#include <complex.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static void usage(char *progname)
{
	fprintf(stderr,
		"\n"
		"usage: %s [options]\n\n"
		" -p [kp]   proportional constant    (default 0.7)\n"
		" -i [ki]   integration constant     (default 0.3)\n"
		" -t [num]  sample period in seconds (default 1.0)\n"
		" -h        prints this message and exits\n"
		"\n",
		progname);
}

static void roots(double p, double i)
{
	double complex z, r;

	r = (p + i) * (p + i) - 4.0 * i;
	r = csqrt(r);
	z = 2.0 - p - i + r;
	z /= 2.0;
	r = conj(z);

	printf("%.9f %.9f %.9f %.9f %.9f %.9f %.9f %.9f\n",
	       creal(z), cimag(z), creal(r), cimag(r),
	       carg(z), cabs(z), carg(r), cabs(r));
}
	
int main(int argc, char *argv[])
{
	char *progname;
	int c;
	double kp = .7;
	double ki = .3;
	double t = 1.0;

	/* Process the command line arguments. */
	progname = strrchr(argv[0], '/');
	progname = progname ? 1+progname : argv[0];
	while (EOF != (c = getopt(argc, argv, "p:i:t:h"))) {
		switch (c) {
		case 'p':
			kp = atof(optarg);
			break;
		case 'i':
			ki = atof(optarg);
			break;
		case 't':
			t = atof(optarg);
			break;
		case 'h':
			usage(progname);
			return 0;
		default:
			usage(progname);
			return -1;
		}
	}

	printf("# kp %f ki %f t %f\n", kp, ki, t);
	roots(kp * t, ki * t);
	return 0;
}