#include <cmath>
#include <fstream>
#include <iostream>

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

using namespace std;

//skybox

float hit_sphere(const vec3& center, float radius, const ray& r) {
    float a, b, c, t;
    a = dot(r.D, r.D);
    b = 2 * (dot(r.D, (r.O - center)));
    c = dot(r.O - center, r.O - center) - radius * radius;
    t = (((-b) - sqrt((b * b) - (4 * a * c))) / (2 * a));
    //cout << a << " " << b << " " << c;
    return t >= 0 ? t : 0;
}

vec3 color(ray& r) {
    vec3 center(0, 0, -1);
    float t = hit_sphere(center, 0.5, r);
    if (t > 0.0) {
        vec3 N = unit_vector(r.point_at_parameter(t) - center);
        vec3 L = unit_vector(vec3(1, 1, 0) - r.point_at_parameter(t));
        vec3 I = vec3(1, 1, 1);  //intensity of lightsource
        cout << t << " " << I * dot(N, L) << endl;
        return (dot(N, L) > 0 ? dot(N, L) : 0) * I;
    }
    vec3 unit_direction = unit_vector(r.direction());
    t = 0.5 * (unit_direction.y() + 1.0);
    return (1.0 - t) * vec3(1, 1, 1) + t * vec3(0.5, 0.7, 1.0);
}

int main() {
    int width = 200;
    int height = 100;

    fstream file;
    file.open("ray.ppm", ios::out);

    vec3 lower_left_corner(-2, -1, -1);
    vec3 origin(0, 0, 0);
    vec3 horizontal(4, 0, 0);
    vec3 vertical(0, 2, 0);
    file << "P3\n"
         << width << " " << height << "\n255\n";
    for (int j = height - 1; j >= 0; j--) {
        for (int i = 0; i < width; i++) {
            float u = float(i) / float(width);
            float v = float(j) / float(height);
            ray r = ray(origin, lower_left_corner + u * horizontal + v * vertical);
            vec3 color2 = color(r);
            file << int(color2.r() * 255) << " " << int(color2.g() * 255) << " " << int(color2.b() * 255) << "\n";
        }
    }
    file.close();
}