package metricsutil

import (
	"sort"
	"time"
)

var bucketBoundaries = []struct {
	Value time.Duration
	Label string
}{
	{1 * time.Minute, "1m"},
	{10 * time.Minute, "10m"},
	{20 * time.Minute, "20m"},
	{1 * time.Hour, "1h"},
	{2 * time.Hour, "2h"},
	{24 * time.Hour, "1d"},
	{2 * 24 * time.Hour, "2d"},
	{7 * 24 * time.Hour, "7d"},
	{30 * 24 * time.Hour, "30d"},
}

const OverflowBucket = "+Inf"

// TTLBucket computes the label to apply for a token TTL.
func TTLBucket(ttl time.Duration) string {
	upperBound := sort.Search(
		len(bucketBoundaries),
		func(i int) bool {
			return ttl <= bucketBoundaries[i].Value
		},
	)
	if upperBound >= len(bucketBoundaries) {
		return OverflowBucket
	} else {
		return bucketBoundaries[upperBound].Label
	}
}

func ExpiryBucket(expiryTime time.Time, leaseEpsilon time.Duration, rollingWindow time.Time, labelNS string, useNS bool) *LeaseExpiryLabel {
	if !useNS {
		labelNS = ""
	}
	leaseExpiryLabel := LeaseExpiryLabel{LabelNS: labelNS}

	// calculate rolling window
	if expiryTime.Before(rollingWindow) {
		leaseExpiryLabel.LabelName = expiryTime.Round(leaseEpsilon).String()
		return &leaseExpiryLabel
	}
	return nil
}

type LeaseExpiryLabel = struct {
	LabelName string
	LabelNS   string
}