server: scrub a departed user's pending invites via a User.invited reverse index instead of scanning every channel on the network per quit — the old O(channels)-per-quit path was O(channels*quits) on a netsplit; the index is maintained at the 4 invite add/remove sites (INVITE cmd, S2S INVITE, join-consume, UNINVITE)

src/channels.rs

@@ -907,6 +907,7 @@ impl Server {
         ch.recent_kicks.remove(&uid); // they got back in; clear any +J rejoin timer
         if let Some(u) = self.users.get_mut(&uid) {
             u.channels.insert(key.clone());
+            u.invited.remove(&key); // invite consumed — drop it from the reverse index
         }
         // chancreate: snotice when a brand-new channel comes into being
         if is_new

src/coremods/core_channel.rs

@@ -323,6 +323,9 @@ impl Command for Invite {
         if let Some(ch) = s.channels.get_mut(&key) {
             ch.invites.insert(tuid);
         }
+        if let Some(u) = s.users.get_mut(&tuid) {
+            u.invited.insert(key.clone()); // reverse index for O(1) quit scrub
+        }
         let who = s.users[&tuid].nick.clone();
         s.numeric(uid, RPL_INVITING, &format!("{who} {chan}"));
         let prefix = s.users[&uid].prefix();
@@ -390,6 +393,9 @@ impl Command for Uninvite {
             .get_mut(&key)
             .map(|ch| ch.invites.remove(&tuid))
             .unwrap_or(false);
+        if let Some(u) = s.users.get_mut(&tuid) {
+            u.invited.remove(&key); // keep the reverse index in sync
+        }
         let who = s.users[&tuid].nick.clone();
         let word = if removed {
             "is no longer invited to"

src/link.rs

@@ -1344,6 +1344,9 @@ impl Server {
             if let Some(ch) = self.channels.get_mut(&key) {
                 ch.invites.insert(luid);
             }
+            if let Some(u) = self.users.get_mut(&luid) {
+                u.invited.insert(key.clone()); // reverse index for O(1) quit scrub
+            }
             let prefix = self.uuid_prefix(&src).unwrap_or_else(|| src.clone());
             let nick = self.users.get(&luid).map(|u| u.nick.clone()).unwrap_or_default();
             self.send(luid, format!(":{prefix} INVITE {nick} :{chan}"));
@@ -2768,6 +2771,7 @@ mod tests {
                 caps: Caps::default(),
                 sasl_mech: None,
                 channels: HashSet::default(),
+                invited: HashSet::default(),
                 watch: Vec::new(),
                 monitor: Vec::new(),
                 silence: Vec::new(),
@@ -2855,6 +2859,7 @@ mod tests {
                 caps,
                 sasl_mech: None,
                 channels: HashSet::default(),
+                invited: HashSet::default(),
                 watch: Vec::new(),
                 monitor: Vec::new(),
                 silence: Vec::new(),

src/modules/reputation.rs

@@ -392,6 +392,7 @@ mod tests {
                 caps: Caps::default(),
                 sasl_mech: None,
                 channels: chans,
+                invited: crate::map::HashSet::default(),
                 watch: Vec::new(),
                 monitor: Vec::new(),
                 silence: Vec::new(),

src/s2s_sim.rs

@@ -92,6 +92,7 @@ impl Node {
                 caps: Caps::default(),
                 sasl_mech: None,
                 channels: HashSet::default(),
+                invited: HashSet::default(),
                 watch: Vec::new(),
                 monitor: Vec::new(),
                 silence: Vec::new(),

src/server.rs

@@ -373,6 +373,7 @@ impl Server {
                 caps: Caps::default(),
                 sasl_mech: None,
                 channels: HashSet::default(),
+                invited: HashSet::default(),
                 watch: Vec::new(),
                 monitor: Vec::new(),
                 silence: Vec::new(),
@@ -724,8 +725,12 @@ impl Server {
             // Scrub any pending +i invite for this user from channels they never joined
             // (a member consumes their invite on join; a never-joined invite for a now-
             // departed uid would otherwise linger forever on a persistent channel).
-            for ch in self.channels.values_mut() {
+            // The `invited` reverse index gives the exact channels, so this is O(pending
-                ch.invites.remove(&uid);
+            // invites) rather than a scan of every channel on the network.
+            for key in &user.invited {
+                if let Some(ch) = self.channels.get_mut(key) {
+                    ch.invites.remove(&uid);
+                }
             }
             self.channels.retain(|_, c| c.keep_alive());
             self.watch_notify_offline(&user.nick); // tell WATCH/MONITOR watchers
@@ -1424,6 +1429,7 @@ mod tests {
                 caps: Caps::default(),
                 sasl_mech: None,
                 channels: HashSet::default(),
+                invited: HashSet::default(),
                 watch: Vec::new(),
                 monitor: Vec::new(),
                 silence: Vec::new(),

src/users.rs

@@ -248,6 +248,7 @@ pub struct User {
     pub caps: Caps,            // enabled IRCv3 capabilities
     pub sasl_mech: Option<String>, // SASL mechanism chosen, mid-handshake
     pub channels: HashSet<String>, // lowercased channel keys
+    pub invited: HashSet<String>,  // channels this user has a pending +i invite to (reverse index)
     pub watch: Vec<String>,    // WATCH list — lowercased nicks
     pub monitor: Vec<String>,  // MONITOR list — lowercased nicks
     pub silence: Vec<String>,  // SILENCE masks — nick!user@host globs