Handle downstream PART messages

downstream.go

@@ -261,6 +261,19 @@ func (c *downstreamConn) handleMessageRegistered(msg *irc.Message) error {
 			Command: irc.ERR_NOSUCHCHANNEL,
 			Params:  []string{name, "Channel name ambiguous"},
 		}}
+	case "PART":
+		var name string
+		if err := parseMessageParams(msg, &name); err != nil {
+			return err
+		}
+
+		ch, err := c.user.getChannel(name)
+		if err != nil {
+			return err
+		}
+
+		ch.conn.messages <- msg
+		// TODO: remove channel from upstream config
 	case "MODE":
 		var name string
 		if err := parseMessageParams(msg, &name); err != nil {

server.go

@@ -75,7 +75,10 @@ func (u *user) getChannel(name string) (*upstreamChannel, error) {
 		}
 	})
 	if channel == nil {
-		return nil, fmt.Errorf("unknown channel %q", name)
+		return nil, ircError{&irc.Message{
+			Command: irc.ERR_NOSUCHCHANNEL,
+			Params:  []string{name, "No such channel"},
+		}}
 	}
 	return channel, nil
 }