Send compact channel name lists

This commit resolves `sendNames`' TODO.

bridge.go

@@ -2,6 +2,7 @@ package soju
 
 import (
 	"gopkg.in/irc.v3"
+	"strings"
 )
 
 func forwardChannel(dc *downstreamConn, ch *upstreamChannel) {
@@ -34,17 +35,40 @@ func sendTopic(dc *downstreamConn, ch *upstreamChannel) {
 }
 
 func sendNames(dc *downstreamConn, ch *upstreamChannel) {
-	// TODO: send multiple members in each message
-
 	downstreamName := dc.marshalEntity(ch.conn.network, ch.Name)
 
+	emptyNameReply := &irc.Message{
+		Prefix:  dc.srv.prefix(),
+		Command: irc.RPL_NAMREPLY,
+		Params:  []string{dc.nick, string(ch.Status), downstreamName, ""},
+	}
+	maxLength := maxMessageLength - len(emptyNameReply.String())
+
+	var buf strings.Builder
 	for nick, memberships := range ch.Members {
 		s := memberships.Format(dc) + dc.marshalEntity(ch.conn.network, nick)
 
+		if buf.Len() != 0 && maxLength < buf.Len()+1+len(s) {
+			// There's not enough space for the next space + nick.
+			dc.SendMessage(&irc.Message{
+				Prefix:  dc.srv.prefix(),
+				Command: irc.RPL_NAMREPLY,
+				Params:  []string{dc.nick, string(ch.Status), downstreamName, buf.String()},
+			})
+			buf.Reset()
+		}
+
+		if buf.Len() != 0 {
+			buf.WriteByte(' ')
+		}
+		buf.WriteString(s)
+	}
+
+	if buf.Len() != 0 {
 		dc.SendMessage(&irc.Message{
 			Prefix:  dc.srv.prefix(),
 			Command: irc.RPL_NAMREPLY,
-			Params:  []string{dc.nick, string(ch.Status), downstreamName, s},
+			Params:  []string{dc.nick, string(ch.Status), downstreamName, buf.String()},
 		})
 	}
 

irc.go

@@ -16,6 +16,8 @@ const (
 	err_invalidcapcmd = "410"
 )
 
+const maxMessageLength = 512
+
 type userModes string
 
 func (ms userModes) Has(c byte) bool {