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use futures::channel::{mpsc, oneshot};
use futures::select;
use futures::stream::FuturesUnordered;
use futures::FutureExt;
use futures::StreamExt;
use std::cell::RefCell;
use std::future::Future;
use std::mem::take;
use std::pin::Pin;
use std::rc::Rc;
use crate::Disposable;
pub struct EventLoop {
state: Rc<RefCell<BusState>>,
tx: mpsc::Sender<Message>,
}
impl EventLoop {
pub fn new() -> (EventLoop, EventLoopHandler) {
let state = Rc::new(RefCell::new(BusState::default()));
let (tx, rx) = mpsc::channel::<Message>(1024);
(
EventLoop {
state: state.clone(),
tx,
},
EventLoopHandler { state, rx },
)
}
pub fn queue<F>(&self, task: F) -> Disposable
where
F: Future<Output = ()> + 'static,
{
let mut pending = self.state.borrow_mut();
let (tx, rx) = oneshot::channel();
pending.additions.push(Box::pin(async move {
let mut rx = rx.fuse();
let mut task = Box::pin(task).fuse();
select! {
_ = rx => {},
_ = task => {},
};
Some(Message::Refresh)
}));
self.tx.clone().try_send(Message::Refresh).unwrap();
Disposable::new(Token { tx: Some(tx) })
}
pub fn queue_retain<F>(&self, task: F)
where
F: Future<Output = ()> + 'static,
{
let mut pending = self.state.borrow_mut();
pending.additions.push(Box::pin(async move {
task.await;
Some(Message::Refresh)
}));
self.tx.clone().try_send(Message::Refresh).unwrap();
}
}
impl Drop for EventLoop {
fn drop(&mut self) {
let _ = self.tx.try_send(Message::Terminate);
}
}
enum Message {
Refresh,
Terminate,
}
#[derive(Default)]
struct BusState {
additions: Vec<Pin<Box<dyn Future<Output = Option<Message>>>>>,
}
pub struct EventLoopHandler {
state: Rc<RefCell<BusState>>,
rx: mpsc::Receiver<Message>,
}
impl EventLoopHandler {
pub async fn main(mut self) {
let mut tasks = FuturesUnordered::<Pin<Box<dyn Future<Output = Option<Message>>>>>::new();
loop {
select! {
message = self.rx.next() => {
match message {
Some(Message::Refresh) => {
let pending = take(&mut self.state.borrow_mut().additions);
tasks.extend(pending);
}
Some(Message::Terminate) => break,
None => {},
}
},
_ = tasks.next() => {},
};
}
}
}
struct Token {
tx: Option<oneshot::Sender<()>>,
}
impl Drop for Token {
fn drop(&mut self) {
if let Some(tx) = self.tx.take() {
let _ = tx.send(());
}
}
}