1package consul
2
3import (
4	"math/rand"
5	"time"
6)
7
8// DurationMinusBuffer returns a duration, minus a buffer and jitter
9// subtracted from the duration.  This function is used primarily for
10// servicing Consul TTL Checks in advance of the TTL.
11func DurationMinusBuffer(intv time.Duration, buffer time.Duration, jitter int64) time.Duration {
12	d := intv - buffer
13	if jitter == 0 {
14		d -= RandomStagger(d)
15	} else {
16		d -= RandomStagger(time.Duration(int64(d) / jitter))
17	}
18	return d
19}
20
21// DurationMinusBufferDomain returns the domain of valid durations from a
22// call to DurationMinusBuffer.  This function is used to check user
23// specified input values to DurationMinusBuffer.
24func DurationMinusBufferDomain(intv time.Duration, buffer time.Duration, jitter int64) (min time.Duration, max time.Duration) {
25	max = intv - buffer
26	if jitter == 0 {
27		min = max
28	} else {
29		min = max - time.Duration(int64(max)/jitter)
30	}
31	return min, max
32}
33
34// RandomStagger returns an interval between 0 and the duration
35func RandomStagger(intv time.Duration) time.Duration {
36	if intv == 0 {
37		return 0
38	}
39	return time.Duration(uint64(rand.Int63()) % uint64(intv))
40}
41