modules: draft/event-playback — record JOIN/PART/QUIT/NICK/MODE/TOPIC/KICK into CHATHISTORY, replayed only for cap clients (event_playback config, default on)

src/modules/event_playback.rs

@@ -0,0 +1,61 @@
+//! draft/event-playback — replay channel *events* (JOIN/PART/QUIT/NICK/MODE/TOPIC/
+//! KICK) in CHATHISTORY, interleaved with messages, for clients that negotiate the
+//! cap. Without it, history stays messages-only (the classic behaviour).
+//!
+//! Events are recorded into the same per-conversation ring as messages
+//! ([`crate::modules::chathistory::record_event`]) and replayed verbatim; the CHATHISTORY
+//! command and the `+H` join-backlog filter them out for clients lacking the cap.
+//! JOIN/PART/QUIT are captured here through the module lifecycle hooks; NICK/MODE/TOPIC/
+//! KICK have no hook, so they call `record_event` directly from their command paths.
+//! The whole feature is gated by `event_playback` (default on) inside `record_event`.
+
+use crate::modules::chathistory::record_event;
+use crate::module::Module;
+use crate::server::Server;
+use crate::Uid;
+
+pub struct EventPlayback;
+
+impl Module for EventPlayback {
+    fn name(&self) -> &'static str {
+        "event-playback"
+    }
+
+    fn on_join(&mut self, srv: &mut Server, uid: Uid, chan: &str) {
+        let Some(prefix) = srv.users.get(&uid).map(|u| u.prefix()) else {
+            return;
+        };
+        let key = chan.to_ascii_lowercase();
+        record_event(srv, &key, &format!(":{prefix} JOIN {chan}"));
+    }
+
+    fn on_part(&mut self, srv: &mut Server, uid: Uid, chan: &str, reason: &str) {
+        let Some(prefix) = srv.users.get(&uid).map(|u| u.prefix()) else {
+            return;
+        };
+        let key = chan.to_ascii_lowercase();
+        let line = if reason.is_empty() {
+            format!(":{prefix} PART {chan}")
+        } else {
+            format!(":{prefix} PART {chan} :{reason}")
+        };
+        record_event(srv, &key, &line);
+    }
+
+    fn on_user_quit(&mut self, srv: &mut Server, uid: Uid, reason: &str) {
+        // A QUIT isn't channel-scoped on the wire, so mirror it into every channel the
+        // user still shares — that's where a scrolling client expects to see it.
+        let Some((prefix, chans)) = srv.users.get(&uid).map(|u| {
+            (
+                u.prefix(),
+                u.channels.iter().cloned().collect::<Vec<String>>(),
+            )
+        }) else {
+            return;
+        };
+        let line = format!(":{prefix} QUIT :{reason}");
+        for key in chans {
+            record_event(srv, &key, &line);
+        }
+    }
+}