repeat channel mode (+K <n>): block recently-repeated lines

src/channels.rs

@@ -19,6 +19,7 @@ pub struct Member {
     pub halfop: bool,             // +h (%)
     pub voice: bool,              // +v (+)
     pub joined: u64,              // unix ts this member joined (for +d delaymsg; 0 = unknown)
+    pub recent_msgs: Vec<String>, // +K repeat: this member's last few lines here
 }
 
 /// Prefix ranks, high→low — gate who may grant a prefix / kick whom.
@@ -157,6 +158,7 @@ pub struct ChanModes {
     pub kicknorejoin: Option<u32>,   // +J <secs> — block rejoin for N secs after a kick
     pub opmoderated: bool,           // +U — unprivileged users' messages go to ops only
     pub delaymsg: Option<u32>,       // +d <secs> — new joiners can't speak for N secs
+    pub repeat: Option<u32>,         // +K <n> — block a line repeated within your last n
 }
 
 impl ChanModes {

src/coremods/core_message.rs

@@ -361,6 +361,37 @@ pub(crate) fn deliver(s: &mut Server, uid: Uid, params: &[String], notice: bool)
                 }
             }
         }
+        // +K repeat — reject a line the sender just repeated; else remember it (ops exempt)
+        if let Some(n) = s.channels.get(&key).and_then(|c| c.modes.repeat) {
+            if s.rank(uid, &key) < RANK_HALFOP {
+                let repeated = s
+                    .channels
+                    .get(&key)
+                    .and_then(|c| c.members.get(&uid))
+                    .map(|m| m.recent_msgs.iter().any(|p| p == &body))
+                    .unwrap_or(false);
+                if repeated {
+                    if !notice {
+                        s.numeric(
+                            uid,
+                            ERR_CANNOTSENDTOCHAN,
+                            &format!("{target} :Cannot send to channel (+K: repeated message)"),
+                        );
+                    }
+                    return CmdResult::Fail;
+                }
+                if let Some(m) = s
+                    .channels
+                    .get_mut(&key)
+                    .and_then(|c| c.members.get_mut(&uid))
+                {
+                    m.recent_msgs.push(body.clone());
+                    while m.recent_msgs.len() > n as usize {
+                        m.recent_msgs.remove(0);
+                    }
+                }
+            }
+        }
         // deliver to every member except the sender and +D (deaf) users, tagging
         // per-recipient (server-time + any client-only tags on the line)
         let line = format!(":{prefix} {cmd} {target} :{body}");

src/mode.rs

@@ -91,6 +91,7 @@ static CHAN_MODES: &[&(dyn ChanMode + Sync)] = &[
     &KICKNOREJOIN,
     &OPMODERATED,
     &DELAYMSG,
+    &REPEAT,
 ];
 
 // --- prefix modes (+q/+a/+o/+h/+v): a per-member rank, needs a nick ----------
@@ -952,6 +953,47 @@ impl ChanMode for DelayMsgMode {
     }
 }
 
+/// +K `<n>` — block a message identical to one of the sender's previous `<n>`
+/// lines in this channel (InspIRCd `m_repeat`, simplified). Ops are exempt.
+struct RepeatMode;
+static REPEAT: RepeatMode = RepeatMode;
+impl ChanMode for RepeatMode {
+    fn letter(&self) -> char {
+        'K'
+    }
+    fn wants_param(&self, adding: bool) -> bool {
+        adding
+    }
+    fn apply(
+        &self,
+        s: &mut Server,
+        _chan: &str,
+        key: &str,
+        _uid: Uid,
+        adding: bool,
+        param: Option<&str>,
+    ) -> Applied {
+        if adding {
+            let Some(n) = param
+                .and_then(|p| p.parse::<u32>().ok())
+                .filter(|&n| n >= 1)
+            else {
+                return Applied::No;
+            };
+            let n = n.min(20);
+            if let Some(c) = s.channels.get_mut(key) {
+                c.modes.repeat = Some(n);
+            }
+            Applied::Yes(Some(n.to_string()))
+        } else {
+            if let Some(c) = s.channels.get_mut(key) {
+                c.modes.repeat = None;
+            }
+            Applied::Yes(None)
+        }
+    }
+}
+
 // === user modes ============================================================
 
 /// A user mode (+i/+w/+o) — same handler-object shape as [`ChanMode`], and the
@@ -1192,7 +1234,7 @@ mod tests {
 
     #[test]
     fn registry_covers_all_channel_modes() {
-        for c in "qaohvbeIklmntiszpONCTcSRMfjFLgGuBQAPJUd".chars() {
+        for c in "qaohvbeIklmntiszpONCTcSRMfjFLgGuBQAPJUdK".chars() {
             assert!(chan_mode(c).is_some(), "missing handler for +{c}");
         }
         assert!(chan_mode('y').is_none());

src/users.rs

@@ -418,7 +418,7 @@ impl Server {
             uid,
             RPL_MYINFO,
             &format!(
-                "{} echoircd-{VERSION} iowxsgBDIHrRzWc qaohvbeIklimnpstzCTcSNORMfjFLgGuBQAPJUd",
+                "{} echoircd-{VERSION} iowxsgBDIHrRzWc qaohvbeIklimnpstzCTcSNORMfjFLgGuBQAPJUdK",
                 self.name
             ),
         );
@@ -426,7 +426,7 @@ impl Server {
             uid,
             RPL_ISUPPORT,
             &format!(
-                "CHANTYPES=# PREFIX=(qaohv)~&@%+ CHANMODES=beIg,k,lfjFLHBJd,ACGMNOPQRSTUcimnpstuz EXTBAN=,cmn WATCH=128 MONITOR=128 SILENCE=32 CALLERID=g WHOX CHATHISTORY=256 MSGREFTYPES=timestamp,msgid UTF8ONLY CASEMAPPING=ascii NICKLEN=30 CHANNELLEN=50 NETWORK={} :are supported by this server",
+                "CHANTYPES=# PREFIX=(qaohv)~&@%+ CHANMODES=beIg,k,lfjFLHBJdK,ACGMNOPQRSTUcimnpstuz EXTBAN=,cmn WATCH=128 MONITOR=128 SILENCE=32 CALLERID=g WHOX CHATHISTORY=256 MSGREFTYPES=timestamp,msgid UTF8ONLY CASEMAPPING=ascii NICKLEN=30 CHANNELLEN=50 NETWORK={} :are supported by this server",
                 self.network
             ),
         );