#include <../src/mat/impls/baij/seq/baij.h>

PETSC_INTERN PetscErrorCode MatConvert_SeqBAIJ_SeqAIJ(Mat A, MatType newtype, MatReuse reuse, Mat *newmat)
{
  Mat          B;
  Mat_SeqAIJ  *b;
  PetscBool    roworiented;
  Mat_SeqBAIJ *a  = (Mat_SeqBAIJ *)A->data;
  PetscInt     bs = A->rmap->bs, *ai = a->i, *aj = a->j, n = A->rmap->N / bs, i, j, k;
  PetscInt    *rowlengths, *rows, *cols, maxlen            = 0, ncols;
  MatScalar   *aa = a->a;

  PetscFunctionBegin;
  if (reuse == MAT_REUSE_MATRIX) {
    B = *newmat;
    for (i = 0; i < n; i++) maxlen = PetscMax(maxlen, ai[i + 1] - ai[i]);
  } else {
    PetscCall(PetscMalloc1(n * bs, &rowlengths));
    for (i = 0; i < n; i++) {
      maxlen = PetscMax(maxlen, ai[i + 1] - ai[i]);
      for (j = 0; j < bs; j++) rowlengths[i * bs + j] = bs * (ai[i + 1] - ai[i]);
    }
    PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &B));
    PetscCall(MatSetType(B, MATSEQAIJ));
    PetscCall(MatSetSizes(B, A->rmap->n, A->cmap->n, A->rmap->N, A->cmap->N));
    PetscCall(MatSetBlockSizes(B, A->rmap->bs, A->cmap->bs));
    PetscCall(MatSeqAIJSetPreallocation(B, 0, rowlengths));
    PetscCall(PetscFree(rowlengths));
  }
  b           = (Mat_SeqAIJ *)B->data;
  roworiented = b->roworiented;

  PetscCall(MatSetOption(B, MAT_ROW_ORIENTED, PETSC_FALSE));
  PetscCall(PetscMalloc1(bs, &rows));
  PetscCall(PetscMalloc1(bs * maxlen, &cols));
  for (i = 0; i < n; i++) {
    for (j = 0; j < bs; j++) rows[j] = i * bs + j;
    ncols = ai[i + 1] - ai[i];
    for (k = 0; k < ncols; k++) {
      for (j = 0; j < bs; j++) cols[k * bs + j] = bs * (*aj) + j;
      aj++;
    }
    PetscCall(MatSetValues(B, bs, rows, bs * ncols, cols, aa, INSERT_VALUES));
    aa = PetscSafePointerPlusOffset(aa, ncols * bs * bs);
  }
  PetscCall(PetscFree(cols));
  PetscCall(PetscFree(rows));
  PetscCall(MatAssemblyBegin(B, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(B, MAT_FINAL_ASSEMBLY));
  PetscCall(MatSetOption(B, MAT_ROW_ORIENTED, roworiented));

  if (reuse == MAT_INPLACE_MATRIX) PetscCall(MatHeaderReplace(A, &B));
  else *newmat = B;
  PetscFunctionReturn(PETSC_SUCCESS);
}

#include <../src/mat/impls/aij/seq/aij.h>

PETSC_INTERN PetscErrorCode MatConvert_SeqAIJ_SeqBAIJ_Preallocate(Mat A, PetscInt **nnz)
{
  Mat_SeqAIJ     *Aa = (Mat_SeqAIJ *)A->data;
  PetscInt        m, n, bs = A->rmap->bs;
  const PetscInt *ai = Aa->i, *aj = Aa->j;

  PetscFunctionBegin;
  PetscCall(MatGetSize(A, &m, &n));

  if (bs == 1) {
    PetscCall(PetscMalloc1(m, nnz));
    for (PetscInt i = 0; i < m; i++) (*nnz)[i] = ai[i + 1] - ai[i];
  } else {
    PetscHSetIJ    ht;
    PetscInt       k;
    PetscHashIJKey key;
    PetscBool      missing;

    PetscCall(PetscHSetIJCreate(&ht));
    PetscCall(PetscCalloc1(m / bs, nnz));
    for (PetscInt i = 0; i < m; i++) {
      key.i = i / bs;
      for (k = ai[i]; k < ai[i + 1]; k++) {
        key.j = aj[k] / bs;
        PetscCall(PetscHSetIJQueryAdd(ht, key, &missing));
        if (missing) (*nnz)[key.i]++;
      }
    }
    PetscCall(PetscHSetIJDestroy(&ht));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

PETSC_INTERN PetscErrorCode MatConvert_SeqAIJ_SeqBAIJ(Mat A, MatType newtype, MatReuse reuse, Mat *newmat)
{
  Mat          B;
  Mat_SeqAIJ  *a = (Mat_SeqAIJ *)A->data;
  Mat_SeqBAIJ *b;
  PetscInt     m = A->rmap->N, n = A->cmap->N, *rowlengths, bs = A->rmap->bs;

  PetscFunctionBegin;
  if (reuse != MAT_REUSE_MATRIX) {
    PetscCall(MatConvert_SeqAIJ_SeqBAIJ_Preallocate(A, &rowlengths));
    PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &B));
    PetscCall(MatSetSizes(B, m, n, m, n));
    PetscCall(MatSetType(B, MATSEQBAIJ));
    PetscCall(MatSeqBAIJSetPreallocation(B, bs, 0, rowlengths));
    PetscCall(PetscFree(rowlengths));
  } else B = *newmat;

  if (bs == 1) {
    b = (Mat_SeqBAIJ *)B->data;

    PetscCall(PetscArraycpy(b->i, a->i, m + 1));
    PetscCall(PetscArraycpy(b->ilen, a->ilen, m));
    PetscCall(PetscArraycpy(b->j, a->j, a->nz));
    PetscCall(PetscArraycpy(b->a, a->a, a->nz));

    PetscCall(MatSetOption(B, MAT_ROW_ORIENTED, PETSC_TRUE));
    PetscCall(MatAssemblyBegin(B, MAT_FINAL_ASSEMBLY));
    PetscCall(MatAssemblyEnd(B, MAT_FINAL_ASSEMBLY));
  } else {
    /* reuse may not be equal to MAT_REUSE_MATRIX, but the basic converter will reallocate or replace newmat if this value is not used */
    /* if reuse is equal to MAT_INITIAL_MATRIX, it has been appropriately preallocated before                                          */
    /*                      MAT_INPLACE_MATRIX, it will be replaced with MatHeaderReplace below                                        */
    PetscCall(MatConvert_Basic(A, newtype, MAT_REUSE_MATRIX, &B));
  }

  if (reuse == MAT_INPLACE_MATRIX) PetscCall(MatHeaderReplace(A, &B));
  else *newmat = B;
  PetscFunctionReturn(PETSC_SUCCESS);
}