#include <../src/mat/utils/freespace.h>

PetscErrorCode PetscFreeSpaceGet(PetscInt n, PetscFreeSpaceList *list)
{
  PetscFreeSpaceList a;

  PetscFunctionBegin;
  PetscCall(PetscNew(&a));
  PetscCall(PetscMalloc1(n, &a->array_head));

  a->array            = a->array_head;
  a->local_remaining  = n;
  a->local_used       = 0;
  a->total_array_size = 0;
  a->more_space       = NULL;

  if (*list) {
    (*list)->more_space = a;
    a->total_array_size = (*list)->total_array_size;
  }

  a->total_array_size += n;
  *list = a;
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscFreeSpaceContiguous(PetscFreeSpaceList *head, PetscInt *space)
{
  PetscFreeSpaceList a;

  PetscFunctionBegin;
  while (*head) {
    a = (*head)->more_space;
    PetscCall(PetscArraycpy(space, (*head)->array_head, (*head)->local_used));
    space = PetscSafePointerPlusOffset(space, (*head)->local_used);
    PetscCall(PetscFree((*head)->array_head));
    PetscCall(PetscFree(*head));
    *head = a;
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*
  PetscFreeSpaceContiguous_LU -
    Copy a linket list obtained from matrix symbolic ILU or LU factorization into a contiguous array
  that enables an efficient matrix triangular solve.

   Input Parameters:
+  head - linked list of column indices obtained from matrix symbolic ILU or LU factorization
.  space - an allocated array with length nnz of factored matrix.
.  n - order of the matrix
.  bi - row pointer of factored matrix L with length n+1.
-  bdiag - array of length n+1. bdiag[i] points to diagonal of U(i,:), and bdiag[n] points to entry of U(n-1,0)-1.

   Output Parameter:
.  space - column indices are copied into this array with contiguous layout of L and U

   See MatILUFactorSymbolic_SeqAIJ_ilu0() for detailed data structure of L and U
*/
PetscErrorCode PetscFreeSpaceContiguous_LU(PetscFreeSpaceList *head, PetscInt *space, PetscInt n, PetscInt *bi, PetscInt *bdiag)
{
  PetscFreeSpaceList a;
  PetscInt           row, nnz, *bj, *array, total, bi_temp;
  PetscInt           nnzL, nnzU;

  PetscFunctionBegin;
  bi_temp = bi[n];
  row     = 0;
  total   = 0;
  nnzL    = bdiag[0];
  while (*head) {
    total += (*head)->local_used;
    array = (*head)->array_head;

    while (row < n) {
      if (bi[row + 1] > total) break;
      /* copy array entries into bj for this row */
      nnz = bi[row + 1] - bi[row];
      /* set bi[row] for new datastruct */
      if (row == 0) {
        bi[row] = 0;
      } else {
        bi[row] = bi[row - 1] + nnzL; /* nnzL of previous row */
      }

      /* L part */
      nnzL = bdiag[row];
      bj   = space + bi[row];
      PetscCall(PetscArraycpy(bj, array, nnzL));

      /* diagonal entry */
      bdiag[row]        = bi_temp - 1;
      space[bdiag[row]] = row;

      /* U part */
      nnzU    = nnz - nnzL;
      bi_temp = bi_temp - nnzU;
      nnzU--; /* exclude diagonal */
      bj = space + bi_temp;
      PetscCall(PetscArraycpy(bj, array + nnzL + 1, nnzU));
      array += nnz;
      row++;
    }

    a = (*head)->more_space;
    PetscCall(PetscFree((*head)->array_head));
    PetscCall(PetscFree(*head));
    *head = a;
  }
  if (n) {
    bi[n]    = bi[n - 1] + nnzL;
    bdiag[n] = bdiag[n - 1] - 1;
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*
  PetscFreeSpaceContiguous_Cholesky -
    Copy a linket list obtained from matrix symbolic ICC or Cholesky factorization into a contiguous array
  that enables an efficient matrix triangular solve.

   Input Parameters:
+  head - linked list of column indices obtained from matrix symbolic ICC or Cholesky factorization
.  space - an allocated array with length nnz of factored matrix.
.  n - order of the matrix
.  ui - row pointer of factored matrix with length n+1. All entries are set based on the traditional layout U matrix.
-  udiag - array of length n.

   Output Parameter:
+  space - column indices are copied into this array with contiguous layout of U, with diagonal located as the last entry in each row
-  udiag - indices of diagonal entries

   See MatICCFactorSymbolic_SeqAIJ_newdatastruct() for detailed description.
*/

PetscErrorCode PetscFreeSpaceContiguous_Cholesky(PetscFreeSpaceList *head, PetscInt *space, PetscInt n, PetscInt *ui, PetscInt *udiag)
{
  PetscFreeSpaceList a;
  PetscInt           row, nnz, *uj, *array, total;

  PetscFunctionBegin;
  row   = 0;
  total = 0;
  while (*head) {
    total += (*head)->local_used;
    array = (*head)->array_head;

    while (row < n) {
      if (ui[row + 1] > total) break;
      udiag[row] = ui[row + 1] - 1;           /* points to the last entry of U(row,:) */
      nnz        = ui[row + 1] - ui[row] - 1; /* exclude diagonal */
      uj         = space + ui[row];
      PetscCall(PetscArraycpy(uj, array + 1, nnz));
      uj[nnz] = array[0]; /* diagonal */
      array += nnz + 1;
      row++;
    }

    a = (*head)->more_space;
    PetscCall(PetscFree((*head)->array_head));
    PetscCall(PetscFree(*head));
    *head = a;
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscFreeSpaceDestroy(PetscFreeSpaceList head)
{
  PetscFreeSpaceList a;

  PetscFunctionBegin;
  while (head) {
    a = (head)->more_space;
    PetscCall(PetscFree((head)->array_head));
    PetscCall(PetscFree(head));
    head = a;
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}