#ifndef BTCSDIFFUSION_H_
#define BTCSDIFFUSION_H_

#include "BoundaryCondition.hpp"

#include <Eigen/Sparse>
#include <Eigen/src/Core/Map.h>
#include <Eigen/src/Core/Matrix.h>
#include <Eigen/src/Core/util/Constants.h>
#include <cstddef>
#include <tuple>
#include <type_traits>
#include <vector>

#define BTCS_MAX_DEP_PER_CELL 3

namespace Diffusion {
/*!
 * Class implementing a solution for a 1/2/3D diffusion equation using backward
 * euler.
 */
class BTCSDiffusion {

public:
  /*!
   * Creates a diffusion module.
   *
   * @param dim Number of dimensions. Should not be greater than 3 and not less
   * than 1.
   */
  BTCSDiffusion(unsigned int dim);

  /*!
   * Define the grid in x direction.
   *
   * @param domain_size Size of the domain in x direction.
   * @param n_grid_cells Number of grid cells in x direction the domain is
   * divided to.
   */
  void setXDimensions(double domain_size, unsigned int n_grid_cells);

  /*!
   * Define the grid in y direction.
   *
   * Throws an error if the module wasn't initialized at least as a 2D model.
   *
   * @param domain_size Size of the domain in y direction.
   * @param n_grid_cells Number of grid cells in y direction the domain is
   * divided to.
   */
  void setYDimensions(double domain_size, unsigned int n_grid_cells);

  /*!
   * Define the grid in z direction.
   *
   * Throws an error if the module wasn't initialized at least as a 3D model.
   *
   * @param domain_size Size of the domain in z direction.
   * @param n_grid_cells Number of grid cells in z direction the domain is
   * divided to.
   */
  void setZDimensions(double domain_size, unsigned int n_grid_cells);

  /*!
   * Returns the number of grid cells in x direction.
   */
  unsigned int getXGridCellsN();
  /*!
   * Returns the number of grid cells in y direction.
   */
  unsigned int getYGridCellsN();
  /*!
   * Returns the number of grid cells in z direction.
   */
  unsigned int getZGridCellsN();

  /*!
   * Returns the domain size in x direction.
   */
  unsigned int getXDomainSize();
  /*!
   * Returns the domain size in y direction.
   */
  unsigned int getYDomainSize();
  /*!
   * Returns the domain size in z direction.
   */
  unsigned int getZDomainSize();

  /*!
   * With given ghost zones simulate diffusion. Only 1D allowed at this moment.
   *
   * @param c Vector describing the concentration of one solution of the grid as
   * continious memory (row major).
   * @param alpha Vector of diffusion coefficients for each grid element.
   */
  void simulate(double *c, double *alpha, Diffusion::boundary_condition *bc);

  /*!
   * Set the timestep of the simulation
   *
   * @param time_step Time step (in seconds ???)
   */
  void setTimestep(double time_step);

private:
  typedef Eigen::Matrix<double, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>
      DMatrixRowMajor;
  typedef Eigen::Matrix<double, 1, Eigen::Dynamic, Eigen::RowMajor>
      DVectorRowMajor;
  typedef Eigen::Matrix<Diffusion::boundary_condition, Eigen::Dynamic,
                        Eigen::Dynamic, Eigen::RowMajor>
      BCMatrixRowMajor;
  typedef Eigen::Matrix<Diffusion::boundary_condition, 1, Eigen::Dynamic,
                        Eigen::RowMajor>
      BCVectorRowMajor;

  // void simulate_base(DVectorRowMajor &c, Eigen::Map<const BCVectorRowMajor>
  // &bc,
  //                    Eigen::Map<const DVectorRowMajor> &alpha, double dx,
  //                    double time_step, int size, DVectorRowMajor &t0_c);

  void simulate1D(Eigen::Map<DVectorRowMajor> &c,
                  Eigen::Map<const DVectorRowMajor> &alpha,
                  Eigen::Map<const BCVectorRowMajor> &bc);

  void simulate2D(Eigen::Map<DMatrixRowMajor> &c,
                  Eigen::Map<const DMatrixRowMajor> &alpha,
                  Eigen::Map<const BCMatrixRowMajor> &bc);

  inline void fillMatrixFromRow(const DVectorRowMajor &alpha,
                                const BCVectorRowMajor &bc, int size, double dx,
                                double time_step);

  inline void fillVectorFromRowADI(const DVectorRowMajor &c,
                                   const DVectorRowMajor alpha,
                                   const BCVectorRowMajor &bc,
                                   const DVectorRowMajor &t0_c, int size,
                                   double dx, double time_step);
  void simulate3D(std::vector<double> &c);

  inline void reserveMemory(int size, int max_count_per_line);
  inline double getBCFromFlux(Diffusion::boundary_condition bc,
                              double nearest_value, double neighbor_alpha);
  void solveLES();
  void updateInternals();

  // std::vector<boundary_condition> bc;
  // Eigen::Matrix<boundary_condition, Eigen::Dynamic, Eigen::Dynamic,
  //               Eigen::RowMajor>
  // bc;

  Eigen::SparseMatrix<double> A_matrix;
  Eigen::VectorXd b_vector;
  Eigen::VectorXd x_vector;

  double time_step;
  int grid_dim;

  std::vector<unsigned int> grid_cells;
  std::vector<double> domain_size;
  std::vector<double> deltas;
};
} // namespace Diffusion
#endif // BTCSDIFFUSION_H_