Simplify module trait by combining produce/consume event methods into a single run method that runs in the module's own thread and can produce and/or consume events. Introduce an Envelope struct that encapsulates event + to/from so we can (eventually) tag every event and also limit where events are sent (e.g. you can have a specific module configured to talk or listen only to a certain other module).

src/event/mod.rs

@@ -1,5 +1,7 @@
 use {Message, Channel, User};
 
+use std::sync::Arc;
+
 pub enum Event {
     Message { message: Message },     // A user sends a message
 
@@ -9,3 +11,19 @@ pub enum Event {
     UserJoin { channel: Channel, user: User }, // A user joins a channel
     UserQuit { channel: Channel, user: User }  // A user quits a channel
 }
+
+pub struct Envelope {
+    pub from: Option<String>,
+    pub event: Arc<Event>,
+    pub to: Vec<String>
+}
+
+impl Envelope {
+    pub fn new (event: Event) -> Envelope {
+        Envelope {
+            from: None,
+            event: Arc::new(event),
+            to: vec![]
+        }
+    }
+}