package util

import (
	"net/netip"
	"testing"

	"github.com/stretchr/testify/assert"
	"tailscale.com/util/dnsname"
	"tailscale.com/util/must"
)


func TestMagicDNSRootDomains100(t *testing.T) {
	domains := GenerateIPv4DNSRootDomain(netip.MustParsePrefix("100.64.0.0/10"))

	assert.Contains(t, domains, must.Get(dnsname.ToFQDN("64.100.in-addr.arpa.")))
	assert.Contains(t, domains, must.Get(dnsname.ToFQDN("100.100.in-addr.arpa.")))
	assert.Contains(t, domains, must.Get(dnsname.ToFQDN("127.100.in-addr.arpa.")))
}

func TestMagicDNSRootDomains172(t *testing.T) {
	domains := GenerateIPv4DNSRootDomain(netip.MustParsePrefix("172.16.0.0/16"))

	assert.Contains(t, domains, must.Get(dnsname.ToFQDN("0.16.172.in-addr.arpa.")))
	assert.Contains(t, domains, must.Get(dnsname.ToFQDN("255.16.172.in-addr.arpa.")))
}

// Happens when netmask is a multiple of 4 bits (sounds likely).
func TestMagicDNSRootDomainsIPv6Single(t *testing.T) {
	domains := GenerateIPv6DNSRootDomain(netip.MustParsePrefix("fd7a:115c:a1e0::/48"))

	assert.Len(t, domains, 1)
	assert.Equal(t, "0.e.1.a.c.5.1.1.a.7.d.f.ip6.arpa.", domains[0].WithTrailingDot())
}

func TestMagicDNSRootDomainsIPv6SingleMultiple(t *testing.T) {
	domains := GenerateIPv6DNSRootDomain(netip.MustParsePrefix("fd7a:115c:a1e0::/50"))

	yieldsRoot := func(dom string) bool {
		for _, candidate := range domains {
			if candidate.WithTrailingDot() == dom {
				return true
			}
		}

		return false
	}

	assert.Len(t, domains, 4)
	assert.True(t, yieldsRoot("0.0.e.1.a.c.5.1.1.a.7.d.f.ip6.arpa."))
	assert.True(t, yieldsRoot("1.0.e.1.a.c.5.1.1.a.7.d.f.ip6.arpa."))
	assert.True(t, yieldsRoot("2.0.e.1.a.c.5.1.1.a.7.d.f.ip6.arpa."))
	assert.True(t, yieldsRoot("3.0.e.1.a.c.5.1.1.a.7.d.f.ip6.arpa."))
}