package dns

import (
	"math/rand"
	"regexp"
)

// MaxLabelLength is the maximum length for a name that can be used in DNS.
const MaxLabelLength = 63

// InvalidNameRe is a regex that matches characters which can not be included in
// a DNS name.
var InvalidNameRe = regexp.MustCompile(`[^A-Za-z0-9\\-]+`)

type RecursorStrategy string

const (
	RecursorStrategySequential RecursorStrategy = "sequential"
	RecursorStrategyRandom     RecursorStrategy = "random"
)

func (s RecursorStrategy) Indexes(max int) []int {
	switch s {
	case RecursorStrategyRandom:
		return rand.Perm(max)
	default:
		idxs := make([]int, max)
		for i := range idxs {
			idxs[i] = i
		}
		return idxs

	}
}