/*
 * Copyright 2005-2017 ECMWF.
 *
 * This software is licensed under the terms of the Apache Licence Version 2.0
 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
 *
 * In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
 * virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
 */

/*
 * C Implementation: set_missing
 *
 * Description: how to set a key as missing.
 *
 */
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "grib_api.h"

int main(int argc, char** argv)
{
  int err = 0, is_missing = 0;

  FILE* in = NULL;
  char* infile = "../../data/reduced_gaussian_pressure_level.grib2";
  FILE* out = NULL;
  char* outfile = "out_surface_level.grib2";
  grib_handle *h = NULL;
  const void* buffer = NULL;
  size_t size=0;
  char str[]="sfc";
  size_t str_len=3;
  long Ni = 0;

  in = fopen(infile,"r");
  if(!in) {
    printf("ERROR: unable to open input file %s\n",infile);
    return 1;
  }

  out = fopen(outfile,"w");
  if(!out) {
    printf("ERROR: unable to open output file %s\n",outfile);
        fclose(in);
    return 1;
  }

  /* create a new handle from a message in a file */
  h = grib_handle_new_from_file(0,in,&err);
  if (h == NULL) {
    printf("Error: unable to create handle from file %s\n",infile);
  }

  GRIB_CHECK(grib_set_string(h,"typeOfFirstFixedSurface",str,&str_len),0);
  GRIB_CHECK(grib_set_missing(h,"scaleFactorOfFirstFixedSurface"),0);
  GRIB_CHECK(grib_set_missing(h,"scaledValueOfFirstFixedSurface"),0);
  
  /* See GRIB-490 */
  GRIB_CHECK(grib_get_long(h,"Ni",&Ni),0);
  is_missing = grib_is_missing(h, "Ni", &err);
  GRIB_CHECK(err,0);
  assert(is_missing == 1);
  GRIB_CHECK(grib_set_long(h,"Ni", Ni),0);

  /* get the coded message in a buffer */
  GRIB_CHECK(grib_get_message(h,&buffer,&size),0);

  /* write the buffer in a file*/
  if(fwrite(buffer,1,size,out) != size) 
  {
     perror(argv[1]);
     exit(1);
  }

  /* delete handle */
  grib_handle_delete(h);

  fclose(in);
  fclose(out);

  return 0;
}
