#pragma once

#include <petsc/private/pcimpl.h>
#include <petsc/private/matisimpl.h>
#include <petscksp.h>

/*
   Context (data structure) common for all Iterative Substructuring preconditioners.
*/

typedef struct {
  /* In naming the variables, we adopted the following convention: */
  /* * B - stands for interface nodes;                             */
  /* * I - stands for interior nodes;                              */
  /* * D - stands for Dirichlet (by extension, refers to interior  */
  /*       nodes) and                                              */
  /* * N - stands for Neumann (by extension, refers to all local   */
  /*       nodes, interior plus interface).                        */
  /* In some cases, I or D would apply equally well (e.g. vec1_D).  */

  PetscInt n;          /* number of nodes (interior+interface) in this subdomain */
  PetscInt n_B;        /* number of interface nodes in this subdomain */
  IS       is_B_local, /* local (sequential) index sets for interface (B) and interior (I) nodes */
    is_I_local, is_B_global, is_I_global;

  Mat A_II, A_IB, /* local (sequential) submatrices */
    A_BI, A_BB;
  Mat pA_II;
  Vec D;     /* diagonal scaling "matrix" (stored as a vector, since it's diagonal) */
  KSP ksp_N, /* linear solver contexts */
    ksp_D;
  Vec vec1_N, /* local (sequential) work vectors */
    vec2_N, vec1_D, vec2_D, vec3_D, vec4_D, vec1_B, vec2_B, vec3_B, vec1_global;

  PetscScalar *work_N;
  VecScatter   N_to_D;      /* scattering context from all local nodes to local interior nodes */
  VecScatter   global_to_D; /* scattering context from global to local interior nodes */
  VecScatter   N_to_B;      /* scattering context from all local nodes to local interface nodes */
  VecScatter   global_to_B; /* scattering context from global to local interface nodes */
  PetscBool    pure_neumann;
  PetscScalar  scaling_factor;
  PetscBool    use_stiffness_scaling;

  ISLocalToGlobalMapping mapping;
  PetscInt               n_neigh;  /* number of neighbours this subdomain has (INCLUDING the subdomain itself).       */
  PetscInt              *neigh;    /* list of neighbouring subdomains                                                 */
  PetscInt              *n_shared; /* n_shared[j] is the number of nodes shared with subdomain neigh[j]               */
  PetscInt             **shared;   /* shared[j][i] is the local index of the i-th node shared with subdomain neigh[j] */
  /* It is necessary some consistency in the                                                  */
  /* numbering of the shared edges from each side.                                            */
  /* For instance:                                                                            */
  /*                                                                                          */
  /* +-------+-------+                                                                        */
  /* |   k   |   l   | subdomains k and l are neighbours                                      */
  /* +-------+-------+                                                                        */
  /*                                                                                          */
  /* Let i and j be s.t. proc[k].neigh[i]==l and                                              */
  /*                     proc[l].neigh[j]==k.                                                 */
  /*                                                                                          */
  /* We need:                                                                                 */
  /* proc[k].loc_to_glob(proc[k].shared[i][m]) == proc[l].loc_to_glob(proc[l].shared[j][m])   */
  /* for all 0 <= m < proc[k].n_shared[i], or equiv'ly, for all 0 <= m < proc[l].n_shared[j]  */
  ISLocalToGlobalMapping BtoNmap;
  PetscBool              reusesubmatrices;
} PC_IS;
