#include <../src/dm/impls/composite/packimpl.h> /*I  "petscdmcomposite.h"  I*/

static PetscErrorCode DMCreateMatrix_Composite_Nest(DM dm, Mat *J)
{
  const DM_Composite           *com = (DM_Composite *)dm->data;
  const struct DMCompositeLink *rlink, *clink;
  IS                           *isg;
  Mat                          *submats;
  PetscInt                      i, j, n;

  PetscFunctionBegin;
  n = com->nDM; /* Total number of entries */

  /* Explicit index sets are not required for MatCreateNest, but getting them here allows MatNest to do consistency
   * checking and allows ISEqual to compare by identity instead of by contents. */
  PetscCall(DMCompositeGetGlobalISs(dm, &isg));

  /* Get submatrices */
  PetscCall(PetscMalloc1(n * n, &submats));
  for (i = 0, rlink = com->next; rlink; i++, rlink = rlink->next) {
    for (j = 0, clink = com->next; clink; j++, clink = clink->next) {
      Mat sub = NULL;
      if (i == j) {
        PetscCall(DMCreateMatrix(rlink->dm, &sub));
      } else PetscCheck(!com->FormCoupleLocations, PetscObjectComm((PetscObject)dm), PETSC_ERR_SUP, "Cannot manage off-diagonal parts yet");
      submats[i * n + j] = sub;
    }
  }

  PetscCall(MatCreateNest(PetscObjectComm((PetscObject)dm), n, isg, n, isg, submats, J));

  /* Disown references */
  for (i = 0; i < n; i++) PetscCall(ISDestroy(&isg[i]));
  PetscCall(PetscFree(isg));

  for (i = 0; i < n * n; i++) {
    if (submats[i]) PetscCall(MatDestroy(&submats[i]));
  }
  PetscCall(PetscFree(submats));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode DMCreateMatrix_Composite_AIJ(DM dm, Mat *J)
{
  DM_Composite           *com = (DM_Composite *)dm->data;
  struct DMCompositeLink *next;
  PetscInt                m, *dnz, *onz, i, j, mA;
  Mat                     Atmp;
  PetscMPIInt             rank;
  PetscBool               dense = PETSC_FALSE;

  PetscFunctionBegin;
  /* use global vector to determine layout needed for matrix */
  m = com->n;

  PetscCall(MatCreate(PetscObjectComm((PetscObject)dm), J));
  PetscCall(MatSetSizes(*J, m, m, PETSC_DETERMINE, PETSC_DETERMINE));
  PetscCall(MatSetType(*J, dm->mattype));

  /*
     Extremely inefficient but will compute entire Jacobian for testing
  */
  PetscCall(PetscOptionsGetBool(((PetscObject)dm)->options, ((PetscObject)dm)->prefix, "-dmcomposite_dense_jacobian", &dense, NULL));
  if (dense) {
    PetscInt     rstart, rend, *indices;
    PetscScalar *values;

    mA = com->N;
    PetscCall(MatMPIAIJSetPreallocation(*J, mA, NULL, mA - m, NULL));
    PetscCall(MatSeqAIJSetPreallocation(*J, mA, NULL));

    PetscCall(MatGetOwnershipRange(*J, &rstart, &rend));
    PetscCall(PetscMalloc2(mA, &values, mA, &indices));
    PetscCall(PetscArrayzero(values, mA));
    for (i = 0; i < mA; i++) indices[i] = i;
    for (i = rstart; i < rend; i++) PetscCall(MatSetValues(*J, 1, &i, mA, indices, values, INSERT_VALUES));
    PetscCall(PetscFree2(values, indices));
    PetscCall(MatAssemblyBegin(*J, MAT_FINAL_ASSEMBLY));
    PetscCall(MatAssemblyEnd(*J, MAT_FINAL_ASSEMBLY));
    PetscFunctionReturn(PETSC_SUCCESS);
  }

  PetscCallMPI(MPI_Comm_rank(PetscObjectComm((PetscObject)dm), &rank));
  MatPreallocateBegin(PetscObjectComm((PetscObject)dm), m, m, dnz, onz);
  /* loop over packed objects, handling one at at time */
  next = com->next;
  while (next) {
    PetscInt        nc, rstart, *ccols, maxnc;
    const PetscInt *cols, *rstarts;
    PetscMPIInt     proc;

    PetscCall(DMCreateMatrix(next->dm, &Atmp));
    PetscCall(MatGetOwnershipRange(Atmp, &rstart, NULL));
    PetscCall(MatGetOwnershipRanges(Atmp, &rstarts));
    PetscCall(MatGetLocalSize(Atmp, &mA, NULL));

    maxnc = 0;
    for (i = 0; i < mA; i++) {
      PetscCall(MatGetRow(Atmp, rstart + i, &nc, NULL, NULL));
      maxnc = PetscMax(nc, maxnc);
      PetscCall(MatRestoreRow(Atmp, rstart + i, &nc, NULL, NULL));
    }
    PetscCall(PetscMalloc1(maxnc, &ccols));
    for (i = 0; i < mA; i++) {
      PetscCall(MatGetRow(Atmp, rstart + i, &nc, &cols, NULL));
      /* remap the columns taking into how much they are shifted on each process */
      for (j = 0; j < nc; j++) {
        proc = 0;
        while (cols[j] >= rstarts[proc + 1]) proc++;
        ccols[j] = cols[j] + next->grstarts[proc] - rstarts[proc];
      }
      PetscCall(MatPreallocateSet(com->rstart + next->rstart + i, nc, ccols, dnz, onz));
      PetscCall(MatRestoreRow(Atmp, rstart + i, &nc, &cols, NULL));
    }
    PetscCall(PetscFree(ccols));
    PetscCall(MatDestroy(&Atmp));
    next = next->next;
  }
  if (com->FormCoupleLocations) PetscCall((*com->FormCoupleLocations)(dm, NULL, dnz, onz, __rstart, __nrows, __start, __end));
  PetscCall(MatMPIAIJSetPreallocation(*J, 0, dnz, 0, onz));
  PetscCall(MatSeqAIJSetPreallocation(*J, 0, dnz));
  MatPreallocateEnd(dnz, onz);

  if (dm->prealloc_only) PetscFunctionReturn(PETSC_SUCCESS);

  next = com->next;
  while (next) {
    PetscInt           nc, rstart, row, maxnc, *ccols;
    const PetscInt    *cols, *rstarts;
    const PetscScalar *values;
    PetscMPIInt        proc;

    PetscCall(DMCreateMatrix(next->dm, &Atmp));
    PetscCall(MatGetOwnershipRange(Atmp, &rstart, NULL));
    PetscCall(MatGetOwnershipRanges(Atmp, &rstarts));
    PetscCall(MatGetLocalSize(Atmp, &mA, NULL));
    maxnc = 0;
    for (i = 0; i < mA; i++) {
      PetscCall(MatGetRow(Atmp, rstart + i, &nc, NULL, NULL));
      maxnc = PetscMax(nc, maxnc);
      PetscCall(MatRestoreRow(Atmp, rstart + i, &nc, NULL, NULL));
    }
    PetscCall(PetscMalloc1(maxnc, &ccols));
    for (i = 0; i < mA; i++) {
      PetscCall(MatGetRow(Atmp, rstart + i, &nc, (const PetscInt **)&cols, &values));
      for (j = 0; j < nc; j++) {
        proc = 0;
        while (cols[j] >= rstarts[proc + 1]) proc++;
        ccols[j] = cols[j] + next->grstarts[proc] - rstarts[proc];
      }
      row = com->rstart + next->rstart + i;
      PetscCall(MatSetValues(*J, 1, &row, nc, ccols, values, INSERT_VALUES));
      PetscCall(MatRestoreRow(Atmp, rstart + i, &nc, (const PetscInt **)&cols, &values));
    }
    PetscCall(PetscFree(ccols));
    PetscCall(MatDestroy(&Atmp));
    next = next->next;
  }
  if (com->FormCoupleLocations) {
    PetscInt __rstart;
    PetscCall(MatGetOwnershipRange(*J, &__rstart, NULL));
    PetscCall((*com->FormCoupleLocations)(dm, *J, NULL, NULL, __rstart, 0, 0, 0));
  }
  PetscCall(MatAssemblyBegin(*J, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(*J, MAT_FINAL_ASSEMBLY));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode DMCreateMatrix_Composite(DM dm, Mat *J)
{
  PetscBool              usenest;
  ISLocalToGlobalMapping ltogmap;

  PetscFunctionBegin;
  PetscCall(DMSetFromOptions(dm));
  PetscCall(DMSetUp(dm));
  PetscCall(PetscStrcmp(dm->mattype, MATNEST, &usenest));
  if (usenest) PetscCall(DMCreateMatrix_Composite_Nest(dm, J));
  else PetscCall(DMCreateMatrix_Composite_AIJ(dm, J));

  PetscCall(DMGetLocalToGlobalMapping(dm, &ltogmap));
  PetscCall(MatSetLocalToGlobalMapping(*J, ltogmap, ltogmap));
  PetscCall(MatSetDM(*J, dm));
  PetscFunctionReturn(PETSC_SUCCESS);
}
