Adding upstream version 0.28.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

tools/cron/schedule.go

@@ -0,0 +1,218 @@
+package cron
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// Moment represents a parsed single time moment.
+type Moment struct {
+	Minute    int `json:"minute"`
+	Hour      int `json:"hour"`
+	Day       int `json:"day"`
+	Month     int `json:"month"`
+	DayOfWeek int `json:"dayOfWeek"`
+}
+
+// NewMoment creates a new Moment from the specified time.
+func NewMoment(t time.Time) *Moment {
+	return &Moment{
+		Minute:    t.Minute(),
+		Hour:      t.Hour(),
+		Day:       t.Day(),
+		Month:     int(t.Month()),
+		DayOfWeek: int(t.Weekday()),
+	}
+}
+
+// Schedule stores parsed information for each time component when a cron job should run.
+type Schedule struct {
+	Minutes    map[int]struct{} `json:"minutes"`
+	Hours      map[int]struct{} `json:"hours"`
+	Days       map[int]struct{} `json:"days"`
+	Months     map[int]struct{} `json:"months"`
+	DaysOfWeek map[int]struct{} `json:"daysOfWeek"`
+
+	rawExpr string
+}
+
+// IsDue checks whether the provided Moment satisfies the current Schedule.
+func (s *Schedule) IsDue(m *Moment) bool {
+	if _, ok := s.Minutes[m.Minute]; !ok {
+		return false
+	}
+
+	if _, ok := s.Hours[m.Hour]; !ok {
+		return false
+	}
+
+	if _, ok := s.Days[m.Day]; !ok {
+		return false
+	}
+
+	if _, ok := s.DaysOfWeek[m.DayOfWeek]; !ok {
+		return false
+	}
+
+	if _, ok := s.Months[m.Month]; !ok {
+		return false
+	}
+
+	return true
+}
+
+var macros = map[string]string{
+	"@yearly":   "0 0 1 1 *",
+	"@annually": "0 0 1 1 *",
+	"@monthly":  "0 0 1 * *",
+	"@weekly":   "0 0 * * 0",
+	"@daily":    "0 0 * * *",
+	"@midnight": "0 0 * * *",
+	"@hourly":   "0 * * * *",
+}
+
+// NewSchedule creates a new Schedule from a cron expression.
+//
+// A cron expression could be a macro OR 5 segments separated by space,
+// representing: minute, hour, day of the month, month and day of the week.
+//
+// The following segment formats are supported:
+//   - wildcard: *
+//   - range:    1-30
+//   - step:     */n or 1-30/n
+//   - list:     1,2,3,10-20/n
+//
+// The following macros are supported:
+//   - @yearly (or @annually)
+//   - @monthly
+//   - @weekly
+//   - @daily (or @midnight)
+//   - @hourly
+func NewSchedule(cronExpr string) (*Schedule, error) {
+	if v, ok := macros[cronExpr]; ok {
+		cronExpr = v
+	}
+
+	segments := strings.Split(cronExpr, " ")
+	if len(segments) != 5 {
+		return nil, errors.New("invalid cron expression - must be a valid macro or to have exactly 5 space separated segments")
+	}
+
+	minutes, err := parseCronSegment(segments[0], 0, 59)
+	if err != nil {
+		return nil, err
+	}
+
+	hours, err := parseCronSegment(segments[1], 0, 23)
+	if err != nil {
+		return nil, err
+	}
+
+	days, err := parseCronSegment(segments[2], 1, 31)
+	if err != nil {
+		return nil, err
+	}
+
+	months, err := parseCronSegment(segments[3], 1, 12)
+	if err != nil {
+		return nil, err
+	}
+
+	daysOfWeek, err := parseCronSegment(segments[4], 0, 6)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Schedule{
+		Minutes:    minutes,
+		Hours:      hours,
+		Days:       days,
+		Months:     months,
+		DaysOfWeek: daysOfWeek,
+		rawExpr:    cronExpr,
+	}, nil
+}
+
+// parseCronSegment parses a single cron expression segment and
+// returns its time schedule slots.
+func parseCronSegment(segment string, min int, max int) (map[int]struct{}, error) {
+	slots := map[int]struct{}{}
+
+	list := strings.Split(segment, ",")
+	for _, p := range list {
+		stepParts := strings.Split(p, "/")
+
+		// step (*/n, 1-30/n)
+		var step int
+		switch len(stepParts) {
+		case 1:
+			step = 1
+		case 2:
+			parsedStep, err := strconv.Atoi(stepParts[1])
+			if err != nil {
+				return nil, err
+			}
+			if parsedStep < 1 || parsedStep > max {
+				return nil, fmt.Errorf("invalid segment step boundary - the step must be between 1 and the %d", max)
+			}
+			step = parsedStep
+		default:
+			return nil, errors.New("invalid segment step format - must be in the format */n or 1-30/n")
+		}
+
+		// find the min and max range of the segment part
+		var rangeMin, rangeMax int
+		if stepParts[0] == "*" {
+			rangeMin = min
+			rangeMax = max
+		} else {
+			// single digit (1) or range (1-30)
+			rangeParts := strings.Split(stepParts[0], "-")
+			switch len(rangeParts) {
+			case 1:
+				if step != 1 {
+					return nil, errors.New("invalid segement step - step > 1 could be used only with the wildcard or range format")
+				}
+				parsed, err := strconv.Atoi(rangeParts[0])
+				if err != nil {
+					return nil, err
+				}
+				if parsed < min || parsed > max {
+					return nil, errors.New("invalid segment value - must be between the min and max of the segment")
+				}
+				rangeMin = parsed
+				rangeMax = rangeMin
+			case 2:
+				parsedMin, err := strconv.Atoi(rangeParts[0])
+				if err != nil {
+					return nil, err
+				}
+				if parsedMin < min || parsedMin > max {
+					return nil, fmt.Errorf("invalid segment range minimum - must be between %d and %d", min, max)
+				}
+				rangeMin = parsedMin
+
+				parsedMax, err := strconv.Atoi(rangeParts[1])
+				if err != nil {
+					return nil, err
+				}
+				if parsedMax < parsedMin || parsedMax > max {
+					return nil, fmt.Errorf("invalid segment range maximum - must be between %d and %d", rangeMin, max)
+				}
+				rangeMax = parsedMax
+			default:
+				return nil, errors.New("invalid segment range format - the range must have 1 or 2 parts")
+			}
+		}
+
+		// fill the slots
+		for i := rangeMin; i <= rangeMax; i += step {
+			slots[i] = struct{}{}
+		}
+	}
+
+	return slots, nil
+}