treaty -


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use core::ops::ControlFlow;

use crate::{
    hkt::hkt,
    nameable,
    protocol::{any_t, walker::HintMeta, Yield, Effect, SyncEffect, Visitor},
};

pub trait Sequence<'ctx, E: Effect<'ctx, ControlFlow<(), ()>>> {
    fn visit<'a>(
        &'a mut self,
        scope: &'a mut dyn SequenceScope<'ctx, E>,
    ) -> Yield<'a, 'ctx, ControlFlow<(), ()>, E>
    where
        'ctx: 'a;
}

nameable! {
    pub struct Name['a, 'ctx, E];

    impl [E] for dyn Sequence<'ctx, E> + 'a where {
        E: Effect<'ctx, ControlFlow<(), ()>> + Effect<'ctx, ControlFlow<(), Status>>,
        'ctx: 'a
    }

    impl [E] where dyn Sequence<'ctx, E> + 'a {
        E: Effect<'ctx, ControlFlow<(), ()>> + Effect<'ctx, ControlFlow<(), Status>>,
        'ctx: 'a
    }
}

pub trait SequenceScope<'ctx, E>
where
    E: Effect<'ctx, ControlFlow<(), Status>>,
{
    fn next<'a>(&'a mut self, visitor: Visitor<'a, 'ctx, E>) -> Yield<'a, 'ctx, ControlFlow<(), Status>, E>
    where
        'ctx: 'a;
}

#[derive(PartialEq, Eq, PartialOrd, Ord, Copy, Clone, Debug)]
pub enum Status {
    Done,
    Continue,
}

hkt!((any_t): for<'a, 'ctx> pub KnownHkt => Known);

#[derive(Default)]
pub struct Known {
    pub len: (usize, Option<usize>),
}

pub struct Hint {
    pub len: (usize, Option<usize>),
}

impl<'a, 'ctx: 'a, E: Effect<'ctx, ControlFlow<(), ()>>> HintMeta<'ctx> for dyn Sequence<'ctx, E> + '_ {
    type Known = KnownHkt<'ctx>;

    type Hint = Hint;
}