From 3966c17dec253962165494cd85646f0e1ffca99c Mon Sep 17 00:00:00 2001
From: Shivaram Lingamneni <slingamn@cs.stanford.edu>
Date: Sun, 15 Jun 2025 13:14:16 -0400
Subject: [PATCH] refactor update broadcast

---
 irc/channel.go  | 15 +++++++++++++++
 irc/handlers.go |  7 +++++--
 irc/metadata.go | 46 ++++++++++++++++++++++------------------------
 3 files changed, 42 insertions(+), 26 deletions(-)

diff --git a/irc/channel.go b/irc/channel.go
index 1b449a70..9e052f37 100644
--- a/irc/channel.go
+++ b/irc/channel.go
@@ -7,6 +7,7 @@ package irc
 
 import (
 	"fmt"
+	"iter"
 	"maps"
 	"strconv"
 	"strings"
@@ -1676,6 +1677,20 @@ func (channel *Channel) auditoriumFriends(client *Client) (friends []*Client) {
 	return
 }
 
+func (channel *Channel) sessionsWithCap(capabs ...caps.Capability) iter.Seq[*Session] {
+	return func(yield func(*Session) bool) {
+		for _, member := range channel.Members() {
+			for _, sess := range member.Sessions() {
+				if sess.capabilities.HasAll(capabs...) {
+					if !yield(sess) {
+						return
+					}
+				}
+			}
+		}
+	}
+}
+
 // returns whether the client is visible to unprivileged users in the channel
 // (i.e., respecting auditorium mode). note that this assumes that the client
 // is a member; if the client is not, it may return true anyway
diff --git a/irc/handlers.go b/irc/handlers.go
index 6d6408a4..c2751a6f 100644
--- a/irc/handlers.go
+++ b/irc/handlers.go
@@ -3129,11 +3129,13 @@ func metadataHandler(server *Server, client *Client, msg ircmsg.Message, rb *Res
 		targetChannel = server.channels.Get(target)
 		if targetChannel != nil {
 			targetObj = targetChannel
+			target = targetChannel.Name() // canonicalize case
 		}
 	} else {
 		targetClient = server.clients.Get(target)
 		if targetClient != nil {
 			targetObj = targetClient
+			target = targetClient.Nick() // canonicalize case
 		}
 	}
 	if targetObj == nil {
@@ -3180,13 +3182,14 @@ func metadataHandler(server *Server, client *Client, msg ircmsg.Message, rb *Res
 			server.logger.Debug("metadata", "setting", key, value, "on", target)
 
 			targetObj.SetMetadata(key, value)
-			notifySubscribers(server, rb.session, target, key, value)
+			notifySubscribers(server, rb.session, targetObj, target, key, value)
 
 			rb.Add(nil, server.name, RPL_KEYVALUE, client.Nick(), originalTarget, key, "*", value)
 		} else {
 			server.logger.Debug("metadata", "deleting", key, "on", target)
+			// TODO check success or failure here
 			targetObj.DeleteMetadata(key)
-			notifySubscribers(server, rb.session, target, key, "")
+			notifySubscribers(server, rb.session, targetObj, target, key, "")
 
 			rb.Add(nil, server.name, RPL_KEYNOTSET, client.Nick(), target, key, client.t("Key deleted"))
 		}
diff --git a/irc/metadata.go b/irc/metadata.go
index 629f3878..1a061454 100644
--- a/irc/metadata.go
+++ b/irc/metadata.go
@@ -2,12 +2,13 @@ package irc
 
 import (
 	"errors"
+	"iter"
+	"maps"
 	"regexp"
 	"strings"
 
 	"github.com/ergochat/ergo/irc/caps"
 	"github.com/ergochat/ergo/irc/modes"
-	"github.com/ergochat/ergo/irc/utils"
 )
 
 var (
@@ -24,34 +25,31 @@ type MetadataHaver = interface {
 	CountMetadata() int
 }
 
-func notifySubscribers(server *Server, session *Session, target string, key string, value string) {
-	var notify utils.HashSet[*Session] = make(utils.HashSet[*Session])
-	targetChannel := server.channels.Get(target)
-	targetClient := server.clients.Get(target)
+func notifySubscribers(server *Server, session *Session, targetObj MetadataHaver, targetName, key, value string) {
+	var recipientSessions iter.Seq[*Session]
 
-	if targetClient != nil {
-		notify = targetClient.FriendsMonitors(caps.Metadata)
-		// notify clients about changes regarding themselves
-		for _, s := range targetClient.Sessions() {
-			notify.Add(s)
-		}
-	}
-	if targetChannel != nil {
-		members := targetChannel.Members()
-		for _, m := range members {
-			for _, s := range m.Sessions() {
-				if s.capabilities.Has(caps.Metadata) {
-					notify.Add(s)
-				}
-			}
+	switch target := targetObj.(type) {
+	case *Client:
+		// TODO this case is expensive and might warrant rate-limiting
+		friends := target.FriendsMonitors(caps.Metadata)
+		// broadcast metadata update to other connected sessions
+		for _, s := range target.Sessions() {
+			friends.Add(s)
 		}
+		recipientSessions = maps.Keys(friends)
+	case *Channel:
+		recipientSessions = target.sessionsWithCap(caps.Metadata)
+	default:
+		return // impossible
 	}
 
-	// don't notify the session that made the change
-	notify.Remove(session)
+	broadcastMetadataUpdate(server, recipientSessions, session, targetName, key, value)
+}
 
-	for s := range notify {
-		if !s.isSubscribedTo(key) {
+func broadcastMetadataUpdate(server *Server, sessions iter.Seq[*Session], originator *Session, target, key, value string) {
+	for s := range sessions {
+		// don't notify the session that made the change
+		if s == originator || !s.isSubscribedTo(key) {
 			continue
 		}