feat(GODT-2802): IMAP Serivce

Handles all IMAP related tasks. Unlike the previous iteration, this new
service automatically adds and removes users from Gluon by interfacing
with server manager.

internal/services/imapservice/helpers.go

@@ -0,0 +1,191 @@
+// Copyright (c) 2023 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail 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.
+//
+// Proton Mail 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 Proton Mail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package imapservice
+
+import (
+	"context"
+	"fmt"
+	"net/mail"
+	"time"
+
+	"github.com/ProtonMail/gluon/imap"
+	"github.com/ProtonMail/gluon/rfc5322"
+	"github.com/ProtonMail/gluon/rfc822"
+	"github.com/ProtonMail/go-proton-api"
+	"github.com/bradenaw/juniper/xslices"
+)
+
+func toIMAPMailbox(label proton.Label, flags, permFlags, attrs imap.FlagSet) imap.Mailbox {
+	if label.Type == proton.LabelTypeLabel {
+		label.Path = append([]string{labelPrefix}, label.Path...)
+	} else if label.Type == proton.LabelTypeFolder {
+		label.Path = append([]string{folderPrefix}, label.Path...)
+	}
+
+	return imap.Mailbox{
+		ID:             imap.MailboxID(label.ID),
+		Name:           label.Path,
+		Flags:          flags,
+		PermanentFlags: permFlags,
+		Attributes:     attrs,
+	}
+}
+
+func isAllMailOrScheduled(mailboxID imap.MailboxID) bool {
+	return (mailboxID == proton.AllMailLabel) || (mailboxID == proton.AllScheduledLabel)
+}
+
+func BuildFlagSetFromMessageMetadata(message proton.MessageMetadata) imap.FlagSet {
+	flags := imap.NewFlagSet()
+
+	if message.Seen() {
+		flags.AddToSelf(imap.FlagSeen)
+	}
+
+	if message.Starred() {
+		flags.AddToSelf(imap.FlagFlagged)
+	}
+
+	if message.IsDraft() {
+		flags.AddToSelf(imap.FlagDraft)
+	}
+
+	if message.IsRepliedAll == true || message.IsReplied == true { //nolint: gosimple
+		flags.AddToSelf(imap.FlagAnswered)
+	}
+
+	return flags
+}
+
+func getLiteralToList(literal []byte) ([]string, error) {
+	headerLiteral, _ := rfc822.Split(literal)
+
+	header, err := rfc822.NewHeader(headerLiteral)
+	if err != nil {
+		return nil, err
+	}
+
+	var result []string
+
+	parseAddress := func(field string) error {
+		if fieldAddr, ok := header.GetChecked(field); ok {
+			addr, err := rfc5322.ParseAddressList(fieldAddr)
+			if err != nil {
+				return fmt.Errorf("failed to parse addresses for '%v': %w", field, err)
+			}
+
+			result = append(result, xslices.Map(addr, func(addr *mail.Address) string {
+				return addr.Address
+			})...)
+
+			return nil
+		}
+
+		return nil
+	}
+
+	if err := parseAddress("To"); err != nil {
+		return nil, err
+	}
+
+	if err := parseAddress("Cc"); err != nil {
+		return nil, err
+	}
+
+	if err := parseAddress("Bcc"); err != nil {
+		return nil, err
+	}
+
+	return result, nil
+}
+
+func toIMAPMessage(message proton.MessageMetadata) imap.Message {
+	flags := BuildFlagSetFromMessageMetadata(message)
+
+	var date time.Time
+
+	if message.Time > 0 {
+		date = time.Unix(message.Time, 0)
+	} else {
+		date = time.Now()
+	}
+
+	return imap.Message{
+		ID:    imap.MessageID(message.ID),
+		Flags: flags,
+		Date:  date,
+	}
+}
+
+func WantLabel(label proton.Label) bool {
+	if label.Type != proton.LabelTypeSystem {
+		return true
+	}
+
+	// nolint:exhaustive
+	switch label.ID {
+	case proton.InboxLabel:
+		return true
+
+	case proton.TrashLabel:
+		return true
+
+	case proton.SpamLabel:
+		return true
+
+	case proton.AllMailLabel:
+		return true
+
+	case proton.ArchiveLabel:
+		return true
+
+	case proton.SentLabel:
+		return true
+
+	case proton.DraftsLabel:
+		return true
+
+	case proton.StarredLabel:
+		return true
+
+	case proton.AllScheduledLabel:
+		return true
+
+	default:
+		return false
+	}
+}
+
+func wantLabels(apiLabels map[string]proton.Label, labelIDs []string) []string {
+	return xslices.Filter(labelIDs, func(labelID string) bool {
+		apiLabel, ok := apiLabels[labelID]
+		if !ok {
+			return false
+		}
+
+		return WantLabel(apiLabel)
+	})
+}
+
+// sleepCtx sleeps for the given duration, or until the context is canceled.
+func sleepCtx(ctx context.Context, d time.Duration) {
+	select {
+	case <-ctx.Done():
+	case <-time.After(d):
+	}
+}