use pin_project::pin_project;
use std::{
    future::Future,
    ops::Deref,
    pin::Pin,
    task::{Context, Poll},
};

#[pin_project]
#[derive(Debug, Clone)]
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct OptionFuture<F>(#[pin] Option<F>);

impl<F: Future> Future for OptionFuture<F> {
    type Output = Option<F::Output>;

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        match self.project().0.as_pin_mut() {
            Some(x) => x.poll(cx).map(Some),
            None => Poll::Ready(None),
        }
    }
}

impl<F> Deref for OptionFuture<F> {
    type Target = Option<F>;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl<T> From<Option<T>> for OptionFuture<T> {
    fn from(option: Option<T>) -> Self {
        OptionFuture(option)
    }
}