static char help[] = "Create a box mesh with DMMoab and test defining a tag on the mesh\n\n";

#include <petscdmmoab.h>

typedef struct {
  DM            dm;    /* DM implementation using the MOAB interface */
  PetscBool     debug; /* The debugging level */
  PetscLogEvent createMeshEvent;
  /* Domain and mesh definition */
  PetscInt  dim;                             /* The topological mesh dimension */
  PetscInt  nele;                            /* Elements in each dimension */
  PetscInt  degree;                          /* Degree of refinement */
  PetscBool simplex;                         /* Use simplex elements */
  PetscInt  nlevels;                         /* Number of levels in mesh hierarchy */
  PetscInt  nghost;                          /* Number of ghost layers in the mesh */
  char      input_file[PETSC_MAX_PATH_LEN];  /* Import mesh from file */
  char      output_file[PETSC_MAX_PATH_LEN]; /* Output mesh file name */
  PetscBool write_output;                    /* Write output mesh and data to file */
} AppCtx;

PetscErrorCode ProcessOptions(MPI_Comm comm, AppCtx *options)
{
  PetscFunctionBegin;
  options->debug         = PETSC_FALSE;
  options->nlevels       = 1;
  options->nghost        = 1;
  options->dim           = 2;
  options->nele          = 5;
  options->degree        = 2;
  options->simplex       = PETSC_FALSE;
  options->write_output  = PETSC_FALSE;
  options->input_file[0] = '\0';
  PetscCall(PetscStrncpy(options->output_file, "ex3.h5m", sizeof(options->output_file)));

  PetscOptionsBegin(comm, "", "Uniform Mesh Refinement Options", "DMMOAB");
  PetscCall(PetscOptionsBool("-debug", "Enable debug messages", "ex2.cxx", options->debug, &options->debug, NULL));
  PetscCall(PetscOptionsRangeInt("-dim", "The topological mesh dimension", "ex3.cxx", options->dim, &options->dim, NULL, 0, 3));
  PetscCall(PetscOptionsBoundedInt("-n", "The number of elements in each dimension", "ex3.cxx", options->nele, &options->nele, NULL, 1));
  PetscCall(PetscOptionsBoundedInt("-levels", "Number of levels in the hierarchy", "ex3.cxx", options->nlevels, &options->nlevels, NULL, 0));
  PetscCall(PetscOptionsBoundedInt("-degree", "Number of degrees at each level of refinement", "ex3.cxx", options->degree, &options->degree, NULL, 0));
  PetscCall(PetscOptionsBoundedInt("-ghost", "Number of ghost layers in the mesh", "ex3.cxx", options->nghost, &options->nghost, NULL, 0));
  PetscCall(PetscOptionsBool("-simplex", "Create simplices instead of tensor product elements", "ex3.cxx", options->simplex, &options->simplex, NULL));
  PetscCall(PetscOptionsString("-input", "The input mesh file", "ex3.cxx", options->input_file, options->input_file, sizeof(options->input_file), NULL));
  PetscCall(PetscOptionsString("-io", "Write out the mesh and solution that is defined on it (Default H5M format)", "ex3.cxx", options->output_file, options->output_file, sizeof(options->output_file), &options->write_output));
  PetscOptionsEnd();

  PetscCall(PetscLogEventRegister("CreateMesh", DM_CLASSID, &options->createMeshEvent));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode CreateMesh(MPI_Comm comm, AppCtx *user)
{
  size_t      len;
  PetscMPIInt rank;

  PetscFunctionBegin;
  PetscCall(PetscLogEventBegin(user->createMeshEvent, 0, 0, 0, 0));
  PetscCallMPI(MPI_Comm_rank(comm, &rank));
  PetscCall(PetscStrlen(user->input_file, &len));
  if (len) {
    if (user->debug) PetscCall(PetscPrintf(comm, "Loading mesh from file: %s and creating the coarse level DM object.\n", user->input_file));
    PetscCall(DMMoabLoadFromFile(comm, user->dim, user->nghost, user->input_file, "", &user->dm));
  } else {
    if (user->debug)
      PetscCall(PetscPrintf(comm, "Creating a %" PetscInt_FMT "-dimensional structured %s mesh of %" PetscInt_FMT "x%" PetscInt_FMT "x%" PetscInt_FMT " in memory and creating a DM object.\n", user->dim, (user->simplex ? "simplex" : "regular"), user->nele,
                            user->nele, user->nele));
    PetscCall(DMMoabCreateBoxMesh(comm, user->dim, user->simplex, NULL, user->nele, user->nghost, &user->dm));
  }
  PetscCall(PetscObjectSetName((PetscObject)user->dm, "Coarse Mesh"));
  PetscCall(PetscLogEventEnd(user->createMeshEvent, 0, 0, 0, 0));
  PetscFunctionReturn(PETSC_SUCCESS);
}

int main(int argc, char **argv)
{
  AppCtx    user; /* user-defined work context */
  MPI_Comm  comm;
  PetscInt  i;
  Mat       R;
  DM       *dmhierarchy;
  PetscInt *degrees;
  PetscBool createR;

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &argv, NULL, help));
  comm    = PETSC_COMM_WORLD;
  createR = PETSC_FALSE;

  PetscCall(ProcessOptions(comm, &user));
  PetscCall(CreateMesh(comm, &user));
  PetscCall(DMSetFromOptions(user.dm));

  /* SetUp the data structures for DMMOAB */
  PetscCall(DMSetUp(user.dm));

  PetscCall(PetscMalloc(sizeof(DM) * (user.nlevels + 1), &dmhierarchy));
  for (i = 0; i <= user.nlevels; i++) dmhierarchy[i] = NULL;

  // coarsest grid = 0
  // finest grid = nlevels
  dmhierarchy[0] = user.dm;
  PetscCall(PetscObjectReference((PetscObject)user.dm));

  if (user.nlevels) {
    PetscCall(PetscMalloc1(user.nlevels, &degrees));
    for (i = 0; i < user.nlevels; i++) degrees[i] = user.degree;
    if (user.debug) PetscCall(PetscPrintf(comm, "Generate the MOAB mesh hierarchy with %" PetscInt_FMT " levels.\n", user.nlevels));
    PetscCall(DMMoabGenerateHierarchy(user.dm, user.nlevels, degrees));

    PetscBool usehierarchy = PETSC_FALSE;
    if (usehierarchy) PetscCall(DMRefineHierarchy(user.dm, user.nlevels, &dmhierarchy[1]));
    else {
      if (user.debug) {
        PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Level %" PetscInt_FMT "\n", 0));
        PetscCall(DMView(user.dm, 0));
      }
      for (i = 1; i <= user.nlevels; i++) {
        if (user.debug) PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Level %" PetscInt_FMT "\n", i));
        PetscCall(DMRefine(dmhierarchy[i - 1], MPI_COMM_NULL, &dmhierarchy[i]));
        if (createR) PetscCall(DMCreateInterpolation(dmhierarchy[i - 1], dmhierarchy[i], &R, NULL));
        if (user.debug) {
          PetscCall(DMView(dmhierarchy[i], 0));
          if (createR) PetscCall(MatView(R, 0));
        }
        /* Solvers could now set operator "R" to the multigrid PC object for level i
            PCMGSetInterpolation(pc,i,R)
        */
        if (createR) PetscCall(MatDestroy(&R));
      }
    }
  }

  if (user.write_output) {
    if (user.debug) PetscCall(PetscPrintf(comm, "Output mesh hierarchy to file: %s.\n", user.output_file));
    PetscCall(DMMoabOutput(dmhierarchy[user.nlevels], (const char *)user.output_file, ""));
  }

  for (i = 0; i <= user.nlevels; i++) PetscCall(DMDestroy(&dmhierarchy[i]));
  PetscCall(PetscFree(degrees));
  PetscCall(PetscFree(dmhierarchy));
  PetscCall(DMDestroy(&user.dm));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

     build:
       requires: moab !complex

     test:
       args: -debug -n 2 -dim 2 -levels 2 -simplex
       filter:  grep -v "DM_0x"

     test:
       args: -debug -n 2 -dim 3 -levels 2
       filter:  grep -v "DM_0x"
       suffix: 1_2

     test:
       args: -debug -n 2 -dim 3 -ghost 1 -levels 2
       filter:  grep -v "DM_0x"
       nsize: 2
       suffix: 2_1

TEST*/
