#include <petsc/private/dmpatchimpl.h> /*I      "petscdmpatch.h"   I*/
#include <petscdmda.h>
#include <petscsf.h>

/*
Solver loop to update \tau:

  DMZoom(dmc, &dmz)
  DMRefine(dmz, &dmf),
  Scatter Xcoarse -> Xzoom,
  Interpolate Xzoom -> Xfine (note that this may be on subcomms),
  Smooth Xfine using two-step smoother
    normal smoother plus Kaczmarz---moves back and forth from dmzoom to dmfine
  Compute residual Rfine
  Restrict Rfine to Rzoom_restricted
  Scatter Rzoom_restricted -> Rcoarse_restricted
  Compute global residual Rcoarse
  TauCoarse = Rcoarse - Rcoarse_restricted
*/

/*@C
  DMPatchZoom - Create patches of a `DMDA` on subsets of processes, indicated by `commz`

  Collective

  Input Parameters:
+ dm    - the `DM`
. lower - the lower left corner of the requested patch
. upper - the upper right corner of the requested patch
- commz - the new communicator for the patch, `MPI_COMM_NULL` indicates that the given rank will not own a patch

  Output Parameters:
+ dmz  - the patch `DM`
. sfz  - the `PetscSF` mapping the patch+halo to the zoomed version (optional)
- sfzr - the `PetscSF` mapping the patch to the restricted zoomed version

  Level: intermediate

.seealso: `DMPatchSolve()`, `DMDACreatePatchIS()`
@*/
PetscErrorCode DMPatchZoom(DM dm, MatStencil lower, MatStencil upper, MPI_Comm commz, DM *dmz, PetscSF *sfz, PetscSF *sfzr)
{
  DMDAStencilType st;
  MatStencil      blower, bupper, loclower, locupper;
  IS              is;
  const PetscInt *ranges, *indices;
  PetscInt       *localPoints  = NULL;
  PetscSFNode    *remotePoints = NULL;
  PetscInt        dim, dof;
  PetscInt        M, N, P, rM, rN, rP, halo = 1, sxb, syb, szb, sxr, syr, szr, exr, eyr, ezr, mxb, myb, mzb, i, j, k, l, q;
  PetscMPIInt     size;
  PetscBool       patchis_offproc = PETSC_TRUE;
  Vec             X;

  PetscFunctionBegin;
  if (!sfz) halo = 0;
  PetscCallMPI(MPI_Comm_size(PetscObjectComm((PetscObject)dm), &size));
  /* Create patch DM */
  PetscCall(DMDAGetInfo(dm, &dim, &M, &N, &P, NULL, NULL, NULL, &dof, NULL, NULL, NULL, NULL, &st));

  /* Get piece for rank r, expanded by halo */
  bupper.i = PetscMin(M, upper.i + halo);
  blower.i = PetscMax(lower.i - halo, 0);
  bupper.j = PetscMin(N, upper.j + halo);
  blower.j = PetscMax(lower.j - halo, 0);
  bupper.k = PetscMin(P, upper.k + halo);
  blower.k = PetscMax(lower.k - halo, 0);
  rM       = bupper.i - blower.i;
  rN       = bupper.j - blower.j;
  rP       = bupper.k - blower.k;

  if (commz != MPI_COMM_NULL) {
    PetscCall(DMDACreate(commz, dmz));
    PetscCall(DMSetDimension(*dmz, dim));
    PetscCall(DMDASetSizes(*dmz, rM, rN, rP));
    PetscCall(DMDASetNumProcs(*dmz, PETSC_DECIDE, PETSC_DECIDE, PETSC_DECIDE));
    PetscCall(DMDASetBoundaryType(*dmz, DM_BOUNDARY_NONE, DM_BOUNDARY_NONE, DM_BOUNDARY_NONE));
    PetscCall(DMDASetDof(*dmz, dof));
    PetscCall(DMDASetStencilType(*dmz, st));
    PetscCall(DMDASetStencilWidth(*dmz, 0));
    PetscCall(DMDASetOwnershipRanges(*dmz, NULL, NULL, NULL));
    PetscCall(DMSetFromOptions(*dmz));
    PetscCall(DMSetUp(*dmz));
    PetscCall(DMDAGetCorners(*dmz, &sxb, &syb, &szb, &mxb, &myb, &mzb));
    sxr = PetscMax(sxb, lower.i - blower.i);
    syr = PetscMax(syb, lower.j - blower.j);
    szr = PetscMax(szb, lower.k - blower.k);
    exr = PetscMin(sxb + mxb, upper.i - blower.i);
    eyr = PetscMin(syb + myb, upper.j - blower.j);
    ezr = PetscMin(szb + mzb, upper.k - blower.k);
    PetscCall(PetscMalloc2(dof * rM * rN * PetscMax(rP, 1), &localPoints, dof * rM * rN * PetscMax(rP, 1), &remotePoints));
  } else {
    sxr = syr = szr = exr = eyr = ezr = sxb = syb = szb = mxb = myb = mzb = 0;
  }

  /* Create SF for restricted map */
  PetscCall(DMCreateGlobalVector(dm, &X));
  PetscCall(VecGetOwnershipRanges(X, &ranges));

  loclower.i = blower.i + sxr;
  locupper.i = blower.i + exr;
  loclower.j = blower.j + syr;
  locupper.j = blower.j + eyr;
  loclower.k = blower.k + szr;
  locupper.k = blower.k + ezr;

  PetscCall(DMDACreatePatchIS(dm, &loclower, &locupper, &is, patchis_offproc));
  PetscCall(ISGetIndices(is, &indices));

  if (dim < 3) {
    mzb = 1;
    ezr = 1;
  }
  q = 0;
  for (k = szb; k < szb + mzb; ++k) {
    if ((k < szr) || (k >= ezr)) continue;
    for (j = syb; j < syb + myb; ++j) {
      if ((j < syr) || (j >= eyr)) continue;
      for (i = sxb; i < sxb + mxb; ++i) {
        for (l = 0; l < dof; l++) {
          const PetscInt lp = l + dof * (((k - szb) * rN + (j - syb)) * rM + i - sxb);
          PetscInt       r;

          if ((i < sxr) || (i >= exr)) continue;
          localPoints[q] = lp;
          PetscCall(PetscFindInt(indices[q], size + 1, ranges, &r));

          remotePoints[q].rank  = r < 0 ? -(r + 1) - 1 : r;
          remotePoints[q].index = indices[q] - ranges[remotePoints[q].rank];
          ++q;
        }
      }
    }
  }
  PetscCall(ISRestoreIndices(is, &indices));
  PetscCall(ISDestroy(&is));
  PetscCall(PetscSFCreate(PetscObjectComm((PetscObject)dm), sfzr));
  PetscCall(PetscObjectSetName((PetscObject)*sfzr, "Restricted Map"));
  PetscCall(PetscSFSetGraph(*sfzr, dof * M * N * P, q, localPoints, PETSC_COPY_VALUES, remotePoints, PETSC_COPY_VALUES));

  if (sfz) {
    /* Create SF for buffered map */
    loclower.i = blower.i + sxb;
    locupper.i = blower.i + sxb + mxb;
    loclower.j = blower.j + syb;
    locupper.j = blower.j + syb + myb;
    loclower.k = blower.k + szb;
    locupper.k = blower.k + szb + mzb;

    PetscCall(DMDACreatePatchIS(dm, &loclower, &locupper, &is, patchis_offproc));
    PetscCall(ISGetIndices(is, &indices));

    q = 0;
    for (k = szb; k < szb + mzb; ++k) {
      for (j = syb; j < syb + myb; ++j) {
        for (i = sxb; i < sxb + mxb; ++i, ++q) {
          PetscInt r;

          localPoints[q] = q;
          PetscCall(PetscFindInt(indices[q], size + 1, ranges, &r));
          remotePoints[q].rank  = r < 0 ? -(r + 1) - 1 : r;
          remotePoints[q].index = indices[q] - ranges[remotePoints[q].rank];
        }
      }
    }
    PetscCall(ISRestoreIndices(is, &indices));
    PetscCall(ISDestroy(&is));
    PetscCall(PetscSFCreate(PetscObjectComm((PetscObject)dm), sfz));
    PetscCall(PetscObjectSetName((PetscObject)*sfz, "Buffered Map"));
    PetscCall(PetscSFSetGraph(*sfz, M * N * P, q, localPoints, PETSC_COPY_VALUES, remotePoints, PETSC_COPY_VALUES));
  }

  PetscCall(VecDestroy(&X));
  PetscCall(PetscFree2(localPoints, remotePoints));
  PetscFunctionReturn(PETSC_SUCCESS);
}

typedef enum {
  PATCH_COMM_TYPE_WORLD = 0,
  PATCH_COMM_TYPE_SELF  = 1
} PatchCommType;

PetscErrorCode DMPatchSolve(DM dm)
{
  MPI_Comm    comm;
  MPI_Comm    commz;
  DM          dmc;
  PetscSF     sfz, sfzr;
  Vec         XC;
  MatStencil  patchSize, commSize, gridRank, lower, upper;
  PetscInt    M, N, P, i, j, k, l, m, n, p = 0;
  PetscMPIInt rank, size;
  PetscInt    debug = 0;

  PetscFunctionBegin;
  PetscCall(PetscObjectGetComm((PetscObject)dm, &comm));
  PetscCallMPI(MPI_Comm_rank(comm, &rank));
  PetscCallMPI(MPI_Comm_size(comm, &size));
  PetscCall(DMPatchGetCoarse(dm, &dmc));
  PetscCall(DMPatchGetPatchSize(dm, &patchSize));
  PetscCall(DMPatchGetCommSize(dm, &commSize));
  PetscCall(DMPatchGetCommSize(dm, &commSize));
  PetscCall(DMGetGlobalVector(dmc, &XC));
  PetscCall(DMDAGetInfo(dmc, NULL, &M, &N, &P, &l, &m, &n, NULL, NULL, NULL, NULL, NULL, NULL));
  M = PetscMax(M, 1);
  l = PetscMax(l, 1);
  N = PetscMax(N, 1);
  m = PetscMax(m, 1);
  P = PetscMax(P, 1);
  n = PetscMax(n, 1);

  gridRank.i = rank % l;
  gridRank.j = rank / l % m;
  gridRank.k = rank / (l * m) % n;

  if (commSize.i * commSize.j * commSize.k == size || commSize.i * commSize.j * commSize.k == 0) {
    commSize.i = l;
    commSize.j = m;
    commSize.k = n;
    commz      = comm;
  } else if (commSize.i * commSize.j * commSize.k == 1) {
    commz = PETSC_COMM_SELF;
  } else {
    const PetscMPIInt newComm = ((gridRank.k / commSize.k) * (m / commSize.j) + gridRank.j / commSize.j) * (l / commSize.i) + (gridRank.i / commSize.i);
    const PetscMPIInt newRank = ((gridRank.k % commSize.k) * commSize.j + gridRank.j % commSize.j) * commSize.i + (gridRank.i % commSize.i);

    PetscCallMPI(MPI_Comm_split(comm, newComm, newRank, &commz));
    if (debug) PetscCall(PetscPrintf(PETSC_COMM_SELF, "Rank %d color %d key %d commz %p\n", rank, newComm, newRank, (void *)(MPI_Aint)commz));
  }
  /*
   Assumptions:
     - patchSize divides gridSize
     - commSize divides gridSize
     - commSize divides l,m,n
   Ignore multiple patches per rank for now

   Multiple ranks per patch:
     - l,m,n divides patchSize
     - commSize divides patchSize
   */
  for (k = 0; k < P; k += PetscMax(patchSize.k, 1)) {
    for (j = 0; j < N; j += PetscMax(patchSize.j, 1)) {
      for (i = 0; i < M; i += PetscMax(patchSize.i, 1), ++p) {
        MPI_Comm commp = MPI_COMM_NULL;
        DM       dmz   = NULL;
#if 0
        DM          dmf     = NULL;
        Mat         interpz = NULL;
#endif
        Vec          XZ      = NULL;
        PetscScalar *xcarray = NULL;
        PetscScalar *xzarray = NULL;

        if ((gridRank.k / commSize.k == p / (l / commSize.i * m / commSize.j) % n / commSize.k) && (gridRank.j / commSize.j == p / (l / commSize.i) % m / commSize.j) && (gridRank.i / commSize.i == p % l / commSize.i)) {
          if (debug) PetscCall(PetscPrintf(PETSC_COMM_SELF, "Rank %d is accepting Patch %" PetscInt_FMT "\n", rank, p));
          commp = commz;
        }
        /* Zoom to coarse patch */
        lower.i = i;
        lower.j = j;
        lower.k = k;
        upper.i = i + patchSize.i;
        upper.j = j + patchSize.j;
        upper.k = k + patchSize.k;
        PetscCall(DMPatchZoom(dmc, lower, upper, commp, &dmz, &sfz, &sfzr));
        lower.c = 0; /* initialize member, otherwise compiler issues warnings */
        upper.c = 0; /* initialize member, otherwise compiler issues warnings */
        if (debug)
          PetscCall(PetscPrintf(comm, "Patch %" PetscInt_FMT ": (%" PetscInt_FMT ", %" PetscInt_FMT ", %" PetscInt_FMT ")--(%" PetscInt_FMT ", %" PetscInt_FMT ", %" PetscInt_FMT ")\n", p, lower.i, lower.j, lower.k, upper.i, upper.j, upper.k));
        if (dmz) PetscCall(DMView(dmz, PETSC_VIEWER_STDOUT_(commz)));
        PetscCall(PetscSFView(sfz, PETSC_VIEWER_STDOUT_(comm)));
        PetscCall(PetscSFView(sfzr, PETSC_VIEWER_STDOUT_(comm)));
        /* Scatter Xcoarse -> Xzoom */
        if (dmz) PetscCall(DMGetGlobalVector(dmz, &XZ));
        if (XZ) PetscCall(VecGetArray(XZ, &xzarray));
        PetscCall(VecGetArray(XC, &xcarray));
        PetscCall(PetscSFBcastBegin(sfz, MPIU_SCALAR, xcarray, xzarray, MPI_REPLACE));
        PetscCall(PetscSFBcastEnd(sfz, MPIU_SCALAR, xcarray, xzarray, MPI_REPLACE));
        PetscCall(VecRestoreArray(XC, &xcarray));
        if (XZ) PetscCall(VecRestoreArray(XZ, &xzarray));
#if 0
        /* Interpolate Xzoom -> Xfine, note that this may be on subcomms */
        PetscCall(DMRefine(dmz, MPI_COMM_NULL, &dmf));
        PetscCall(DMCreateInterpolation(dmz, dmf, &interpz, NULL));
        PetscCall(DMInterpolate(dmz, interpz, dmf));
        /* Smooth Xfine using two-step smoother, normal smoother plus Kaczmarz---moves back and forth from dmzoom to dmfine */
        /* Compute residual Rfine */
        /* Restrict Rfine to Rzoom_restricted */
#endif
        /* Scatter Rzoom_restricted -> Rcoarse_restricted */
        if (XZ) PetscCall(VecGetArray(XZ, &xzarray));
        PetscCall(VecGetArray(XC, &xcarray));
        PetscCall(PetscSFReduceBegin(sfzr, MPIU_SCALAR, xzarray, xcarray, MPIU_SUM));
        PetscCall(PetscSFReduceEnd(sfzr, MPIU_SCALAR, xzarray, xcarray, MPIU_SUM));
        PetscCall(VecRestoreArray(XC, &xcarray));
        if (XZ) PetscCall(VecRestoreArray(XZ, &xzarray));
        if (dmz) PetscCall(DMRestoreGlobalVector(dmz, &XZ));
        /* Compute global residual Rcoarse */
        /* TauCoarse = Rcoarse - Rcoarse_restricted */

        PetscCall(PetscSFDestroy(&sfz));
        PetscCall(PetscSFDestroy(&sfzr));
        PetscCall(DMDestroy(&dmz));
      }
    }
  }
  PetscCall(DMRestoreGlobalVector(dmc, &XC));
  PetscFunctionReturn(PETSC_SUCCESS);
}

static PetscErrorCode DMPatchView_ASCII(DM dm, PetscViewer viewer)
{
  DM_Patch         *mesh = (DM_Patch *)dm->data;
  PetscViewerFormat format;
  const char       *name;

  PetscFunctionBegin;
  PetscCall(PetscViewerGetFormat(viewer, &format));
  /* if (format == PETSC_VIEWER_ASCII_INFO_DETAIL) */
  PetscCall(PetscObjectGetName((PetscObject)dm, &name));
  PetscCall(PetscViewerASCIIPrintf(viewer, "Patch DM %s\n", name));
  PetscCall(PetscViewerASCIIPushTab(viewer));
  PetscCall(PetscViewerASCIIPrintf(viewer, "Coarse DM\n"));
  PetscCall(DMView(mesh->dmCoarse, viewer));
  PetscCall(PetscViewerASCIIPopTab(viewer));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode DMView_Patch(DM dm, PetscViewer viewer)
{
  PetscBool iascii, isbinary;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm, DM_CLASSID, 1);
  PetscValidHeaderSpecific(viewer, PETSC_VIEWER_CLASSID, 2);
  PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
  PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERBINARY, &isbinary));
  if (iascii) PetscCall(DMPatchView_ASCII(dm, viewer));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode DMDestroy_Patch(DM dm)
{
  DM_Patch *mesh = (DM_Patch *)dm->data;

  PetscFunctionBegin;
  if (--mesh->refct > 0) PetscFunctionReturn(PETSC_SUCCESS);
  PetscCall(DMDestroy(&mesh->dmCoarse));
  /* This was originally freed in DMDestroy(), but that prevents reference counting of backend objects */
  PetscCall(PetscFree(mesh));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode DMSetUp_Patch(DM dm)
{
  DM_Patch *mesh = (DM_Patch *)dm->data;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm, DM_CLASSID, 1);
  PetscCall(DMSetUp(mesh->dmCoarse));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode DMCreateGlobalVector_Patch(DM dm, Vec *g)
{
  DM_Patch *mesh = (DM_Patch *)dm->data;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm, DM_CLASSID, 1);
  PetscCall(DMCreateGlobalVector(mesh->dmCoarse, g));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode DMCreateLocalVector_Patch(DM dm, Vec *l)
{
  DM_Patch *mesh = (DM_Patch *)dm->data;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm, DM_CLASSID, 1);
  PetscCall(DMCreateLocalVector(mesh->dmCoarse, l));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode DMCreateSubDM_Patch(DM dm, PetscInt numFields, const PetscInt fields[], IS *is, DM *subdm)
{
  SETERRQ(PetscObjectComm((PetscObject)dm), PETSC_ERR_SUP, "Tell me to code this");
}

PetscErrorCode DMPatchGetCoarse(DM dm, DM *dmCoarse)
{
  DM_Patch *mesh = (DM_Patch *)dm->data;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm, DM_CLASSID, 1);
  *dmCoarse = mesh->dmCoarse;
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode DMPatchGetPatchSize(DM dm, MatStencil *patchSize)
{
  DM_Patch *mesh = (DM_Patch *)dm->data;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm, DM_CLASSID, 1);
  PetscAssertPointer(patchSize, 2);
  *patchSize = mesh->patchSize;
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode DMPatchSetPatchSize(DM dm, MatStencil patchSize)
{
  DM_Patch *mesh = (DM_Patch *)dm->data;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm, DM_CLASSID, 1);
  mesh->patchSize = patchSize;
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode DMPatchGetCommSize(DM dm, MatStencil *commSize)
{
  DM_Patch *mesh = (DM_Patch *)dm->data;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm, DM_CLASSID, 1);
  PetscAssertPointer(commSize, 2);
  *commSize = mesh->commSize;
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode DMPatchSetCommSize(DM dm, MatStencil commSize)
{
  DM_Patch *mesh = (DM_Patch *)dm->data;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm, DM_CLASSID, 1);
  mesh->commSize = commSize;
  PetscFunctionReturn(PETSC_SUCCESS);
}
