maddy - date.go

 1/*
 2Maddy Mail Server - Composable all-in-one email server.
 3Copyright © 2019-2020 Max Mazurov <fox.cpp@disroot.org>, Maddy Mail Server contributors
 4
 5This program is free software: you can redistribute it and/or modify
 6it under the terms of the GNU General Public License as published by
 7the Free Software Foundation, either version 3 of the License, or
 8(at your option) any later version.
 9
10This program is distributed in the hope that it will be useful,
11but WITHOUT ANY WARRANTY; without even the implied warranty of
12MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13GNU General Public License for more details.
14
15You should have received a copy of the GNU General Public License
16along with this program.  If not, see <https://www.gnu.org/licenses/>.
17*/
18
19package smtp
20
21import (
22	"fmt"
23	"regexp"
24	"time"
25)
26
27// Taken from https://github.com/emersion/go-imap/blob/09c1d69/date.go.
28
29var dateTimeLayouts = [...]string{
30	// Defined in RFC 5322 section 3.3, mentioned as env-date in RFC 3501 page 84.
31	"Mon, 02 Jan 2006 15:04:05 -0700",
32	"_2 Jan 2006 15:04:05 -0700",
33	"_2 Jan 2006 15:04:05 MST",
34	"_2 Jan 2006 15:04 -0700",
35	"_2 Jan 2006 15:04 MST",
36	"_2 Jan 06 15:04:05 -0700",
37	"_2 Jan 06 15:04:05 MST",
38	"_2 Jan 06 15:04 -0700",
39	"_2 Jan 06 15:04 MST",
40	"Mon, _2 Jan 2006 15:04:05 -0700",
41	"Mon, _2 Jan 2006 15:04:05 MST",
42	"Mon, _2 Jan 2006 15:04 -0700",
43	"Mon, _2 Jan 2006 15:04 MST",
44	"Mon, _2 Jan 06 15:04:05 -0700",
45	"Mon, _2 Jan 06 15:04:05 MST",
46	"Mon, _2 Jan 06 15:04 -0700",
47	"Mon, _2 Jan 06 15:04 MST",
48}
49
50// TODO: this is a blunt way to strip any trailing CFWS (comment). A sharper
51// one would strip multiple CFWS, and only if really valid according to
52// RFC5322.
53var commentRE = regexp.MustCompile(`[ \t]+\(.*\)$`)
54
55// Try parsing the date based on the layouts defined in RFC 5322, section 3.3.
56// Inspired by https://github.com/golang/go/blob/master/src/net/mail/message.go
57func parseMessageDateTime(maybeDate string) (time.Time, error) {
58	maybeDate = commentRE.ReplaceAllString(maybeDate, "")
59	for _, layout := range dateTimeLayouts {
60		parsed, err := time.Parse(layout, maybeDate)
61		if err == nil {
62			return parsed, nil
63		}
64	}
65	return time.Time{}, fmt.Errorf("date %s could not be parsed", maybeDate)
66}