From a80b86b50d50d75e2f1d9820526068eb2f7961a8 Mon Sep 17 00:00:00 2001
From: reverse <mike.chevronnet@gmail.com>
Date: Wed, 19 Aug 2026 00:47:32 +0000
Subject: [PATCH] =?UTF-8?q?perf:=20S2S=20channel-message=20fanout=20shares?=
 =?UTF-8?q?=20the=20line=20by=20Arc=20across=20members=20(relay=5Fchannel?=
 =?UTF-8?q?=5Fmessage)=20instead=20of=20cloning=20a=20String=20per=20recip?=
 =?UTF-8?q?ient=20=E2=80=94=20mirrors=20the=20client=20PRIVMSG=20fanout;?=
 =?UTF-8?q?=20builds=20at=20most=20three=20variants=20(plain=20/=20server-?=
 =?UTF-8?q?time=20/=20echo-services-tagged)=20whatever=20the=20channel=20s?=
 =?UTF-8?q?ize,=20behaviour=20unchanged?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 src/link.rs   | 17 ++++-------------
 src/server.rs | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 13 deletions(-)

diff --git a/src/link.rs b/src/link.rs
index 1446698..1abdb9f 100644
--- a/src/link.rs
+++ b/src/link.rs
@@ -1453,20 +1453,11 @@ impl Server {
             if !self.channels.contains_key(&key) {
                 return;
             }
+            // echo/services badges a service source for message-tags clients; the
+            // line is built once and shared by Arc across all members (not cloned
+            // per recipient).
             let base = format!(":{prefix} {cmd} {target} :{text}");
-            // echo/services: tag messages from a network service so capable
-            // clients can badge them. Per-recipient (needs the message-tags cap).
-            let is_service = src_is_service;
-            let tagged = format!("@echo/services {base}");
-            let members: Vec<Uid> = self.channels[&key].members.keys().copied().collect();
-            for m in members {
-                if self.users.get(&m).map(|u| u.flags.deaf).unwrap_or(false) {
-                    continue;
-                }
-                let want_tag = is_service
-                    && self.users.get(&m).map(|u| u.caps.message_tags).unwrap_or(false);
-                self.send(m, if want_tag { tagged.clone() } else { base.clone() });
-            }
+            self.relay_channel_message(&key, &base, src_is_service);
             // forward to the other links that have members in this channel
             for l in self.channel_link_targets(&key, Some(via)) {
                 self.link_out(l, format!(":{src} {cmd} {target} :{text}"));
diff --git a/src/server.rs b/src/server.rs
index e220738..1f82967 100644
--- a/src/server.rs
+++ b/src/server.rs
@@ -1018,6 +1018,44 @@ impl Server {
         }
     }
 
+    /// Fan an already-composed S2S channel message (`:prefix PRIVMSG #c :text`) out
+    /// to local members, sharing the line by `Arc` instead of cloning a String per
+    /// recipient. When `service`, message-tags clients get the `echo/services` badge;
+    /// server-time and +D deaf filtering are applied per recipient. At most three
+    /// distinct lines are built (plain / time-tagged / service-tagged) whatever the
+    /// channel size.
+    pub fn relay_channel_message(&self, key: &str, base: &str, service: bool) {
+        let Some(ch) = self.channels.get(key) else {
+            return;
+        };
+        let sourced = base.starts_with(':'); // only `:prefix …` lines carry server-time
+        let plain: std::sync::Arc<str> = std::sync::Arc::from(base);
+        let tagged: Option<std::sync::Arc<str>> =
+            service.then(|| std::sync::Arc::from(format!("@echo/services {base}").as_str()));
+        let mut plain_time: Option<std::sync::Arc<str>> = None;
+        for &m in ch.members.keys() {
+            let Some(u) = self.users.get(&m) else {
+                continue;
+            };
+            if u.flags.deaf {
+                continue;
+            }
+            // a service-badged line already carries a tag block, so — as before — it
+            // isn't additionally server-time tagged.
+            let buf = if service && u.caps.message_tags {
+                LineBuf::Shared(tagged.clone().unwrap())
+            } else if sourced && u.caps.server_time {
+                let t = plain_time.get_or_insert_with(|| {
+                    std::sync::Arc::from(format!("@time={} {base}", iso_time(now())).as_str())
+                });
+                LineBuf::Shared(t.clone())
+            } else {
+                LineBuf::Shared(plain.clone())
+            };
+            self.emit_to(m, buf);
+        }
+    }
+
     /// Send a message body (`:prefix CMD …`) from `src` to `uid`, composing its
     /// IRCv3 tag prefix from *that recipient's* caps: `time=` (server-time),
     /// `account=` (account-tag, from the sender's login) plus the client-only tags