/**
 * PCMSolver, an API for the Polarizable Continuum Model
 * Copyright (C) 2017 Roberto Di Remigio, Luca Frediani and collaborators.
 *
 * This file is part of PCMSolver.
 *
 * PCMSolver is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * PCMSolver 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with PCMSolver.  If not, see <http://www.gnu.org/licenses/>.
 *
 * For information on the complete list of contributors to the
 * PCMSolver API, see: <http://pcmsolver.readthedocs.io/>
 */

#ifndef COLLOCATION_HPP
#define COLLOCATION_HPP

#include <vector>

#include "Config.hpp"

#include <Eigen/Core>

namespace pcm {
struct BIOperatorData;
namespace cavity {
class Element;
} // namespace cavity
class IGreensFunction;
} // namespace pcm

#include "IBoundaryIntegralOperator.hpp"

namespace pcm {
namespace bi_operators {
/*! \file Collocation.hpp
 *  \class Collocation
 *  \brief Implementation of the single and double layer operators matrix
 *representation using one-point collocation
 *  \author Roberto Di Remigio
 *  \date 2015, 2016
 *
 *  Calculates the diagonal elements of S as:
 *  \f[
 *   S_{ii} = factor * \sqrt{\frac{4\pi}{a_i}}
 *  \f]
 *  while the diagonal elements of D are:
 *  \f[
 *   D_{ii} = -factor * \sqrt{\frac{\pi}{a_i}} \frac{1}{R_I}
 *  \f]
 */
class Collocation __final : public IBoundaryIntegralOperator {
public:
  Collocation();
  Collocation(double fac);
  virtual ~Collocation() {}

private:
  /*! Scaling factor for the diagonal elements of the matrix representation of
   * the S and D operators
   */
  double factor_;
  virtual Eigen::MatrixXd computeS_impl(const std::vector<cavity::Element> & elems,
                                        const IGreensFunction & gf) const __override;
  virtual Eigen::MatrixXd computeD_impl(const std::vector<cavity::Element> & elems,
                                        const IGreensFunction & gf) const __override;
};

IBoundaryIntegralOperator * createCollocation(const BIOperatorData & data);
} // namespace bi_operators
} // namespace pcm

#endif // COLLOCATION_HPP
