From 71fd0ef390a1cc68ebad5738642a1c1c4afd5170 Mon Sep 17 00:00:00 2001
From: reugn <reugpro@gmail.com>
Date: Mon, 3 Feb 2025 09:48:30 +0200
Subject: [PATCH] feat(cron): allow LW characters combination in the
 day-of-month field

---
 internal/csm/day_node.go |  6 +++---
 quartz/cron.go           | 22 ++++++++++++++--------
 quartz/cron_test.go      |  5 +++++
 3 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/internal/csm/day_node.go b/internal/csm/day_node.go
index 8ba682c..3a2e3c9 100644
--- a/internal/csm/day_node.go
+++ b/internal/csm/day_node.go
@@ -140,8 +140,8 @@ func (n *DayNode) max() int {
 }
 
 func (n *DayNode) nextDayN() (overflowed bool) {
-	switch n.n {
-	case NWeekday:
+	switch {
+	case n.n > 0 && n.n&NWeekday != 0:
 		n.nextWeekdayOfMonth()
 	default:
 		n.nextLastDayOfMonth()
@@ -155,7 +155,7 @@ func (n *DayNode) nextWeekdayOfMonth() {
 
 	monthLastDate := lastDayOfMonth(year, month)
 	date := n.c.values[0]
-	if date > monthLastDate {
+	if date > monthLastDate || n.n&NLastDayOfMonth != 0 {
 		date = monthLastDate
 	}
 
diff --git a/quartz/cron.go b/quartz/cron.go
index 8a216ea..5bec075 100644
--- a/quartz/cron.go
+++ b/quartz/cron.go
@@ -288,16 +288,22 @@ func parseDayOfMonthField(field string, min, max int, translate ...[]string) (*c
 		return newCronFieldN([]int{}, -n), nil
 	}
 
-	if strings.ContainsRune(field, weekdayRune) && cronWeekdayRegex.MatchString(field) {
-		day := strings.TrimSuffix(field, string(weekdayRune))
-		if day == "" {
-			return nil, newInvalidCronFieldError("weekday", field)
+	if strings.ContainsRune(field, weekdayRune) {
+		if field == fmt.Sprintf("%c%c", lastRune, weekdayRune) {
+			return newCronFieldN([]int{0}, cronLastDayOfMonthN|cronWeekdayN), nil
 		}
-		dayOfMonth, err := strconv.Atoi(day)
-		if err != nil || !inScope(dayOfMonth, min, max) {
-			return nil, newInvalidCronFieldError("weekday", field)
+
+		if cronWeekdayRegex.MatchString(field) {
+			day := strings.TrimSuffix(field, string(weekdayRune))
+			if day == "" {
+				return nil, newInvalidCronFieldError("weekday", field)
+			}
+			dayOfMonth, err := strconv.Atoi(day)
+			if err != nil || !inScope(dayOfMonth, min, max) {
+				return nil, newInvalidCronFieldError("weekday", field)
+			}
+			return newCronFieldN([]int{dayOfMonth}, cronWeekdayN), nil
 		}
-		return newCronFieldN([]int{dayOfMonth}, cronWeekdayN), nil
 	}
 
 	return parseField(field, min, max, translate...)
diff --git a/quartz/cron_test.go b/quartz/cron_test.go
index a29f8b4..b1da8c5 100644
--- a/quartz/cron_test.go
+++ b/quartz/cron_test.go
@@ -264,6 +264,10 @@ func TestCronExpressionDayOfMonth(t *testing.T) {
 			expression: "0 15 10 31W * ?",
 			expected:   "Mon Mar 31 10:15:00 2025",
 		},
+		{
+			expression: "0 15 10 LW * ?",
+			expected:   "Mon Mar 31 10:15:00 2025",
+		},
 	}
 
 	prev := time.Date(2024, 1, 1, 12, 00, 00, 00, time.UTC).UnixNano()
@@ -419,6 +423,7 @@ func TestCronExpressionParseError(t *testing.T) {
 		"0 15 10 L- * ?",
 		"0 15 10 L-a * ?",
 		"0 15 10 L-32 * ?",
+		"0 15 10 WL * ?",
 	}
 
 	for _, tt := range tests {