extern crate vec3;
use super::object::Object;
use super::ray::Ray;

pub struct Sphere {}

fn return_min(root1: f64, root2: f64) -> Option<f64> {
    if root1 < root2 && root1 > 0. {
        Some(root1)
    } else if root2 < root1 && root2 > 0. {
        Some(root2)
    } else {
        None
    }
}

impl Object for Sphere {
    fn get_intersection(&self, ray: Ray) -> Option<f64> {
        let a = ray.direction[0].powi(2) + ray.direction[1].powi(2) + ray.direction[2].powi(2);
        let b = (2. * ray.origin[0] * ray.direction[0])
            + (2. * ray.origin[1] * ray.direction[1])
            + (2. * ray.origin[2] * ray.direction[2]);
        let c = ray.origin[0].powi(2) + ray.origin[1].powi(2) + ray.origin[2].powi(2) - 1.;
        let delta = b * b - 4. * a * c;

        if delta > 0. {
            let root1 = ((-1. * b - delta.sqrt()) / (a + a)) - 0.00001;
            let root2 = ((-1. * b + delta.sqrt()) / (a + a)) - 0.00001;
            return_min(root1, root2)
        } else {
            None
        }
    }
    fn get_normal(&self, n: [f64; 3]) -> [f64; 3] {
        let scalar = (n[0].powi(2) + n[1].powi(2) + n[2].powi(2)).sqrt();
        [n[0] / scalar, n[1] / scalar, n[2] / scalar]
    }
}