AppFlowy/shared-lib/lib-infra/src/future.rs

use futures_core::future::BoxFuture;
use futures_core::ready;
use pin_project::pin_project;
use std::{
    fmt::Debug,
    future::Future,
    pin::Pin,
    task::{Context, Poll},
};

pub fn to_future<T, O>(f: T) -> Fut<O>
where
    T: Future<Output = O> + Send + Sync + 'static,
{
    Fut { fut: Box::pin(f) }
}

#[pin_project]
pub struct Fut<T> {
    #[pin]
    pub fut: Pin<Box<dyn Future<Output = T> + Sync + Send>>,
}

impl<T> Future for Fut<T>
where
    T: Send + Sync,
{
    type Output = T;

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let this = self.as_mut().project();
        Poll::Ready(ready!(this.fut.poll(cx)))
    }
}

#[pin_project]
pub struct FutureResult<T, E> {
    #[pin]
    pub fut: Pin<Box<dyn Future<Output = Result<T, E>> + Sync + Send>>,
}

impl<T, E> FutureResult<T, E> {
    pub fn new<F>(f: F) -> Self
    where
        F: Future<Output = Result<T, E>> + Send + Sync + 'static,
    {
        Self {
            fut: Box::pin(async { f.await }),
        }
    }
}

impl<T, E> Future for FutureResult<T, E>
where
    T: Send + Sync,
    E: Debug,
{
    type Output = Result<T, E>;

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let this = self.as_mut().project();
        let result = ready!(this.fut.poll(cx));
        Poll::Ready(result)
    }
}

pub type BoxResultFuture<'a, T, E> = BoxFuture<'a, Result<T, E>>;