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 * OpenSpace                                                                             *
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 * Copyright (c) 2014-2021                                                               *
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#include <modules/exoplanets/rendering/renderableorbitdisc.h>

#include <openspace/documentation/documentation.h>
#include <openspace/documentation/verifier.h>
#include <openspace/engine/globals.h>
#include <openspace/rendering/renderengine.h>
#include <openspace/scene/scenegraphnode.h>
#include <openspace/scene/scene.h>
#include <openspace/util/distanceconstants.h>
#include <ghoul/logging/logmanager.h>
#include <ghoul/filesystem/filesystem.h>
#include <ghoul/io/texture/texturereader.h>
#include <ghoul/opengl/openglstatecache.h>
#include <ghoul/opengl/programobject.h>
#include <ghoul/opengl/texture.h>
#include <ghoul/opengl/textureunit.h>

namespace {
    constexpr const std::array<const char*, 6> UniformNames = {
        "modelViewProjectionTransform", "offset", "opacity",
        "discTexture", "eccentricity", "semiMajorAxis"
    };

    static const openspace::properties::Property::PropertyInfo TextureInfo = {
        "Texture",
        "Texture",
        "This value is the path to a texture on disk that contains a one-dimensional "
        "texture which is used for these rings."
    };

    static const openspace::properties::Property::PropertyInfo SizeInfo = {
        "Size",
        "Size",
        "This value specifies the semi-major axis of the orbit, in meter."
    };

    static const openspace::properties::Property::PropertyInfo EccentricityInfo = {
        "Eccentricity",
        "Eccentricity",
        "This value determines the eccentricity, that is the deviation from a perfect "
        "sphere, for this orbit."
    };

    static const openspace::properties::Property::PropertyInfo OffsetInfo = {
        "Offset",
        "Offset",
        "This property determines the width of the disc. The values specify the lower "
        "and upper deviation from the semi major axis, respectively. The values are "
        "relative to the size of the semi-major axis. That is, 0 means no deviation "
        "from the semi-major axis and 1 is a whole semi-major axis's worth of deviation."
    };
} // namespace

namespace openspace {

documentation::Documentation RenderableOrbitDisc::Documentation() {
    using namespace documentation;
    return {
        "Renderable Orbit Disc",
        "exoplanets_renderable_orbit_disc",
        {
            {
                "Type",
                new StringEqualVerifier("RenderableOrbitDisc"),
                Optional::No
            },
            {
                TextureInfo.identifier,
                new StringVerifier,
                Optional::No,
                TextureInfo.description
            },
            {
                SizeInfo.identifier,
                new DoubleVerifier,
                Optional::No,
                SizeInfo.description
            },
            {
                EccentricityInfo.identifier,
                new DoubleVerifier,
                Optional::No,
                EccentricityInfo.description
            },
            {
                OffsetInfo.identifier,
                new DoubleVector2Verifier,
                Optional::Yes,
                OffsetInfo.description
            }
        }
    };
}

RenderableOrbitDisc::RenderableOrbitDisc(const ghoul::Dictionary& dictionary)
    : Renderable(dictionary)
    , _texturePath(TextureInfo)
    , _size(SizeInfo, 1.f, 0.f, 3.0e12f)
    , _eccentricity(EccentricityInfo, 0.f, 0.f, 1.f)
    , _offset(OffsetInfo, glm::vec2(0.f), glm::vec2(0.f), glm::vec2(1.f))
{
    using ghoul::filesystem::File;

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

    if (dictionary.hasKey(OffsetInfo.identifier)) {
        _offset = dictionary.value<glm::dvec2>(OffsetInfo.identifier);
    }
    _offset.onChange([&]() { _planeIsDirty = true; });
    addProperty(_offset);

    _size = static_cast<float>(dictionary.value<double>(SizeInfo.identifier));
    _size.onChange([&]() { _planeIsDirty = true; });
    addProperty(_size);

    setBoundingSphere(_size + _offset.value().y * _size);

    _texturePath = absPath(dictionary.value<std::string>(TextureInfo.identifier));
    _textureFile = std::make_unique<File>(_texturePath);

    _texturePath.onChange([&]() { _textureIsDirty = true; });
    addProperty(_texturePath);

    _textureFile->setCallback([&](const File&) { _textureIsDirty = true; });

    _eccentricity = static_cast<float>(
        dictionary.value<double>(EccentricityInfo.identifier)
    );
    _eccentricity.onChange([&]() { _planeIsDirty = true; });
    addProperty(_eccentricity);

    addProperty(_opacity);
}

bool RenderableOrbitDisc::isReady() const {
    return _shader && _texture;
}

void RenderableOrbitDisc::initializeGL() {
    _shader = global::renderEngine->buildRenderProgram(
        "OrbitdiscProgram",
        absPath("${BASE}/modules/exoplanets/shaders/orbitdisc_vs.glsl"),
        absPath("${BASE}/modules/exoplanets/shaders/orbitdisc_fs.glsl")
    );

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

    glGenVertexArrays(1, &_quad);
    glGenBuffers(1, &_vertexPositionBuffer);

    createPlane();
    loadTexture();
}

void RenderableOrbitDisc::deinitializeGL() {
    glDeleteVertexArrays(1, &_quad);
    _quad = 0;

    glDeleteBuffers(1, &_vertexPositionBuffer);
    _vertexPositionBuffer = 0;

    _textureFile = nullptr;
    _texture = nullptr;

    global::renderEngine->removeRenderProgram(_shader.get());
    _shader = nullptr;
}

void RenderableOrbitDisc::render(const RenderData& data, RendererTasks&) {
    _shader->activate();

    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::dmat4 modelViewTransform = data.camera.combinedViewMatrix() * modelTransform;

    _shader->setUniform(
        _uniformCache.modelViewProjection,
        data.camera.projectionMatrix() * glm::mat4(modelViewTransform)
    );
    _shader->setUniform(_uniformCache.offset, _offset);
    _shader->setUniform(_uniformCache.opacity, _opacity);
    _shader->setUniform(_uniformCache.eccentricity, _eccentricity);
    _shader->setUniform(_uniformCache.semiMajorAxis, _size);

    ghoul::opengl::TextureUnit unit;
    unit.activate();
    _texture->bind();
    _shader->setUniform(_uniformCache.texture, unit);

    glEnablei(GL_BLEND, 0);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glDepthMask(false);
    glDisable(GL_CULL_FACE);

    glBindVertexArray(_quad);
    glDrawArrays(GL_TRIANGLES, 0, 6);

    _shader->deactivate();

    // Restores GL State
    global::renderEngine->openglStateCache().resetBlendState();
    global::renderEngine->openglStateCache().resetDepthState();
    global::renderEngine->openglStateCache().resetPolygonAndClippingState();
}

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

    if (_planeIsDirty) {
        createPlane();
        _planeIsDirty = false;
    }

    if (_textureIsDirty) {
        loadTexture();
        _textureIsDirty = false;
    }
}

void RenderableOrbitDisc::loadTexture() {
    if (!_texturePath.value().empty()) {
        std::unique_ptr<ghoul::opengl::Texture> texture =
            ghoul::io::TextureReader::ref().loadTexture(absPath(_texturePath));

        if (texture) {
            LDEBUGC(
                "RenderableOrbitDisc",
                fmt::format("Loaded texture from '{}'", absPath(_texturePath))
            );
            _texture = std::move(texture);

            _texture->uploadTexture();
            _texture->setFilter(ghoul::opengl::Texture::FilterMode::AnisotropicMipMap);

            _textureFile = std::make_unique<ghoul::filesystem::File>(_texturePath);
            _textureFile->setCallback(
                [&](const ghoul::filesystem::File&) { _textureIsDirty = true; }
            );
        }
    }
}

void RenderableOrbitDisc::createPlane() {
    const GLfloat outerDistance = (_size + _offset.value().y * _size);
    const GLfloat size = outerDistance * (1.f + _eccentricity);

    struct VertexData {
        GLfloat x;
        GLfloat y;
        GLfloat s;
        GLfloat t;
    };

    VertexData data[] = {
        { -size, -size, 0.f, 0.f },
        {  size,  size, 1.f, 1.f },
        { -size,  size, 0.f, 1.f },
        { -size, -size, 0.f, 0.f },
        {  size, -size, 1.f, 0.f },
        {  size,  size, 1.f, 1.f },
    };

    glBindVertexArray(_quad);
    glBindBuffer(GL_ARRAY_BUFFER, _vertexPositionBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(data), data, GL_STATIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(
        0,
        2,
        GL_FLOAT,
        GL_FALSE,
        sizeof(VertexData),
        nullptr
    );
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(
        1,
        2,
        GL_FLOAT,
        GL_FALSE,
        sizeof(VertexData),
        reinterpret_cast<void*>(offsetof(VertexData, s))
    );
}

} // namespace openspace