/**
 * @file Simulation.hpp
 * @brief API of Simulation class, that holds all information regarding a
 * specific simulation run like its timestep, number of iterations and output
 * options. Simulation object also holds a predefined Grid and Boundary object.
 *
 */

#ifndef SIMULATION_H_
#define SIMULATION_H_

#include "Boundary.hpp"
#include "Grid.hpp"
#include <string>
#include <vector>

#ifdef _OPENMP
#include <omp.h>
#else
#define omp_get_num_procs() 1
#endif

/**
 * @brief Enum defining the two implemented solution approaches.
 *
 */
enum APPROACH {
  FTCS_APPROACH, // Forward Time-Centered Space
  BTCS_APPROACH, // Backward Time-Centered Space solved with EigenLU solver
  CRANK_NICOLSON_APPROACH
};

/**
 * @brief Enum defining the Linear Equation solvers
 *
 */
enum SOLVER {
  EIGEN_LU_SOLVER,        // EigenLU solver
  THOMAS_ALGORITHM_SOLVER // Thomas Algorithm solver; more efficient for
                          // tridiagonal matrices
};

/**
 * @brief Enum holding different options for .csv output.
 *
 */
enum CSV_OUTPUT {
  CSV_OUTPUT_OFF,     // do not produce csv output
  CSV_OUTPUT_ON,      // produce csv output with last concentration matrix
  CSV_OUTPUT_VERBOSE, // produce csv output with all concentration matrices
  CSV_OUTPUT_XTREME   // csv output like VERBOSE but additional boundary
                      // conditions at beginning
};

/**
 * @brief Enum holding different options for console output.
 *
 */
enum CONSOLE_OUTPUT {
  CONSOLE_OUTPUT_OFF,    // do not print any output to console
  CONSOLE_OUTPUT_ON,     // print before and after concentrations to console
  CONSOLE_OUTPUT_VERBOSE // print all concentration matrices to console
};

/**
 * @brief Enum holding different options for time measurement.
 *
 */
enum TIME_MEASURE {
  TIME_MEASURE_OFF, // do not print any time measures
  TIME_MEASURE_ON   // print time measure after last iteration
};

/**
 * @brief The class forms the interface for performing the diffusion simulations
 * and contains all the methods for controlling the desired parameters, such as
 * time step, number of simulations, etc.
 *
 */
class Simulation {
public:
  /**
   * @brief Set up a simulation environment. The timestep and number of
   * iterations must be set. For the BTCS approach, the Thomas algorithm is used
   * as the default linear equation solver as this is faster for tridiagonal
   *        matrices. CSV output, console output and time measure are off by
   * default. Also, the number of cores is set to the maximum number of cores -1
   * by default.
   *
   * @param grid Valid grid object
   * @param bc Valid boundary condition object
   * @param approach Approach to solving the problem. Either FTCS or BTCS.
   */
  Simulation(Grid &grid, Boundary &bc, APPROACH approach);

  /**
   * @brief Set the option to output the results to a CSV file. Off by default.
   *
   *
   * @param csv_output Valid output option. The following options can be set
   *                   here:
   *                     - CSV_OUTPUT_OFF: do not produce csv output
   *                     - CSV_OUTPUT_ON: produce csv output with last
   *                       concentration matrix
   *                     - CSV_OUTPUT_VERBOSE: produce csv output with all
   *                       concentration matrices
   *                     - CSV_OUTPUT_XTREME: produce csv output with all
   *                       concentration matrices and simulation environment
   */
  void setOutputCSV(CSV_OUTPUT csv_output);

  /**
   * @brief Set the options for outputting information to the console. Off by
   * default.
   *
   * @param console_output Valid output option. The following options can be set
   *                       here:
   *                        - CONSOLE_OUTPUT_OFF: do not print any output to
   * console
   *                        - CONSOLE_OUTPUT_ON: print before and after
   * concentrations to console
   *                        - CONSOLE_OUTPUT_VERBOSE: print all concentration
   * matrices to console
   */
  void setOutputConsole(CONSOLE_OUTPUT console_output);

  /**
   * @brief Set the Time Measure option. Off by default.
   *
   * @param time_measure The following options are allowed:
   *                     - TIME_MEASURE_OFF: Time of simulation is not printed
   * to console
   *                     - TIME_MEASURE_ON: Time of simulation run is printed to
   * console
   */
  void setTimeMeasure(TIME_MEASURE time_measure);

  /**
   * @brief Setting the time step for each iteration step. Time step must be
   *        greater than zero. Setting the timestep is required.
   *
   * @param timestep Valid timestep greater than zero.
   */
  void setTimestep(double timestep);

  /**
   * @brief Currently set time step is returned.
   *
   * @return double timestep
   */
  double getTimestep();

  /**
   * @brief Set the desired iterations to be calculated. A value greater
   *        than zero must be specified here. Setting iterations is required.
   *
   * @param iterations Number of iterations to be simulated.
   */
  void setIterations(int iterations);

  /**
   * @brief Set the desired linear equation solver to be used for BTCS approach.
   * Without effect in case of FTCS approach.
   *
   * @param solver Solver to be used. Default is Thomas Algorithm as it is more
   * efficient for tridiagonal Matrices.
   */
  void setSolver(SOLVER solver);

  /**
   * @brief Set the number of desired openMP Threads.
   *
   * @param num_threads Number of desired threads. Must have a value between
   *                    1 and the maximum available number of processors. The
   * maximum number of processors is set as the default case during Simulation
   * construction.
   */
  void setNumberThreads(int num_threads);

  /**
   * @brief Return the currently set iterations to be calculated.
   *
   * @return int Number of iterations.
   */
  int getIterations();

  /**
   * @brief Outputs the current concentrations of the grid on the console.
   *
   */
  void printConcentrationsConsole();

  /**
   * @brief Creates a CSV file with a name containing the current simulation
   *        parameters. If the data name already exists, an additional counter
   * is appended to the name. The name of the file is built up as follows:
   *        <approach> + <number rows> + <number columns> + <number of
   * iterations>+<counter>.csv
   *
   * @return string Filename with configured simulation parameters.
   */
  std::string createCSVfile();

  /**
   * @brief Writes the currently calculated concentration values of the grid
   *        into the CSV file with the passed filename.
   *
   * @param filename Name of the file to which the concentration values are
   *                 to be written.
   */
  void printConcentrationsCSV(const std::string &filename);

  /**
   * @brief Method starts the simulation process with the previously set
   *        parameters.
   */
  void run();

private:
  double timestep{-1};
  int iterations{-1};
  int innerIterations{1};
  int numThreads{omp_get_num_procs()};
  CSV_OUTPUT csv_output{CSV_OUTPUT_OFF};
  CONSOLE_OUTPUT console_output{CONSOLE_OUTPUT_OFF};
  TIME_MEASURE time_measure{TIME_MEASURE_OFF};

  Grid &grid;
  Boundary &bc;
  APPROACH approach;
  SOLVER solver{THOMAS_ALGORITHM_SOLVER};

  const std::vector<std::string> approach_names = {"FTCS", "BTCS", "CRNI"};
};

#endif // SIMULATION_H_