#ifndef FLUID_PROBLEM_H
#define FLUID_PROBLEM_H

#include "mesh.h"
#include "mesh_find.h"
#include "hxt_linear_system.h"

#if DIMENSION==2
#define N_N 3
#else
#define N_N 4
#endif

typedef struct {
  char *tag;
  int field;
  void (*apply)(int n, const double *x, double *bnd);
}StrongBoundary;

typedef struct {
  double epsilon;
  double rho;
  double mu;
  double alpha;
  double g;
  Mesh *mesh;
  MeshTree *mesh_tree;
  double *porosity;
  double *new_porosity;
  double *solution;
  double *solution_explicit;
  double *node_volume;
  int n_strong_boundaries;
  StrongBoundary *strong_boundaries;
  HXTLinearSystem *linear_system;

  int n_particles;
  double *particle_uvw;
  double *particle_position;
  double *particle_volume;
  double *particle_velocity;
  double *particle_new_velocity;
  double *particle_drag;
  double *particle_mass;
  double *particle_force;
  int *particle_element_id;
} FluidProblem;

int fluid_problem_export(const FluidProblem *problem, const char *output_dir, double t, int iter);
int fluid_problem_export_vtk(const FluidProblem *problem, const char *output_dir, double t, int iter);
int fluid_problem_import_vtk(FluidProblem *problem, const char *filename);
// complete force on the particle (including gravity)
void fluid_problem_compute_node_particle_force(FluidProblem *problem, double dt, double *particle_force);
int fluid_problem_implicit_euler(FluidProblem *problem, double dt);
void fluid_problem_set_particles(FluidProblem *problem, int n, double *mass, double *volume, double *position, double *velocity, long int *elid);
void fluid_problem_free(FluidProblem *problem);
FluidProblem *fluid_problem_new(const char *mesh_file_name, double g, double mu, double rho, double epsilon, int n_strong_boundaries, StrongBoundary *strong_boundaries);
void fluid_problem_adapt_mesh(FluidProblem *problem, double lcmax, double lcmin, double n_el);
int *fluid_problem_particle_element_id(FluidProblem *problem);
int fluid_problem_n_particles(FluidProblem *problem);
void fluid_problem_after_import(FluidProblem *problem);
#endif