initial commit

pattern.go

@@ -0,0 +1,103 @@
+package cron
+
+import(
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type UnitMatcher interface {
+	Matches(timePart int) bool
+}
+
+type Wildcard struct {
+	subpattern string
+}
+
+func (_ *Wildcard) Matches(timePart int) bool {
+	return true
+}
+
+type Constant struct {
+	subpattern string
+	value int
+}
+
+func (constant *Constant) Matches(timePart int) bool {
+	return constant.value == timePart
+}
+
+type Range struct {
+	subpattern string
+	min, max int
+}
+
+func (r *Range) Matches(timePart int) bool {
+	return timePart >= r.min && timePart <= r.max
+}
+
+type CronSchedule struct {
+	minutes UnitMatcher
+	hours UnitMatcher
+	dayOfMonth UnitMatcher
+	monthOfYear UnitMatcher
+	dayOfWeek UnitMatcher
+	year UnitMatcher
+}
+
+type Schedule interface {
+	ShouldRun(t time.Time) bool
+}
+
+func (schedule CronSchedule) ShouldRun(t time.Time) bool {
+	return schedule.minutes.Matches(t.Minute()) && schedule.hours.Matches(t.Hour()) && schedule.dayOfMonth.Matches(t.Day()) && schedule.monthOfYear.Matches(int(t.Month())) && schedule.dayOfWeek.Matches(int(t.Weekday())) && schedule.year.Matches(t.Year())
+
+}
+
+func parsePart(subpattern string) UnitMatcher {
+	constantRegexp, err := regexp.Compile(`\A\d+\z`)
+	if err != nil {
+		panic("invalid hardcoded regexp!")
+	}
+	rangeRegexp, err := regexp.Compile(`\A\d+\-\d+\z`)
+	if err != nil {
+		panic("invalid hardcoded regexp!")
+	}
+
+	if "*" == subpattern {
+		return &Wildcard{subpattern}
+	} else if constantRegexp.MatchString(subpattern) {
+		number, err := strconv.Atoi(subpattern)
+		if err != nil {
+			panic(fmt.Sprintf("regexp matched integer, but couldn't convert %q to int", subpattern))
+		}
+		return &Constant{subpattern, number}
+	} else if rangeRegexp.MatchString(subpattern) {
+		rangeParts := strings.Split(subpattern, "-")
+		min, err := strconv.Atoi(rangeParts[0])
+		if err != nil {
+			panic(fmt.Sprintf("regexp matched integer, but couldn't convert %q to int", rangeParts[0]))
+		}
+		max, err := strconv.Atoi(rangeParts[1])
+		if err != nil {
+			panic(fmt.Sprintf("regexp matched integer, but couldn't convert %q to int", rangeParts[1]))
+		}
+		return &Range{subpattern, min, max}
+	}
+	return nil
+}
+
+func Parse(pattern string) Schedule {
+	parts := strings.Split(pattern, " ")
+
+	return &CronSchedule{
+		minutes: parsePart(parts[0]),
+		hours: parsePart(parts[1]),
+		dayOfMonth: parsePart(parts[2]),
+		monthOfYear: parsePart(parts[3]),
+		dayOfWeek: parsePart(parts[4]),
+		year: parsePart(parts[4]),
+	}
+}

pattern_test.go

@@ -0,0 +1,46 @@
+package cron
+
+import(
+	"testing"
+	"time"
+)
+
+type TimeTestCase struct {
+	when time.Time
+	runs bool
+}
+
+func IsScheduled(t *testing.T, pattern string, tests []TimeTestCase) {
+	schedule := Parse(pattern)
+
+	for _, test := range(tests) {
+		if test.runs != schedule.ShouldRun(test.when) {
+			should := ""
+			if !test.runs {
+				should = "not "
+			}
+
+			t.Errorf("pattern %q should %vrun at time %v", pattern, should, test.when)
+		}
+	}
+}
+
+func TestAllStars(t *testing.T) {
+	IsScheduled(t, "* * * * * *", []TimeTestCase{{time.Now(), true}})
+}
+
+func TestFiveMinutesAfterTheHour(t *testing.T) {
+	IsScheduled(t, "5 * * * * *", []TimeTestCase{
+		{time.Date(2016, time.January, 5, 10, 15, 0, 0, time.UTC), false},
+		{time.Date(2016, time.January, 5, 10, 5, 0, 0, time.UTC), true},
+	})
+}
+
+func TestRanges(t *testing.T) {
+	IsScheduled(t, "4-8 * * * * *", []TimeTestCase{
+		{time.Date(2016, time.January, 5, 10, 15, 0, 0, time.UTC), false},
+		{time.Date(2016, time.January, 5, 10, 5, 0, 0, time.UTC), true},
+		{time.Date(2016, time.January, 5, 10, 4, 0, 0, time.UTC), true},
+		{time.Date(2016, time.January, 5, 10, 8, 0, 0, time.UTC), true},
+	})
+}