#include <osgProducer/Viewer>

#include <osg/Group>
#include <osg/Geode>

#include <osgParticle/Particle>
#include <osgParticle/ParticleSystem>
#include <osgParticle/ParticleSystemUpdater>
#include <osgParticle/ModularEmitter>
#include <osgParticle/ModularProgram>
#include <osgParticle/RandomRateCounter>
#include <osgParticle/SectorPlacer>
#include <osgParticle/RadialShooter>
#include <osgParticle/AccelOperator>
#include <osgParticle/FluidFrictionOperator>



//////////////////////////////////////////////////////////////////////////////
// CUSTOM OPERATOR CLASS
//////////////////////////////////////////////////////////////////////////////

// This class demonstrates Operator subclassing. This way you can create
// custom operators to apply your motion effects to the particles. See docs
// for more details.
class VortexOperator: public osgParticle::Operator {
public:
	VortexOperator() 
		: osgParticle::Operator(), center_(0, 0, 0), axis_(0, 0, 1), intensity_(0.1f) {}

	VortexOperator(const VortexOperator &copy, const osg::CopyOp &copyop = osg::CopyOp::SHALLOW_COPY)
		: osgParticle::Operator(copy, copyop), center_(copy.center_), axis_(copy.axis_), intensity_(copy.intensity_) {}

	META_Object(osgParticle, VortexOperator);

	void setCenter(const osg::Vec3 &c)
	{
		center_ = c;
	}

	void setAxis(const osg::Vec3 &a)
	{
		axis_ = a / a.length();
	}

	// this method is called by ModularProgram before applying
	// operators on the particle set via the operate() method.	
	void beginOperate(osgParticle::Program *prg)
	{
		// we have to check whether the reference frame is relative to parents
		// or it's absolute; in the first case, we must transform the vectors
		// from local to world space.
		if (prg->getReferenceFrame() == osgParticle::Program::RELATIVE_TO_PARENTS) {
			// transform the center point (full transformation)
			xf_center_ = prg->transformLocalToWorld(center_);
			// transform the axis vector (only rotation and scale)
			xf_axis_ = prg->rotateLocalToWorld(axis_);
		} else {
			xf_center_ = center_;
			xf_axis_ = axis_;
		}
	}

	// apply a vortex-like acceleration. This code is not optimized,
	// it's here only for demonstration purposes.
	void operate(osgParticle::Particle *P, double dt)
	{
		float l = xf_axis_ * (P->getPosition() - xf_center_);
		osg::Vec3 lc = xf_center_ + xf_axis_ * l;
		osg::Vec3 R = P->getPosition() - lc;
		osg::Vec3 v = (R ^ xf_axis_) * P->getMassInv() * intensity_;

		// compute new position
		osg::Vec3 newpos = P->getPosition() + v * dt;

		// update the position of the particle without modifying its
		// velocity vector (this is unusual, normally you should call
		// the Particle::setVelocity() or Particle::addVelocity()
		// methods).
		P->setPosition(newpos);	
	}

protected:
	virtual ~VortexOperator() {}

private:
	osg::Vec3 center_;
	osg::Vec3 xf_center_;
	osg::Vec3 axis_;
	osg::Vec3 xf_axis_;
	float intensity_;
};


//////////////////////////////////////////////////////////////////////////////
// SIMPLE PARTICLE SYSTEM CREATION
//////////////////////////////////////////////////////////////////////////////


osgParticle::ParticleSystem *create_simple_particle_system(osg::Group *root)
{

	// Ok folks, this is the first particle system we build; it will be
	// very simple, with no textures and no special effects, just default
	// values except for a couple of attributes.

	// First of all, we create the ParticleSystem object; it will hold
	// our particles and expose the interface for managing them; this object
	// is a Drawable, so we'll have to add it to a Geode later.

	osgParticle::ParticleSystem *ps = new osgParticle::ParticleSystem;

	// As for other Drawable classes, the aspect of graphical elements of
	// ParticleSystem (the particles) depends on the StateAttribute's we
	// give it. The ParticleSystem class has an helper function that let
	// us specify a set of the most common attributes: setDefaultAttributes().
	// This method can accept up to three parameters; the first is a texture
	// name (std::string), which can be empty to disable texturing, the second
	// sets whether particles have to be "emissive" (additive blending) or not;
	// the third parameter enables or disables lighting.

	ps->setDefaultAttributes("", true, false);

	// Now that our particle system is set we have to create an emitter, that is
	// an object (actually a Node descendant) that generate new particles at 
	// each frame. The best choice is to use a ModularEmitter, which allow us to
	// achieve a wide variety of emitting styles by composing the emitter using
	// three objects: a "counter", a "placer" and a "shooter". The counter must
	// tell the ModularEmitter how many particles it has to create for the
	// current frame; then, the ModularEmitter creates these particles, and for
	// each new particle it instructs the placer and the shooter to set its
	// position vector and its velocity vector, respectively.
	// By default, a ModularEmitter object initializes itself with a counter of
	// type RandomRateCounter, a placer of type PointPlacer and a shooter of
	// type RadialShooter (see documentation for details). We are going to leave
	// these default objects there, but we'll modify the counter so that it
	// counts faster (more particles are emitted at each frame).

	osgParticle::ModularEmitter *emitter = new osgParticle::ModularEmitter;

	// the first thing you *MUST* do after creating an emitter is to set the
	// destination particle system, otherwise it won't know where to create
	// new particles.

	emitter->setParticleSystem(ps);

	// Ok, get a pointer to the emitter's Counter object. We could also
	// create a new RandomRateCounter object and assign it to the emitter,
	// but since the default counter is already a RandomRateCounter, we
	// just get a pointer to it and change a value.

	osgParticle::RandomRateCounter *rrc = 
		static_cast<osgParticle::RandomRateCounter *>(emitter->getCounter());

	// Now set the rate range to a better value. The actual rate at each frame
	// will be chosen randomly within that range.

	rrc->setRateRange(20, 30);	// generate 20 to 30 particles per second

	// The emitter is done! Let's add it to the scene graph. The cool thing is
	// that any emitter node will take into account the accumulated local-to-world
	// matrix, so you can attach an emitter to a transform node and see it move.

	root->addChild(emitter);

	// Ok folks, we have almost finished. We don't add any particle modifier 
	// here (see ModularProgram and Operator classes), so all we still need is
	// to create a Geode and add the particle system to it, so it can be
	// displayed.

	osg::Geode *geode = new osg::Geode;	
	geode->addDrawable(ps);

	// add the geode to the scene graph
	root->addChild(geode);

	return ps;

}



//////////////////////////////////////////////////////////////////////////////
// COMPLEX PARTICLE SYSTEM CREATION
//////////////////////////////////////////////////////////////////////////////


osgParticle::ParticleSystem *create_complex_particle_system(osg::Group *root)
{
	// Are you ready for a more complex particle system? Well, read on!

	// Now we take one step we didn't before: create a particle template.
	// A particle template is simply a Particle object for which you set
	// the desired properties (see documentation for details). When the
	// particle system has to create a new particle and it's been assigned
	// a particle template, the new particle will inherit the template's
	// properties.
	// You can even assign different particle templates to each emitter; in
	// this case, the emitter's template will override the particle system's
	// default template.

	osgParticle::Particle ptemplate;

	ptemplate.setLifeTime(3);		// 3 seconds of life

	// the following ranges set the envelope of the respective 
	// graphical properties in time.
	ptemplate.setSizeRange(osgParticle::rangef(0.75f, 3.0f));
	ptemplate.setAlphaRange(osgParticle::rangef(0.0f, 1.5f));
	ptemplate.setColorRange(osgParticle::rangev4(
		osg::Vec4(1, 0.5f, 0.3f, 1.5f), 
		osg::Vec4(0, 0.7f, 1.0f, 0.0f)));

	// these are physical properties of the particle
	ptemplate.setRadius(0.05f);	// 5 cm wide particles
	ptemplate.setMass(0.05f);	// 50 g heavy

	// As usual, let's create the ParticleSystem object and set its
	// default state attributes. This time we use a texture named
	// "smoke.rgb", you can find it in the data distribution of OSG.
	// We turn off the additive blending, because smoke has no self-
	// illumination.
	osgParticle::ParticleSystem *ps = new osgParticle::ParticleSystem;
	ps->setDefaultAttributes("Images/smoke.rgb", false, false);

	// assign the particle template to the system.
	ps->setDefaultParticleTemplate(ptemplate);

	// now we have to create an emitter; this will be a ModularEmitter, for which
	// we define a RandomRateCounter as counter, a SectorPlacer as placer, and
	// a RadialShooter as shooter.
	osgParticle::ModularEmitter *emitter = new osgParticle::ModularEmitter;
	emitter->setParticleSystem(ps);

	// setup the counter
	osgParticle::RandomRateCounter *counter = new osgParticle::RandomRateCounter;
	counter->setRateRange(60, 60);
	emitter->setCounter(counter);

	// setup the placer; it will be a circle of radius 5 (the particles will
	// be placed inside this circle).
	osgParticle::SectorPlacer *placer = new osgParticle::SectorPlacer;
	placer->setCenter(8, 0, 10);
	placer->setRadiusRange(2.5, 5);
	placer->setPhiRange(0, 2 * osg::PI);	// 360° angle to make a circle
	emitter->setPlacer(placer);

	// now let's setup the shooter; we use a RadialShooter but we set the
	// initial speed to zero, because we want the particles to fall down
	// only under the effect of the gravity force. Since we se the speed
	// to zero, there is no need to setup the shooting angles.
	osgParticle::RadialShooter *shooter = new osgParticle::RadialShooter;
	shooter->setInitialSpeedRange(0, 0);
	emitter->setShooter(shooter);

	// add the emitter to the scene graph
	root->addChild(emitter);

	// WELL, we got our particle system and a nice emitter. Now we want to
	// simulate the effect of the earth gravity, so first of all we have to
	// create a Program. It is a particle processor just like the Emitter
	// class, but it allows to modify particle properties *after* they have
	// been created.
	// The ModularProgram class can be thought as a sequence of operators,
	// each one performing some actions on the particles. So, the trick is:
	// create the ModularProgram object, create one or more Operator objects,
	// add those operators to the ModularProgram, and finally add the
	// ModularProgram object to the scene graph.
	// NOTE: since the Program objects perform actions after the particles
	// have been emitted by one or more Emitter objects, all instances of
	// Program (and its descendants) should be placed *after* the instances
	// of Emitter objects in the scene graph.

	osgParticle::ModularProgram *program = new osgParticle::ModularProgram;
	program->setParticleSystem(ps);

	// create an operator that simulates the gravity acceleration.
	osgParticle::AccelOperator *op1 = new osgParticle::AccelOperator;
	op1->setToGravity();
	program->addOperator(op1);

	// now create a custom operator, we have defined it before (see
	// class VortexOperator).
	VortexOperator *op2 = new VortexOperator;
	op2->setCenter(osg::Vec3(8, 0, 0));
	program->addOperator(op2);

	// let's add a fluid operator to simulate air friction.
	osgParticle::FluidFrictionOperator *op3 = new osgParticle::FluidFrictionOperator;
	op3->setFluidToAir();
	program->addOperator(op3);

	// add the program to the scene graph
	root->addChild(program);

	// create a Geode to contain our particle system.
	osg::Geode *geode = new osg::Geode;
	geode->addDrawable(ps);

	// add the geode to the scene graph.
	root->addChild(geode);

	return ps;
}


//////////////////////////////////////////////////////////////////////////////
// MAIN SCENE GRAPH BUILDING FUNCTION
//////////////////////////////////////////////////////////////////////////////


void build_world(osg::Group *root)
{

	// In this function we are going to create two particle systems;
	// the first one will be very simple, based mostly on default properties;
	// the second one will be a little bit more complex, showing how to
	// create custom operators.
	// To avoid inserting too much code in a single function, we have
	// splitted the work into two functions which accept a Group node as
	// parameter, and return a pointer to the particle system they created.

	osgParticle::ParticleSystem *ps1 = create_simple_particle_system(root);
	osgParticle::ParticleSystem *ps2 = create_complex_particle_system(root);

	// Now that the particle systems and all other related objects have been
	// created, we have to add an "updater" node to the scene graph. This node
	// will react to cull traversal by updating the specified particles system.

	osgParticle::ParticleSystemUpdater *psu = new osgParticle::ParticleSystemUpdater;
	psu->addParticleSystem(ps1);
	psu->addParticleSystem(ps2);

	// add the updater node to the scene graph
	root->addChild(psu);

}


//////////////////////////////////////////////////////////////////////////////
// main()
//////////////////////////////////////////////////////////////////////////////


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 use of particle systems.");
    arguments.getApplicationUsage()->setCommandLineUsage(arguments.getApplicationName()+" [options] image_file_left_eye image_file_right_eye");
    arguments.getApplicationUsage()->addCommandLineOption("-h or --help","Display this information");
    

    // construct the viewer.
    osgProducer::Viewer viewer(arguments);

    // set up the value with sensible default event handlers.
    viewer.setUpViewer(osgProducer::Viewer::STANDARD_SETTINGS);

    // get details on keyboard and mouse bindings used by the viewer.
    viewer.getUsage(*arguments.getApplicationUsage());

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

    // any option left unread are converted into errors to write out later.
    arguments.reportRemainingOptionsAsUnrecognized();

    // report any errors if they have occured when parsing the program aguments.
    if (arguments.errors())
    {
        arguments.writeErrorMessages(std::cout);
        return 1;
    }
    
    osg::Group *root = new osg::Group;
    build_world(root);
   
    // add a viewport to the viewer and attach the scene graph.
    viewer.setSceneData(root);
        
    // create the windows and run the threads.
    viewer.realize();

    while( !viewer.done() )
    {
        // wait for all cull and draw threads to complete.
        viewer.sync();

        // update the scene by traversing it with the the update visitor which will
        // call all node update callbacks and animations.
        viewer.update();
         
        // fire off the cull and draw traversals of the scene.
        viewer.frame();
        
    }
    
    // wait for all cull and draw threads to complete before exit.
    viewer.sync();

    return 0;
}
