#include <../src/vec/is/sf/impls/basic/allgatherv/sfallgatherv.h>

#define PetscSFPackGet_Allgather PetscSFPackGet_Allgatherv

/* Reuse the type. The difference is some fields (i.e., displs, recvcounts) are not used in Allgather on rank != 0, which is not a big deal */
typedef PetscSF_Allgatherv PetscSF_Allgather;

PETSC_INTERN PetscErrorCode PetscSFBcastAndOpBegin_Gather(PetscSF,MPI_Datatype,PetscMemType,const void*,PetscMemType,void*,MPI_Op);

static PetscErrorCode PetscSFBcastAndOpBegin_Allgather(PetscSF sf,MPI_Datatype unit,PetscMemType rootmtype,const void *rootdata,PetscMemType leafmtype,void *leafdata,MPI_Op op)
{
  PetscErrorCode        ierr;
  PetscSFPack           link;
  PetscMPIInt           sendcount;
  MPI_Comm              comm;
  const void            *rootbuf_mpi; /* buffer used by MPI */
  void                  *leafbuf_mpi;
  PetscMemType          rootmtype_mpi,leafmtype_mpi;

  PetscFunctionBegin;
  ierr = PetscSFPackGet_Allgather(sf,unit,rootmtype,rootdata,leafmtype,leafdata,&link);CHKERRQ(ierr);
  ierr = PetscObjectGetComm((PetscObject)sf,&comm);CHKERRQ(ierr);
  ierr = PetscMPIIntCast(sf->nroots,&sendcount);CHKERRQ(ierr);
  ierr = PetscSFBcastPrepareMPIBuffers_Allgatherv(sf,link,op,&rootmtype_mpi,&rootbuf_mpi,&leafmtype_mpi,&leafbuf_mpi);CHKERRQ(ierr);
  ierr = MPIU_Iallgather(rootbuf_mpi,sendcount,unit,leafbuf_mpi,sendcount,unit,comm,link->rootreqs[PETSCSF_ROOT2LEAF_BCAST][rootmtype_mpi]);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

static PetscErrorCode PetscSFReduceBegin_Allgather(PetscSF sf,MPI_Datatype unit,PetscMemType leafmtype,const void *leafdata,PetscMemType rootmtype,void *rootdata,MPI_Op op)
{
  PetscErrorCode        ierr;
  PetscSFPack           link;
  PetscMPIInt           sendcount;
  PetscInt              rstart;
  MPI_Comm              comm;
  const void            *leafbuf_mpi;
  void                  *rootbuf_mpi;
  PetscMemType          leafmtype_mpi,rootmtype_mpi;

  PetscFunctionBegin;
  ierr = PetscSFPackGet_Allgather(sf,unit,rootmtype,rootdata,leafmtype,leafdata,&link);CHKERRQ(ierr);
  ierr = PetscObjectGetComm((PetscObject)sf,&comm);CHKERRQ(ierr);

  if (op == MPIU_REPLACE) {
    /* REPLACE is only meaningful when all processes have the same leafdata to reduce. Therefore copy from local leafdata is fine */
    ierr = PetscLayoutGetRange(sf->map,&rstart,NULL);CHKERRQ(ierr);
    ierr = PetscMemcpyWithMemType(rootmtype,leafmtype,rootdata,(const char*)leafdata+(size_t)rstart*link->unitbytes,(size_t)sf->nroots*link->unitbytes);CHKERRQ(ierr);
  } else {
    ierr = PetscMPIIntCast(sf->nroots,&sendcount);CHKERRQ(ierr);
    ierr = PetscSFReducePrepareMPIBuffers_Allgatherv(sf,link,op,&rootmtype_mpi,&rootbuf_mpi,&leafmtype_mpi,&leafbuf_mpi);CHKERRQ(ierr);
    ierr = MPIU_Iscatter(leafbuf_mpi,sendcount,unit,rootbuf_mpi,sendcount,unit,0/*rank 0*/,comm,link->rootreqs[PETSCSF_LEAF2ROOT_REDUCE][rootmtype_mpi]);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

static PetscErrorCode PetscSFBcastToZero_Allgather(PetscSF sf,MPI_Datatype unit,PetscMemType rootmtype,const void *rootdata,PetscMemType leafmtype,void *leafdata)
{
  PetscErrorCode        ierr;
  PetscSFPack           link;
  PetscMPIInt           rank;

  PetscFunctionBegin;
  ierr = PetscSFBcastAndOpBegin_Gather(sf,unit,rootmtype,rootdata,leafmtype,leafdata,MPIU_REPLACE);CHKERRQ(ierr);
  ierr = PetscSFPackGetInUse(sf,unit,rootdata,leafdata,PETSC_OWN_POINTER,&link);CHKERRQ(ierr);
  ierr = PetscSFPackWaitall(link,PETSCSF_ROOT2LEAF_BCAST);CHKERRQ(ierr);
  ierr = MPI_Comm_rank(PetscObjectComm((PetscObject)sf),&rank);CHKERRQ(ierr);
  if (!rank && leafmtype == PETSC_MEMTYPE_DEVICE && !use_gpu_aware_mpi) {
    ierr = PetscMemcpyWithMemType(PETSC_MEMTYPE_DEVICE,PETSC_MEMTYPE_HOST,leafdata,link->leafbuf[PETSC_MEMTYPE_HOST],link->leafbuflen*link->unitbytes);CHKERRQ(ierr);
  }
  ierr = PetscSFPackReclaim(sf,&link);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PETSC_INTERN PetscErrorCode PetscSFCreate_Allgather(PetscSF sf)
{
  PetscErrorCode    ierr;
  PetscSF_Allgather *dat = (PetscSF_Allgather*)sf->data;

  PetscFunctionBegin;

  /* Inherit from Allgatherv */
  sf->ops->Reset           = PetscSFReset_Allgatherv;
  sf->ops->Destroy         = PetscSFDestroy_Allgatherv;
  sf->ops->BcastAndOpEnd   = PetscSFBcastAndOpEnd_Allgatherv;
  sf->ops->ReduceEnd       = PetscSFReduceEnd_Allgatherv;
  sf->ops->FetchAndOpBegin = PetscSFFetchAndOpBegin_Allgatherv;
  sf->ops->FetchAndOpEnd   = PetscSFFetchAndOpEnd_Allgatherv;
  sf->ops->GetRootRanks    = PetscSFGetRootRanks_Allgatherv;
  sf->ops->CreateLocalSF   = PetscSFCreateLocalSF_Allgatherv;
  sf->ops->GetGraph        = PetscSFGetGraph_Allgatherv;
  sf->ops->GetLeafRanks    = PetscSFGetLeafRanks_Allgatherv;

  /* Allgather stuff */
  sf->ops->BcastAndOpBegin = PetscSFBcastAndOpBegin_Allgather;
  sf->ops->ReduceBegin     = PetscSFReduceBegin_Allgather;
  sf->ops->BcastToZero     = PetscSFBcastToZero_Allgather;

  ierr = PetscNewLog(sf,&dat);CHKERRQ(ierr);
  sf->data = (void*)dat;
  PetscFunctionReturn(0);
}