#include "vec3.h"
#include "ray.h"

#include <draw.h>
#include <event.h>


void
eresized(int new)
{
	if(new&& getwindow(display, Refnone) < 0)
		sysfatal("can't reattach to window");
}


double 
hit_sphere(vec3 centr, double rad, ray r)
{
	vec3 oc = vecsub(r.origin, centr);
	double a = length_sq(r.direction);
	double h_b = dot(oc, r.direction);
	double c = length_sq(oc) - rad*rad;
	double dis = h_b*h_b - a*c;

	if (dis < 0) {
		return -1.0;
	} else {
		return (-h_b - sqrt(dis) ) / a;
	}
}

vec3
ray_color(ray r)
{
	double t = hit_sphere(point3(0,0,-1), 0.5, r);
	if (t > 0.0) {
		vec3 N = unit_vector(vecsub(at(r, t), point3(0,0,-1)));
		N.e[0] += 1;
		N.e[1] += 1;
		N.e[2] += 1;
		vec3 col = vecscale(0.5, N);
		return col;
	}
	vec3 u_dir = unit_vector(r.direction);
	t = 0.5 * (u_dir.e[1] + 1.0);
	vec3 o = vecadd(vecscale((1.0-t), color(1.0, 1.0, 1.0)), vecscale(t, color(0.5, 0.7, 1.0)));
	return o;
}

void
main(int argc, char* argv[])
{
	USED(argc, argv);
	
	Mouse m;
	Image *color;
	Point min, max;
	int i, j;
	unsigned int ir, ig, ib, rgb;
	double u, v;

	// Camera
	vec3 llc = {-2.0, -1.0, -1.0};
	vec3 hor = {4.0, 0.0, 0.0};
	vec3 ver = {0.0, 2.0, 0.0};
	vec3 ori = {0.0, 0.0, 0.0};
	vec3 dir = {0.0, 0.0, 0.0};

	ray r;
	r.origin = ori;
	r.direction = dir;

	initdraw(0, 0, "Plan9 Raytracer");
	eresized(0);
	einit(Emouse);

	min = screen->r.min;
	max = screen->r.max;

	for(j = max.y; j >= min.y; --j)
	{
		for(i = min.x; i < max.x; ++i)
		{
			u = (double)(i - min.x)/(double)(max.x - min.x);
			v = (double)(j - min.y)/(double)(max.y - min.y);

			r.origin = ori;
			r.direction = vecsub(vecadd(vecadd(llc, vecscale(u,hor)), vecscale(v,ver)), ori);
			vec3 rc = ray_color(r);
			
			ir = (unsigned char)255.99*rc.e[0];
			ig = (unsigned char)255.99*rc.e[1];
			ib = (unsigned char)255.99*rc.e[2];

			rgb = ((ir & 0xFF) << 24) + ((ig & 0xFF) << 16) + ((ib & 0xFF) << 8) + (255 & 0xFF);
			color = allocimage(display, Rect(0,0,1,1), RGBA32, 1, rgb);
			draw(screen,  Rect(i, j, i+1, j+1), color, nil, ZP);
			freeimage(color);
		}
	}
	flushimage(display, Refnone);


	/* Main loop */
	for(;;) {
		m = emouse();
		if(m.buttons & 4)
			break;
	}
}