#include <u.h>
#include <libc.h>
#include <draw.h>
#include <event.h>
enum{N = 4096, ½N = N >> 1};
int y, barwid;
Rectangle r;
Image *grad, *mask;
void
eresized(int i){
	int x, f, n;
	char *buf;
	Image *paint;
	if(i && getwindow(display, Refnone) < 0) sysfatal("can't reattach to window: %r");
	x = Dx(screen->r);
	y = Dy(screen->r) - font->height;
	barwid = x / (16 * 7);
	if((buf = malloc(x > y ? x : y)) == nil) sysfatal("malloc: %r");
	freeimage(grad);
	grad = allocimage(display, Rect(0, 0, x, y), RGB24, 0, DRed);
	mask = allocimage(display, Rect(0, 0, 1, y), GREY8, 1, DNofill);
	paint = allocimage(display, Rect(0, 0, 1, 1), RGB24, 1, DGreen);
	if(grad == nil || mask == nil || paint == nil) sysfatal("allocimage: %r");
	for(i = 0; i < y; i++) buf[i] = 255.0 * i / y;
	loadimage(mask, mask->r, (uchar*)buf, y);
	draw(grad, grad->r, paint, mask, ZP);
	freeimage(mask); freeimage(paint);
	mask = allocimage(display, Rect(0, 0, x, 1), GREY8, 1, DNofill);
	paint = allocimage(display, Rect(0, 0, 1, 1), RGB24, 1, DBlue);
	if(mask == nil || paint == nil) sysfatal("allocimage: %r");
	for(i = 0; i < x; i++) buf[i] = 255.0 * i / 2 / x;
	loadimage(mask, mask->r, (uchar*)buf, x);
	draw(grad, grad->r, paint, mask, ZP);
	freeimage(mask); freeimage(paint);
	mask = allocimage(display, Rect(0, 0, Dx(screen->r), y), GREY1, 0, DNofill);
	if(mask == nil) sysfatal("allocimage: %r");
	r = screen->r;
	r.max.y = r.min.y + font->height;
	draw(screen, r, display->black, nil, ZP);
	r.max.y = r.min.y;
	for(f = 1, n = 16; n < ½N; n <<= 1){
		r.min.x += 16 * barwid;
		sprint(buf, "%d Hz|", (f += n) * 22050 / ½N);
		r.max.x = r.min.x - stringwidth(font, buf);
		string(screen, r.max, display->white, ZP, font, buf);
	}
	free(buf);
}
void
main(int, char**){
	char io[N << 2];
	int i₀, i₁, i₂, i₃, i₄, fd, ←[N];
	double d₀, d₁, re[N], im[N], w[N], costab[½N], sintab[½N];
	read(0, io, 0); /* allow pressing Del to exit if forgot to pipe something in */
	if((fd = open("/dev/audio", OWRITE)) < 0) sysfatal("open: %r");
	for(i₀ = 0; i₀ < N; i₀++){
/* windowing factors:
• Goertzel: 1
• Hanning: 0.5 - 0.25 * cos(i₀ * 2.0 * PI / N)
• Hamming: 0.54 - 0.46 * cos(i₀ * 2.0 * PI / N)
• Blackman: 0.426551 - 0.496561 * cos(i₀ * 2.0 * PI / N) + 0.076848 * cos(i₀ * 4.0 * PI / N)
*/		w[i₀] = 0.426551 - 0.496561 * cos(i₀ * 2.0 * PI / N) + 0.076848 * cos(i₀ * 4.0 * PI / N);
		for(←[i₀] = 0, i₁ = i₀, i₂ = ½N; i₂; i₂ >>= 1, i₁ >>= 1)
			←[i₀] = ←[i₀] << 1 | i₁ & 1;
	}
	for(i₀ = 0; i₀ < ½N; i₀++){
		costab[i₀] = cos(PI * i₀ / ½N);
		sintab[i₀] = sin(PI * i₀ / ½N);
	}
	if(initdraw(nil, nil, "frequency analyzer") < 0) sysfatal("initdraw: %r");
	einit(Emouse|Ekeyboard);
	eresized(0);
	while(readn(0, io, sizeof(io)) == sizeof(io) && write(fd, io, sizeof(io)) == sizeof(io)
	&& (!ecankbd() || ekbd() != 0x7F && ekbd() != 0x7F)){
		for(i₀ = i₁ = 0; i₀ < N; i₀++, i₁ += 4){
			re[←[i₀]] = w[i₀] * ((s16int)(io[i₁] | io[i₁ + 1] << 8) + (s16int)(io[i₁ + 2] | io[i₁ + 3] << 8));
			im[i₀] = 0.0;
		}
		for(i₀ = 1, i₁ = ½N; i₁; i₀ <<= 1, i₁ >>= 1)
			for(i₂ = 0; i₂ < N; i₂ += i₀ << 1)
				for(i₃ = i₄ = 0; i₃ < i₀; i₃++, i₄ += i₁){
					d₀ = costab[i₄] * re[i₀ + i₂ + i₃] - sintab[i₄] * im[i₀ + i₂ + i₃];
					d₁ = costab[i₄] * im[i₀ + i₂ + i₃] + sintab[i₄] * re[i₀ + i₂ + i₃];
					re[i₀ + i₂ + i₃] = re[i₂ + i₃] - d₀;
					re[i₂ + i₃] += d₀;
					im[i₀ + i₂ + i₃] = im[i₂ + i₃] - d₁;
					im[i₂ + i₃] += d₁;
				}
		r = screen->r;
		r.min.y += font->height;
		draw(screen, r, grad, nil, ZP);
		draw(mask, mask->r, display->white, nil, ZP);
		r = Rect(0, 0, barwid, y);
		for(i₀ = i₁ = 1; i₀ < ½N; i₁ <<= 1)
			for(i₂ = 0; i₂ < 16; i₂++){
				for(d₁ = 0.0, i₃ = i₀ + i₁; i₀ < i₃; i₀++){
					d₀ = re[i₀] * re[i₀] + im[i₀] * im[i₀];
					if(d₀ > 0.0 && (d₀ = (log10(d₀) - 10) * 0.25) > d₁) /* ¯\_(ツ)_/¯ */
						d₁ = d₀;
				}
				r.min.y = y - d₁ * y;
				draw(mask, r, display->black, nil, ZP);
				r.min.x = r.max.x;
				r.max.x += barwid;
			}
		draw(screen, screen->r, display->black, mask, Pt(0, -font->height));
		flushimage(display, 1);
	}
	exits(nil);
}