#pragma once

#include "matrices.h"
#include "materials.h"

struct sphere {
  struct mat4x4 transform;
  struct material material;
};

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

inline static struct tuple sphere_normal_at(struct sphere const * const s, struct tuple world_point)
{
  struct mat4x4 inv = mat4x4_inverse(&s->transform);
  struct tuple object_point = mat4x4_mul_t(&inv, &world_point);
  struct tuple object_normal = tuple_sub(object_point, point(0.0f, 0.0f, 0.0f));
  struct mat4x4 inv_t = mat4x4_transpose(&inv);
  struct tuple world_normal = mat4x4_mul_t(&inv_t, &object_normal);
  world_normal.w = 0.0f;
  return tuple_normalize(world_normal);
}