Abstract away connection logic

cove-server/src/conn.rs

@@ -0,0 +1,156 @@
+use std::result;
+use std::sync::Arc;
+use std::time::Duration;
+
+use cove_core::packets::Packet;
+use futures::stream::{SplitSink, SplitStream};
+use futures::StreamExt;
+use rand::Rng;
+use tokio::net::TcpStream;
+use tokio::sync::mpsc::{self, UnboundedReceiver, UnboundedSender};
+use tokio::sync::Mutex;
+use tokio::try_join;
+use tokio_stream::wrappers::UnboundedReceiverStream;
+use tokio_tungstenite::tungstenite::{self, Message};
+use tokio_tungstenite::WebSocketStream;
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("WS error: {0}")]
+    Ws(#[from] tungstenite::Error),
+    #[error("MPSC error: {0}")]
+    Mpsc(#[from] mpsc::error::SendError<Message>),
+    #[error("Serde error: {0}")]
+    Serde(#[from] serde_json::Error),
+    #[error("client did not pong")]
+    NoPong,
+    #[error("illegal binary packet")]
+    IllegalBinaryPacket,
+}
+
+pub type Result<T> = result::Result<T, Error>;
+
+#[derive(Clone)]
+pub struct ConnTx {
+    tx: UnboundedSender<Message>,
+}
+
+impl ConnTx {
+    pub fn send(&self, packet: &Packet) -> Result<()> {
+        let msg = Message::Text(serde_json::to_string(packet)?);
+        self.tx.send(msg)?;
+        Ok(())
+    }
+}
+
+pub struct ConnRx {
+    ws_rx: SplitStream<WebSocketStream<TcpStream>>,
+    last_ping_payload: Arc<Mutex<Vec<u8>>>,
+}
+
+impl ConnRx {
+    pub async fn recv(&mut self) -> Result<Option<Packet>> {
+        loop {
+            let msg = match self.ws_rx.next().await {
+                None => return Ok(None),
+                Some(msg) => msg?,
+            };
+            let str = match msg {
+                Message::Text(str) => str,
+                Message::Pong(payload) => {
+                    *self.last_ping_payload.lock().await = payload;
+                    continue;
+                }
+                Message::Ping(_) => {
+                    // Tungstenite automatically replies to pings
+                    continue;
+                }
+                Message::Binary(_) => return Err(Error::IllegalBinaryPacket),
+                Message::Close(_) => return Ok(None),
+            };
+            let packet = serde_json::from_str(&str)?;
+            return Ok(Some(packet));
+        }
+    }
+}
+
+pub struct ConnMaintenance {
+    // Shoveling packets into the WS connection
+    rx: UnboundedReceiver<Message>,
+    ws_tx: SplitSink<WebSocketStream<TcpStream>, Message>,
+    // Pinging and ponging
+    tx: UnboundedSender<Message>,
+    ping_delay: Duration,
+    last_ping_payload: Arc<Mutex<Vec<u8>>>,
+}
+
+impl ConnMaintenance {
+    pub async fn perform(self) -> Result<()> {
+        let result = try_join!(
+            Self::shovel(self.rx, self.ws_tx),
+            Self::ping_pong(self.tx, self.ping_delay, self.last_ping_payload)
+        );
+        result.map(|_| ())
+    }
+
+    async fn shovel(
+        rx: UnboundedReceiver<Message>,
+        ws_tx: SplitSink<WebSocketStream<TcpStream>, Message>,
+    ) -> Result<()> {
+        UnboundedReceiverStream::new(rx)
+            .map(Ok)
+            .forward(ws_tx)
+            .await?;
+        Ok(())
+    }
+
+    async fn ping_pong(
+        tx: UnboundedSender<Message>,
+        ping_delay: Duration,
+        last_ping_payload: Arc<Mutex<Vec<u8>>>,
+    ) -> Result<()> {
+        let mut payload = [0u8; 8];
+
+        rand::thread_rng().fill(&mut payload);
+        // debug!("Sending first ping with payload {:?}", payload);
+        tx.send(Message::Ping(payload.to_vec()))?;
+        tokio::time::sleep(ping_delay).await;
+
+        loop {
+            let last_payload = last_ping_payload.lock().await;
+            if (&payload as &[u8]) != (&last_payload as &[u8]) {
+                // warn!("Invalid ping payload, client probably dead");
+                return Err(Error::NoPong);
+            }
+
+            rand::thread_rng().fill(&mut payload);
+            // debug!("Sending ping with payload {:?}", payload);
+            tx.send(Message::Ping(payload.to_vec()))?;
+            tokio::time::sleep(ping_delay).await;
+        }
+    }
+}
+
+pub async fn new(
+    stream: TcpStream,
+    ping_delay: Duration,
+) -> Result<(ConnTx, ConnRx, ConnMaintenance)> {
+    let (ws_tx, ws_rx) = tokio_tungstenite::accept_async(stream).await?.split();
+    let (tx, rx) = mpsc::unbounded_channel();
+    let last_ping_payload = Arc::new(Mutex::new(vec![]));
+
+    let conn_tx = ConnTx { tx: tx.clone() };
+    let conn_rx = ConnRx {
+        ws_rx,
+        last_ping_payload: last_ping_payload.clone(),
+    };
+    let conn_maintenance = ConnMaintenance {
+        ws_tx,
+        rx,
+        tx,
+        ping_delay,
+        last_ping_payload,
+    };
+
+    Ok((conn_tx, conn_rx, conn_maintenance))
+}