use crate::func::*;

pub struct CompositionInstance<U, V>(U, V);

impl<U: WeakFunctor, V: WeakFunctor> WeakFunctor for CompositionInstance<U, V> {
    type F<'a, A: 'a> = U::F<'a, V::F<'a, A>> where Self: 'a;
}

impl<U: Functor, V: Functor> Functor for CompositionInstance<U, V> {
    fn fmap<'a, A: 'a, B: 'a>(f: impl 'a + FnOnce(A) -> B, fa: Self::F<'a, A>) -> Self::F<'a, B>
    where
        Self: 'a,
    {
        U::fmap(|ua| V::fmap(f, ua), fa)
    }

    fn replace<'a, A: 'a, B: 'a>(fa: Self::F<'a, A>, b: B) -> Self::F<'a, B>
    where
        Self: 'a,
    {
        U::fmap(|ua| V::replace(ua, b), fa)
    }

    fn void<'a, A: 'a>(fa: Self::F<'a, A>) -> Self::F<'a, ()>
    where
        Self: 'a,
    {
        U::fmap(|ua| V::void(ua), fa)
    }
}

impl<U: Pure, V: Pure> Pure for CompositionInstance<U, V> {
    fn pure<'a, A: 'a>(a: A) -> Self::F<'a, A>
    where
        Self: 'a,
    {
        U::pure(V::pure(a))
    }
}

impl<U: ApplicativeLA2, V: ApplicativeSeq> ApplicativeSeq for CompositionInstance<U, V> {
    fn seq<'a, A: 'a, B: 'a>(
        ff: Self::F<'a, impl 'a + FnOnce(A) -> B>,
        fa: Self::F<'a, A>,
    ) -> Self::F<'a, B>
    where
        Self: 'a,
    {
        U::la2(|uf, ua| V::seq(uf, ua), ff, fa)
    }
}

impl<U: ApplicativeLA2, V: ApplicativeLA2> ApplicativeLA2 for CompositionInstance<U, V> {
    fn la2<'a, A: 'a, B: 'a, C: 'a>(
        f: impl 'a + FnOnce(A, B) -> C,
        fa: Self::F<'a, A>,
        fb: Self::F<'a, B>,
    ) -> Self::F<'a, C>
    where
        Self: 'a,
    {
        U::la2(|ua, ub| V::la2(f, ua, ub), fa, fb)
    }
}

impl<U: ApplicativeTuple, V: ApplicativeTuple> ApplicativeTuple for CompositionInstance<U, V> {
    fn tuple<'a, A: 'a, B: 'a>(fab: (Self::F<'a, A>, Self::F<'a, B>)) -> Self::F<'a, (A, B)>
    where
        Self: 'a,
    {
        U::fmap(V::tuple, U::tuple(fab))
    }
}

impl<U: ApplicativeSelect, V: Functor> ApplicativeSelect for CompositionInstance<U, V> {
    fn select<'a, A: 'a, B: 'a>(
        fa: Self::F<'a, A>,
        fb: Self::F<'a, B>,
    ) -> SelectedWrapped<'a, A, B, Self>
    where
        Self: 'a,
    {
        U::fmap(
            |selected| match selected {
                Selected::A(ua, fb) => V::fmap(|a| Selected::A(a, fb), ua),
                Selected::B(fa, ub) => V::fmap(|b| Selected::B(fa, b), ub),
            },
            U::select(fa, fb),
        )
    }
}

impl<U: Applicative, V: Applicative> Applicative for CompositionInstance<U, V> {
    fn discard_first<'a, A: 'a, B: 'a>(fa: Self::F<'a, A>, fb: Self::F<'a, B>) -> Self::F<'a, B>
    where
        Self: 'a,
    {
        U::la2(|ua, ub| V::discard_first(ua, ub), fa, fb)
    }

    fn discard_second<'a, A: 'a, B: 'a>(fa: Self::F<'a, A>, fb: Self::F<'a, B>) -> Self::F<'a, A>
    where
        Self: 'a,
    {
        U::la2(|ua, ub| V::discard_second(ua, ub), fa, fb)
    }
}

impl<U: Monad, V: Monad + LocalFunctor> Monad for CompositionInstance<U, V> {
    fn bind<'a, A: 'a, B: 'a>(
        fa: Self::F<'a, A>,
        f: impl 'a + FnOnce(A) -> Self::F<'a, B>,
    ) -> Self::F<'a, B>
    where
        Self: 'a,
    {
        U::bind(fa, |ua| U::fmap(V::join, V::stuff::<_, U>(V::fmap(f, ua))))
    }

    fn iterate<'a, B: 'a>(f: impl Iterative<'a, T = Self, B = B>) -> Self::F<'a, B>
    where
        Self: 'a,
    {
        U::iterate(ComposedIterative(f))
    }

    fn join<'a, A: 'a>(ffa: Self::F<'a, Self::F<'a, A>>) -> Self::F<'a, A>
    where
        Self::F<'a, A>: 'a,
        Self: 'a,
    {
        U::join(U::fmap(|ufa| U::fmap(V::join, V::stuff::<_, U>(ufa)), ffa))
    }
}

struct ComposedIterative<F>(F);

impl<
        'a,
        U: 'a + Monad,
        V: 'a + Monad + LocalFunctor,
        F: Iterative<'a, T = CompositionInstance<U, V>>,
    > Iterative<'a> for ComposedIterative<F>
{
    type B = Wrap<'a, F::B, V>;
    type T = U;

    fn next(self) -> IterativeWrapped<'a, Self> {
        let fstate = self.0.next();
        U::fmap(
            |ustate| match V::unstuff(ustate) {
                ControlFlow::Continue(next_f) => ControlFlow::Continue(Self(next_f)),
                ControlFlow::Break(b) => ControlFlow::Break(b),
            },
            fstate,
        )
    }
}

impl<E, U: Monad, V: Fail<E> + LocalFunctor> Fail<E> for CompositionInstance<U, V> {
    fn fail<'a, A: 'a>(e: E) -> Self::F<'a, A>
    where
        Self: 'a,
        E: 'a,
    {
        U::pure(V::fail(e))
    }
}

impl<U: LocalFunctor + Functor, V: LocalFunctor> LocalFunctor for CompositionInstance<U, V> {
    fn unstuff<'a, A: 'a, B: 'a>(
        state: Self::F<'a, ControlFlow<B, A>>,
    ) -> ControlFlow<Self::F<'a, B>, A>
    where
        Self: 'a,
    {
        U::unstuff(U::fmap(V::unstuff, state))
    }

    fn stuff<'a, A: 'a, T: 'a + Pure>(fa: Self::F<'a, T::F<'a, A>>) -> T::F<'a, Self::F<'a, A>>
    where
        Self: 'a,
    {
        U::stuff::<_, T>(U::fmap(V::stuff::<_, T>, fa))
    }
}

impl<U: SharedFunctor + Functor, V: SharedFunctor> SharedFunctor for CompositionInstance<U, V> {
    type Shared<'a, A: 'a + Clone> = U::Shared<'a, V::Shared<'a, A>>
    where
        Self: 'a;

    fn share<'a, A: 'a + Clone>(fa: Self::F<'a, A>) -> Self::Shared<'a, A>
    where
        Self: 'a,
    {
        U::share(U::fmap(V::share, fa))
    }

    fn unshare<'a, A: 'a + Clone>(sa: Self::Shared<'a, A>) -> Self::F<'a, A>
    where
        Self: 'a,
    {
        U::fmap(V::unshare, U::unshare(sa))
    }
}

impl<U: CovariantFunctor + Functor, V: CovariantFunctor> CovariantFunctor
    for CompositionInstance<U, V>
{
    fn variate<'a: 'b, 'b, A: 'a>(fa: Self::F<'a, A>) -> Self::F<'b, A>
    where
        Self: 'a,
    {
        U::fmap(V::variate, U::variate(fa))
    }
}