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

@@ -51,11 +51,6 @@ 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
@@ -63,7 +58,6 @@ type downstreamConn struct {
 	srv      *Server
 	logger   Logger
 	outgoing chan *irc.Message
-	ringMessages chan ringMessage
 	closed   chan struct{}
 
 	registered  bool
@@ -95,7 +89,6 @@ func newDownstreamConn(srv *Server, netConn net.Conn, id uint64) *downstreamConn
 		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{}),
@@ -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
 			}