Consume ring messages outside of writer goroutine

This fixes out-of-order JOIN and PRIVMSG messages.

Closes: https://todo.sr.ht/~emersion/soju/36

downstream.go

@@ -51,20 +51,14 @@ var errAuthFailed = ircError{&irc.Message{
 	Params:  []string{"*", "Invalid username or password"},
 }}
 
-type ringMessage struct {
-	consumer     *RingConsumer
-	upstreamConn *upstreamConn
-}
-
 type downstreamConn struct {
-	id           uint64
-	net          net.Conn
-	irc          *irc.Conn
-	srv          *Server
-	logger       Logger
-	outgoing     chan *irc.Message
-	ringMessages chan ringMessage
-	closed       chan struct{}
+	id       uint64
+	net      net.Conn
+	irc      *irc.Conn
+	srv      *Server
+	logger   Logger
+	outgoing chan *irc.Message
+	closed   chan struct{}
 
 	registered  bool
 	user        *user
@@ -89,16 +83,15 @@ type downstreamConn struct {
 
 func newDownstreamConn(srv *Server, netConn net.Conn, id uint64) *downstreamConn {
 	dc := &downstreamConn{
-		id:           id,
-		net:          netConn,
-		irc:          irc.NewConn(netConn),
-		srv:          srv,
-		logger:       &prefixLogger{srv.Logger, fmt.Sprintf("downstream %q: ", netConn.RemoteAddr())},
-		outgoing:     make(chan *irc.Message, 64),
-		ringMessages: make(chan ringMessage),
-		closed:       make(chan struct{}),
-		caps:         make(map[string]bool),
-		ourMessages:  make(map[*irc.Message]struct{}),
+		id:          id,
+		net:         netConn,
+		irc:         irc.NewConn(netConn),
+		srv:         srv,
+		logger:      &prefixLogger{srv.Logger, fmt.Sprintf("downstream %q: ", netConn.RemoteAddr())},
+		outgoing:    make(chan *irc.Message, 64),
+		closed:      make(chan struct{}),
+		caps:        make(map[string]bool),
+		ourMessages: make(map[*irc.Message]struct{}),
 	}
 	dc.hostname = netConn.RemoteAddr().String()
 	if host, _, err := net.SplitHostPort(dc.hostname); err == nil {
@@ -257,42 +250,6 @@ func (dc *downstreamConn) writeMessages() error {
 				dc.logger.Printf("sent: %v", msg)
 			}
 			err = dc.irc.WriteMessage(msg)
-		case ringMessage := <-dc.ringMessages:
-			consumer, uc := ringMessage.consumer, ringMessage.upstreamConn
-			for {
-				msg := consumer.Peek()
-				if msg == nil {
-					break
-				}
-
-				dc.lock.Lock()
-				_, ours := dc.ourMessages[msg]
-				delete(dc.ourMessages, msg)
-				dc.lock.Unlock()
-				if ours {
-					// The message comes from our connection, don't echo it
-					// back
-					consumer.Consume()
-					continue
-				}
-
-				msg = msg.Copy()
-				switch msg.Command {
-				case "PRIVMSG":
-					msg.Prefix = dc.marshalUserPrefix(uc, msg.Prefix)
-					msg.Params[0] = dc.marshalEntity(uc, msg.Params[0])
-				default:
-					panic("expected to consume a PRIVMSG message")
-				}
-				if dc.srv.Debug {
-					dc.logger.Printf("sent: %v", msg)
-				}
-				err = dc.irc.WriteMessage(msg)
-				if err != nil {
-					break
-				}
-				consumer.Consume()
-			}
 		case <-dc.closed:
 			closed = true
 		}
@@ -774,7 +731,36 @@ func (dc *downstreamConn) runNetwork(net *network, loadHistory bool) {
 					dc.logger.Printf("ignoring messages for upstream %q: upstream is disconnected", net.Addr)
 					break
 				}
-				dc.ringMessages <- ringMessage{consumer, uc}
+
+				for {
+					msg := consumer.Peek()
+					if msg == nil {
+						break
+					}
+
+					dc.lock.Lock()
+					_, ours := dc.ourMessages[msg]
+					delete(dc.ourMessages, msg)
+					dc.lock.Unlock()
+					if ours {
+						// The message comes from our connection, don't echo it
+						// back
+						consumer.Consume()
+						continue
+					}
+
+					msg = msg.Copy()
+					switch msg.Command {
+					case "PRIVMSG":
+						msg.Prefix = dc.marshalUserPrefix(uc, msg.Prefix)
+						msg.Params[0] = dc.marshalEntity(uc, msg.Params[0])
+					default:
+						panic("expected to consume a PRIVMSG message")
+					}
+
+					dc.SendMessage(msg)
+					consumer.Consume()
+				}
 			case <-dc.closed:
 				closed = true
 			}