typedef struct CMPI_Gcomm {
  $gcomm p2p; // point-to-point communication
  $gcomm col; // collective communication
} CMPI_Gcomm;

CMPI_Gcomm CMPI_Gcomm_create($scope scope, int size) {
  CMPI_Gcomm result;

  result.p2p = $gcomm_create(scope, size);
  result.col = $gcomm_create(scope, size);
  return result;
}

void CMPI_Gcomm_destroy(CMPI_Gcomm gc) {
  $gcomm_destroy(gc.p2p);
  $gcomm_destroy(gc.col);
}

typedef struct MPI_Comm {
  $comm p2p; // point-to-point communication
  $comm col; // collective communication
} MPI_Comm;

MPI_Comm MPI_Comm_create($scope scope, CMPI_Gcomm gc, int rank) {
  MPI_Comm result;
  
  result.p2p = $comm_create(scope, gc.p2p, rank);
  result.col = $comm_create(scope, gc.col, rank);
  return result;
}

void MPI_Comm_destroy(MPI_Comm comm) {
  $comm_destroy(comm.p2p);
  $comm_destroy(comm.col);
}

typedef enum {
  MPI_INT,
  MPI_FLOAT,
  MPI_DOUBLE,
  MPI_CHAR
} MPI_Datatype;

#define BCAST_TAG 999

#define MPI_PROC_NULL -3

typedef struct {
  int MPI_SOURCE;
  int MPI_TAG;
  int MPI_ERROR;
  int size;
} MPI_Status;

#define MPI_STATUS_IGNORE NULL

#define MPI_STATUSES_IGNORE NULL

int sizeofDatatype(MPI_Datatype datatype) {
  switch (datatype) {
  case MPI_INT:
    return sizeof(int);
  case MPI_FLOAT:
    return sizeof(float);
  case MPI_DOUBLE:
    return sizeof(double);
  case MPI_CHAR:
    return sizeof(char);
  default:
    $assert(0, "Unreachable");
  }
}

int MPI_Init() {
  return 0;
}

int MPI_Finalize() {
  return 0;
}

int MPI_Comm_size(MPI_Comm comm, int *size) {
  *size = $comm_size(comm.p2p);
  return 0;
}

int MPI_Comm_rank(MPI_Comm comm, int *rank) {
  *rank = $comm_place(comm.p2p);
  return 0;
}


int CMPI_Send(void *buf, int count, MPI_Datatype datatype, int dest,
	      int tag, $comm comm) {
  if (dest >= 0) {
    int size = count*sizeofDatatype(datatype);
    int place = $comm_place(comm);
    $message out = $message_pack(place, dest, tag, buf, size);

    $comm_enqueue(comm, out);
  }
  return 0;
}

int MPI_Send(void *buf, int count, MPI_Datatype datatype, int dest,
	     int tag, MPI_Comm comm) {
  return CMPI_Send(buf, count, datatype, dest, tag, comm.p2p);
}


int CMPI_Recv(void *buf, int count, MPI_Datatype datatype, int source,
	      int tag, $comm comm, MPI_Status *status) {
  if (source >= 0) {
    $message in = $comm_dequeue(comm, source, tag);
    int size = count*sizeofDatatype(datatype);

    $message_unpack(in, buf, size);
    if (status != MPI_STATUS_IGNORE) {
      status->size = $message_size(in);
      status->MPI_SOURCE = $message_source(in);
      status->MPI_TAG = $message_tag(in);
      status->MPI_ERROR = 0;
    }
  }
  return 0;
}

int MPI_Recv(void *buf, int count, MPI_Datatype datatype, int source,
	     int tag, MPI_Comm comm, MPI_Status *status) {
  return CMPI_Recv(buf, count, datatype, source, tag, comm.p2p, status);
}

int MPI_Get_count(MPI_Status *status, MPI_Datatype datatype, int *count) {
  *count = status->size/sizeofDatatype(datatype);
  return 0;
}

int MPI_Sendrecv(void *sendbuf, int sendcount, MPI_Datatype sendtype,
		 int dest, int sendtag,
		 void *recvbuf, int recvcount, MPI_Datatype recvtype,
		 int source, int recvtag,
		 MPI_Comm comm, MPI_Status *status) {
  MPI_Send(sendbuf, sendcount, sendtype, dest, sendtag, comm);
  MPI_Recv(recvbuf, recvcount, recvtype, source, recvtag, comm, status);
  return 0;
}

/* Broadcasts a message from root to everyone else.
 * Need to use a differnt comm.
 */
int MPI_Bcast(void *buf, int count, MPI_Datatype datatype, int root,
	      MPI_Comm comm) {
  int place = $comm_place(comm.col);

#ifdef DEBUG
  printf("MPI_Bcast: place=%d, count=%d, root=%d\n", place, count, root);
#endif
  if (place == root) {
    int nprocs = $comm_size(comm.col);

    for (int i=0; i<nprocs; i++)
      if (i != root)
	CMPI_Send(buf, count, datatype, i, BCAST_TAG, comm.col);
  } else {
    CMPI_Recv(buf, count, datatype, root, BCAST_TAG, comm.col,
	     MPI_STATUS_IGNORE);
  }
  return 0;
}