Events: Add (re)connect success/fail events.

These should allow bots to hook up events to a variety of important connection events as required. This was primarily motivated by the user who raised dcb6ad9.

Although I really would have liked to squeeze in (finite) reconnection attempts with exponential backoff, so that automated repeat attempts could be neatly handled, `Config` was accidentally *not* made non-exhaustive. Adding this and its needed configuration would then be a breaking change. This should warn users about an accidentally dead connection, until the next version can be put forth.

src/driver/tasks/mod.rs

@@ -12,6 +12,7 @@ use super::{
     connection::{error::Error as ConnectionError, Connection},
     Config,
 };
+use crate::events::CoreContext;
 use flume::{Receiver, RecvError, Sender};
 use message::*;
 use tokio::runtime::Handle;
@@ -75,12 +76,21 @@ async fn runner(mut config: Config, rx: Receiver<CoreMessage>, tx: Sender<CoreMe
                     Ok(connection) => {
                         // Other side may not be listening: this is fine.
                         let _ = tx.send(Ok(()));
+
+                        let _ = interconnect
+                            .events
+                            .send(EventMessage::FireCoreEvent(CoreContext::DriverConnect));
+
                         Some(connection)
                     },
                     Err(why) => {
                         // See above.
                         let _ = tx.send(Err(why));
 
+                        let _ = interconnect.events.send(EventMessage::FireCoreEvent(
+                            CoreContext::DriverConnectFailed,
+                        ));
+
                         None
                     },
                 };
@@ -145,10 +155,19 @@ async fn runner(mut config: Config, rx: Receiver<CoreMessage>, tx: Sender<CoreMe
                             .await
                             .map_err(|e| {
                                 error!("Catastrophic connection failure. Stopping. {:?}", e);
+                                let _ = interconnect.events.send(EventMessage::FireCoreEvent(
+                                    CoreContext::DriverReconnectFailed,
+                                ));
                                 e
                             })
                             .ok();
                     }
+
+                    if connection.is_some() {
+                        let _ = interconnect
+                            .events
+                            .send(EventMessage::FireCoreEvent(CoreContext::DriverReconnect));
+                    }
                 }
             },
             Ok(CoreMessage::FullReconnect) =>
@@ -159,9 +178,18 @@ async fn runner(mut config: Config, rx: Receiver<CoreMessage>, tx: Sender<CoreMe
                         .await
                         .map_err(|e| {
                             error!("Catastrophic connection failure. Stopping. {:?}", e);
+                            let _ = interconnect.events.send(EventMessage::FireCoreEvent(
+                                CoreContext::DriverReconnectFailed,
+                            ));
                             e
                         })
                         .ok();
+
+                    if connection.is_some() {
+                        let _ = interconnect
+                            .events
+                            .send(EventMessage::FireCoreEvent(CoreContext::DriverReconnect));
+                    }
                 },
             Ok(CoreMessage::RebuildInterconnect) => {
                 interconnect.restart_volatile_internals();

src/events/context.rs

@@ -69,6 +69,16 @@ pub enum EventContext<'a> {
     ClientConnect(ClientConnect),
     /// Fired whenever a client disconnects.
     ClientDisconnect(ClientDisconnect),
+    /// Fires when this driver successully connects to a voice channel.
+    DriverConnect,
+    /// Fires when this driver successful reconnects after a network error.
+    DriverReconnect,
+    /// Fires when this driver fails to connect to a voice channel.
+    DriverConnectFailed,
+    /// Fires when this driver fails to reconnect to a voice channel after a network error.
+    ///
+    /// Users will need to manually reconnect on receipt of this error.
+    DriverReconnectFailed,
 }
 
 #[derive(Clone, Debug)]
@@ -91,6 +101,10 @@ pub enum CoreContext {
     },
     ClientConnect(ClientConnect),
     ClientDisconnect(ClientDisconnect),
+    DriverConnect,
+    DriverReconnect,
+    DriverConnectFailed,
+    DriverReconnectFailed,
 }
 
 impl<'a> CoreContext {
@@ -125,6 +139,10 @@ impl<'a> CoreContext {
             },
             ClientConnect(evt) => EventContext::ClientConnect(*evt),
             ClientDisconnect(evt) => EventContext::ClientDisconnect(*evt),
+            DriverConnect => EventContext::DriverConnect,
+            DriverReconnect => EventContext::DriverReconnect,
+            DriverConnectFailed => EventContext::DriverConnectFailed,
+            DriverReconnectFailed => EventContext::DriverReconnectFailed,
         }
     }
 }
@@ -142,6 +160,10 @@ impl EventContext<'_> {
             RtcpPacket { .. } => Some(CoreEvent::RtcpPacket),
             ClientConnect { .. } => Some(CoreEvent::ClientConnect),
             ClientDisconnect { .. } => Some(CoreEvent::ClientDisconnect),
+            DriverConnect => Some(CoreEvent::DriverConnect),
+            DriverReconnect => Some(CoreEvent::DriverReconnect),
+            DriverConnectFailed => Some(CoreEvent::DriverConnectFailed),
+            DriverReconnectFailed => Some(CoreEvent::DriverReconnectFailed),
             _ => None,
         }
     }

src/events/core.rs

@@ -29,4 +29,14 @@ pub enum CoreEvent {
     ClientConnect,
     /// Fires whenever a user disconnects from the same stream as the bot.
     ClientDisconnect,
+    /// Fires when this driver successully connects to a voice channel.
+    DriverConnect,
+    /// Fires when this driver successful reconnects after a network error.
+    DriverReconnect,
+    /// Fires when this driver fails to connect to a voice channel.
+    DriverConnectFailed,
+    /// Fires when this driver fails to reconnect to a voice channel after a network error.
+    ///
+    /// Users will need to manually reconnect on receipt of this error.
+    DriverReconnectFailed,
 }