// Gmsh - Copyright (C) 1997-2025 C. Geuzaine, J.-F. Remacle
//
// See the LICENSE.txt file in the Gmsh root directory for license information.
// Please report all issues on https://gitlab.onelab.info/gmsh/gmsh/issues.

#ifndef BACKGROUND_MESH2D_H
#define BACKGROUND_MESH2D_H

#include <string>
#include <map>
#include <vector>
#include "STensor3.h"
#include "BGMBase.h"

class MTriangle;

/*
   The backgroundMesh2D creates a bunch of triangles on the parametric space of
   a GFace. Those triangles are local to the backgroundMesh2D so that they do
   not depend on the actual mesh that can be deleted. It extends the sizefield
   from the edges.
*/
class backgroundMesh2D : public BGMBase {
protected:
  virtual void propagateValues(DoubleStorageType &dirichlet,
                               simpleFunction<double> &eval_diffusivity,
                               bool in_parametric_plane = false);
  virtual void computeSizeField();
  virtual inline unsigned int getNumMeshElements() const
  {
    return elements.size();
  }
  virtual const MElement *getElement(unsigned int i) const;
  virtual GPoint get_GPoint_from_MVertex(const MVertex *) const;

  // only 2D:
  void updateSizes();
  // copy the mesh stored in GFace in local
  void create_mesh_copy();
  // creates a mesh of GFace and store it in local !!!, does not store the mesh
  // in GFace !
  void create_face_mesh();

  double sizeFactor;
  std::vector<MTriangle *> tempTR;
  std::vector<MElement *> elements;
  std::vector<MVertex *> vertices;
  std::map<MVertex const *const, MVertex *> _3Dto2D;
  std::map<MVertex const *const, MVertex *> _2Dto3D;

public:
  backgroundMesh2D(GFace *, bool erase_2D3D = true);
  virtual ~backgroundMesh2D();
  virtual MElementOctree *getOctree();

  // TODO: only 2D
  virtual void
  reset(bool erase_2D3D = true); // deletes everything and rebuild with GFace*
  virtual void unset(); // deletes everything... called by destructor.

  // not used !!!! TODO !!!
  void setSizeFactor(double s) { sizeFactor = s; }

  virtual std::vector<MVertex *>::iterator beginvertices()
  {
    return vertices.begin();
  }
  virtual std::vector<MVertex *>::iterator endvertices()
  {
    return vertices.end();
  }
  virtual std::vector<MElement *>::iterator beginelements()
  {
    return elements.begin();
  }
  virtual std::vector<MElement *>::iterator endelements()
  {
    return elements.end();
  }
  virtual std::vector<MVertex *>::const_iterator beginvertices() const
  {
    return vertices.begin();
  }
  virtual std::vector<MVertex *>::const_iterator endvertices() const
  {
    return vertices.end();
  }
  virtual std::vector<MElement *>::const_iterator beginelements() const
  {
    return elements.begin();
  }
  virtual std::vector<MElement *>::const_iterator endelements() const
  {
    return elements.end();
  }
};

class RK_form { // informations for RK at one point
public:
  RK_form() : angle(0.), localsize(0.) {}
  SMetric3 metricField;
  SVector3 t1, t2; // 3D cross field directions
  SVector3 normal; // 3D cross field directions
  std::pair<double, double> h; // 3D sizes
  std::pair<double, double> paramh; // sizes in parametric domain
  SPoint2 paramt1, paramt2;
  double angle, localsize;
};

class frameFieldBackgroundMesh2D : public backgroundMesh2D {
private:
  // specification for cross field
  DoubleStorageType angles; // an attached angle
  DoubleStorageType smoothness;
  void computeCrossField(simpleFunction<double> &eval_diffusivity);
  void computeSmoothness();

public:
  frameFieldBackgroundMesh2D(GFace *_gf);
  virtual ~frameFieldBackgroundMesh2D();

  virtual void reset(bool erase_2D3D = true);

  double angle(double u, double v);
  double angle(MVertex *v);

  double get_smoothness(double u, double v);
  double get_smoothness(MVertex *v);

  void eval_crossfield(double u, double v, STensor3 &cf);
  void eval_crossfield(MVertex *vert, STensor3 &cf);

  void exportCrossField(const std::string &filename);
  std::pair<SVector3, SVector3> compute_crossfield_directions(double u, double v,
                                                              double angle_current);
  bool compute_RK_infos(double u, double v, double x, double y, double z,
                        RK_form &infos);

  void exportSmoothness(const std::string &filename) const
  {
    export_scalar(filename, smoothness);
  }
};

#endif
