#pragma once

#include "matrices.h"
#include "materials.h"
#include "shapes.h"
#include "rays.h"
#include "intersections.h"

inline static struct shape sphere()
{
  return (struct shape){
    mat4x4_identity(),
    material(),
    SHAPE_SPHERE,
  };
}

inline static struct tuple sphere_normal_at(struct tuple local_point)
{
  return tuple_sub(local_point, point(0.0f, 0.0f, 0.0f));
}

inline static void sphere_intersect(struct shape const * const s, struct ray local_ray, struct intersections * intersections)
{
  struct tuple sphere_to_ray = tuple_sub(local_ray.origin, point(0.0f, 0.0f, 0.0f));

  float a = tuple_dot(local_ray.direction, local_ray.direction);
  float b = 2 * tuple_dot(local_ray.direction, sphere_to_ray);
  float c = tuple_dot(sphere_to_ray, sphere_to_ray) - 1;

  float discriminant = b * b - 4 * a * c;

  if (discriminant < 0) {
    return;
  } else {
    float root = sqrtf(discriminant);
    float t1 = (-b - root) / (2 * a);
    float t2 = (-b + root) / (2 * a);

    intersections->i[intersections->count++] = intersection(t1, s);
    intersections->i[intersections->count++] = intersection(t2, s);
    return;
  }
}