channel +H chanhistory: replay recent messages to joiners (m_chanhistory), reuses the history store

src/channels.rs

@@ -6,7 +6,7 @@ use std::collections::{HashMap, HashSet};
 
 use crate::module::Hook;
 use crate::numeric::*;
-use crate::server::{now, Server};
+use crate::server::{iso_time, now, HistMsg, Server};
 use crate::Uid;
 
 /// Per-member prefix modes (+q/+a/+o/+h/+v). Flag modes live in [`ChanModes`].
@@ -146,6 +146,7 @@ pub struct ChanModes {
     pub joinflood: Option<Rate>,     // +j
     pub nickflood: Option<Rate>,     // +F
     pub redirect: Option<String>,    // +L <#target> — when full, send there
+    pub history: Option<(u32, u64)>, // +H <lines>:<secs> — replay recent messages to joiners
 }
 
 impl ChanModes {
@@ -217,6 +218,9 @@ impl ChanModes {
         if self.redirect.is_some() {
             s.push('L');
         }
+        if self.history.is_some() {
+            s.push('H');
+        }
         if params {
             if let Some(k) = &self.key {
                 s.push(' ');
@@ -240,6 +244,9 @@ impl ChanModes {
                 s.push(' ');
                 s.push_str(t);
             }
+            if let Some((n, t)) = &self.history {
+                s.push_str(&format!(" {n}:{t}"));
+            }
         }
         s
     }
@@ -518,10 +525,64 @@ impl Server {
             self.numeric(uid, RPL_TOPIC, &format!("{name} :{text}"));
         }
         self.send_names(uid, &key);
+        self.replay_chanhistory(uid, &key); // +H: replay recent messages to the joiner
         self.propagate_join(uid, name); // tell linked servers this user joined
         self.events.push_back(Hook::Join(uid, key));
     }
 
+    /// +H chanhistory: replay a channel's recent messages to a user who just
+    /// joined — the last `<lines>` (within `<secs>`, 0 = no limit) from the store,
+    /// wrapped in a `chathistory` batch for batch-capable clients.
+    fn replay_chanhistory(&mut self, uid: Uid, key: &str) {
+        let Some((lines, secs)) = self.channels.get(key).and_then(|c| c.modes.history) else {
+            return;
+        };
+        let Some(name) = self.channels.get(key).map(|c| c.name.clone()) else {
+            return;
+        };
+        let batch = self.users.get(&uid).map(|u| u.caps.batch).unwrap_or(false);
+        let cutoff = if secs > 0 {
+            now().saturating_sub(secs)
+        } else {
+            0
+        };
+        let bref = if batch {
+            Some(self.next_msgid().replace('-', ""))
+        } else {
+            None
+        };
+        let out: Vec<String> = match self.history.get(key) {
+            Some(buf) => {
+                let mut recent: Vec<&HistMsg> = buf.iter().filter(|m| m.ts >= cutoff).collect();
+                let start = recent.len().saturating_sub(lines as usize);
+                recent.drain(..start);
+                recent
+                    .iter()
+                    .map(|m| {
+                        let mut tags = format!("time={};msgid={}", iso_time(m.ts), m.msgid);
+                        if let Some(b) = &bref {
+                            tags.push_str(&format!(";batch={b}"));
+                        }
+                        format!("@{tags} :{} {} {name} :{}", m.prefix, m.verb, m.text)
+                    })
+                    .collect()
+            }
+            None => return,
+        };
+        if out.is_empty() {
+            return;
+        }
+        if let Some(b) = &bref {
+            self.send(uid, format!(":{} BATCH +{b} chathistory {name}", self.name));
+        }
+        for l in out {
+            self.send(uid, l);
+        }
+        if let Some(b) = &bref {
+            self.send(uid, format!(":{} BATCH -{b}", self.name));
+        }
+    }
+
     pub fn send_names(&self, uid: Uid, key: &str) {
         let Some(ch) = self.channels.get(key) else {
             self.numeric(uid, RPL_ENDOFNAMES, &format!("{key} :End of /NAMES list"));

src/mode.rs

@@ -83,6 +83,7 @@ static CHAN_MODES: &[&(dyn ChanMode + Sync)] = &[
     &JOINFLOOD,
     &NICKFLOOD,
     &REDIRECT,
+    &CHANHISTORY,
 ];
 
 // --- prefix modes (+q/+a/+o/+h/+v): a per-member rank, needs a nick ----------
@@ -390,6 +391,49 @@ impl ChanMode for Limit {
     }
 }
 
+// --- +H chanhistory: replay recent messages to joiners ----------------------
+
+struct ChanHistory;
+static CHANHISTORY: ChanHistory = ChanHistory;
+impl ChanMode for ChanHistory {
+    fn letter(&self) -> char {
+        'H'
+    }
+    fn wants_param(&self, adding: bool) -> bool {
+        adding // +H <lines>[:<secs>]; -H takes nothing
+    }
+    fn apply(
+        &self,
+        s: &mut Server,
+        _chan: &str,
+        key: &str,
+        _uid: Uid,
+        adding: bool,
+        param: Option<&str>,
+    ) -> Applied {
+        if adding {
+            let Some(p) = param else {
+                return Applied::No;
+            };
+            let (lines_s, secs_s) = p.split_once(':').unwrap_or((p, "0"));
+            let Some(lines) = lines_s.parse::<u32>().ok().filter(|&n| n > 0) else {
+                return Applied::No;
+            };
+            let lines = lines.min(crate::server::HISTORY_CAP as u32);
+            let secs = secs_s.parse::<u64>().unwrap_or(0);
+            if let Some(c) = s.channels.get_mut(key) {
+                c.modes.history = Some((lines, secs));
+            }
+            Applied::Yes(Some(format!("{lines}:{secs}")))
+        } else {
+            if let Some(c) = s.channels.get_mut(key) {
+                c.modes.history = None;
+            }
+            Applied::Yes(None)
+        }
+    }
+}
+
 // --- list modes (+b bans, +e ban exceptions, +I invite exceptions) ----------
 
 #[derive(Clone, Copy)]

src/users.rs

@@ -416,7 +416,7 @@ impl Server {
             uid,
             RPL_ISUPPORT,
             &format!(
-                "CHANTYPES=# PREFIX=(qaohv)~&@%+ CHANMODES=beIg,k,lfjFL,CGMNORSTcimnpstuz 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,lfjFLH,CGMNORSTcimnpstuz 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
             ),
         );