#include "sphere.h"

bool Sphere::hit(const Ray& r, double tmin, double tmax, hit_record& rec) const {
    compute_sphere_uv((rec.p - center)/radius, rec.u, rec.v);
    Vec3 oc = r.origin() - center;
    auto a = r.direction().length_squared();
    auto half_b = dot(oc, r.direction());
    auto c = oc.length_squared() - radius * radius;
    auto discriminant = half_b*half_b - a*c;
    if (discriminant > 0) {
        auto root = std::sqrt(discriminant);
        auto temp = (-half_b - root) / a;
        if (temp < tmax && temp > tmin) {
            rec.t = temp;
            rec.p = r.at(rec.t);
            Vec3 outward_normal = (rec.p - center) / radius;
            rec.set_face_normal(r, outward_normal);
            rec.mat_ptr = mat_ptr;
            return true;
        }
        temp = (-half_b + root) / a;
        if (temp < tmax && temp > tmin) {
            rec.t = temp;
            rec.p = r.at(rec.t);
            Vec3 outward_normal = (rec.p - center) / radius;
            rec.set_face_normal(r, outward_normal);
            rec.mat_ptr = mat_ptr;
            return true;
        }
    }
    return false;
}

bool Sphere::bounding_box(double t0, double t1, Aabb& output_box) const {
    output_box = Aabb(
            center - Vec3(radius, radius, radius),
            center + Vec3(radius, radius, radius));
    return true;
}