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// Copyright 2013-2014 The CGMath Developers. For a full listing of the authors,
// refer to the Cargo.toml file at the top-level directory of this distribution.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Bounding sphere

use bound::*;
use intersect::Intersect;
use Plane;
use Ray3;
use cgmath::{BaseFloat, EuclideanSpace};
use cgmath::{InnerSpace, Point3};

#[derive(Copy, Clone, PartialEq, Debug)]
pub struct Sphere<S: BaseFloat> {
    pub center: Point3<S>,
    pub radius: S,
}

impl<S: BaseFloat> Intersect<Option<Point3<S>>> for (Sphere<S>, Ray3<S>) {
    fn intersection(&self) -> Option<Point3<S>> {
        let (ref s, ref r) = *self;

        let l = s.center - r.origin;
        let tca = l.dot(r.direction);
        if tca < S::zero() { return None; }
        let d2 = l.dot(l) - tca*tca;
        if d2 > s.radius*s.radius { return None; }
        let thc = (s.radius*s.radius - d2).sqrt();
        Some(r.origin + r.direction * (tca - thc))
    }
}

impl<S: BaseFloat + 'static> Bound<S> for Sphere<S> {
    fn relate_plane(self, plane: Plane<S>) -> Relation {
        let dist = self.center.dot(plane.n) - plane.d;
        if dist > self.radius {
            Relation::In
        } else if dist < - self.radius {
            Relation::Out
        } else {
            Relation::Cross
        }
    }
}