1 files changed, 141 insertions, 0 deletions
diff --git a/p2p/src/listener.rs b/p2p/src/listener.rs
new file mode 100644
index 0000000..ee92536
--- /dev/null
+++ b/p2p/src/listener.rs
@@ -0,0 +1,141 @@
+use std::{future::Future, sync::Arc};
+
+use log::{error, info, trace};
+
+use karyons_core::{
+    async_utils::{TaskGroup, TaskResult},
+    Executor,
+};
+
+use karyons_net::{listen, Conn, Endpoint, Listener as NetListener};
+
+use crate::{
+    monitor::{ConnEvent, Monitor},
+    slots::ConnectionSlots,
+    Result,
+};
+
+/// Responsible for creating inbound connections with other peers.
+pub struct Listener {
+    /// Managing spawned tasks.
+    task_group: TaskGroup,
+
+    /// Manages available inbound slots.
+    connection_slots: Arc<ConnectionSlots>,
+
+    /// Responsible for network and system monitoring.
+    monitor: Arc<Monitor>,
+}
+
+impl Listener {
+    /// Creates a new Listener
+    pub fn new(connection_slots: Arc<ConnectionSlots>, monitor: Arc<Monitor>) -> Arc<Self> {
+        Arc::new(Self {
+            connection_slots,
+            task_group: TaskGroup::new(),
+            monitor,
+        })
+    }
+
+    /// Starts a listener on the given `endpoint`. For each incoming connection
+    /// that is accepted, it invokes the provided `callback`, and pass the
+    /// connection to the callback.
+    ///
+    /// Returns the resloved listening endpoint.
+    pub async fn start<'a, Fut>(
+        self: &Arc<Self>,
+        ex: Executor<'a>,
+        endpoint: Endpoint,
+        // https://github.com/rust-lang/rfcs/pull/2132
+        callback: impl FnOnce(Conn) -> Fut + Clone + Send + 'a,
+    ) -> Result<Endpoint>
+    where
+        Fut: Future<Output = Result<()>> + Send + 'a,
+    {
+        let listener = match listen(&endpoint).await {
+            Ok(listener) => {
+                self.monitor
+                    .notify(&ConnEvent::Listening(endpoint.clone()).into())
+                    .await;
+                listener
+            }
+            Err(err) => {
+                error!("Failed to listen on {endpoint}: {err}");
+                self.monitor
+                    .notify(&ConnEvent::ListenFailed(endpoint).into())
+                    .await;
+                return Err(err.into());
+            }
+        };
+
+        let resolved_endpoint = listener.local_endpoint()?;
+
+        info!("Start listening on {endpoint}");
+
+        let selfc = self.clone();
+        self.task_group.spawn(
+            ex.clone(),
+            selfc.listen_loop(ex.clone(), listener, callback),
+            |res| async move {
+                if let TaskResult::Completed(Err(err)) = res {
+                    error!("Listen loop stopped: {endpoint} {err}");
+                }
+            },
+        );
+        Ok(resolved_endpoint)
+    }
+
+    /// Shuts down the listener
+    pub async fn shutdown(&self) {
+        self.task_group.cancel().await;
+    }
+
+    async fn listen_loop<'a, Fut>(
+        self: Arc<Self>,
+        ex: Executor<'a>,
+        listener: Box<dyn NetListener>,
+        callback: impl FnOnce(Conn) -> Fut + Clone + Send + 'a,
+    ) -> Result<()>
+    where
+        Fut: Future<Output = Result<()>> + Send + 'a,
+    {
+        loop {
+            // Wait for an available inbound slot.
+            self.connection_slots.wait_for_slot().await;
+            let result = listener.accept().await;
+
+            let conn = match result {
+                Ok(c) => {
+                    self.monitor
+                        .notify(&ConnEvent::Accepted(c.peer_endpoint()?).into())
+                        .await;
+                    c
+                }
+                Err(err) => {
+                    error!("Failed to accept a new connection: {err}");
+                    self.monitor.notify(&ConnEvent::AcceptFailed.into()).await;
+                    return Err(err.into());
+                }
+            };
+
+            self.connection_slots.add();
+
+            let selfc = self.clone();
+            let endpoint = conn.peer_endpoint()?;
+            let on_disconnect = |res| async move {
+                if let TaskResult::Completed(Err(err)) = res {
+                    trace!("Inbound connection dropped: {err}");
+                }
+                selfc
+                    .monitor
+                    .notify(&ConnEvent::Disconnected(endpoint).into())
+                    .await;
+                selfc.connection_slots.remove().await;
+            };
+
+            let callback = callback.clone();
+            self.task_group
+                .spawn(ex.clone(), callback(conn), on_disconnect);
+        }
+    }
+}