#include <stdio.h>
#include <stdint.h>

#include "rtweekend.hpp"

#include "color.hpp"
#include "hittable_list.hpp"
#include "sphere.hpp"

color ray_color(const ray& r, const hittable& world);
double hit_sphere(const point3& center, double radius, const ray& r);

color ray_color(const ray& r, const hittable& world)
{
    hit_record rec;
    if (world.hit(r, 0, INFINITY, rec))
    {
        return 0.5 * (rec.normal + color(1,1,1));
    }
    vec3 unit_direction = normalize(r.direction);
    double t = 0.5 * (unit_direction.y + 1.0);
    return (1-t) * color(1,1,1) + t*color(0.5,0.7,1.0);
}

double hit_sphere(const point3& center, double radius, const ray& r)
{
    vec3 oc = r.origin - center;
    double a = r.direction.length_squared();
    double half_b = dot(oc, r.direction);
    double c = oc.length_squared() - radius*radius;
    double discriminant = half_b*half_b - a*c;

    if (discriminant < 0)
        return -1;
    else
        return (-half_b - sqrt(discriminant)) / a;
}

int main()
{
    // Image
    double aspect_ratio = 16.0 / 9;
    const int32_t image_width = 400;
    const int32_t image_height = (int32_t) (image_width / aspect_ratio);

    // World
    hittable_list world;
    world.add(std::make_shared<sphere>(point3(0,0,-1), 0.5));
    world.add(std::make_shared<sphere>(point3(0,-100.5,-1), 100));

    // Camera
    double viewport_height = 2.0;
    double viewport_width = aspect_ratio * viewport_height;
    double focal_length = 1.0;

    point3 origin = point3(0,0,0);
    vec3 horizontal = vec3(viewport_width, 0, 0);
    vec3 vertical = vec3(0, viewport_height, 0);
    vec3 lower_left_corner = origin - horizontal/2 - vertical/2 - vec3(0, 0, focal_length);

    // Render
    printf("P3\n%d %d\n255\n", image_width, image_height);

    for (int32_t j = image_height - 1; j >= 0; --j)
    {
        fprintf(stderr, "\rScanlines remaining: %d ", j);
        fflush(stderr);
        for (int32_t i = 0; i < image_width; ++i)
        {
            double u = (double)i / (image_width-1);
            double v = (double)j / (image_height-1);            
            ray r = ray(origin, lower_left_corner + u*horizontal + v*vertical - origin);            
            color pixel_color = ray_color(r, world);
            
            write_color(stdout, pixel_color);
        }        
    }
    fprintf(stderr, "\nDone\n");
}