Relay detached channel backlog as BouncerServ NOTICE if necessary

Instead of ignoring detached channels wehn replaying backlog,
process them as usual and relay messages as BouncerServ NOTICEs
if necessary. Advance the delivery receipts as if the channel was
attached.

Closes: https://todo.sr.ht/~emersion/soju/98

downstream.go

@@ -1030,9 +1030,8 @@ func (dc *downstreamConn) sendTargetBacklog(net *network, target, msgID string)
 	if dc.caps["draft/chathistory"] || dc.user.msgStore == nil {
 		return
 	}
-	if ch := net.channels.Value(target); ch != nil && ch.Detached {
-		return
-	}
+
+	ch := net.channels.Value(target)
 
 	limit := 4000
 	targetCM := net.casemap(target)
@@ -1056,11 +1055,17 @@ func (dc *downstreamConn) sendTargetBacklog(net *network, target, msgID string)
 			continue
 		}
 
+		if ch != nil && ch.Detached {
+			if net.detachedMessageNeedsRelay(ch, msg) {
+				dc.relayDetachedMessage(net, msg)
+			}
+		} else {
 			if dc.caps["batch"] {
 				msg.Tags["batch"] = irc.TagValue(batchRef)
 			}
 			dc.SendMessage(dc.marshalMessage(msg, net))
 		}
+	}
 
 	if dc.caps["batch"] {
 		dc.SendMessage(&irc.Message{
@@ -1071,6 +1076,20 @@ func (dc *downstreamConn) sendTargetBacklog(net *network, target, msgID string)
 	}
 }
 
+func (dc *downstreamConn) relayDetachedMessage(net *network, msg *irc.Message) {
+	if msg.Command != "PRIVMSG" && msg.Command != "NOTICE" {
+		return
+	}
+
+	sender := msg.Prefix.Name
+	target, text := msg.Params[0], msg.Params[1]
+	if net.isHighlight(msg) {
+		sendServiceNOTICE(dc, fmt.Sprintf("highlight in %v: <%v> %v", dc.marshalEntity(net, target), sender, text))
+	} else {
+		sendServiceNOTICE(dc, fmt.Sprintf("message in %v: <%v> %v", dc.marshalEntity(net, target), sender, text))
+	}
+}
+
 func (dc *downstreamConn) runUntilRegistered() error {
 	for !dc.registered {
 		msg, err := dc.ReadMessage()

upstream.go

@@ -391,10 +391,10 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 			ch := uc.network.channels.Value(target)
 			if ch != nil {
 				if ch.Detached {
-					uc.handleDetachedMessage(msg.Prefix.Name, text, ch)
+					uc.handleDetachedMessage(ch, msg)
 				}
 
-				highlight := msg.Prefix.Name != uc.nick && isHighlight(text, uc.nick)
+				highlight := uc.network.isHighlight(msg)
 				if ch.DetachOn == FilterMessage || ch.DetachOn == FilterDefault || (ch.DetachOn == FilterHighlight && highlight) {
 					uc.updateChannelAutoDetach(target)
 				}
@@ -1437,18 +1437,13 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 	return nil
 }
 
-func (uc *upstreamConn) handleDetachedMessage(sender string, text string, ch *Channel) {
-	highlight := sender != uc.nick && isHighlight(text, uc.nick)
-	if ch.RelayDetached == FilterMessage || ((ch.RelayDetached == FilterHighlight || ch.RelayDetached == FilterDefault) && highlight) {
+func (uc *upstreamConn) handleDetachedMessage(ch *Channel, msg *irc.Message) {
+	if uc.network.detachedMessageNeedsRelay(ch, msg) {
 		uc.forEachDownstream(func(dc *downstreamConn) {
-			if highlight {
-				sendServiceNOTICE(dc, fmt.Sprintf("highlight in %v: <%v> %v", dc.marshalEntity(uc.network, ch.Name), sender, text))
-			} else {
-				sendServiceNOTICE(dc, fmt.Sprintf("message in %v: <%v> %v", dc.marshalEntity(uc.network, ch.Name), sender, text))
-			}
+			dc.relayDetachedMessage(uc.network, msg)
 		})
 	}
-	if ch.ReattachOn == FilterMessage || (ch.ReattachOn == FilterHighlight && highlight) {
+	if ch.ReattachOn == FilterMessage || (ch.ReattachOn == FilterHighlight && uc.network.isHighlight(msg)) {
 		uc.network.attach(ch)
 		if err := uc.srv.db.StoreChannel(uc.network.ID, ch); err != nil {
 			uc.logger.Printf("failed to update channel %q: %v", ch.Name, err)
@@ -1743,12 +1738,10 @@ func (uc *upstreamConn) produce(target string, msg *irc.Message, origin *downstr
 
 	// Don't forward messages if it's a detached channel
 	ch := uc.network.channels.Value(target)
-	if ch != nil && ch.Detached {
-		return
-	}
+	detached := ch != nil && ch.Detached
 
 	uc.forEachDownstream(func(dc *downstreamConn) {
-		if dc != origin || dc.caps["echo-message"] {
+		if !detached && (dc != origin || dc.caps["echo-message"]) {
 			dc.sendMessageWithID(dc.marshalMessage(msg, uc.network), msgID)
 		} else {
 			dc.advanceMessageWithID(msg, msgID)

user.go

@@ -351,6 +351,27 @@ func (net *network) storeClientDeliveryReceipts(clientName string) {
 	}
 }
 
+func (net *network) isHighlight(msg *irc.Message) bool {
+	if msg.Command != "PRIVMSG" && msg.Command != "NOTICE" {
+		return false
+	}
+
+	text := msg.Params[1]
+
+	nick := net.Nick
+	if net.conn != nil {
+		nick = net.conn.nick
+	}
+
+	// TODO: use case-mapping aware comparison here
+	return msg.Prefix.Name != nick && isHighlight(text, nick)
+}
+
+func (net *network) detachedMessageNeedsRelay(ch *Channel, msg *irc.Message) bool {
+	highlight := net.isHighlight(msg)
+	return ch.RelayDetached == FilterMessage || ((ch.RelayDetached == FilterHighlight || ch.RelayDetached == FilterDefault) && highlight)
+}
+
 type user struct {
 	User
 	srv    *Server