use super::Point3;
use super::Ray;
use super::Vec3;

pub struct HitRecord {
    p: Point3,
    normal: Vec3,
    t: f64,
}

pub struct Sphere {
    center: Point3,
    radius: f64,
}

pub trait Hittable {
    fn hit(&self, r: Ray, t_min: f64, t_max: f64, rec: &mut HitRecord) -> bool;
}

impl Sphere {
    fn new(cen: Point3, r: f64) -> Self {
        Sphere {
            center: cen,
            radius: r,
        }
    }
}

impl Hittable for Sphere {
    fn hit(&self, r: Ray, t_min: f64, t_max: f64, rec: &mut HitRecord) -> bool {
        let oc = r.origin() - self.center;
        let a = r.direction().length_squared(); // gleiches Ergebnis wie Skalarprodukt
        let b = 2.0 * Vec3::dot(oc, r.direction());
        let c = oc.length_squared() - self.radius * self.radius;

        let discriminant = b * b - 4.0 * a * c;
        if discriminant < 0.0 {
            return false;
        }

        let sqrtd = discriminant.sqrt();

        let root = (-b / 2.0 - sqrtd) / a;
        if root < t_min || t_max < root {
            let root2 = (-b / 2.0 + sqrtd) / a;
            if root2 < t_min || t_max < root {
                return false;
            }
        }

        rec.t = root;
        rec.p = r.at(rec.t);
        rec.normal = (rec.p - self.center) / self.radius;

        return true;
    }
}