Initial Hotplug support (#8)

This allows to dynamically add clients when an event is received from an unknown IP address.

The user is asked to confirm any unknown connection from new clients.

Currently the back-ends for event producing and consuming are not yet notified, so events will not be received and sent to the newly created clients.

src/client.rs

@@ -1,4 +1,4 @@
-use std::{net::SocketAddr, error::Error, fmt::Display};
+use std::{net::SocketAddr, error::Error, fmt::Display, sync::{Arc, atomic::{AtomicBool, Ordering, AtomicU32}, RwLock}};
 
 use crate::{config, dns};
 
@@ -29,8 +29,9 @@ pub enum ClientEvent {
 }
 
 pub struct ClientManager {
-    next_id: u32,
-    clients: Vec<Client>,
+    next_id: AtomicU32,
+    clients: RwLock<Vec<Client>>,
+    subscribers: RwLock<Vec<Arc<AtomicBool>>>,
 }
 
 pub type ClientHandle = u32;
@@ -47,7 +48,7 @@ impl Display for ClientConfigError {
 impl Error for ClientConfigError {}
 
 impl ClientManager {
-    fn add_client(&mut self, client: &config::Client, pos: Position) -> Result<(), Box<dyn Error>> {
+    fn add_client(&self, client: &config::Client, pos: Position) -> Result<(), Box<dyn Error>> {
         let ip = match client.ip {
             Some(ip) => ip,
             None => match &client.host_name {
@@ -60,16 +61,24 @@ impl ClientManager {
         Ok(())
     }
 
-    fn new_id(&mut self) -> ClientHandle {
-        self.next_id += 1;
-        self.next_id
+    fn notify(&self) {
+        for subscriber in self.subscribers.read().unwrap().iter() {
+            subscriber.store(true, Ordering::SeqCst);
+        }
+    }
+
+    fn new_id(&self) -> ClientHandle {
+        let id = self.next_id.load(Ordering::Acquire);
+        self.next_id.store(id + 1, Ordering::Release);
+        id as ClientHandle
     }
 
     pub fn new(config: &config::Config) -> Result<Self, Box<dyn Error>> {
 
-        let mut client_manager = ClientManager {
-            next_id: 0,
-            clients: Vec::new(),
+        let client_manager = ClientManager {
+            next_id: AtomicU32::new(0),
+            clients: RwLock::new(Vec::new()),
+            subscribers: RwLock::new(vec![]),
         };
 
         // add clients from config
@@ -80,13 +89,18 @@ impl ClientManager {
         Ok(client_manager)
     }
 
-    pub fn register_client(&mut self, addr: SocketAddr, pos: Position) {
+    pub fn register_client(&self, addr: SocketAddr, pos: Position) {
         let handle = self.new_id();
         let client = Client { addr, pos, handle };
-        self.clients.push(client);
+        self.clients.write().unwrap().push(client);
+        self.notify();
     }
 
     pub fn get_clients(&self) -> Vec<Client> {
-        self.clients.clone()
+        self.clients.read().unwrap().clone()
+    }
+
+    pub fn subscribe(&self, subscriber: Arc<AtomicBool>) {
+        self.subscribers.write().unwrap().push(subscriber);
     }
 }