path: root/src/Coxeter_triangulation/include/gudhi/Coxeter_triangulation/Cell_complex/Hasse_diagram_cell.h

/*    This file is part of the Gudhi Library - https://gudhi.inria.fr/ - which is released under MIT.
 *    See file LICENSE or go to https://gudhi.inria.fr/licensing/ for full license details.
 *    Author(s):       Pawel Dlotko
 *
 *    Copyright (C) 2017 Swansea University UK
 *
 *    Modification(s):
 *      - YYYY/MM Author: Description of the modification
 */

#ifndef HASSE_DIAGRAM_CELL_H
#define HASSE_DIAGRAM_CELL_H

#include <vector>
#include <utility>  // for std::pair
#include <ostream>
#include <string>
#include <type_traits>  // for std::is_same
#include <cstdlib>  // for std::size_t

namespace Gudhi {
namespace Hasse_diagram {

template <typename Cell_type>
class Hasse_diagram;

/**
 * \class Hasse_diagram_cell
 * \brief Data structure to store a cell in a Hasse diagram.
 *
 * \ingroup Hasse_diagram
 *
 * \details
 * The use and interfaces of this Hasse diagram cell is limited to the \ref coxeter_triangulation implementation.
 * 
 * This is a data structure to store a cell in a general Hasse diagram data structure. 	It stores the following
 * information about the cell: References to boundary and coBoundary elements, dimension of a cell and its filtration.
 * It also allow to store any additional information of a type Additional_information which is a template parameter of
 * the class (set by default to void).
 *
 * The complex is a template class requiring the following parameters:
 * Incidence_type_ - determine the type of incidence coefficients. Use integers in most general case.
 * Filtration_type_ - type of filtration of cells.
 * Additional_information_ (set by default to void) - allows to store any
 * additional information in the cells of Hasse diagrams.
 *
 */
template <typename Incidence_type_, typename Filtration_type_, typename Additional_information_ = void>
class Hasse_diagram_cell {
 public:
  typedef Incidence_type_ Incidence_type;
  typedef Filtration_type_ Filtration_type;
  typedef Additional_information_ Additional_information;
  using Cell_range = std::vector<std::pair<Hasse_diagram_cell*, Incidence_type> >;

  /**
   * Default constructor.
   **/
  Hasse_diagram_cell() : dimension(0), position(0), deleted_(false) {}

  /**
   * Constructor of a cell of dimension dim.
   **/
  Hasse_diagram_cell(int dim) : dimension(dim), position(0), deleted_(false) {}

  /**
   * Constructor of a cell of dimension dim.
   **/
  Hasse_diagram_cell(int dim, Filtration_type filt_)
      : dimension(dim), position(0), deleted_(false), filtration(filt_) {}

  /**
   * Constructor of a cell of dimension dim with a given boundary.
   **/
  Hasse_diagram_cell(const Cell_range& boundary_, int dim)
      : dimension(dim), boundary(boundary_), position(0), deleted_(false) {}

  /**
   * Constructor of a cell of dimension dim with a given boundary and coboundary.
   **/
  Hasse_diagram_cell(const Cell_range& boundary_, const Cell_range& coboundary_, int dim)
      : dimension(dim), boundary(boundary_), coBoundary(coboundary_), position(0), deleted_(false) {}

  /**
   * Constructor of a cell of dimension dim with a given boundary, coboundary and
   * additional information.
   **/
  Hasse_diagram_cell(const Cell_range& boundary_, const Cell_range& coboundary_, const Additional_information& ai,
                     int dim)
      : dimension(dim),
        boundary(boundary_),
        coBoundary(coboundary_),
        additional_info(ai),
        position(0),
        deleted_(false) {}

  /**
   * Constructor of a cell of dimension dim having given additional information.
   **/
  Hasse_diagram_cell(Additional_information ai, int dim)
      : dimension(dim), additional_info(ai), position(0), deleted_(false) {}

  /**
   * Procedure to get the boundary of a fiven cell. The output format
   * is a vector of pairs of pointers to boundary elements and incidence
   * coefficients.
   **/
  inline Cell_range& get_boundary() { return this->boundary; }

  /**
   * Procedure to get the coboundary of a fiven cell. The output format
   * is a vector of pairs of pointers to coboundary elements and incidence
   * coefficients.
   **/
  inline Cell_range& get_coBoundary() { return this->coBoundary; }

  /**
   * Procedure to get the dimension of a cell.
   **/
  inline int& get_dimension() { return this->dimension; }

  /**
   * Procedure to get additional information about the cell.s
   **/
  inline Additional_information& get_additional_information() { return this->additional_info; }

  /**
   * Procedure to retrieve the position of the cell in the structure. It is used in
   * the implementation of Hasse diagram and set by it. Note that removal of
   * cell and subsequent call of clean_up_the_structure will change those
   * positions.
   **/
  inline unsigned& get_position() { return this->position; }

  /**
   * Accessing the filtration of the cell.
   **/
  inline Filtration_type& get_filtration() {
    // std::cout << "Accessing the filtration of a cell : " << *this << std::endl;
    return this->filtration;
  }

  /**
   * A procedure used to check if the cell is deleted. It is used by the
   * subsequent implementation of Hasse diagram that is absed on lazy
   * delete.
   **/
  inline bool deleted() { return this->deleted_; }

  template <typename Cell_type>
  friend class Hasse_diagram;

  template <typename Cell_type>
  friend class is_before_in_filtration;

  template <typename Complex_type, typename Cell_type>
  friend std::vector<Cell_type*> convert_to_vector_of_Cell_type(Complex_type& cmplx);

  /**
   * Procedure to remove deleted boundary and coboundary elements from the
   * vectors of boundary and coboundary elements of this cell.
   **/
  void remove_deleted_elements_from_boundary_and_coboundary() {
    Cell_range new_boundary;
    new_boundary.reserve(this->boundary.size());
    for (std::size_t bd = 0; bd != this->boundary.size(); ++bd) {
      if (!this->boundary[bd].first->deleted()) {
        new_boundary.push_back(this->boundary[bd]);
      }
    }
    this->boundary.swap(new_boundary);

    Cell_range new_coBoundary;
    new_coBoundary.reserve(this->coBoundary.size());
    for (std::size_t cbd = 0; cbd != this->coBoundary.size(); ++cbd) {
      if (!this->coBoundary[cbd].first->deleted()) {
        new_coBoundary.push_back(this->coBoundary[cbd]);
      }
    }
    this->coBoundary.swap(new_coBoundary);
  }

  /**
   * Writing to a stream operator.
   **/
  friend std::ostream& operator<<(
      std::ostream& out, const Hasse_diagram_cell<Incidence_type, Filtration_type, Additional_information>& c) {
    // cout << "position : " << c.position << ", dimension : " << c.dimension << ", filtration: " << c.filtration << ",
    // size of boundary : " <<  c.boundary.size() << "\n";
    out << c.position << " " << c.dimension << " " << c.filtration << std::endl;
    for (std::size_t bd = 0; bd != c.boundary.size(); ++bd) {
      // do not write out the cells that has been deleted
      if (c.boundary[bd].first->deleted()) continue;
      out << c.boundary[bd].first->position << " " << c.boundary[bd].second << " ";
    }
    out << std::endl;
    return out;
  }

  /**
   * Procedure that return vector of pointers to boundary elements of a given cell.
   **/
  inline std::vector<Hasse_diagram_cell*> get_list_of_boundary_elements() {
    std::vector<Hasse_diagram_cell*> result;
    std::size_t size_of_boundary = this->boundary.size();
    result.reserve(size_of_boundary);
    for (std::size_t bd = 0; bd != size_of_boundary; ++bd) {
      result.push_back(this->boundary[bd].first);
    }
    return result;
  }

  /**
   * Procedure that return vector of positios of boundary elements of a given cell.
   **/
  inline std::vector<unsigned> get_list_of_positions_of_boundary_elements() {
    std::vector<unsigned> result;
    std::size_t size_of_boundary = this->boundary.size();
    result.reserve(size_of_boundary);
    for (std::size_t bd = 0; bd != size_of_boundary; ++bd) {
      result.push_back(this->boundary[bd].first->position);
    }
    return result;
  }

  /**
   * Function that display a string being a signature of a structure.
   * Used mainly for debugging purposes.
   **/
  std::string full_signature_of_the_structure() {
    std::string result;
    result += "dimension: ";
    result += std::to_string(this->dimension);
    result += " filtration: ";
    result += std::to_string(this->filtration);
    result += " position: ";
    result += std::to_string(this->position);
    result += " deleted_: ";
    result += std::to_string(this->deleted_);

    // if the Additional_information is not void, add them to
    // the signature as well.
    if (std::is_same<Additional_information, void>::value) {
      result += " Additional_information: ";
      result += std::to_string(this->additional_info);
    }
    result += " boundary ";
    for (std::size_t bd = 0; bd != this->boundary.size(); ++bd) {
      result += "( " + std::to_string(this->boundary[bd].first->position);
      result += " " + std::to_string(this->boundary[bd].second);
      result += ") ";
    }

    result += " coBoundary ";
    for (std::size_t cbd = 0; cbd != this->coBoundary.size(); ++cbd) {
      result += "( " + std::to_string(this->coBoundary[cbd].first->position);
      result += " " + std::to_string(this->coBoundary[cbd].second);
      result += ") ";
    }

    return result;
  }

 protected:
  Cell_range boundary;
  Cell_range coBoundary;
  int dimension;
  Additional_information additional_info;
  unsigned position;
  bool deleted_;
  Filtration_type filtration;

  /**
   * A procedure to delete a cell. It is a private function of the Hasse_diagram_cell
   * class, since in the Hasse_diagram class I want to have a control
   * of removal of cells. Therefore, to remove cell please use
   * remove_cell in the Hasse_diagram structure.
   **/
  void delete_cell() { this->deleted_ = true; }
};  // Hasse_diagram_cell

}  // namespace Hasse_diagram
}  // namespace Gudhi

#endif  // CELL_H