use std::task::{Context, Poll, Waker};

pub struct Signal{
    waker: Option<Waker>,
    active: bool,
}
impl Signal{
    pub fn new() -> Self{
        Self{
            waker: None,
            active: false,
        }
    }
    pub fn wake(&mut self){
        self.active = true;
        if let Some(w) = self.waker.take(){
            w.wake();
        }
    }
    pub fn poll(&mut self, ctx: &mut Context<'_>) -> Poll<()>{
        if self.active{
            self.active = false;
            Poll::Ready(())
        }else{
            self.waker = Some(ctx.waker().clone());
            Poll::Pending
        }
    }
}