Extend cron patterns to support dow and dom

core/cron.go

@@ -13,6 +13,8 @@ func GetNextUpdate(lastUpdated time.Time, spec string) (nextUpdate time.Time, er
 		nextUpdates, err = parseEverySpec(lastUpdated, spec[len("every "):])
 	case strings.HasPrefix(spec, "at "):
 		nextUpdates, err = parseAtSpec(lastUpdated, spec[len("at "):])
+	case strings.HasPrefix(spec, "on "):
+		nextUpdates, err = parseOnSpec(lastUpdated, spec[len("on "):])
 	default:
 		return time.Time{}, fmt.Errorf("unknown spec format: %v", spec)
 	}
@@ -45,8 +47,7 @@ func parseEverySpec(base time.Time, everySpec string) (nextUpdates []time.Time,
 // Get the next instances of the at-spec times after the base time.
 // An at-spec is in the patterm HH:MM[,HH:MM,[...]].
 func parseAtSpec(base time.Time, atSpec string) (nextUpdates []time.Time, err error) {
-	timeSpecs := strings.Split(atSpec, ",")
+	for _, timeSpec := range strings.Split(atSpec, ",") {
-	for _, timeSpec := range timeSpecs {
 		var hour, minute int
 		_, err = fmt.Sscanf(timeSpec, "%d:%d", &hour, &minute)
 		if err != nil {
@@ -62,3 +63,87 @@ func parseAtSpec(base time.Time, atSpec string) (nextUpdates []time.Time, err er
 	}
 	return
 }
+
+var weekdays = map[string]time.Weekday{
+	"Sun": time.Sunday,
+	"Mon": time.Monday,
+	"Tue": time.Tuesday,
+	"Wed": time.Wednesday,
+	"Thu": time.Thursday,
+	"Fri": time.Friday,
+	"Sat": time.Saturday,
+}
+
+// Get the next instances of the on-spec times after the base time.
+// An on-spec is in the pattern DOW[,DOW[...]] where DOW is an abbreviated weekday
+// or M/D[,M/D[...]] where M/D is a month and day.
+// As a special case, "*/N" matches the Nth day of every month.
+// An on-spec may be followed by an at-spec; otherwise, "at 00:00" is implied.
+func parseOnSpec(base time.Time, onSpec string) (nextUpdates []time.Time, err error) {
+	type Date struct {
+		Year  int
+		Month time.Month
+		Day   int
+	}
+	type Time struct {
+		Hour   int
+		Minute int
+	}
+
+	atSpec := "00:00"
+	if on := strings.Index(onSpec, " at "); on > -1 {
+		atSpec = onSpec[on+len(" at "):]
+		onSpec = onSpec[:on]
+	}
+	var atTimes []Time
+	for _, timeSpec := range strings.Split(atSpec, ",") {
+		var hour, minute int
+		_, err := fmt.Sscanf(timeSpec, "%d:%d", &hour, &minute)
+		if err != nil {
+			return nil, fmt.Errorf("could not parse at-spec %s: %v", timeSpec, err)
+		}
+		atTimes = append(atTimes, Time{hour, minute})
+	}
+
+	var dates []Date
+	for _, daySpec := range strings.Split(onSpec, ",") {
+		if weekday, ok := weekdays[daySpec]; ok {
+			// For a weekday, add the next of that weekday 0-6 days ahead and 7-13 days ahead.
+			// The first date ensures that we don't miss multiple updates on the same day of the week
+			// (e.g. "on Sun at 06:00,18:00") and the second date ensures that we don't get stuck with
+			// only a date in the past (e.g. "on Sun at 02:00" when base is Sun 03:00).
+			daysForward := (int(weekday) - int(base.Weekday()) + 7) % 7 // value in [0,6]
+			day0_6 := base.AddDate(0, 0, daysForward)
+			dates = append(dates, Date{day0_6.Year(), day0_6.Month(), day0_6.Day()})
+			day7_13 := base.AddDate(0, 0, daysForward+7)
+			dates = append(dates, Date{day7_13.Year(), day7_13.Month(), day7_13.Day()})
+		} else if strings.HasPrefix(daySpec, "*/") {
+			// For every-month, add the date for the current month and the date for the next month.
+			var day int
+			_, err := fmt.Sscanf(daySpec, "*/%d", &day)
+			if err != nil {
+				return nil, fmt.Errorf("could not parse month/day %s: %v", daySpec, err)
+			}
+			dates = append(dates, Date{base.Year(), base.Month(), day})
+			nextMonth := base.AddDate(0, 1, 0)
+			dates = append(dates, Date{nextMonth.Year(), nextMonth.Month(), day})
+		} else {
+			// For month/day, add the date for the base year and the next year.
+			var month, day int
+			_, err := fmt.Sscanf(daySpec, "%d/%d", &month, &day)
+			if err != nil {
+				return nil, fmt.Errorf("could not parse month/day %s: %v", daySpec, err)
+			}
+			dates = append(dates, Date{base.Year(), time.Month(month), day})
+			dates = append(dates, Date{base.Year() + 1, time.Month(month), day})
+		}
+	}
+
+	// Now, for each date, create a datetime based on the at-spec.
+	for _, date := range dates {
+		for _, atTime := range atTimes {
+			nextUpdates = append(nextUpdates, time.Date(date.Year, date.Month, date.Day, atTime.Hour, atTime.Minute, 0, 0, base.Location()))
+		}
+	}
+	return
+}

core/cron_test.go

@@ -7,103 +7,163 @@ import (
 )
 
 func TestGetNextUpdate(t *testing.T) {
-	tests := []struct {
+	date := func(year int, month time.Month, day, hour, minute int) time.Time {
-		lastUpdated time.Time
+		return time.Date(year, month, day, hour, minute, 0, 0, time.UTC)
-		spec        string
-		expected    time.Time
-		expectErr   bool
-	}{
-		{
-			lastUpdated: time.Date(2020, 10, 22, 12, 0, 0, 0, time.UTC),
-			spec:        "every 1h#1",
-			expected:    time.Date(2020, 10, 22, 13, 0, 0, 0, time.UTC),
-			expectErr:   false,
-		},
-		{
-			lastUpdated: time.Date(2020, 10, 22, 12, 0, 5, 0, time.UTC),
-			spec:        "every 1h#2",
-			expected:    time.Date(2020, 10, 22, 13, 0, 0, 0, time.UTC),
-			expectErr:   false,
-		},
-		{
-			lastUpdated: time.Date(2020, 10, 22, 11, 0, 0, 0, time.UTC),
-			spec:        "every 2h30m#1",
-			expected:    time.Date(2020, 10, 22, 11, 30, 0, 0, time.UTC),
-			expectErr:   false,
-		},
-		{
-			lastUpdated: time.Date(2020, 10, 22, 11, 30, 0, 0, time.UTC),
-			spec:        "every 2h30m#2",
-			expected:    time.Date(2020, 10, 22, 14, 00, 0, 0, time.UTC),
-			expectErr:   false,
-		},
-		{
-			lastUpdated: time.Date(2020, 10, 22, 11, 30, 0, 0, time.UTC),
-			spec:        "every 3",
-			expected:    time.Time{},
-			expectErr:   true,
-		},
-		{
-			lastUpdated: time.Date(2020, 10, 22, 12, 0, 0, 0, time.UTC),
-			spec:        "at 14:00#1",
-			expected:    time.Date(2020, 10, 22, 14, 0, 0, 0, time.UTC),
-			expectErr:   false,
-		},
-		{
-			lastUpdated: time.Date(2020, 10, 22, 14, 0, 0, 0, time.UTC),
-			spec:        "at 14:00#2",
-			expected:    time.Date(2020, 10, 23, 14, 0, 0, 0, time.UTC),
-			expectErr:   false,
-		},
-		{
-			lastUpdated: time.Date(2020, 10, 22, 15, 0, 0, 0, time.UTC),
-			spec:        "at 14:00#3",
-			expected:    time.Date(2020, 10, 23, 14, 0, 0, 0, time.UTC),
-			expectErr:   false,
-		},
-		{
-			lastUpdated: time.Date(2020, 10, 22, 9, 0, 0, 0, time.UTC),
-			spec:        "at 10:00,15:00#1",
-			expected:    time.Date(2020, 10, 22, 10, 0, 0, 0, time.UTC),
-			expectErr:   false,
-		},
-		{
-			lastUpdated: time.Date(2020, 10, 22, 12, 0, 0, 0, time.UTC),
-			spec:        "at 10:00,15:00#2",
-			expected:    time.Date(2020, 10, 22, 15, 0, 0, 0, time.UTC),
-			expectErr:   false,
-		},
-		{
-			lastUpdated: time.Date(2020, 10, 22, 15, 0, 0, 0, time.UTC),
-			spec:        "at 10:00,15:00#3",
-			expected:    time.Date(2020, 10, 23, 10, 0, 0, 0, time.UTC),
-			expectErr:   false,
-		},
-		{
-			lastUpdated: time.Date(2020, 10, 22, 16, 0, 0, 0, time.UTC),
-			spec:        "at 10:00,15:00#4",
-			expected:    time.Date(2020, 10, 23, 10, 0, 0, 0, time.UTC),
-			expectErr:   false,
-		},
 	}
 
-	for _, test := range tests {
+	expect := func(lastUpdated time.Time, spec string, expected time.Time) {
-		t.Run(test.spec, func(t *testing.T) {
+		t.Run(spec, func(t *testing.T) {
-			spec := test.spec
 			if comment := strings.Index(spec, "#"); comment > -1 {
 				spec = spec[:comment]
 			}
-			nextUpdate, err := GetNextUpdate(test.lastUpdated, spec)
+			nextUpdate, err := GetNextUpdate(lastUpdated, spec)
-			if test.expectErr && err == nil {
+			if err != nil {
-				t.Error("test did not fail as expected")
+				t.Fatalf("unexpected error: %v", err)
 			}
-			if !test.expectErr && err != nil {
+			if !nextUpdate.Equal(expected) {
-				t.Errorf("error: %v", err)
+				t.Errorf("\nexpected: %v\n     got: %v", expected, nextUpdate)
-			}
-			if !nextUpdate.Equal(test.expected) {
-				t.Errorf("\nexpected: %v\n     got: %v", test.expected, nextUpdate)
 			}
 		})
 	}
 
+	expectFail := func(lastUpdated time.Time, spec string) {
+		t.Run(spec, func(t *testing.T) {
+			if comment := strings.Index(spec, "#"); comment > -1 {
+				spec = spec[:comment]
+			}
+			_, err := GetNextUpdate(lastUpdated, spec)
+			if err == nil {
+				t.Error("expected error")
+			}
+		})
+	}
+
+	expect(
+		date(2020, 10, 22, 12, 0),
+		"every 1h#1",
+		date(2020, 10, 22, 13, 0),
+	)
+	expect(
+		date(2020, 10, 22, 12, 1),
+		"every 1h#2",
+		date(2020, 10, 22, 13, 0),
+	)
+
+	expect(
+		date(2020, 10, 22, 11, 0),
+		"every 2h30m#1",
+		date(2020, 10, 22, 11, 30),
+	)
+	expect(
+		date(2020, 10, 22, 11, 30),
+		"every 2h30m#2",
+		date(2020, 10, 22, 14, 0),
+	)
+
+	expectFail(
+		date(2020, 10, 22, 11, 30),
+		"every 3",
+	)
+
+	expect(
+		date(2020, 10, 22, 12, 0),
+		"at 14:00#1",
+		date(2020, 10, 22, 14, 0),
+	)
+	expect(
+		date(2020, 10, 22, 14, 0),
+		"at 14:00#2",
+		date(2020, 10, 23, 14, 0),
+	)
+	expect(
+		date(2020, 10, 22, 15, 0),
+		"at 14:00#3",
+		date(2020, 10, 23, 14, 0),
+	)
+
+	expect(
+		date(2020, 10, 22, 9, 0),
+		"at 10:00,15:00#1",
+		date(2020, 10, 22, 10, 0),
+	)
+	expect(
+		date(2020, 10, 22, 12, 0),
+		"at 10:00,15:00#2",
+		date(2020, 10, 22, 15, 0),
+	)
+	expect(
+		date(2020, 10, 22, 15, 0),
+		"at 10:00,15:00#3",
+		date(2020, 10, 23, 10, 0),
+	)
+	expect(
+		date(2020, 10, 22, 16, 0),
+		"at 10:00,15:00#4",
+		date(2020, 10, 23, 10, 0),
+	)
+
+	expect(
+		date(2020, 10, 22, 6, 0),
+		"on Sun#1",
+		date(2020, 10, 25, 0, 0),
+	)
+	expect(
+		date(2020, 10, 25, 0, 0),
+		"on Sun#2",
+		date(2020, 11, 1, 0, 0),
+	)
+
+	expect(
+		date(2020, 10, 19, 0, 0),
+		"on Tue,Thu at 04:00#1",
+		date(2020, 10, 20, 4, 0),
+	)
+	expect(
+		date(2020, 10, 20, 3, 0),
+		"on Tue,Thu at 04:00#2",
+		date(2020, 10, 20, 4, 0),
+	)
+	expect(
+		date(2020, 10, 20, 4, 0),
+		"on Tue,Thu at 04:00#3",
+		date(2020, 10, 22, 4, 0),
+	)
+	expect(
+		date(2020, 10, 21, 4, 0),
+		"on Tue,Thu at 04:00#4",
+		date(2020, 10, 22, 4, 0),
+	)
+	expect(
+		date(2020, 10, 22, 4, 0),
+		"on Tue,Thu at 04:00#5",
+		date(2020, 10, 27, 4, 0),
+	)
+
+	expect(
+		date(2020, 10, 21, 12, 0),
+		"on 10/22 at 12:00#1",
+		date(2020, 10, 22, 12, 0),
+	)
+	expect(
+		date(2020, 10, 22, 10, 0),
+		"on 10/22 at 12:00#2",
+		date(2020, 10, 22, 12, 0),
+	)
+	expect(
+		date(2020, 10, 22, 12, 0),
+		"on 10/22 at 12:00#3",
+		date(2021, 10, 22, 12, 0),
+	)
+
+	expect(
+		date(2020, 10, 21, 12, 0),
+		"on */22#1",
+		date(2020, 10, 22, 0, 0),
+	)
+	expect(
+		date(2020, 10, 22, 0, 0),
+		"on */22#2",
+		date(2020, 11, 22, 0, 0),
+	)
+
 }