#include <osg/Group>
#include <osg/Notify>
#include <osg/Depth>
#include <osg/StateSet>
#include <osg/ClearNode>
#include <osg/Transform>

#include <osgUtil/CullVisitor>

#include <osgDB/Registry>
#include <osgDB/ReadFile>

#include <osgViewer/Viewer>

#include "GliderManipulator.h"

#include <iostream>

extern osg::Node *makeTerrain( void );
extern osg::Node *makeTrees( void );
extern osg::Node *makeTank( void );
extern osg::Node *makeWindsocks( void );
extern osg::Node *makeGliders( void );
extern osg::Node *makeGlider( void );
extern osg::Node *makeSky( void );
extern osg::Node *makeBase( void );
extern osg::Node *makeClouds( void );

class MoveEarthySkyWithEyePointTransform : public osg::Transform
{
public:
    /** Get the transformation matrix which moves from local coords to world coords.*/
    virtual bool computeLocalToWorldMatrix(osg::Matrix& matrix,osg::NodeVisitor* nv) const 
    {
        osgUtil::CullVisitor* cv = dynamic_cast<osgUtil::CullVisitor*>(nv);
        if (cv)
        {
            osg::Vec3 eyePointLocal = cv->getEyeLocal();
            matrix.preMult(osg::Matrix::translate(eyePointLocal.x(),eyePointLocal.y(),0.0f));
        }
        return true;
    }

    /** Get the transformation matrix which moves from world coords to local coords.*/
    virtual bool computeWorldToLocalMatrix(osg::Matrix& matrix,osg::NodeVisitor* nv) const
    {
        std::cout<<"computing transform"<<std::endl;
    
        osgUtil::CullVisitor* cv = dynamic_cast<osgUtil::CullVisitor*>(nv);
        if (cv)
        {
            osg::Vec3 eyePointLocal = cv->getEyeLocal();
            matrix.postMult(osg::Matrix::translate(-eyePointLocal.x(),-eyePointLocal.y(),0.0f));
        }
        return true;
    }
};

osg::Group* createModel()
{
    // no database loaded so automatically create Ed Levin Park..
    osg::Group* group = new osg::Group;

    // the base and sky subgraphs go to set the earth sky of the
    // model and clear the color and depth buffer for us, by using
    // osg::Depth, and setting their bin numbers to less than 0,
    // to force them to draw before the rest of the scene.

    osg::ClearNode* clearNode = new osg::ClearNode;
    clearNode->setRequiresClear(false); // we've got base and sky to do it.

    // use a transform to make the sky and base around with the eye point.
    osg::Transform* transform = new MoveEarthySkyWithEyePointTransform;

    // transform's value isn't knowm until in the cull traversal so its bounding
    // volume is can't be determined, therefore culling will be invalid,
    // so switch it off, this cause all our paresnts to switch culling
    // off as well. But don't worry culling will be back on once underneath
    // this node or any other branch above this transform.
    transform->setCullingActive(false);

    // add the sky and base layer.
    transform->addChild(makeSky());  // bin number -2 so drawn first.
    transform->addChild(makeBase()); // bin number -1 so draw second.      

    // add the transform to the earth sky.
    clearNode->addChild(transform);

    // add to earth sky to the scene.
    group->addChild(clearNode);

    // the rest of the scene drawn after the base and sky above.
    group->addChild(makeTrees()); // will drop into a transparent, depth sorted bin (1)
    group->addChild(makeTerrain()); // will drop into default bin - state sorted 0
    group->addChild(makeTank()); // will drop into default bin - state sorted 0
    // add the following in the future...
    // makeGliders
    // makeClouds

    return group;
}

int main( int argc, char **argv )
{

    // use an ArgumentParser object to manage the program arguments.
    osg::ArgumentParser arguments(&argc,argv);

    // set up the usage document, in case we need to print out how to use this program.
    arguments.getApplicationUsage()->setDescription(arguments.getApplicationName()+" is the example which demonstrates how to create a scene programatically, in this case a hang gliding flying site.");
    arguments.getApplicationUsage()->setCommandLineUsage(arguments.getApplicationName()+" [options] filename ...");
    arguments.getApplicationUsage()->addCommandLineOption("-h or --help","Display this information");

    // construct the viewer.
    osgViewer::Viewer viewer;

    // if user request help write it out to cout.
    if (arguments.read("-h") || arguments.read("--help"))
    {
        arguments.getApplicationUsage()->write(std::cout);
        return 1;
    }
    
    bool customWindows = false;
    while(arguments.read("-2")) customWindows = true;

    if (customWindows)
    {
        osg::GraphicsContext::WindowingSystemInterface* wsi = osg::GraphicsContext::getWindowingSystemInterface();
        if (!wsi) 
        {
            osg::notify(osg::NOTICE)<<"View::setUpViewAcrossAllScreens() : Error, no WindowSystemInterface available, cannot create windows."<<std::endl;
            return 0;
        }

        osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits;
        traits->x = 250;
        traits->y = 200;
        traits->width = 800;
        traits->height = 600;
        traits->windowDecoration = true;
        traits->doubleBuffer = true;
        traits->sharedContext = 0;

        osg::ref_ptr<osg::GraphicsContext> gc = osg::GraphicsContext::createGraphicsContext(traits.get());
        if (gc.valid())
        {
            // need to ensure that the window is cleared make sure that the complete window is set the correct colour
            // rather than just the parts of the window that are under the camera's viewports
            gc->setClearColor(osg::Vec4f(0.2f,0.2f,0.6f,1.0f));
            gc->setClearMask(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        }
        else
        {
            osg::notify(osg::NOTICE)<<"  GraphicsWindow has not been created successfully."<<std::endl;
        }

        unsigned int numCameras = 2;
        double aspectRatioScale = 1.0;
        for(unsigned int i=0; i<numCameras;++i)
        {
            osg::ref_ptr<osg::Camera> camera = new osg::Camera;
            camera->setGraphicsContext(gc.get());
            camera->setViewport(new osg::Viewport((i* traits->width)/numCameras,(i* traits->height)/numCameras,  traits->width/numCameras,  traits->height/numCameras));
            GLenum buffer = traits->doubleBuffer ? GL_BACK : GL_FRONT;
            camera->setDrawBuffer(buffer);
            camera->setReadBuffer(buffer);

            viewer.addSlave(camera.get(), osg::Matrixd(), osg::Matrixd::scale(aspectRatioScale,1.0,1.0));
        }
    }    
    else
    {
        viewer.setUpViewAcrossAllScreens();
    
    }

    // set up the camera manipulation with out custom manipultor
    viewer.setCameraManipulator(new GliderManipulator());

    // pass the scene graph to the viewer    
    viewer.setSceneData( createModel() );

    return viewer.run();
}