/*
 * 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: grib_iterator
 *
 * Description: how to use an iterator on lat/lon/values.
 *
 */

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

#include "grib_api.h"  

static 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;
    double missingValue = 1e+20; /* A value out of range */
	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=strdup(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);

		/* Set the double representing the missing value in the field. */
        /* Choose a missingValue that does not correspond to any real value in the data array */
		GRIB_CHECK(grib_set_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=%.6e lon=%.6e 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;
}
