start tutorial

src/bin/server.rs

@@ -3,8 +3,8 @@
 use std::{collections::HashMap, net::ToSocketAddrs};
 
 use futures::{
-    io::{BufReader, WriteHalf},
-    stream::FuturesUnordered,
+    io::{BufReader, WriteHalf, AsyncRead},
+    stream::{FuturesUnordered, Stream},
     channel::mpsc::{self, unbounded},
     SinkExt,
     select,

src/main.rs

@@ -0,0 +1,178 @@
+#![feature(async_await)]
+
+use std::{
+    net::ToSocketAddrs,
+    sync::Arc,
+    collections::hash_map::{HashMap, Entry},
+};
+
+use futures::{
+    channel::mpsc,
+    SinkExt,
+    select,
+};
+
+use async_std::{
+    io::BufReader,
+    prelude::*,
+    task,
+    net::{TcpListener, TcpStream},
+};
+
+type Result<T> = std::result::Result<T, Box<dyn std::error::Error + Send + Sync>>;
+type Sender<T> = mpsc::UnboundedSender<T>;
+type Receiver<T> = mpsc::UnboundedReceiver<T>;
+
+#[derive(Debug)]
+enum Void {}
+
+fn main() -> Result<()> {
+    task::block_on(server("127.0.0.1:8080"))
+}
+
+async fn server(addr: impl ToSocketAddrs) -> Result<()> {
+    let listener = TcpListener::bind(addr).await?;
+
+    let (broker_sender, broker_receiver) = mpsc::unbounded();
+    let broker = task::spawn(broker(broker_receiver));
+    let mut incoming = listener.incoming();
+    while let Some(stream) = incoming.next().await {
+        let stream = stream?;
+        println!("Accepting from: {}", stream.peer_addr()?);
+        spawn_and_log_error(client(broker_sender.clone(), stream));
+    }
+    drop(broker_sender);
+    broker.await;
+    Ok(())
+}
+
+async fn client(mut broker: Sender<Event>, stream: TcpStream) -> Result<()> {
+    let stream = Arc::new(stream);
+    let reader = BufReader::new(&*stream);
+    let mut lines = reader.lines();
+
+    let name = match lines.next().await {
+        None => Err("peer disconnected immediately")?,
+        Some(line) => line?,
+    };
+    let (_shutdown_sender, shutdown_receiver) = mpsc::unbounded::<Void>();
+    broker.send(Event::NewPeer {
+        name: name.clone(),
+        stream: Arc::clone(&stream),
+        shutdown: shutdown_receiver,
+    }).await.unwrap();
+
+    while let Some(line) = lines.next().await {
+        let line = line?;
+        let (dest, msg) = match line.find(':') {
+            None => continue,
+            Some(idx) => (&line[..idx], line[idx + 1 ..].trim()),
+        };
+        let dest: Vec<String> = dest.split(',').map(|name| name.trim().to_string()).collect();
+        let msg: String = msg.trim().to_string();
+
+        broker.send(Event::Message {
+            from: name.clone(),
+            to: dest,
+            msg,
+        }).await.unwrap();
+    }
+
+    Ok(())
+}
+
+async fn client_writer(
+    messages: &mut Receiver<String>,
+    stream: Arc<TcpStream>,
+    mut shutdown: Receiver<Void>,
+) -> Result<()> {
+    let mut stream = &*stream;
+    loop {
+        select! {
+            msg = messages.next() => match msg {
+                Some(msg) => stream.write_all(msg.as_bytes()).await?,
+                None => break,
+            },
+            void = shutdown.next() => match void {
+                Some(void) => match void {},
+                None => break,
+            }
+        }
+    }
+    Ok(())
+}
+
+#[derive(Debug)]
+enum Event {
+    NewPeer {
+        name: String,
+        stream: Arc<TcpStream>,
+        shutdown: Receiver<Void>,
+    },
+    Message {
+        from: String,
+        to: Vec<String>,
+        msg: String,
+    },
+}
+
+async fn broker(mut events: Receiver<Event>) {
+    let (disconnect_sender, mut disconnect_receiver) =
+        mpsc::unbounded::<(String, Receiver<String>)>();
+    let mut peers: HashMap<String, Sender<String>> = HashMap::new();
+
+    loop {
+        let event = select! {
+            event = events.next() => match event {
+                None => break,
+                Some(event) => event,
+            },
+            disconnect = disconnect_receiver.next() => {
+                let (name, _pending_messages) = disconnect.unwrap();
+                assert!(peers.remove(&name).is_some());
+                continue;
+            },
+        };
+        match event {
+            Event::Message { from, to, msg } => {
+                for addr in to {
+                    if let Some(peer) = peers.get_mut(&addr) {
+                        peer.send(format!("from {}: {}\n", from, msg)).await
+                            .unwrap()
+                    }
+                }
+            }
+            Event::NewPeer { name, stream, shutdown } => {
+                match peers.entry(name.clone()) {
+                    Entry::Occupied(..) => (),
+                    Entry::Vacant(entry) => {
+                        let (client_sender, mut client_receiver) = mpsc::unbounded();
+                        entry.insert(client_sender);
+                        let mut disconnect_sender = disconnect_sender.clone();
+                        spawn_and_log_error(async move {
+                            let res = client_writer(&mut client_receiver, stream, shutdown).await;
+                            disconnect_sender.send((name, client_receiver)).await
+                                .unwrap();
+                            res
+                        });
+                    }
+                }
+            }
+        }
+    }
+    drop(peers);
+    drop(disconnect_sender);
+    while let Some((_name, _pending_messages)) = disconnect_receiver.next().await {
+    }
+}
+
+fn spawn_and_log_error<F>(fut: F) -> task::JoinHandle<()>
+where
+    F: Future<Output = Result<()>> + Send + 'static,
+{
+    task::spawn(async move {
+        if let Err(e) = fut.await {
+            eprintln!("{}", e)
+        }
+    })
+}