changeover features in progress

msp/changeover.go

@@ -0,0 +1,51 @@
+package msp
+
+import (
+	"sort"
+	"time"
+)
+
+func GetChangeOvers(periods ...Period) (changeovers []time.Time) {
+	timeStamps := []time.Time{}
+	for _, x := range periods {
+		timeStamps = append(timeStamps, x.GetEndTime())
+		timeStamps = append(timeStamps, x.GetStartTime())
+	}
+	sort.Slice(timeStamps, func(i, j int) bool {
+		return timeStamps[i].Before(timeStamps[j])
+	})
+
+	for _, ts := range timeStamps {
+		before := ts.Add(-1 * time.Nanosecond)
+		after := ts.Add(1 * time.Nanosecond)
+		from, _ := MostSpecificPeriod(before, periods...)
+		to, _ := MostSpecificPeriod(after, periods...)
+		if from == to {
+			continue
+		}
+		changeovers = append(changeovers, ts)
+	}
+	return
+}
+
+func GetNextChangeOver(t time.Time, periods ...Period) (ts time.Time, err error) {
+	changeOvers := GetChangeOvers(periods...)
+	for _, ts := range changeOvers {
+		if ts.After(t) {
+			return ts, nil
+		}
+	}
+	return time.Unix(0, 0), ErrNoNextChangeover
+}
+
+func FlattenPeriods(periods ...Period) (ids []string) {
+	changeovers := GetChangeOvers(periods...)
+	for _, c := range changeovers {
+		id, err := MostSpecificPeriod(c, periods...)
+		if err != nil {
+			continue
+		}
+		ids = append(ids, id)
+	}
+	return
+}

msp/errors.go

@@ -9,4 +9,6 @@ var (
 	ErrEndAfterStart = errors.New("error: start time is after end time")
 	// ErrNoValidPeriods occurs when an empty set of periods is passed or when ll periods are invalid
 	ErrNoValidPeriods = errors.New("error: no valid periods available")
+	// ErrNoNextChangeover occurs when GetNextChangeover is called but there are no changeovers after t
+	ErrNoNextChangeover = errors.New("error: no valid periods available")
 )