#include "../include/petscutils.h"

// -----------------------------------------------------------------------------
// Convert PETSc MemType to libCEED MemType
// -----------------------------------------------------------------------------
CeedMemType MemTypeP2C(PetscMemType mem_type) {
  return PetscMemTypeDevice(mem_type) ? CEED_MEM_DEVICE : CEED_MEM_HOST;
}

// -----------------------------------------------------------------------------
// Apply 3D Kershaw mesh transformation
// -----------------------------------------------------------------------------
// Transition from a value of "a" for x=0, to a value of "b" for x=1.  Optionally
// smooth -- see the commented versions at the end.
static double step(const double a, const double b, double x) {
  if (x <= 0) return a;
  if (x >= 1) return b;
  return a + (b-a) * (x);
}

// 1D transformation at the right boundary
static double right(const double eps, const double x) {
  return (x <= 0.5) ? (2-eps) * x : 1 + eps*(x-1);
}

// 1D transformation at the left boundary
static double left(const double eps, const double x) {
  return 1-right(eps,1-x);
}

// Apply 3D Kershaw mesh transformation
// The eps parameters are in (0, 1]
// Uniform mesh is recovered for eps=1
PetscErrorCode Kershaw(DM dm_orig, PetscScalar eps) {
  PetscErrorCode ierr;
  Vec coord;
  PetscInt ncoord;
  PetscScalar *c;

  PetscFunctionBeginUser;
  ierr = DMGetCoordinatesLocal(dm_orig, &coord); CHKERRQ(ierr);
  ierr = VecGetLocalSize(coord, &ncoord); CHKERRQ(ierr);
  ierr = VecGetArray(coord, &c); CHKERRQ(ierr);

  for (PetscInt i = 0; i < ncoord; i += 3) {
    PetscScalar x = c[i], y = c[i+1], z = c[i+2];
    PetscInt layer = x*6;
    PetscScalar lambda = (x-layer/6.0)*6;
    c[i] = x;

    switch (layer) {
    case 0:
      c[i+1] = left(eps, y);
      c[i+2] = left(eps, z);
      break;
    case 1:
    case 4:
      c[i+1] = step(left(eps, y), right(eps, y), lambda);
      c[i+2] = step(left(eps, z), right(eps, z), lambda);
      break;
    case 2:
      c[i+1] = step(right(eps, y), left(eps, y), lambda/2);
      c[i+2] = step(right(eps, z), left(eps, z), lambda/2);
      break;
    case 3:
      c[i+1] = step(right(eps, y), left(eps, y), (1+lambda)/2);
      c[i+2] = step(right(eps, z), left(eps, z), (1+lambda)/2);
      break;
    default:
      c[i+1] = right(eps, y);
      c[i+2] = right(eps, z);
    }
  }
  ierr = VecRestoreArray(coord, &c); CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

// -----------------------------------------------------------------------------
// Create BC label
// -----------------------------------------------------------------------------
static PetscErrorCode CreateBCLabel(DM dm, const char name[]) {
  int ierr;
  DMLabel label;

  PetscFunctionBeginUser;

  ierr = DMCreateLabel(dm, name); CHKERRQ(ierr);
  ierr = DMGetLabel(dm, name, &label); CHKERRQ(ierr);
  ierr = DMPlexMarkBoundaryFaces(dm, 1, label); CHKERRQ(ierr);

  PetscFunctionReturn(0);
};

// -----------------------------------------------------------------------------
// This function sets up a DM for a given degree
// -----------------------------------------------------------------------------
PetscErrorCode SetupDMByDegree(DM dm, PetscInt degree, PetscInt num_comp_u,
                               PetscInt dim, bool enforce_bc, BCFunction bc_func) {
  PetscInt ierr, marker_ids[1] = {1};
  PetscFE fe;
  MPI_Comm comm;

  PetscFunctionBeginUser;

  // Setup FE
  ierr = PetscObjectGetComm((PetscObject)dm, &comm); CHKERRQ(ierr);
  ierr = PetscFECreateLagrange(comm, dim, num_comp_u, PETSC_FALSE, degree, degree,
                               &fe); CHKERRQ(ierr);
  ierr = DMAddField(dm, NULL, (PetscObject)fe); CHKERRQ(ierr);
  {
    /* create FE field for coordinates */
    PetscFE fe_coords;
    PetscInt num_comp_coord;
    ierr = DMGetCoordinateDim(dm, &num_comp_coord); CHKERRQ(ierr);
    ierr = PetscFECreateLagrange(comm, dim, num_comp_coord, PETSC_FALSE, 1, 1,
                                 &fe_coords); CHKERRQ(ierr);
    ierr = DMProjectCoordinates(dm, fe_coords); CHKERRQ(ierr);
    ierr = PetscFEDestroy(&fe_coords); CHKERRQ(ierr);
  }

  // Setup DM
  ierr = DMCreateDS(dm); CHKERRQ(ierr);
  if (enforce_bc) {
    PetscBool has_label;
    DMHasLabel(dm, "marker", &has_label);
    if (!has_label) {CreateBCLabel(dm, "marker");}
    DMLabel label;
    ierr = DMGetLabel(dm, "marker", &label); CHKERRQ(ierr);
    ierr = DMAddBoundary(dm, DM_BC_ESSENTIAL, "wall", label, 1,
                         marker_ids, 0, 0, NULL, (void(*)(void))bc_func,
                         NULL, NULL, NULL); CHKERRQ(ierr);
  }
  ierr = DMPlexSetClosurePermutationTensor(dm, PETSC_DETERMINE, NULL);
  CHKERRQ(ierr);
  ierr = PetscFEDestroy(&fe); CHKERRQ(ierr);

  PetscFunctionReturn(0);
};

// -----------------------------------------------------------------------------
// Utility function - essential BC dofs are encoded in closure indices as -(i+1)
// -----------------------------------------------------------------------------
PetscInt Involute(PetscInt i) {
  return i >= 0 ? i : -(i + 1);
};

// -----------------------------------------------------------------------------
// Get CEED restriction data from DMPlex
// -----------------------------------------------------------------------------
PetscErrorCode CreateRestrictionFromPlex(Ceed ceed, DM dm, CeedInt height,
    DMLabel domain_label, CeedInt value, CeedElemRestriction *elem_restr) {
  PetscInt num_elem, elem_size, num_dof, num_comp, *elem_restr_offsets;
  PetscErrorCode ierr;

  PetscFunctionBeginUser;

  ierr = DMPlexGetLocalOffsets(dm, domain_label, value, height, 0, &num_elem,
                               &elem_size, &num_comp, &num_dof, &elem_restr_offsets);
  CHKERRQ(ierr);

  CeedElemRestrictionCreate(ceed, num_elem, elem_size, num_comp,
                            1, num_dof, CEED_MEM_HOST, CEED_COPY_VALUES,
                            elem_restr_offsets, elem_restr);
  ierr = PetscFree(elem_restr_offsets); CHKERRQ(ierr);

  PetscFunctionReturn(0);
};

// -----------------------------------------------------------------------------