#include <u.h>
#include <libc.h>
#include <thread.h>
#include "guic.h"

char *keywords[] = {
	"w",
	"freq",
	"exit",
	0,
};

enum {
	Gw = 500,
	Gh = 300,
};

void
printpoly(double *x, int deg)
{
	int i;
	print("(");
	for(i=0; i<deg; i++){
		if(i > 0)
			print(", ");
		print("%f", x[i]);
	}
	print(")\n");
}

double
evalpoly(double *x, int deg, double w)
{
	double re, im;
	int i;

	/* degrees: x_0 + x_1*z^{-1} + x_2*z^2 + ... */
	for(i=0; i<deg; i++){
		re += x[i] * cos(-i*w);
		im += x[i] * sin(-i*w);
	}
	return re*re + im*im;
}

void
mulpoly(double *x, int deg, double c)
{
	while(deg--)
		*x++ *= c;
}

double
evalfilt(double *Y, double *X, int a, int b, double w)
{
	if(a <= 0 || b <= 0)
		sysfatal("zero numerator/denominator");
	if(Y[0] == 0)
		sysfatal("zero constant in denominator");
	mulpoly(X, b, 1/Y[0]);
	mulpoly(Y, a, 1/Y[0]);
	return evalpoly(X, b, w) / evalpoly(Y, a, w);
}

/*
 * 1/(0.5 - 0.5z^-1 + z^-2)
 */

void
draw(int f)
{
	int y, i;
	guiwrite("set w ");
	for(i=0; i<Gw; i++){
		y = - sin(i*f*2*PI/500) * Gh / 2 + Gh / 2;
		guiwrite("%d,", y);
	}
	guiwrite("\n");
}

double X[4] = { 1 };
double Y[4] = { 1, -0.5, -0.5 };


void
threadmain(int argc, char *argv[])
{
	Event ev;

	if(argc < 2)
		sysfatal("not enough args");

	printpoly(Y, 3);
	//mulpoly(X, b, 1/Y[0]);
	mulpoly(Y, 3, 1/Y[0]);
	printpoly(Y, 3);
	//return evalpoly(X, b, w) / evalpoly(Y, a, w);
	print("\nv=%f\n", evalfilt(Y, X, 3, 1, 1));
	/*
	guistart(argv[1]);
	guiload("gsine.gui");
	for(;;){
		recv(guichan, &ev);
		if(ev.k == 1){
			draw(ev.n);
		}
	}
	*/

	threadexits(0);
}