Add existing codebase

pkg/brainbuffer/scheduling/pattern.go

@@ -0,0 +1,112 @@
+package scheduling
+
+import (
+	apperrors "brainbuffer/pkg/brainbuffer/errors"
+	"github.com/pkg/errors"
+	"github.com/robfig/cron/v3"
+	"time"
+)
+
+type Pattern string
+
+func (pattern Pattern) NextTime(fromTime time.Time) (*time.Time, error) {
+	schedule, err := pattern.Parse()
+	if err != nil {
+		return nil, err
+	}
+
+	nextTime := schedule.Next(fromTime)
+
+	return &nextTime, nil
+}
+
+func (pattern Pattern) NextTimesUntil(fromTime time.Time, untilTime time.Time) ([]time.Time, error) {
+	schedule, err := pattern.Parse()
+	if err != nil {
+		return nil, err
+	}
+
+	nextTimes := make([]time.Time, 0, 0)
+
+	for nextTime := schedule.Next(fromTime); nextTime.Before(untilTime); nextTime = schedule.Next(nextTime) {
+		nextTimes = append(nextTimes, nextTime)
+	}
+
+	return nextTimes, nil
+}
+
+func (pattern Pattern) NextNTimes(fromTime time.Time, n int) ([]time.Time, error) {
+	schedule, err := pattern.Parse()
+	if err != nil {
+		return nil, err
+	}
+
+	nextTimes := make([]time.Time, n)
+
+	for nextTime, i := schedule.Next(fromTime), 0; i < n; i++ {
+		nextTimes = append(nextTimes, nextTime)
+		nextTime = schedule.Next(nextTime)
+	}
+
+	return nextTimes, nil
+}
+
+func (pattern Pattern) MatchesTime(t time.Time, precision time.Duration) (*time.Time, error) {
+	if precision > 24*time.Hour {
+		return nil, errors.New("unsupported precision value")
+	}
+
+	matchingTime, err := pattern.NextTime(time.Now())
+	if err != nil {
+		return nil, err
+	}
+
+	truncMatchingTime := matchingTime.Truncate(precision)
+	truncT := t.Truncate(precision)
+
+	for !truncMatchingTime.Equal(truncT) && truncMatchingTime.Before(truncT) {
+		matchingTime, _ = pattern.NextTime(*matchingTime)
+		truncMatchingTime = matchingTime.Truncate(precision)
+	}
+
+	if truncMatchingTime.Equal(truncT) {
+		return matchingTime, nil
+	} else {
+		return nil, nil
+	}
+}
+
+func (pattern Pattern) Parse() (cron.Schedule, error) {
+	schedule, err := cron.ParseStandard(string(pattern))
+	if err != nil {
+		return nil, apperrors.UnknownError{Err: err}
+	}
+
+	return schedule, nil
+}
+
+type Patterns []Pattern
+
+func (patterns Patterns) NextTime(fromTime time.Time) (*time.Time, Pattern, error) {
+	nextTimes := make(map[Pattern]time.Time)
+
+	for i, val := range patterns {
+		nextTime, err := patterns[i].NextTime(fromTime)
+		if err != nil {
+			return nil, "", err
+		}
+
+		nextTimes[val] = *nextTime
+	}
+
+	earliestNextTime := nextTimes[patterns[0]]
+	earliestNextTimePattern := patterns[0]
+	for k, v := range nextTimes {
+		if v.Before(earliestNextTime) {
+			earliestNextTime = v
+			earliestNextTimePattern = k
+		}
+	}
+
+	return &earliestNextTime, earliestNextTimePattern, nil
+}