support setting the last 1 to 3 days of the month to scheduled transaction frequency

pkg/utils/datetimes.go

@@ -286,6 +286,12 @@ func IsUnixTimeEqualsYearAndMonth(unixTime int64, timezone *time.Location, year
 	return date.Year() == int(year) && int(date.Month()) == int(month)
 }
 
+// GetMaxDayOfMonth returns the maximum day of the month for the specified year and month
+func GetMaxDayOfMonth(year int, month time.Month) int {
+	t := time.Date(year, month+1, 0, 0, 0, 0, 0, time.UTC)
+	return t.Day()
+}
+
 // GetTimezoneOffsetMinutes returns offset minutes according specified timezone
 func GetTimezoneOffsetMinutes(unixTime int64, timezone *time.Location) int16 {
 	_, tzOffset := parseFromUnixTime(unixTime).In(timezone).Zone()

pkg/utils/datetimes_test.go

@@ -333,6 +333,32 @@ func TestIsUnixTimeEqualsYearAndMonth(t *testing.T) {
 	assert.Equal(t, false, actualValue)
 }
 
+func TestGetMaxDayOfMonth(t *testing.T) {
+	expectedValue := 31
+	actualValue := GetMaxDayOfMonth(2023, 1)
+	assert.Equal(t, expectedValue, actualValue)
+
+	expectedValue = 28
+	actualValue = GetMaxDayOfMonth(2023, 2)
+	assert.Equal(t, expectedValue, actualValue)
+
+	expectedValue = 29
+	actualValue = GetMaxDayOfMonth(2024, 2)
+	assert.Equal(t, expectedValue, actualValue)
+
+	expectedValue = 30
+	actualValue = GetMaxDayOfMonth(2023, 4)
+	assert.Equal(t, expectedValue, actualValue)
+
+	expectedValue = 31
+	actualValue = GetMaxDayOfMonth(2023, 12)
+	assert.Equal(t, expectedValue, actualValue)
+
+	expectedValue = 28
+	actualValue = GetMaxDayOfMonth(2100, 2)
+	assert.Equal(t, expectedValue, actualValue)
+}
+
 func TestGetTimezoneOffsetMinutes_FixedTimezone(t *testing.T) {
 	timezone := time.FixedZone("Test Timezone", 120*60)
 	expectedValue := int16(120)