GODT-1161: Guarantee order of responses when creating new message

internal/imap/idle/extension.go

@@ -0,0 +1,85 @@
+// Copyright (c) 2021 Proton Technologies AG
+//
+// This file is part of ProtonMail Bridge.
+//
+// ProtonMail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// ProtonMail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with ProtonMail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package idle
+
+import (
+	"bufio"
+	"errors"
+	"strings"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/server"
+)
+
+const (
+	idleCommand = "IDLE" // Capability and Command identificator
+	doneLine    = "DONE"
+)
+
+// Handler for IDLE extension.
+type Handler struct{}
+
+// Command for IDLE handler.
+func (h *Handler) Command() *imap.Command {
+	return &imap.Command{Name: idleCommand}
+}
+
+// Parse for IDLE handler.
+func (h *Handler) Parse(fields []interface{}) error {
+	return nil
+}
+
+// Handle the IDLE request.
+func (h *Handler) Handle(conn server.Conn) error {
+	cont := &imap.ContinuationReq{Info: "idling"}
+	if err := conn.WriteResp(cont); err != nil {
+		return err
+	}
+
+	// Wait for DONE
+	scanner := bufio.NewScanner(conn)
+	scanner.Scan()
+	if err := scanner.Err(); err != nil {
+		return err
+	}
+
+	if strings.ToUpper(scanner.Text()) != doneLine {
+		return errors.New("expected DONE")
+	}
+	return nil
+}
+
+type extension struct{}
+
+func (ext *extension) Capabilities(c server.Conn) []string {
+	return []string{idleCommand}
+}
+
+func (ext *extension) Command(name string) server.HandlerFactory {
+	if name != idleCommand {
+		return nil
+	}
+
+	return func() server.Handler {
+		return &Handler{}
+	}
+}
+
+func NewExtension() server.Extension {
+	return &extension{}
+}