treaty -


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use crate::{
    build::Builder,
    effect::{Effect, Future},
    hkt::Marker,
    Walk, Walker, WalkerTypes,
};

#[inline]
#[allow(clippy::type_complexity)]
pub fn transform<'a, 'ctx, B: Builder<'ctx, E> + 'a, W: Walker<'ctx, E> + 'a, E: Effect>(
    seed: B::Seed,
    walker: W,
) -> Future<'a, (Result<B::Value, B::Error>, Result<W::Output, W::Error>), E> {
    E::wrap(async {
        // Create builder from seed value;
        let mut builder = B::from_seed(seed).await;

        // Walk the walker with the builder as the visitor.
        let walker_result = walker.walk(builder.as_visitor()).await;

        // Finish building the value.
        let builder_result = builder.build().await;

        (builder_result, walker_result)
    })
}

/// For use in a lens.
pub struct Projection<T, B, U, M> {
    value: T,
    builder: B,
    _marker: Marker<(U, M)>,
}

#[allow(clippy::type_complexity)]
impl<T, B, U: Send + Sync, M> Projection<T, B, U, M> {
    pub fn project_ref<'a, E: Effect>(
        &'a self,
    ) -> Future<
        'a,
        (
            Result<&'a U, B::Error>,
            Result<<&'a T as WalkerTypes>::Output, <&'a T as WalkerTypes>::Error>,
        ),
        E,
    >
    where
        &'a T: Walk<'a, M, E>,
        B: Clone + Builder<'a, E, Value = &'a U>,
    {
        let walker = self.value.into_walker();
        let mut builder = self.builder.clone();

        E::wrap(async {
            let result = walker.walk(builder.as_visitor()).await;

            (builder.build().await, result)
        })
    }

    pub fn project_mut<'a, E: Effect>(
        &'a mut self,
    ) -> Future<
        'a,
        (
            Result<&'a mut U, B::Error>,
            Result<<&'a mut T as WalkerTypes>::Output, <&'a mut T as WalkerTypes>::Error>,
        ),
        E,
    >
    where
        &'a mut T: Walk<'a, M, E>,
        B: Clone + Builder<'a, E, Value = &'a mut U>,
    {
        let walker = self.value.into_walker();
        let mut builder = self.builder.clone();

        E::wrap(async {
            let result = walker.walk(builder.as_visitor()).await;

            (builder.build().await, result)
        })
    }

    pub fn project<'a, E: Effect>(
        self,
    ) -> Future<
        'a,
        (
            Result<U, B::Error>,
            Result<<T as WalkerTypes>::Output, <T as WalkerTypes>::Error>,
        ),
        E,
    >
    where
        T: Walk<'a, M, E> + 'a,
        M: 'a,
        B: Clone + Builder<'a, E, Value = U> + 'a,
    {
        let walker = self.value.into_walker();
        let mut builder = self.builder.clone();

        E::wrap(async {
            let result = walker.walk(builder.as_visitor()).await;

            (builder.build().await, result)
        })
    }
}