feat: custom address/date parser based on rfc5322 abnf

pkg/message/rfc5322/offset.go

@@ -0,0 +1,73 @@
+// 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 rfc5322
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/ProtonMail/proton-bridge/pkg/message/rfc5322/parser"
+	"github.com/sirupsen/logrus"
+)
+
+type offset struct {
+	rep   string
+	value int
+}
+
+func (w *walker) EnterOffset(ctx *parser.OffsetContext) {
+	logrus.WithField("text", ctx.GetText()).Trace("Entering offset")
+
+	text := ctx.GetText()
+
+	// NOTE: RFC5322 date-time should always begin with + or -
+	// but we relax that requirement a bit due to many messages
+	// in the wild that skip the +; we add the "+" if missing.
+	if !strings.HasPrefix(text, "+") && !strings.HasPrefix(text, "-") {
+		text = "+" + text
+	}
+
+	sgn := text[0:1]
+	hrs := text[1:3]
+	min := text[3:5]
+
+	dur, err := time.ParseDuration(fmt.Sprintf("%v%vh%vm", sgn, hrs, min))
+	if err != nil {
+		w.err = err
+	}
+
+	w.enter(&offset{
+		rep:   text,
+		value: int(dur.Seconds()),
+	})
+}
+
+func (w *walker) ExitOffset(ctx *parser.OffsetContext) {
+	logrus.WithField("text", ctx.GetText()).Trace("Exiting offset")
+
+	type withOffset interface {
+		withOffset(*offset)
+	}
+
+	res := w.exit().(*offset)
+
+	if parent, ok := w.parent().(withOffset); ok {
+		parent.withOffset(res)
+	}
+}