/*
 * Copyright 2005-2018 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: iterator
 *
 * Description: how to use an iterator on lat/lon/values.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "grib_api.h"  

void usage(const char* prog) {
  printf("Usage: %s grib_file\n",prog);
  exit(1);
}

int main(int argc, char** argv)
{
  FILE* in = NULL;
  int err = 0;
  double lat,lon,value,missingValue=0;
  int n=0;
  char* filename = NULL;

  /* Message handle. Required in all the grib_api calls acting on a message.*/
  grib_handle *h = NULL;   
  /* Iterator on lat/lon/values.*/
  grib_iterator* iter=NULL;  
  
  if (argc != 2) usage(argv[0]);

    filename=argv[1];

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

  /* Loop on all the messages in a file.*/
  while ((h = grib_handle_new_from_file(0,in,&err)) != NULL ) { 
	/* Check of errors after reading a message. */
    if (err != GRIB_SUCCESS) GRIB_CHECK(err,0);                       

	/* Get the double representing the missing value in the field. */
	GRIB_CHECK(grib_get_double(h,"missingValue",&missingValue),0);  

	/* A new iterator on lat/lon/values is created from the message handle h. */
	iter=grib_iterator_new(h,0,&err);                                     
    if (err != GRIB_SUCCESS) GRIB_CHECK(err,0);                       

    n = 0;
	/* Loop on all the lat/lon/values. */
    while(grib_iterator_next(iter,&lat,&lon,&value)) {   
	  /* You can now print lat and lon,  */
      printf("- %d - lat=%f lon=%f value=",n,lat,lon);   
	  /* decide what to print if a missing value is found. */
      if (value == missingValue ) printf("missing\n");   
	  /* and print the value if is not missing. */
	  else printf("%f\n",value);
      n++;
    }

	/* At the end the iterator is deleted to free memory. */
    grib_iterator_delete(iter);               

    /* At the end the grib_handle is deleted to free memory. */
    grib_handle_delete(h);            
  }

  fclose(in);

  return 0;
}
