From c13356b51e4fe512e99e80784500508ea0ac5be9 Mon Sep 17 00:00:00 2001
From: Zack Schuster <email@zackschuster.com>
Date: Fri, 30 Oct 2020 13:46:42 -0700
Subject: [PATCH] smtp/date: add isRFC2822Date api & use in tests

---
 smtp/date.ts | 15 +++++++++++++++
 test/date.ts | 15 ++++++---------
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/smtp/date.ts b/smtp/date.ts
index 00ed767..2bb81f6 100644
--- a/smtp/date.ts
+++ b/smtp/date.ts
@@ -33,3 +33,18 @@ export function getRFC2822DateUTC(date = new Date()) {
 	dates.push('+0000');
 	return dates.join(' ');
 }
+
+/**
+ * RFC 2822 regex
+ * @see https://tools.ietf.org/html/rfc2822#section-3.3
+ * @see https://github.com/moment/moment/blob/a831fc7e2694281ce31e4f090bbcf90a690f0277/src/lib/create/from-string.js#L101
+ */
+const rfc2822re = /^(?:(Mon|Tue|Wed|Thu|Fri|Sat|Sun),?\s)?(\d{1,2})\s(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)\s(\d{2,4})\s(\d\d):(\d\d)(?::(\d\d))?\s(?:(UT|GMT|[ECMP][SD]T)|([Zz])|([+-]\d{4}))$/.compile();
+
+/**
+ * @param {string} [date] a string to check for conformance to the [rfc2822](https://tools.ietf.org/html/rfc2822#section-3.3) standard
+ * @returns {boolean} the result of the conformance check
+ */
+export function isRFC2822Date(date: string) {
+	return rfc2822re.test(date);
+}
diff --git a/test/date.ts b/test/date.ts
index 7f3ab00..57a36a8 100644
--- a/test/date.ts
+++ b/test/date.ts
@@ -1,18 +1,15 @@
 import test from 'ava';
-import { getRFC2822Date, getRFC2822DateUTC } from '../email';
+import { getRFC2822Date, getRFC2822DateUTC, isRFC2822Date } from '../email';
 
 const toD_utc = (dt: number) => getRFC2822DateUTC(new Date(dt));
 const toD = (dt: number, utc = false) => getRFC2822Date(new Date(dt), utc);
 
 test('rfc2822 non-UTC', async (t) => {
-	// RFC 2822 regex: For details see https://tools.ietf.org/html/rfc2822#section-3.3
-	// thanks to moment.js for the listing: https://github.com/moment/moment/blob/a831fc7e2694281ce31e4f090bbcf90a690f0277/src/lib/create/from-string.js#L101
-	const rfc2822re = /^(?:(Mon|Tue|Wed|Thu|Fri|Sat|Sun),?\s)?(\d{1,2})\s(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)\s(\d{2,4})\s(\d\d):(\d\d)(?::(\d\d))?\s(?:(UT|GMT|[ECMP][SD]T)|([Zz])|([+-]\d{4}))$/;
-	t.regex(toD(0), rfc2822re);
-	t.regex(toD(329629726785), rfc2822re);
-	t.regex(toD(729629726785), rfc2822re);
-	t.regex(toD(1129629726785), rfc2822re);
-	t.regex(toD(1529629726785), rfc2822re);
+	t.true(isRFC2822Date(toD(0)));
+	t.true(isRFC2822Date(toD(329629726785)));
+	t.true(isRFC2822Date(toD(729629726785)));
+	t.true(isRFC2822Date(toD(1129629726785)));
+	t.true(isRFC2822Date(toD(1529629726785)));
 });
 
 test('rfc2822 UTC', async (t) => {