Detect Gmail labels from All Mail mbox export

internal/transfer/provider_mbox_gmail_labels.go

@@ -0,0 +1,89 @@
+// Copyright (c) 2020 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 transfer
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"os"
+	"strings"
+)
+
+const xGmailLabelsHeader = "X-Gmail-Labels"
+
+func getGmailLabelsFromMboxFile(filePath string) ([]string, error) {
+	f, err := os.Open(filePath) //nolint[gosec]
+	if err != nil {
+		return nil, err
+	}
+	return getGmailLabelsFromMboxReader(f)
+}
+
+func getGmailLabelsFromMboxReader(f io.Reader) ([]string, error) {
+	allLabels := []string{}
+
+	r := bufio.NewReader(f)
+	for {
+		b, isPrefix, err := r.ReadLine()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+		if isPrefix {
+			for !isPrefix {
+				_, isPrefix, err = r.ReadLine()
+				if err != nil {
+					break
+				}
+			}
+			continue
+		}
+		if bytes.HasPrefix(b, []byte(xGmailLabelsHeader)) {
+			for _, label := range getGmailLabelsFromValue(string(b)) {
+				allLabels = appendIfNew(allLabels, label)
+			}
+		}
+	}
+
+	return allLabels, nil
+}
+
+func getGmailLabelsFromMessage(body []byte) ([]string, error) {
+	header, err := getMessageHeader(body)
+	if err != nil {
+		return nil, err
+	}
+	labels := header.Get(xGmailLabelsHeader)
+	return getGmailLabelsFromValue(labels), nil
+}
+
+func getGmailLabelsFromValue(value string) []string {
+	value = strings.TrimPrefix(value, xGmailLabelsHeader+":")
+	labels := []string{}
+	for _, label := range strings.Split(value, ",") {
+		label = strings.TrimSpace(label)
+		if label == "" {
+			continue
+		}
+		labels = appendIfNew(labels, label)
+	}
+	return labels
+}