/*
  This file is part of CDO. CDO is a collection of Operators to
  manipulate and analyse Climate model Data.

  Copyright (C) 2003-2018 Uwe Schulzweida, <uwe.schulzweida AT mpimet.mpg.de>
  See COPYING file for copying and redistribution conditions.

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; version 2 of the License.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
*/

/*
   This module contains the following operators:

      Arithc     addc            Add by constant
      Arithc     subc            Subtract by constant
      Arithc     mulc            Multiply by constant
      Arithc     divc            Divide by constant
      Arithc     mod             Modulo operator
*/


#include <cdi.h>
#include "cdo.h"
#include "cdo_int.h"
#include "pstream.h"


int *fill_vars(int vlistID)
{
  int varID;
  int nvars = vlistNvars(vlistID);
  int *vars = (int*) Malloc(nvars*sizeof(int));

  if ( cdoNumVarnames )
    {
      int nfound = 0;
      char varname[CDI_MAX_NAME];

      for ( varID = 0; varID < nvars; ++varID )
	{
	  vars[varID] = 0;

	  vlistInqVarName(vlistID, varID, varname);

	  for ( int i = 0; i < cdoNumVarnames; ++i )
	    if ( strcmp(varname, cdoVarnames[i]) == 0 )
	      {
		vars[varID] = 1;
		nfound++;
		break;
	      }
	}

      if ( nfound == 0 )
	cdoAbort("Variable -n %s%s not found!", cdoVarnames[0], cdoNumVarnames > 1 ? ",..." : "");
    }
  else
    {
      for ( varID = 0; varID < nvars; ++varID ) vars[varID] = 1;
    }

  return vars;
}


void *Arithc(void *argument)
{
  size_t nmiss;
  int nrecs;
  int varID, levelID;

  cdoInitialize(argument);

  // clang-format off
  cdoOperatorAdd("addc", func_add, 0, "constant value");
  cdoOperatorAdd("subc", func_sub, 0, "constant value");
  cdoOperatorAdd("mulc", func_mul, 0, "constant value");
  cdoOperatorAdd("divc", func_div, 0, "constant value");
  cdoOperatorAdd("mod",  func_mod, 0, "divisor");
  // clang-format on

  int operatorID = cdoOperatorID();
  int operfunc = cdoOperatorF1(operatorID);

  operatorInputArg(cdoOperatorEnter(operatorID));
  operatorCheckArgc(1);
  double rconst = parameter2double(operatorArgv()[0]);

  int streamID1 = pstreamOpenRead(cdoStreamName(0));

  int vlistID1 = pstreamInqVlist(streamID1);
  int vlistID2 = vlistDuplicate(vlistID1);

  int *vars = fill_vars(vlistID1);

  int taxisID1 = vlistInqTaxis(vlistID1);
  int taxisID2 = taxisDuplicate(taxisID1);
  vlistDefTaxis(vlistID2, taxisID2);

  int streamID2 = pstreamOpenWrite(cdoStreamName(1), cdoFiletype());
  pstreamDefVlist(streamID2, vlistID2);

  int gridsize = vlistGridsizeMax(vlistID1);

  field_type field;
  field_init(&field);
  field.ptr    = (double*) Malloc(gridsize*sizeof(double));
  field.weight = NULL;

  int tsID = 0;
  while ( (nrecs = pstreamInqTimestep(streamID1, tsID)) )
    {
      taxisCopyTimestep(taxisID2, taxisID1);

      pstreamDefTimestep(streamID2, tsID);

      for ( int recID = 0; recID < nrecs; recID++ )
	{
	  pstreamInqRecord(streamID1, &varID, &levelID);
	  pstreamReadRecord(streamID1, field.ptr, &nmiss);
          field.nmiss = nmiss;

	  if ( vars[varID] )
	    {
	      field.grid    = vlistInqVarGrid(vlistID1, varID);
	      field.missval = vlistInqVarMissval(vlistID1, varID);

	      farcfun(&field, rconst, operfunc);

	      /* recalculate number of missing values */
	      gridsize = gridInqSize(field.grid);
	      field.nmiss = 0;
	      for ( int i = 0; i < gridsize; ++i )
		if ( DBL_IS_EQUAL(field.ptr[i], field.missval) ) field.nmiss++;
	    }

          nmiss = field.nmiss;
	  pstreamDefRecord(streamID2, varID, levelID);
	  pstreamWriteRecord(streamID2, field.ptr, nmiss);
	}
      tsID++;
    }

  pstreamClose(streamID2);
  pstreamClose(streamID1);

  if ( field.ptr ) Free(field.ptr);
  if ( vars ) Free(vars);

  vlistDestroy(vlistID2);

  cdoFinish();

  return 0;
}
