use num::{Zero, One};

use alga::general::{AbstractMagma, AbstractGroupAbelian, AbstractGroup, AbstractLoop,
                    AbstractMonoid, AbstractQuasigroup, AbstractSemigroup, AbstractModule,
                    Module, Field, RingCommutative, Real, Inverse, Additive, Multiplicative,
                    MeetSemilattice, JoinSemilattice, Lattice, Identity,
                    ClosedAdd, ClosedNeg, ClosedMul};
use alga::linear::{VectorSpace, NormedSpace, InnerSpace, FiniteDimVectorSpace, FiniteDimInnerSpace};

use core::{DefaultAllocator, Scalar, MatrixMN, MatrixN};
use core::dimension::{Dim, DimName};
use core::storage::{Storage, StorageMut};
use core::allocator::Allocator;

/*
 *
 * Additive structures.
 *
 */
impl<N, R: DimName, C: DimName> Identity<Additive> for MatrixMN<N, R, C>
    where N: Scalar + Zero,
          DefaultAllocator: Allocator<N, R, C> {
    #[inline]
    fn identity() -> Self {
        Self::from_element(N::zero())
    }
}

impl<N, R: DimName, C: DimName> AbstractMagma<Additive> for MatrixMN<N, R, C>
    where N: Scalar + ClosedAdd,
          DefaultAllocator: Allocator<N, R, C> {
    #[inline]
    fn operate(&self, other: &Self) -> Self {
        self + other
    }
}

impl<N, R: DimName, C: DimName> Inverse<Additive> for MatrixMN<N, R, C>
    where N: Scalar + ClosedNeg,
          DefaultAllocator: Allocator<N, R, C> {
    #[inline]
    fn inverse(&self) -> MatrixMN<N, R, C> {
        -self
    }

    #[inline]
    fn inverse_mut(&mut self) {
        *self = -self.clone()
    }
}

macro_rules! inherit_additive_structure(
    ($($marker: ident<$operator: ident> $(+ $bounds: ident)*),* $(,)*) => {$(
        impl<N, R: DimName, C: DimName> $marker<$operator> for MatrixMN<N, R, C>
            where N: Scalar + $marker<$operator> $(+ $bounds)*,
                  DefaultAllocator: Allocator<N, R, C> { }
    )*}
);

inherit_additive_structure!(
    AbstractSemigroup<Additive>    + ClosedAdd,
    AbstractMonoid<Additive>       + Zero + ClosedAdd,
    AbstractQuasigroup<Additive>   + ClosedAdd + ClosedNeg,
    AbstractLoop<Additive>         + Zero + ClosedAdd + ClosedNeg,
    AbstractGroup<Additive>        + Zero + ClosedAdd + ClosedNeg,
    AbstractGroupAbelian<Additive> + Zero + ClosedAdd + ClosedNeg
);

impl<N, R: DimName, C: DimName> AbstractModule for MatrixMN<N, R, C>
    where N: Scalar + RingCommutative,
          DefaultAllocator: Allocator<N, R, C> {
    type AbstractRing = N;

    #[inline]
    fn multiply_by(&self, n: N) -> Self {
        self * n
    }
}

impl<N, R: DimName, C: DimName> Module for MatrixMN<N, R, C>
    where N: Scalar + RingCommutative,
          DefaultAllocator: Allocator<N, R, C> {
    type Ring = N;
}

impl<N, R: DimName, C: DimName> VectorSpace for MatrixMN<N, R, C>
    where N: Scalar + Field,
          DefaultAllocator: Allocator<N, R, C> {
    type Field = N;
}

impl<N, R: DimName, C: DimName> FiniteDimVectorSpace for MatrixMN<N, R, C>
    where N: Scalar + Field,
          DefaultAllocator: Allocator<N, R, C> {
    #[inline]
    fn dimension() -> usize {
        R::dim() * C::dim()
    }

    #[inline]
    fn canonical_basis_element(i: usize) -> Self {
        assert!(i < Self::dimension(), "Index out of bound.");

        let mut res = Self::zero();
        unsafe { *res.data.get_unchecked_linear_mut(i) = N::one(); }

        res
    }

    #[inline]
    fn dot(&self, other: &Self) -> N {
        self.dot(other)
    }

    #[inline]
    unsafe fn component_unchecked(&self, i: usize) -> &N {
        self.data.get_unchecked_linear(i)
    }

    #[inline]
    unsafe fn component_unchecked_mut(&mut self, i: usize) -> &mut N {
        self.data.get_unchecked_linear_mut(i)
    }
}

impl<N: Real, R: DimName, C: DimName> NormedSpace for MatrixMN<N, R, C>
    where DefaultAllocator: Allocator<N, R, C> {
    #[inline]
    fn norm_squared(&self) -> N {
        self.norm_squared()
    }

    #[inline]
    fn norm(&self) -> N {
        self.norm()
    }

    #[inline]
    fn normalize(&self) -> Self {
        self.normalize()
    }

    #[inline]
    fn normalize_mut(&mut self) -> N {
        self.normalize_mut()
    }

    #[inline]
    fn try_normalize(&self, min_norm: N) -> Option<Self> {
        self.try_normalize(min_norm)
    }

    #[inline]
    fn try_normalize_mut(&mut self, min_norm: N) -> Option<N> {
        self.try_normalize_mut(min_norm)
    }
}

impl<N: Real, R: DimName, C: DimName> InnerSpace for MatrixMN<N, R, C>
    where DefaultAllocator: Allocator<N, R, C> {
    type Real = N;

    #[inline]
    fn angle(&self, other: &Self) -> N {
        self.angle(other)
    }

    #[inline]
    fn inner_product(&self, other: &Self) -> N {
        self.dot(other)
    }
}

// FIXME: specialization will greatly simplify this implementation in the future.
// In particular:
//   − use `x()` instead of `::canonical_basis_element`
//   − use `::new(x, y, z)` instead of `::from_slice`
impl<N: Real, R: DimName, C: DimName> FiniteDimInnerSpace for MatrixMN<N, R, C>
    where DefaultAllocator: Allocator<N, R, C> {
    #[inline]
    fn orthonormalize(vs: &mut [MatrixMN<N, R, C>]) -> usize {
        let mut nbasis_elements = 0;

        for i in 0 .. vs.len() {
            {
                let (elt, basis) = vs[.. i + 1].split_last_mut().unwrap();

                for basis_element in &basis[.. nbasis_elements] {
                    *elt -= &*basis_element * elt.dot(basis_element)
                }
            }

            if vs[i].try_normalize_mut(N::zero()).is_some() {
                // FIXME: this will be efficient on dynamically-allocated vectors but for
                // statically-allocated ones, `.clone_from` would be better.
                vs.swap(nbasis_elements, i);
                nbasis_elements += 1;

                // All the other vectors will be dependent.
                if nbasis_elements == Self::dimension() {
                    break;
                }
            }
        }

        nbasis_elements
    }

    #[inline]
    fn orthonormal_subspace_basis<F>(vs: &[Self], mut f: F)
        where F: FnMut(&Self) -> bool {
        // FIXME: is this necessary?
        assert!(vs.len() <= Self::dimension(), "The given set of vectors has no chance of being a free family.");

        match Self::dimension() {
            1 => {
                if vs.len() == 0 {
                    f(&Self::canonical_basis_element(0));
                }
            },
            2 => {
                if vs.len() == 0 {
                    let _ = f(&Self::canonical_basis_element(0)) &&
                            f(&Self::canonical_basis_element(1));
                }
                else if vs.len() == 1 {
                    let v = &vs[0];
                    let res = Self::from_column_slice(&[-v[1], v[0]]);

                    f(&res.normalize());
                }

                // Otherwise, nothing.
            },
            3 => {
                if vs.len() == 0 {
                    let _ = f(&Self::canonical_basis_element(0)) &&
                            f(&Self::canonical_basis_element(1)) &&
                            f(&Self::canonical_basis_element(2));
                }
                else if vs.len() == 1 {
                    let v = &vs[0];
                    let mut a;

                    if v[0].abs() > v[1].abs() {
                        a = Self::from_column_slice(&[v[2], N::zero(), -v[0]]);
                    }
                    else {
                        a = Self::from_column_slice(&[N::zero(), -v[2], v[1]]);
                    };

                    let _ = a.normalize_mut();

                    if f(&a.cross(v)) {
                        f(&a);
                    }
                }
                else if vs.len() == 2 {
                    f(&vs[0].cross(&vs[1]).normalize());
                }
            },
            _ => {
                // XXX: use a GenericArray instead.
                let mut known_basis = Vec::new();

                for v in vs.iter() {
                    known_basis.push(v.normalize())
                }

                for i in 0 .. Self::dimension() - vs.len() {
                    let mut elt = Self::canonical_basis_element(i);

                    for v in &known_basis {
                        elt -= v * elt.dot(v)
                    };

                    if let Some(subsp_elt) = elt.try_normalize(N::zero()) {
                        if !f(&subsp_elt) { return };

                        known_basis.push(subsp_elt);
                    }
                }
            }
        }
    }
}


/*
 *
 *
 * Multiplicative structures.
 *
 *
 */
impl<N, D: DimName> Identity<Multiplicative> for MatrixN<N, D>
    where N: Scalar + Zero + One,
          DefaultAllocator: Allocator<N, D, D> {
    #[inline]
    fn identity() -> Self {
        Self::identity()
    }
}

impl<N, D: DimName> AbstractMagma<Multiplicative> for MatrixN<N, D>
    where N: Scalar + Zero + One + ClosedAdd + ClosedMul,
          DefaultAllocator: Allocator<N, D, D> {
    #[inline]
    fn operate(&self, other: &Self) -> Self {
        self * other
    }
}

macro_rules! impl_multiplicative_structure(
    ($($marker: ident<$operator: ident> $(+ $bounds: ident)*),* $(,)*) => {$(
        impl<N, D: DimName> $marker<$operator> for MatrixN<N, D>
            where N: Scalar + Zero + One + ClosedAdd + ClosedMul + $marker<$operator> $(+ $bounds)*,
                  DefaultAllocator: Allocator<N, D, D> { }
    )*}
);

impl_multiplicative_structure!(
    AbstractSemigroup<Multiplicative>,
    AbstractMonoid<Multiplicative> + One
);


/*
 *
 * Ordering
 *
 */
impl<N, R: Dim, C: Dim> MeetSemilattice for MatrixMN<N, R, C>
    where N: Scalar + MeetSemilattice,
          DefaultAllocator: Allocator<N, R, C> {
    #[inline]
    fn meet(&self, other: &Self) -> Self {
        self.zip_map(other, |a, b| a.meet(&b))
    }
}

impl<N, R: Dim, C: Dim> JoinSemilattice for MatrixMN<N, R, C>
    where N: Scalar + JoinSemilattice,
          DefaultAllocator: Allocator<N, R, C> {
    #[inline]
    fn join(&self, other: &Self) -> Self {
        self.zip_map(other, |a, b| a.join(&b))
    }
}


impl<N, R: Dim, C: Dim> Lattice for MatrixMN<N, R, C>
    where N: Scalar + Lattice,
          DefaultAllocator: Allocator<N, R, C> {
    #[inline]
    fn meet_join(&self, other: &Self) -> (Self, Self) {
        let shape = self.data.shape();
        assert!(shape == other.data.shape(), "Matrix meet/join error: mismatched dimensions.");

        let mut mres = unsafe { Self::new_uninitialized_generic(shape.0, shape.1) };
        let mut jres = unsafe { Self::new_uninitialized_generic(shape.0, shape.1) };

        for i in 0 .. shape.0.value() * shape.1.value() {
            unsafe {
                let mj = self.data.get_unchecked_linear(i).meet_join(other.data.get_unchecked_linear(i));
                *mres.data.get_unchecked_linear_mut(i) = mj.0;
                *jres.data.get_unchecked_linear_mut(i) = mj.1;
            }
        }

        (mres, jres)
    }
}