From cb1b3ec801b48c2b7cb0ced1948526af964ee765 Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Fri, 16 Jul 2021 22:25:26 -0700
Subject: [PATCH] sphere: use Intersections as the return type from
 `intersect`.

---
 rtchallenge/src/intersections.rs |  1 +
 rtchallenge/src/spheres.rs       | 20 ++++++++++----------
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/rtchallenge/src/intersections.rs b/rtchallenge/src/intersections.rs
index 219cbf6..fb93503 100644
--- a/rtchallenge/src/intersections.rs
+++ b/rtchallenge/src/intersections.rs
@@ -51,6 +51,7 @@ impl<'i> Intersection<'i> {
 /// assert_eq!(xs[0].object, &s);
 /// assert_eq!(xs[1].object, &s);
 /// ```
+#[derive(Debug, Default, PartialEq)]
 pub struct Intersections<'i>(Vec<Intersection<'i>>);
 
 impl<'i> Intersections<'i> {
diff --git a/rtchallenge/src/spheres.rs b/rtchallenge/src/spheres.rs
index 67311c2..d479196 100644
--- a/rtchallenge/src/spheres.rs
+++ b/rtchallenge/src/spheres.rs
@@ -1,5 +1,5 @@
 use crate::{
-    intersections::Intersection,
+    intersections::{Intersection, Intersections},
     matrices::Matrix4x4,
     rays::Ray,
     tuples::{dot, Tuple},
@@ -39,7 +39,7 @@ impl Default for Sphere {
 /// # Examples
 /// ```
 /// use rtchallenge::{
-///     intersections::Intersection,
+///     intersections::{Intersection, Intersections},
 ///     matrices::Matrix4x4,
 ///     rays::Ray,
 ///     spheres::{intersect, Sphere},
@@ -52,14 +52,14 @@ impl Default for Sphere {
 /// let xs = intersect(&s, &r);
 /// assert_eq!(
 ///     xs,
-///     vec![Intersection::new(4., &s), Intersection::new(6., &s)]
+///     Intersections::new(vec![Intersection::new(4., &s), Intersection::new(6., &s)])
 /// );
 ///
 /// // A ray intersects a sphere at a tangent.
 /// let r = Ray::new(Tuple::point(0., 2., -5.), Tuple::vector(0., 0., 1.));
 /// let s = Sphere::default();
 /// let xs = intersect(&s, &r);
-/// assert_eq!(xs, vec![]);
+/// assert_eq!(xs, Intersections::default());
 ///
 /// // A ray originates inside a sphere.
 /// let r = Ray::new(Tuple::point(0., 0., 0.), Tuple::vector(0., 0., 1.));
@@ -67,7 +67,7 @@ impl Default for Sphere {
 /// let xs = intersect(&s, &r);
 /// assert_eq!(
 ///     xs,
-///     vec![Intersection::new(-1., &s), Intersection::new(1., &s)]
+///     Intersections::new(vec![Intersection::new(-1., &s), Intersection::new(1., &s)])
 /// );
 ///
 /// // A sphere is behind a ray.
@@ -76,7 +76,7 @@ impl Default for Sphere {
 /// let xs = intersect(&s, &r);
 /// assert_eq!(
 ///     xs,
-///     vec![Intersection::new(-6., &s), Intersection::new(-4., &s)]
+///     Intersections::new(vec![Intersection::new(-6., &s), Intersection::new(-4., &s)])
 /// );
 ///
 /// // Intersect a scaled sphere with a ray.
@@ -95,7 +95,7 @@ impl Default for Sphere {
 /// let xs = intersect(&s, &r);
 /// assert_eq!(xs.len(), 0);
 /// ```
-pub fn intersect<'s>(sphere: &'s Sphere, ray: &Ray) -> Vec<Intersection<'s>> {
+pub fn intersect<'s>(sphere: &'s Sphere, ray: &Ray) -> Intersections<'s> {
     let ray = ray.transform(sphere.transform.inverse());
     let sphere_to_ray = ray.origin - Tuple::point(0., 0., 0.);
     let a = dot(ray.direction, ray.direction);
@@ -103,11 +103,11 @@ pub fn intersect<'s>(sphere: &'s Sphere, ray: &Ray) -> Vec<Intersection<'s>> {
     let c = dot(sphere_to_ray, sphere_to_ray) - 1.;
     let discriminant = b * b - 4. * a * c;
     if discriminant < 0. {
-        vec![]
+        Intersections::default()
     } else {
-        vec![
+        Intersections::new(vec![
             Intersection::new((-b - discriminant.sqrt()) / (2. * a), &sphere),
             Intersection::new((-b + discriminant.sqrt()) / (2. * a), &sphere),
-        ]
+        ])
     }
 }