refactor(networkmanager): store property watcher join handles & stop them when no longer needed

Also optimise dbus connection and proxy creation.

src/clients/networkmanager/mod.rs

@@ -1,9 +1,10 @@
 use color_eyre::Result;
 use color_eyre::eyre::Ok;
 use futures_lite::StreamExt;
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
 use std::sync::Arc;
 use tokio::sync::{RwLock, broadcast};
+use tokio::task::JoinHandle;
 use tracing::debug;
 use zbus::Connection;
 use zbus::zvariant::ObjectPath;
@@ -45,17 +46,27 @@ struct ClientInner {
     controller_sender: broadcast::Sender<ClientToModuleEvent>,
     sender: broadcast::Sender<ModuleToClientEvent>,
     devices: RwLock<HashSet<ObjectPath<'static>>>,
+    watchers: RwLock<HashMap<ObjectPath<'static>, Device>>,
+    // TODO: Maybe find some way to late-init a dbus connection here
+    //     so we can just clone it when we need it instead of awaiting it every time
+}
+
+#[derive(Debug)]
+struct Device {
+    state_watcher: JoinHandle<Result<()>>,
 }
 
 impl ClientInner {
     fn new() -> ClientInner {
         let (controller_sender, _) = broadcast::channel(64);
         let (sender, _) = broadcast::channel(8);
-        let devices = RwLock::new(HashSet::<ObjectPath>::new());
+        let devices = RwLock::new(HashSet::new());
+        let watchers = RwLock::new(HashMap::new());
         ClientInner {
             controller_sender,
             sender,
             devices,
+            watchers,
         }
     }
 
@@ -70,11 +81,11 @@ impl ClientInner {
         Ok(())
     }
 
-    pub fn subscribe(&self) -> broadcast::Receiver<ClientToModuleEvent> {
+    fn subscribe(&self) -> broadcast::Receiver<ClientToModuleEvent> {
         self.controller_sender.subscribe()
     }
 
-    pub fn get_sender(&self) -> broadcast::Sender<ModuleToClientEvent> {
+    fn get_sender(&self) -> broadcast::Sender<ModuleToClientEvent> {
         self.sender.clone()
     }
 
@@ -94,6 +105,8 @@ impl ClientInner {
                 .map(ObjectPath::to_owned)
                 .collect::<HashSet<_>>();
 
+            // TODO: Use `self.watchers` instead of `self.devices`, which requires creating all property watchers straightaway
+
             // Atomic read-then-write of `devices`
             let mut devices_locked = self.devices.write().await;
             let devices_snapshot = devices_locked.clone();
@@ -105,9 +118,16 @@ impl ClientInner {
                 spawn(self.watch_device(added_device.to_owned()));
             }
 
-            let _removed_devices = devices_snapshot.difference(&new_devices);
-            // TODO: Store join handles for watchers and abort them when their device is removed
             // TODO: Inform module of removed devices
+            let removed_devices = devices_snapshot.difference(&new_devices);
+            for removed_device in removed_devices {
+                let mut watchers = self.watchers.write().await;
+                let device = watchers.get(removed_device).unwrap();
+                device.state_watcher.abort();
+                watchers.remove(removed_device);
+
+                debug!("D-bus device state watcher for {} stopped", removed_device);
+            }
         }
 
         Ok(())
@@ -117,13 +137,13 @@ impl ClientInner {
         &'static self,
         mut receiver: broadcast::Receiver<ModuleToClientEvent>,
     ) -> Result<()> {
+        let dbus_connection = Connection::system().await?;
+
         while let Result::Ok(event) = receiver.recv().await {
             match event {
                 ModuleToClientEvent::NewController => {
                     debug!("Client received NewController event");
 
-                    let dbus_connection = Connection::system().await?;
-
                     // We create a local clone here to avoid holding the lock for too long
                     let devices_snapshot = self.devices.read().await.clone();
 
@@ -148,16 +168,20 @@ impl ClientInner {
     }
 
     async fn watch_device(&'static self, path: ObjectPath<'static>) -> Result<()> {
-        let dbus_connection = Connection::system().await?;
-        let device = DeviceDbusProxy::new(&dbus_connection, path).await?;
+        debug_assert!(!self.watchers.read().await.contains_key(&path));
 
-        spawn(self.watch_device_state(device));
+        let state_watcher = spawn(self.watch_device_state(path.clone()));
+        self.watchers
+            .write()
+            .await
+            .insert(path, Device { state_watcher });
 
         Ok(())
     }
 
-    async fn watch_device_state(&'static self, device: DeviceDbusProxy<'_>) -> Result<()> {
-        let path = device.inner().path();
+    async fn watch_device_state(&'static self, path: ObjectPath<'_>) -> Result<()> {
+        let dbus_connection = Connection::system().await?;
+        let device = DeviceDbusProxy::new(&dbus_connection, path.clone()).await?;
 
         debug!("D-Bus device state watcher for {} starting", path);