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use crate::Stopper;
use event_listener::EventListener;
use std::{
    future::{Future, IntoFuture},
    pin::Pin,
    task::{ready, Context, Poll},
};

/// A future that awaits this Stopper being stopped
#[derive(Debug)]
pub struct Stopped {
    stopper: Stopper,
    event_listener: Option<EventListener>,
}

impl From<Stopper> for Stopped {
    fn from(value: Stopper) -> Self {
        value.into_future()
    }
}

impl From<Stopped> for Stopper {
    fn from(value: Stopped) -> Self {
        value.stopper
    }
}

impl Future for Stopped {
    type Output = ();

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let Self {
            stopper,
            event_listener,
        } = &mut *self;
        loop {
            if stopper.is_stopped_relaxed() {
                return Poll::Ready(());
            }

            let listener = match event_listener {
                Some(listener) => listener,
                None => {
                    let listener = event_listener.insert(stopper.listener());
                    if stopper.is_stopped() {
                        return Poll::Ready(());
                    }
                    listener
                }
            };

            ready!(Pin::new(listener).poll(cx));

            *event_listener = None;
        }
    }
}

impl IntoFuture for Stopper {
    type Output = ();
    type IntoFuture = Stopped;

    fn into_future(self) -> Self::IntoFuture {
        Stopped {
            stopper: self,
            event_listener: None,
        }
    }
}