use super::*;

pub enum Selected<'a, A: 'a, B: 'a, T: ?Sized + WeakFunctorA<'a>> {
    A(A, T::Fa<B>),
    B(T::Fa<A>, B),
}

pub type SelectedWrapped<'a, A, B, T> = Wrap<'a, Selected<'a, A, B, T>, T>;

pub trait ApplicativeSelect<'a>: Functor<'a> {
    fn select<A: 'a, B: 'a>(fa: Self::Fa<A>, fb: Self::Fa<B>) -> SelectedWrapped<'a, A, B, Self> {
        Self::fmap(|a| Selected::A(a, fb), fa)
    }
}

pub trait ApplicativeSelectExt<'a>: ApplicativeSelect<'a> {
    fn select_map<A: 'a, B: 'a, C: 'a>(
        f: impl 'a + FnOnce(Selected<'a, A, B, Self>) -> C,
        fa: Self::Fa<A>,
        fb: Self::Fa<B>,
    ) -> Self::Fa<C> {
        Self::fmap(f, Self::select(fa, fb))
    }
}

impl<'a, T: ApplicativeSelect<'a>> ApplicativeSelectExt<'a> for T {}