//! Axis Aligned Bounding Box.

use na;

use math::Point;
use utils;
use bounding_volume::{BoundingVolume, HasBoundingVolume};

// Seems useful to help type inference. See issue #84.
/// Computes the axis-aligned bounding box of a shape `g` transformed by `m`.
///
/// Same as `g.aabb(m)`.
pub fn aabb<P, M, G: ?Sized>(g: &G, m: &M) -> AABB<P>
where
    G: HasBoundingVolume<M, AABB<P>>,
{
    g.bounding_volume(m)
}

/// An Axis Aligned Bounding Box.
#[derive(Debug, PartialEq, Clone)]
pub struct AABB<P> {
    mins: P,
    maxs: P,
}

impl<P: Point> AABB<P> {
    /// Creates a new AABB.
    ///
    /// # Arguments:
    ///   * `mins` - position of the point with the smallest coordinates.
    ///   * `maxs` - position of the point with the highest coordinates. Each component of `mins`
    ///   must be smaller than the related components of `maxs`.
    pub fn new(mins: P, maxs: P) -> AABB<P> {
        assert!(na::partial_le(&mins, &maxs));

        AABB {
            mins: mins,
            maxs: maxs,
        }
    }

    /// Reference to the AABB point with the smallest components along each axis.
    #[inline]
    pub fn mins(&self) -> &P {
        &self.mins
    }

    /// Reference to the AABB point with the biggest components along each axis.
    #[inline]
    pub fn maxs(&self) -> &P {
        &self.maxs
    }

    /// The center of this AABB.
    #[inline]
    pub fn center(&self) -> P {
        na::center(&self.mins, &self.maxs)
    }

    /// The half extents of this AABB.
    #[inline]
    pub fn half_extents(&self) -> P::Vector {
        (self.maxs - self.mins) / na::convert(2.0f64)
    }
}

// XXX: we should not keep this
// impl<P: Point> AABB<P> {
//     /// Creates an invalid AABB with:
//     /// * `mins = Bounded::max_value()`
//     /// * `maxs = Bounded::max_value()`.
//     /// This is useful to build aabb using merges.
//     pub fn new_invalid() -> AABB<P> {
//         let _max: P = Bounded::max_value();
//         AABB {
//             mins: Bounded::max_value(),
//             maxs: -_max,
//         }
//     }
// }

impl<P: Point> BoundingVolume<P> for AABB<P> {
    #[inline]
    fn center(&self) -> P {
        self.center()
    }

    #[inline]
    fn intersects(&self, other: &AABB<P>) -> bool {
        na::partial_le(&self.mins, &other.maxs) && na::partial_ge(&self.maxs, &other.mins)
    }

    #[inline]
    fn contains(&self, other: &AABB<P>) -> bool {
        na::partial_le(&self.mins, &other.mins) && na::partial_ge(&self.maxs, &other.maxs)
    }

    #[inline]
    fn merge(&mut self, other: &AABB<P>) {
        self.mins = na::inf(&self.mins, &other.mins);
        self.maxs = na::sup(&self.maxs, &other.maxs);
    }

    #[inline]
    fn merged(&self, other: &AABB<P>) -> AABB<P> {
        AABB {
            mins: na::inf(&self.mins, &other.mins),
            maxs: na::sup(&self.maxs, &other.maxs),
        }
    }

    #[inline]
    fn loosen(&mut self, amount: P::Real) {
        assert!(
            amount >= na::zero(),
            "The loosening margin must be positive."
        );
        self.mins = self.mins + utils::repeat(-amount);
        self.maxs = self.maxs + utils::repeat(amount);
    }

    #[inline]
    fn loosened(&self, amount: P::Real) -> AABB<P> {
        assert!(
            amount >= na::zero(),
            "The loosening margin must be positive."
        );
        AABB {
            mins: self.mins + utils::repeat(-amount),
            maxs: self.maxs + utils::repeat(amount),
        }
    }

    #[inline]
    fn tighten(&mut self, amount: P::Real) {
        assert!(
            amount >= na::zero(),
            "The tightening margin must be positive."
        );
        self.mins = self.mins + utils::repeat(amount);
        self.maxs = self.maxs + utils::repeat(-amount);
        assert!(
            na::partial_le(&self.mins, &self.maxs),
            "The tightening margin is to large."
        );
    }

    #[inline]
    fn tightened(&self, amount: P::Real) -> AABB<P> {
        assert!(
            amount >= na::zero(),
            "The tightening margin must be positive."
        );

        AABB::new(
            self.mins + utils::repeat(amount),
            self.maxs + utils::repeat(-amount),
        )
    }
}

// impl<P> Translation<P::Vector> for AABB<P>
//     where P: Point,
//           P::Vector: Translate<P> {
//     #[inline]
//     fn translation(&self) -> P::Vector {
//         na::center(&self.mins, &self.maxs).to_vector()
//     }
//
//     #[inline]
//     fn inverse_translation(&self) -> P::Vector {
//         -self.translation()
//     }
//
//     #[inline]
//     fn append_translation_mut(&mut self, dv: &P::Vector) {
//         self.mins = self.mins + *dv;
//         self.maxs = self.maxs + *dv;
//     }
//
//     #[inline]
//     fn append_translation(&self, dv: &P::Vector) -> AABB<P> {
//         AABB::new(self.mins + *dv, self.maxs + *dv)
//     }
//
//     #[inline]
//     fn prepend_translation_mut(&mut self, dv: &P::Vector) {
//         self.append_translation_mut(dv)
//     }
//
//     #[inline]
//     fn prepend_translation(&self, dv: &P::Vector) -> AABB<P> {
//         self.append_translation(dv)
//     }
//
//     #[inline]
//     fn set_translation(&mut self, v: P::Vector) {
//         let center = self.translation();
//         let total_translation = center + v;
//
//         self.mins = na::inverse_translate(&total_translation, &self.mins);
//         self.maxs = na::inverse_translate(&total_translation, &self.maxs);
//     }
// }