/*    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):       Siargey Kachanovich
 *
 *    Copyright (C) 2019 Inria
 *
 *    Modification(s):
 *      - YYYY/MM Author: Description of the modification
 */

#ifndef FUNCTIONS_FUNCTION_IRON_IN_R3_H_
#define FUNCTIONS_FUNCTION_IRON_IN_R3_H_

#include <cstdlib>  // for std::size_t
#include <cmath>    // for std::pow

#include <Eigen/Dense>

namespace Gudhi {

namespace coxeter_triangulation {

/**
 * \class Function_iron_in_R3
 * \brief A class that encodes the function, the zero-set of which is a surface
 * embedded in R^3 that ressembles an iron.
 */
struct Function_iron_in_R3 {
  /**
   * \brief Value of the function at a specified point.
   * @param[in] p The input point. The dimension needs to coincide with the ambient dimension.
   */
  Eigen::VectorXd operator()(const Eigen::VectorXd& p) const {
    double x = p(0), y = p(1), z = p(2);
    Eigen::VectorXd result(cod_d());
    result(0) = -std::pow(x, 6) / 300. - std::pow(y, 6) / 300. - std::pow(z, 6) / 300. + x * y * y * z / 2.1 + y * y +
                std::pow(z - 2, 4) - 1;
    return result;
  }

  /** \brief Returns the domain (ambient) dimension. */
  std::size_t amb_d() const { return 3; };

  /** \brief Returns the codomain dimension. */
  std::size_t cod_d() const { return 1; };

  /** \brief Returns a point on the surface. */
  Eigen::VectorXd seed() const {
    Eigen::Vector3d result(std::pow(4500, 1. / 6), 0, 0);
    return result;
  }

  /**
   * \brief Constructor of the function that defines a surface embedded in R^3
   * that ressembles an iron.
   *
   * @param[in] off Offset vector.
   */
  Function_iron_in_R3(Eigen::Vector3d off = Eigen::Vector3d::Zero()) : off_(off) {}

 private:
  Eigen::Vector3d off_;
};

}  // namespace coxeter_triangulation

}  // namespace Gudhi

#endif