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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

//! Vector representations for use in high dimensional vector spaces.

#![cfg_attr(not(feature = "std"), no_std)]

#![cfg_attr(feature = "missing_mpl", feature(plugin))]
#![cfg_attr(feature = "missing_mpl", plugin(missing_mpl))]
#![cfg_attr(feature = "missing_mpl", deny(missing_mpl))]

#![warn(missing_docs)]

#[cfg(not(feature = "std"))]
extern crate core as std;

#[cfg(not(feature = "std"))]
#[macro_use]
extern crate std;

#[cfg(test)]
#[macro_use(expect)]
extern crate expectest;

extern crate num_traits;
extern crate ordered_iter;
extern crate arrayvec;

pub mod dense;
pub mod sparse;

use std::ops::{Add, AddAssign, Sub, SubAssign, Mul, MulAssign, Div, DivAssign};

use num_traits::{MulAdd, MulAddAssign, real::Real};

/// The crate's prelude
pub mod prelude {
    pub use super::{
        VectorOps, VectorAssignOps,
        Vector, VectorRef,
        VectorAssign, VectorAssignRef,
        Dot, Distance
    };
}

/// The trait for vector types implementing basic numeric operations.
pub trait VectorOps<Vector, Scalar>: Sized
    + Add<Vector, Output = Self>
    + Sub<Vector, Output = Self>
    + Mul<Scalar, Output = Self>
    + Div<Scalar, Output = Self>
    + MulAdd<Scalar, Vector, Output = Self>
{}

/// The trait for vector types implementing numeric assignment operators (like `+ = `).
pub trait VectorAssignOps<Vector, Scalar>: Sized
    + AddAssign<Vector>
    + SubAssign<Vector>
    + MulAssign<Scalar>
    + DivAssign<Scalar>
    + MulAddAssign<Scalar, Vector>
{}

/// The base trait for vector types, covering comparisons,
/// basic numeric operations, and the dot product.
pub trait Vector<Scalar>: PartialEq + VectorOps<Self, Scalar> {
    /// The type of the `Vector`'s scalar components.
    type Scalar;

    // /// Calculates the dot-product between `self` and `rhs`.
    // fn dot(self, rhs: &Self) -> Self::Scalar;
    //
    // /// Calculates the squared euclidian distance between `self` and `rhs`.
    // fn squared_distance(&self, rhs: &Self) -> Self::Scalar;
    //
    // /// Calculates the euclidian distance between `self` and `rhs`.
    // fn distance(&self, rhs: &Self) -> Self::Scalar
    // where
    //     Self::Scalar: Real,
    // {
    //     self.squared_distance(rhs).sqrt()
    // }
}

/// The trait for `Vector` types which also implement numeric operations
// taking the second operand by reference.
pub trait VectorRef<Scalar>: Vector<Scalar> + for<'a> VectorOps<&'a Self, Scalar> { }

impl<T, S> VectorRef<S> for T
where
    T: Vector<S> + for<'a> VectorOps<&'a T, S>
{}

/// The trait for `Vector` types which also implement assignment operators.
pub trait VectorAssign<Scalar>: Vector<Scalar> + VectorAssignOps<Self, Scalar> {}

impl<T, S> VectorAssign<S> for T
where
    T: Vector<S> + VectorAssignOps<Self, S>
{}

/// The trait for `VectorAssign` types which also implement
/// assignment operations taking the second operand by reference.
pub trait VectorAssignRef<Scalar>: VectorAssign<Scalar> + for<'a> VectorAssignOps<&'a Self, Scalar> { }

impl<T, S> VectorAssignRef<S> for T
where
    T: VectorAssign<S> + for<'a> VectorAssignOps<&'a T, S>
{}

/// The trait for types supporting the calculation of the dot product
pub trait Dot: Sized {
    /// The scalar type returned by `self`'s dot product
    type Scalar;

    /// Calculates the dot-product between `self` and `rhs`.
    fn dot(&self, rhs: &Self) -> Self::Scalar;
}

/// The trait for types supporting the calculation of distance
pub trait Distance: Sized {
    /// The scalar type returned by `self`'s distance
    type Scalar;

    /// Calculates the squared euclidian distance between `self` and `rhs`.
    fn squared_distance(&self, rhs: &Self) -> Self::Scalar;

    /// Calculates the euclidian distance between `self` and `rhs`.
    fn distance(&self, rhs: &Self) -> Self::Scalar
    where
        Self::Scalar: Real,
    {
        self.squared_distance(rhs).sqrt()
    }
}