treaty -


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use core::ops::ControlFlow;

use crate::{
    effect::{Effect, Future},
    higher_ranked_type,
    hkt::AnySend,
    nameable,
    protocol::{walker::hint::HintMeta, Visitor},
};

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

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

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

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

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

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

higher_ranked_type! {
    pub type KnownHkt['ctx]: (AnySend) = for<'lt> 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>> HintMeta<'ctx> for dyn Sequence<'ctx, E> + '_ {
    type Known = KnownHkt<'ctx>;

    type Hint = Hint;
}