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

echoircd.conf.example

@@ -181,6 +181,8 @@ limits {
     # multiline_maxlines 24;      # draft/multiline: max lines
     # chathistory_limit  256;     # CHATHISTORY messages kept per conversation
     # chathistory_maxage 604800;  # max age (secs) a client may request (7 days)
+    # event_playback     yes;     # record JOIN/PART/QUIT/NICK/MODE/TOPIC/KICK into
+    #                             # history for draft/event-playback clients (no = off)
     # dccallow_maxentries 20;     # /DCCALLOW list entries per user
     # http_max_concurrent 32;     # in-flight outbound HTTP requests (API modules)
 }

src/channels.rs

@@ -1198,9 +1198,18 @@ impl Server {
         } else {
             None
         };
+        // draft/event-playback: JOIN/PART/… events in the +H backlog only for cap clients.
+        let want_events = self
+            .users
+            .get(&uid)
+            .map(|u| u.caps.event_playback)
+            .unwrap_or(false);
         let out: Vec<String> = match self.ext.get::<History>().and_then(|h| h.0.get(key)) {
             Some(buf) => {
-                let mut recent: Vec<&HistMsg> = buf.iter().filter(|m| m.ts >= cutoff).collect();
+                let mut recent: Vec<&HistMsg> = buf
+                    .iter()
+                    .filter(|m| m.ts >= cutoff && (want_events || !m.is_event()))
+                    .collect();
                 let start = recent.len().saturating_sub(lines as usize);
                 recent.drain(..start);
                 recent
@@ -1210,7 +1219,10 @@ impl Server {
                         if let Some(b) = &bref {
                             tags.push_str(&format!(";batch={b}"));
                         }
-                        format!("@{tags} :{} {} {name} :{}", m.prefix, m.verb, m.text)
+                        match &m.raw {
+                            Some(raw) => format!("@{tags} {raw}"),
+                            None => format!("@{tags} :{} {} {name} :{}", m.prefix, m.verb, m.text),
+                        }
                     })
                     .collect()
             }

src/coremods/core_channel.rs

@@ -622,7 +622,9 @@ impl Command for Kick {
                         .get(&vuuid)
                         .map(|r| r.nick.clone())
                         .unwrap_or_else(|| victim.to_string());
-                    s.to_channel(&key, &format!(":{prefix} KICK {chan} {vnick} :{reason}"), None);
+                    let kline = format!(":{prefix} KICK {chan} {vnick} :{reason}");
+                    crate::modules::chathistory::record_event(s, &key, &kline);
+                    s.to_channel(&key, &kline, None);
                     s.propagate_kick(uid, chan, victim, &reason);
                     if let Some(ch) = s.channels.get_mut(&key) {
                         ch.rmembers.remove(&vuuid);
@@ -760,7 +762,9 @@ impl Command for TopicCmd {
                 ts: now(),
             });
         }
-        s.to_channel(&key, &format!(":{prefix} TOPIC {target} :{text}"), None);
+        let tline = format!(":{prefix} TOPIC {target} :{text}");
+        crate::modules::chathistory::record_event(s, &key, &tline);
+        s.to_channel(&key, &tline, None);
         s.propagate_topic(uid, target, &text); // tell links
         CmdResult::Ok
     }

src/coremods/core_mode.rs

@@ -175,11 +175,9 @@ pub fn apply_mode(s: &mut Server, uid: Uid, params: &[String]) -> CmdResult {
         {
             crate::modules::hidemode::broadcast(s, &key, target, uid, &prefix, &changes);
         } else {
-            s.to_channel(
-                &key,
-                &format!(":{prefix} MODE {target} {applied}{pstr}"),
-                None,
-            );
+            let mline = format!(":{prefix} MODE {target} {applied}{pstr}");
+            crate::modules::chathistory::record_event(s, &key, &mline);
+            s.to_channel(&key, &mline, None);
         }
         // links: a timestamped FMODE sourced from the acting user's uuid
         let src_uuid = s.users[&uid].uuid.clone();

src/modules/chathistory.rs

@@ -28,9 +28,19 @@ pub struct HistMsg {
     pub ts: u64,
     pub msgid: String,
     pub prefix: String,     // sender's nick!user@host at send time
-    pub verb: &'static str, // "PRIVMSG" or "NOTICE"
+    pub verb: &'static str, // "PRIVMSG"/"NOTICE" for messages; the event verb otherwise
     pub target: String,     // original target (channel, or the DM recipient)
     pub text: String,
+    /// `Some(full ":prefix VERB …" line)` for a channel *event* (JOIN/PART/QUIT/NICK/
+    /// MODE/TOPIC/KICK) replayed under `draft/event-playback`; `None` for a message.
+    pub raw: Option<String>,
+}
+
+impl HistMsg {
+    /// An event (non-message) entry — filtered out for clients without event-playback.
+    pub fn is_event(&self) -> bool {
+        self.raw.is_some()
+    }
 }
 
 /// conversation key (`#chan` or a DM-pair key) -> capped ring. Stored in `Server.ext`.
@@ -62,6 +72,43 @@ pub fn record(
         verb,
         target: target.to_string(),
         text: text.to_string(),
+        raw: None,
+    });
+    while buf.len() > cap {
+        buf.pop_front();
+    }
+}
+
+/// Record a channel *event* (`line` = the full `:prefix VERB …` wire form) into the
+/// same per-conversation ring, for replay under `draft/event-playback`. It carries a
+/// fresh msgid and replays verbatim; clients without the cap never see it. Off when
+/// `event_playback = no`. Called from the local JOIN/PART/QUIT/NICK/MODE/TOPIC/KICK
+/// paths — see [`crate::modules::event_playback`] and the channel/mode command code.
+pub fn record_event(s: &mut Server, key: &str, line: &str) {
+    if !s.conf_bool("event_playback", true) {
+        return;
+    }
+    let cap = limit(s);
+    let msgid = s.next_msgid();
+    let prefix = line
+        .strip_prefix(':')
+        .and_then(|l| l.split(' ').next())
+        .unwrap_or("")
+        .to_string();
+    let buf = s
+        .ext
+        .get_or_insert_with::<History>(History::default)
+        .0
+        .entry(key.to_string())
+        .or_default();
+    buf.push_back(HistMsg {
+        ts: now(),
+        msgid,
+        prefix,
+        verb: "*",
+        target: key.to_string(),
+        text: String::new(),
+        raw: Some(line.to_string()),
     });
     while buf.len() > cap {
         buf.pop_front();
@@ -230,6 +277,12 @@ impl Command for ChatHistory {
             .and_then(|l| l.parse::<usize>().ok())
             .unwrap_or(50)
             .clamp(1, limit(s));
+        // draft/event-playback: include JOIN/PART/… events only for clients that asked.
+        let want_events = s
+            .users
+            .get(&uid)
+            .map(|u| u.caps.event_playback)
+            .unwrap_or(false);
 
         let bref = s.next_msgid().replace('-', "");
         let mut lines: Vec<String> = Vec::new();
@@ -303,7 +356,15 @@ impl Command for ChatHistory {
                     }
                 };
                 for m in picked {
-                    lines.push(format!(
+                    if m.is_event() && !want_events {
+                        continue;
+                    }
+                    lines.push(match &m.raw {
+                        // an event replays as its exact wire line + history tags
+                        Some(raw) => {
+                            format!("@time={};msgid={};batch={bref} {raw}", iso_time(m.ts), m.msgid)
+                        }
+                        None => format!(
                             "@time={};msgid={};batch={bref} :{} {} {} :{}",
                             iso_time(m.ts),
                             m.msgid,
@@ -311,7 +372,8 @@ impl Command for ChatHistory {
                             m.verb,
                             m.target,
                             m.text
-                    ));
+                        ),
+                    });
                 }
             }
         }
@@ -437,6 +499,7 @@ mod tests {
             verb: "PRIVMSG",
             target: "#c".into(),
             text: "hi".into(),
+            raw: None,
         };
         {
             let h = s.ext.get_or_insert_with::<History>(History::default);
@@ -448,4 +511,20 @@ mod tests {
         assert!(h.0.contains_key("#fresh"), "recent conversation kept");
         assert!(!h.0.contains_key("#stale"), "stale conversation GC'd");
     }
+
+    // draft/event-playback: record_event stores a verbatim event entry flagged so
+    // CHATHISTORY/+H can filter it out for clients without the cap; messages aren't.
+    #[test]
+    fn event_playback_records_and_flags_events() {
+        let (tx, _rx) = mpsc::channel();
+        let mut s = Server::new(Config::default(), tx, Arc::new(AtomicU64::new(1)));
+        record(&mut s, "#c", "a!u@h", "PRIVMSG", "#c", "hi", "m1");
+        record_event(&mut s, "#c", ":a!u@h JOIN #c");
+        let buf = &s.ext.get::<History>().unwrap().0["#c"];
+        assert_eq!(buf.len(), 2, "one message + one event stored");
+        assert!(!buf[0].is_event(), "the PRIVMSG is not an event");
+        assert!(buf[1].is_event(), "the recorded JOIN is an event");
+        assert_eq!(buf[1].raw.as_deref(), Some(":a!u@h JOIN #c"));
+        assert!(!buf[1].msgid.is_empty(), "event carries a msgid for replay");
+    }
 }

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);
+        }
+    }
+}

src/modules/mod.rs

@@ -24,6 +24,7 @@ pub mod connflood;
 pub mod customprefix;
 pub mod customtitle;
 pub mod dccallow;
+pub mod event_playback;
 pub mod denychans;
 pub mod disable;
 pub mod dnsbl;
@@ -117,6 +118,7 @@ pub fn default_modules() -> Vec<Box<dyn Module>> {
         Box::new(opertypes::OperTypes),
         Box::new(permchannels::PermChannels::default()),
         Box::new(chathistory::ChatHistoryGc),
+        Box::new(event_playback::EventPlayback),
         Box::new(account_registration::AcctRegGc),
     ]
 }

src/users.rs

@@ -157,6 +157,7 @@ define_caps! {
     "labeled-response" => labeled_response,
     "batch" => batch,
     "draft/chathistory" => chathistory,
+    "draft/event-playback" => event_playback,
     "draft/message-redaction" => message_redaction,
     "draft/pre-away" => pre_away,
     "draft/metadata-2" => metadata,
@@ -424,6 +425,7 @@ impl Server {
             targets.insert(uid);
             let chans: Vec<String> = self.users[&uid].channels.iter().cloned().collect();
             for key in &chans {
+                crate::modules::chathistory::record_event(self, key, &line);
                 if let Some(ch) = self.channels.get(key) {
                     // +D delayjoin: a still-hidden member's NICK isn't shown here
                     if ch.members.get(&uid).map(|m| m.hidden).unwrap_or(false) {