/*
 * Critical_points.h
 *  Created on: Jan 27, 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 CRITICAL_POINTS_H_
#define CRITICAL_POINTS_H_

#include <deque>
#include "utils/Edge_contractor.h"

/**
 * Iteratively tries to anticollapse smallest edge non added so far.
 * If its link is contractible then no topological change and else possible topological change.
 *
 * todo do a sparsification with some parameter eps while growing
 */
template<typename SkBlComplex> class Critical_points{
private:
	SkBlComplex filled_complex_;
	const SkBlComplex& input_complex_;
	double max_length_;
	std::ostream& stream_;
public:
	typedef typename SkBlComplex::Vertex_handle Vertex_handle;
	typedef typename SkBlComplex::Edge_handle Edge_handle;
	typedef typename std::pair<Vertex_handle,Vertex_handle> Edge;

	/**
	 * @brief check all pair of points with length smaller than max_length
	 */
	Critical_points(const SkBlComplex& input_complex,std::ostream& stream,double max_length):
		input_complex_(input_complex),max_length_(max_length),stream_(stream)
	{

		std::deque<Edge> edges;
		auto vertices = input_complex.vertex_range();
		for(auto p = vertices.begin(); p!= vertices.end(); ++p){
			filled_complex_.add_vertex(input_complex.point(*p));
			for (auto q = p; ++q != vertices.end(); /**/)
				if (squared_eucl_distance(input_complex.point(*p),input_complex.point(*q)) < max_length_*max_length_)
					edges.emplace_back(*p,*q);
		}

		std::sort(edges.begin(),edges.end(),
				[&](Edge e1,Edge e2){
			return squared_edge_length(e1) < squared_edge_length(e2);
		});

		anti_collapse_edges(edges);

	}

private:
	double squared_eucl_distance(const Point& p1,const Point& p2) const{
		return Geometry_trait::Squared_distance_d()(p1,p2);
	}


	void anti_collapse_edges(const std::deque<Edge>& edges){
		unsigned pos = 0;
		for(Edge e : edges){
			std::cout<<"edge "<<pos++<<"/"<<edges.size()<<"\n";
			auto eh = filled_complex_.add_edge(e.first,e.second);
			int is_contractible(is_link_reducible(eh));

			switch (is_contractible) {
				case 0:
					stream_<<"alpha="<<std::sqrt(squared_edge_length(e))<< " topological change"<<std::endl;
					break;
				case 2:
					stream_<<"alpha="<<std::sqrt(squared_edge_length(e))<< " maybe a topological change"<<std::endl;
					break;
				default:
					break;
			}
		}

	}


	//0 -> not
	//1 -> yes
	//2 -> maybe
	int is_link_reducible(Edge_handle e){
		auto link = filled_complex_.link(e);

		if(link.empty()) return 0;

		Edge_contractor<Complex> contractor(link,link.num_vertices()-1);

		if(link.num_connected_components()>1) return 0; //one than more CC -> not contractible

		if (link.num_vertices()==1) return 1; //reduced to one point -> contractible
		else return 2; //we dont know
	}


	double squared_edge_length(Edge_handle e) const{
		return squared_eucl_distance(input_complex_.point(input_complex_.first_vertex(e)),input_complex_.point(input_complex_.second_vertex(e)));
	}

	double squared_edge_length(Edge e) const{
		return squared_eucl_distance(input_complex_.point(e.first),input_complex_.point(e.second));
	}



};





#endif /* CRITICAL_POINTS_H_ */