#include <osg/Geode>
#include <osg/Geometry>
#include <osg/PointSprite>
#include <osgViewer/Viewer>
#include <osgViewer/ViewerEventHandlers>

static const float RADIUS = 55.f;
static const osg::Vec4f DOT_COLORS(1.f, 0.f, 1.f, 1.f);

// Creates a Geode with 120 points in a circle at a given scale (radius), rotation angle, and color
osg::Geode* createCircle(const osg::Vec4f& color, float radius, float extraRotateDeg)
{
    osg::Geode* geode = new osg::Geode;
    osg::Geometry* geom = new osg::Geometry;
    geom->setUseVertexArrayObject(true);
    geom->setUseVertexBufferObjects(true);

    // Draw a simple circle, every 3 degrees
    osg::Vec3Array* vertices = new osg::Vec3Array();
    for (int k = 0; k < 120; ++k)
    {
        double asRadians = osg::DegreesToRadians(3.0 * k + extraRotateDeg);
        vertices->push_back(osg::Vec3(radius * sin(asRadians), 0.0, radius * cos(asRadians)));
    }

    osg::Vec4Array* colors = new osg::Vec4Array(osg::Array::BIND_OVERALL);
    colors->push_back(color);

    geom->addPrimitiveSet(new osg::DrawArrays(GL_POINTS, 0, 120));
    geom->setVertexArray(vertices);
    geom->setColorArray(colors);
    geode->addDrawable(geom);

    return geode;
}

// Creates the top level group for the scene
osg::Group* createScene()
{
    osg::Group* group = new osg::Group;
    osgText::Text* text = new osgText::Text;
    text->setText("Demo of missing glDeleteVertexArrays.");
    text->setCharacterSize(10.f);
    text->setFont("fonts/times.ttf");
    text->setAxisAlignment(osgText::Text::XZ_PLANE);
    text->setAlignment(osgText::Text::CENTER_CENTER);
    group->addChild(text);

    return group;
}

// On every frame, this handler removes the circle geode and recreates it.  I know this is not efficient,
// but this test application is only intended to demonstrate the problem found in a real app.
struct NewGeodeOnFrame : public osgGA::GUIEventHandler
{
    explicit NewGeodeOnFrame(osg::Group* group)
        : group_(group)
    {
    }

    virtual bool handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa, osg::Object* obj, osg::NodeVisitor* nv)
    {
        if (ea.getEventType() == ea.FRAME)
        {
            group_->removeChildren(0, group_->getNumChildren());
            group_->addChild(createCircle(DOT_COLORS, RADIUS, 3.0 * ea.getTime()));
        }
        return GUIEventHandler::handle(ea, aa, obj, nv);
    }

    osg::ref_ptr<osg::Group> group_;
};

int main(int argc, char** argv)
{
    osg::ArgumentParser arguments(&argc, argv);

    // construct the viewer.
    osgViewer::Viewer viewer(arguments);
    osg::Group* scene = createScene();

    // Add a holder for our rotating circle
    osg::Group* geodeHolder = new osg::Group;
    scene->addChild(geodeHolder);

    viewer.setSceneData(scene);
    viewer.setUpViewInWindow(100, 100, 800, 600);
    viewer.addEventHandler(new osgViewer::StatsHandler());
    // Recreate the circle on every FRAME event
    viewer.addEventHandler(new NewGeodeOnFrame(geodeHolder));

    return viewer.run();
}