include sorting for days of week

data/types/common/day.go

@@ -21,3 +21,37 @@ func DaysOfWeek() []string {
 		DaySaturday,
 	}
 }
+
+type DaysOfWeekByDayIndex []string
+
+func (d DaysOfWeekByDayIndex) Len() int {
+	return len(d)
+}
+func (d DaysOfWeekByDayIndex) Swap(i int, j int) {
+	d[i], d[j] = d[j], d[i]
+}
+
+func (d DaysOfWeekByDayIndex) Less(i int, j int) bool {
+	return DayIndex(d[i]) < DayIndex(d[j])
+}
+
+func DayIndex(day string) int {
+	switch day {
+	case DaySunday:
+		return 1
+	case DayMonday:
+		return 2
+	case DayTuesday:
+		return 3
+	case DayWednesday:
+		return 4
+	case DayThursday:
+		return 5
+	case DayFriday:
+		return 6
+	case DaySaturday:
+		return 7
+	default:
+		return 0
+	}
+}

data/types/common/day_test.go

@@ -49,4 +49,28 @@ var _ = Describe("Day", func() {
 			common.DaySaturday,
 		}))
 	})
+
+	Context("DayIndex", func() {
+		DescribeTable("return the expected index when the day",
+			func(day string, expectedIndex int) {
+				Expect(common.DayIndex(day)).To(Equal(expectedIndex))
+			},
+			Entry("is an empty string", "", 0),
+			Entry("is sunday", "sunday", 1),
+			Entry("is constant sunday", common.DaySunday, 1),
+			Entry("is monday", "monday", 2),
+			Entry("is constant monday", common.DayMonday, 2),
+			Entry("is tuesday", "tuesday", 3),
+			Entry("is constant tuesday", common.DayTuesday, 3),
+			Entry("is wednesday", "wednesday", 4),
+			Entry("isconstant  wednesday", common.DayWednesday, 4),
+			Entry("is thursday", "thursday", 5),
+			Entry("is constant thursday", common.DayThursday, 5),
+			Entry("is friday", "friday", 6),
+			Entry("is constant friday", common.DayFriday, 6),
+			Entry("is saturday", "saturday", 7),
+			Entry("is constant saturday", common.DaySaturday, 7),
+			Entry("is an invalid string", "invalid", 0),
+		)
+	})
 })