#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

static void usage(char* progname)
{
	fprintf(stderr,
		"usage: %s [options] \n"
		" -d            output data only, do not produce gnuplot commands \n"
		" -h            prints this message and exits \n"
		" -i [file]     input file to use \n"
		,progname);
}

static void header(FILE *fp, char *fname)
{
	fprintf(fp,
		"set term x11\n"
		"set title '%s'\n"
		"set xlabel 'SECONDS'\n"
		"set ylabel 'OFFSET NANOSECONDS'\n"
		"set grid\n"
		"set xrange [180:1800]\n"
		"set yrange [0:1000]\n"
		"plot '-' notitle with points\n", fname);
}

int main(int argc, char *argv[])
{
	int sec, ns;
	int c, cnt, data_only = 0, index;
	FILE *infp, *outfp;
	char buf[PATH_MAX], *infile = NULL, *progname;

	/* Process the command line arguments. */
	progname = strrchr(argv[0],'/');
	progname = progname ? 1+progname : argv[0];
	while (EOF != (c = getopt(argc,argv,"dhi:"))) {
		switch (c) {
		case 'd': data_only = 1; break;
		case 'i': infile = optarg; break;
		case 'h': usage(progname); return(0);
		case '?': usage(progname); return(-1);
		default:  usage(progname); return(-1);
		}
	}

	if (!infile) {
		usage(progname);
		return -1;
	}

	snprintf(buf, sizeof(buf), "%s.gp", infile);

	infp = fopen(infile, "r");
	if (!infp) {
		perror("fopen");
		return -1;
	}
	outfp = fopen(buf, "w");
	if (!outfp) {
		perror("fopen");
		return -1;
	}

	if (!data_only) {
		header(outfp, infile);
	}

	while (fgets(buf, sizeof(buf), infp)) {
		cnt = sscanf(buf, "event index %d at %d.%d", &index, &sec, &ns);
		if (3 == cnt) {
			if (ns > 500000000) {
				ns = ns - 1000000000;
			}
			fprintf(outfp, "%d\n", ns);
		}
		if (feof(infp)) {
			break;
		}
	}

	if (!data_only) {
		fprintf(outfp, "e\n");
	}

	fclose(infp);
	fclose(outfp);
	return 0;
}