Adding some IPC.

src/event_manager.rs

@@ -0,0 +1,89 @@
+use std::{collections::VecDeque, path::Path, sync::Arc};
+
+use color_eyre::Result;
+use tokio::{
+    io::AsyncWriteExt,
+    net::{UnixListener, UnixStream},
+    sync::{RwLock, broadcast},
+};
+use tracing::error;
+
+use crate::event::Event;
+
+// Hard coding for now.  Maybe make this a parameter to new.
+const EVENT_BUF_MAX: usize = 1000;
+
+// Manager for communication with plugins.
+pub struct EventManager {
+    announce: broadcast::Sender<String>, // Everything broadcasts here.
+    events: Arc<RwLock<VecDeque<String>>>, // Ring buffer.
+}
+
+impl EventManager {
+    pub fn new() -> Result<Self> {
+        let (announce, _) = broadcast::channel(100);
+
+        Ok(Self {
+            announce,
+            events: Arc::new(RwLock::new(VecDeque::<String>::new())),
+        })
+    }
+
+    pub async fn broadcast(&self, event: &Event) -> Result<()> {
+        let msg = serde_json::to_string(event)? + "\n";
+
+        let mut events = self.events.write().await;
+
+        if events.len() >= EVENT_BUF_MAX {
+            events.pop_front();
+        }
+
+        events.push_back(msg.clone());
+        drop(events);
+
+        let _ = self.announce.send(msg);
+
+        Ok(())
+    }
+
+    pub async fn start_listening(self: Arc<Self>, path: impl AsRef<Path>) {
+        let listener = UnixListener::bind(path).unwrap();
+
+        loop {
+            match listener.accept().await {
+                Ok((stream, _)) => {
+                    // Spawn a new stream for the plugin.  The loop
+                    // runs recursively from there.
+                    let broadcaster = Arc::clone(&self);
+                    tokio::spawn(async move {
+                        // send events.
+                        let _ = broadcaster.send_events(stream).await;
+                    });
+                }
+                Err(e) => error!("Accept error: {e}"),
+            }
+        }
+    }
+
+    async fn send_events(&self, stream: UnixStream) -> Result<()> {
+        let mut writer = stream;
+
+        // Take care of history.
+        let events = self.events.read().await;
+        for event in events.iter() {
+            writer.write_all(event.as_bytes()).await?;
+        }
+        drop(events);
+
+        // Now just broadcast the new events.
+        let mut rx = self.announce.subscribe();
+        while let Ok(event) = rx.recv().await {
+            if writer.write_all(event.as_bytes()).await.is_err() {
+                // *click*
+                break;
+            }
+        }
+
+        Ok(())
+    }
+}