glm::transpose(glm::inverse(modelViewTransform));

        _program->setUniform(
            _uniformCache.normalTransform,
            glm::mat4(normalTransform)
        );

        _program->setUniform(
            _uniformCache.projectionTransform,
            data.camera.projectionMatrix()
        );
        _program->setUniform(_uniformCache.ambientIntensity, _ambientIntensity);
        _program->setUniform(_uniformCache.diffuseIntensity, _diffuseIntensity);
        _program->setUniform(_uniformCache.specularIntensity, _specularIntensity);
        _program->setUniform(_uniformCache.performShading, _performShading);
        _program->setUniform(_uniformCache.opacityBlending, _enableOpacityBlending);

        if (_disableFaceCulling) {
            glDisable(GL_CULL_FACE);
        }

        glEnablei(GL_BLEND, 0);
        switch (_blendingFuncOption) {
            case DefaultBlending:
                glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
                break;
            case AdditiveBlending:
                glBlendFunc(GL_ONE, GL_ONE);
                break;
            case PointsAndLinesBlending:
                glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
                break;
            case PolygonBlending:
                glBlendFunc(GL_SRC_ALPHA_SATURATE, GL_ONE);
                break;
            case ColorAddingBlending:
                glBlendFunc(GL_SRC_COLOR, GL_DST_COLOR);
                break;
        };

        if (_disableDepthTest) {
            glDisable(GL_DEPTH_TEST);
        }

        _geometry->render(*_program);
        if (_disableFaceCulling) {
            glEnable(GL_CULL_FACE);
        }

        global::renderEngine->openglStateCache().resetBlendState();

        if (_disableDepthTest) {
            glEnable(GL_DEPTH_TEST);
        }

        _program->deactivate();
    }
}

void RenderableModel::update(const UpdateData& data) {
    if (_program->isDirty()) {
        _program->rebuildFromFile();
        ghoul::opengl::updateUniformLocations(*_program, _uniformCache, UniformNames);
    }

    setBoundingSphere(_geometry->boundingRadius() * _modelScale *
        glm::compMax(data.modelTransform.scale)
    );
    // Set Interaction sphere size to be 10% of the bounding sphere
    setInteractionSphere(_boundingSphere * 0.1);

    if (_geometry->hasAnimation() && !_animationStart.empty()) {
        double relativeTime;
        double now = data.time.j2000Seconds();
        double startTime = data.time.convertTime(_animationStart);
        double duration = _geometry->animationDuration();

        // The animation works in a time range 0 to duration where 0 in the animation is
        // the given _animationStart time in OpenSpace. The time in OpenSpace then has to
        // be converted to the animation time range, so the animation knows which
        // keyframes it should interpolate between for each frame. The conversion is
        // done in different ways depending on the animation mode.
        // Explanation: s indicates start time, / indicates animation is played once
        // forwards, \ indicates animation is played once backwards, time moves to the
        // right.
        switch (_animationMode) {
            case AnimationMode::LoopFromStart:
                // Start looping from the start time
                // s//// ...
                relativeTime = std::fmod(now - startTime, duration);
                break;
            case AnimationMode::LoopInfinitely:
                // Loop both before and after the start time where the model is
                // in the initial position at the start time. std::fmod is not a
                // true modulo function, it just calculates the remainder of the division
                // which can be negative. To make it true modulo it is bumped up to
                // positive values when it is negative
                // //s// ...
                relativeTime = std::fmod(now - startTime, duration);
                if (relativeTime < 0.0) {
                    relativeTime += duration;
                }
                break;
            case AnimationMode::BounceFromStart:
                // Bounce from the start position. Bounce means to do the animation
                // and when it ends, play the animation in reverse to make sure the model
                // goes back to its initial position before starting again. Avoids a
                // visible jump from the last position to the first position when loop
                // starts again
                // s/\/\/\/\ ...
                relativeTime =
                    duration - abs(fmod(now - startTime, 2 * duration) - duration);
                break;
            case AnimationMode::BounceInfinitely: {
                // Bounce both before and after the start time where the model is
                // in the initial position at the start time
                // /\/\s/\/\ ...
                double modulo = fmod(now - startTime, 2 * duration);
                if (modulo < 0.0) {
                    modulo += 2 * duration;
                }
                relativeTime = duration - abs(modulo - duration);
                break;
            }
            case AnimationMode::Once:
                // Play animation once starting from the start time and stay at the
                // animation's last position when animation is over
                // s/
                relativeTime = now - startTime;
                if (relativeTime > duration) {
                    relativeTime = duration;
                }
                break;
            default:
                throw ghoul::MissingCaseException();
        }
        _geometry->update(relativeTime);
    }
}

}  // namespace openspace
