/*
 * Garland_heckbert.h
 *  Created on: Feb 10, 2015
 * This file is part of the Gudhi Library. The Gudhi library 
 *    (Geometric Understanding in Higher Dimensions) is a generic C++ 
 *    library for computational topology.
 *
 *    Author(s):       David Salinas
 *
 *    Copyright (C) 2014  INRIA Sophia Antipolis-Méditerranée (France)
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation, either version 3 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 * 
 */


#ifndef GARLAND_HECKBERT_H_
#define GARLAND_HECKBERT_H_

#include <boost/timer/timer.hpp>
#include <iostream>
#include "gudhi/Point.h"
#include "gudhi/Edge_contraction.h"
#include "gudhi/Skeleton_blocker.h"
#include "gudhi/Off_reader.h"

#include "Garland_heckbert/Error_quadric.h"

using namespace std;
using namespace Gudhi;
using namespace skbl;
using namespace contraction;


struct Geometry_trait{
	typedef Point_d Point;
};

/**
 * The vertex stored in the complex contains a quadric.
 */
struct Garland_heckbert_traits : public Skeleton_blocker_simple_geometric_traits<Geometry_trait> {

public:
	struct Garland_heckbert_vertex : public Simple_geometric_vertex{
		Error_quadric<Geometry_trait::Point> quadric;
	};
	typedef Garland_heckbert_vertex Graph_vertex;
};

typedef Skeleton_blocker_geometric_complex< Garland_heckbert_traits > Complex;
typedef Edge_profile<Complex> EdgeProfile;
typedef Skeleton_blocker_contractor<Complex> Complex_contractor;


/**
 * How the new vertex is placed after an edge collapse : here it is placed at
 * the point minimizing the cost of the quadric.
 */
class GH_placement : public Gudhi::contraction::Placement_policy<EdgeProfile>{
	Complex& complex_;
public:
	typedef typename Gudhi::contraction::Placement_policy<EdgeProfile>::Placement_type Placement_type;

	GH_placement(Complex& complex):complex_(complex){}

	Placement_type operator()(const EdgeProfile& profile) const override{
		auto sum_quad(profile.v0().quadric);
		sum_quad += profile.v1().quadric;

		boost::optional<Point> min_quadric_pt(sum_quad.min_cost());
		if (min_quadric_pt)
			return Placement_type(*min_quadric_pt);
		else
			return profile.p0();
	}
};

/**
 * How much cost an edge collapse : here the costs is given by a quadric
 * which expresses a squared distances with triangles planes.
 */
class GH_cost : public Gudhi::contraction::Cost_policy<EdgeProfile>{
	Complex& complex_;
public:

	typedef typename Gudhi::contraction::Cost_policy<EdgeProfile>::Cost_type Cost_type;

	GH_cost(Complex& complex):complex_(complex){}

	Cost_type operator()( EdgeProfile const& profile, boost::optional<Point> const& new_point ) const override {
		Cost_type res;
		if (new_point){
			auto sum_quad(profile.v0().quadric);
			sum_quad += profile.v1().quadric;
			res = sum_quad.cost(*new_point);
		}
		return res;
	}
};

/**
 * Visitor that is called at several moment.
 * Here we initializes the quadrics of every vertex at the on_started call back
 * and we update them when contracting an edge (the quadric become the sum of both quadrics).
 */
class GH_visitor: public Gudhi::contraction::Contraction_visitor<EdgeProfile> {
	Complex& complex_;
public:
	GH_visitor(Complex& complex):complex_(complex){}

	//Compute quadrics for every vertex v
	//The quadric of v consists in the sum of quadric
	//of every triangles passing through v weighted by its area
	void on_started(Complex & complex) override{
		for(auto v : complex.vertex_range()){
			auto & quadric_v(complex[v].quadric);
			for(auto t : complex.triangle_range(v)){
				auto t_it = t.begin();
				const auto& p0(complex.point(*t_it++));
				const auto& p1(complex.point(*t_it++));
				const auto& p2(complex.point(*t_it++));
				quadric_v+=Error_quadric<Point>(p0,p1,p2);
			}
		}
	}

	/**
	 * @brief Called when an edge is about to be contracted and replaced by a vertex whose position is *placement.
	 */
	void on_contracting(EdgeProfile const &profile, boost::optional< Point > placement)
	override{
		profile.v0().quadric += profile.v1().quadric;
	}
};


int main(int argc, char *argv[]){
	if (argc!=4){
		std::cerr << "Usage "<<argv[0]<<" input.off output.off N to load the file input.off, contract N edges and save the result to output.off.\n";
		return EXIT_FAILURE;
	}

	Complex complex;

	// load the points
	Skeleton_blocker_off_reader<Complex> off_reader(argv[1],complex);
	if(!off_reader.is_valid()){
		std::cerr << "Unable to read file:"<<argv[1]<<std::endl;
		return EXIT_FAILURE;
	}

	std::cout << "Load complex with "<<complex.num_vertices()<<" vertices"<<std::endl;


	int num_contractions = atoi(argv[3]);

	boost::timer::auto_cpu_timer t;

	// constructs the contractor object with Garland Heckbert policies.
	Complex_contractor contractor(complex,
			new GH_cost(complex),
			new GH_placement(complex),
			contraction::make_link_valid_contraction<EdgeProfile>(),
			new GH_visitor(complex)
	);

	std::cout<<"Contract "<<num_contractions<<" edges"<<std::endl;
	contractor.contract_edges(num_contractions);

	std::cout << "Final complex has "<<
			complex.num_vertices()<<" vertices, "<<
			complex.num_edges()<<" edges and" <<
			complex.num_triangles()<<" triangles."<<std::endl;

	//write simplified complex
	Skeleton_blocker_off_writer<Complex> off_writer(argv[2],complex);

	return EXIT_SUCCESS;
}



#endif /* GARLAND_HECKBERT_H_ */