// Package ldap is a CoreDNS plugin that resolves A, AAAA y PTR RR from a ldap backend.
//
// It serves as a backend connector for autoritative zone data.
// Ldap is often used for bare metal inventories. This use is the main use case
// for this plugin. Other use cases might eventually be supported.
// fqdn and ip4 / ip6 information is mapped from it's respective ldap schema and
// served as DNS records over coredns. Mapping is configurable. To reduce load
// on the backend, a configurable cache is bundled.
package ldap

import (
	"net"
	"sync"
	"time"

	"github.com/coredns/coredns/plugin"
	"github.com/coredns/coredns/plugin/file"
	"github.com/coredns/coredns/plugin/pkg/fall"
	"github.com/coredns/coredns/plugin/pkg/upstream"

	"github.com/miekg/dns"
	"github.com/go-ldap/ldap/v3"
)

type ldapRecord struct {
	fqdn string
	ip4   net.IP
	ip6   net.IP
}

func (r *ldapRecord) A() (a *dns.A) {
	return &dns.A{Hdr: dns.RR_Header{Name: r.fqdn, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 0}, A: r.ip4}
}

func (r *ldapRecord) AAAA() (a *dns.AAAA) {
	return &dns.AAAA{Hdr: dns.RR_Header{Name: r.fqdn, Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: 86400}, AAAA: r.ip6}
}


// Ldap is an ldap plugin to serve zone entries from a ldap backend.
type Ldap struct {
	Next     plugin.Handler
	Fall     fall.F
	Upstream *upstream.Upstream
	Client   ldap.Client
	Zones    file.Zones

	// Exported for mocking in test
	SearchRequest *ldap.SearchRequest
	FqdnAttr      string
	Ip4Attr       string
	Ip6Attr       string

	ldapURL      string
	pagingLimit  uint32
	syncInterval time.Duration
	username     string
	password     string
	sasl         bool
	zMu          sync.RWMutex
	ttl          time.Duration
}

// New returns an initialized Ldap with defaults.
func New(zoneNames []string) *Ldap {
	l := new(Ldap)
	l.Zones.Names = zoneNames
	l.pagingLimit = 0
	l.syncInterval = 60 * time.Second
	// SearchRequest defaults
	l.SearchRequest = new(ldap.SearchRequest)
	l.SearchRequest.DerefAliases = ldap.NeverDerefAliases // TODO: Reason
	l.SearchRequest.Scope = ldap.ScopeWholeSubtree        // search whole subtree
	l.SearchRequest.SizeLimit = 500                       // TODO: Reason
	l.SearchRequest.TimeLimit = 500                       // TODO: Reason
	l.SearchRequest.TypesOnly = false                     // TODO: Reason
	l.Zones.Z = make(map[string]*file.Zone, len(zoneNames))

	for _, zn := range zoneNames {
		l.Zones.Z[zn] = nil
	}

	return l
}

// InitClient initializes a Ldap client.
func (l *Ldap) InitClient() (err error) {
	l.Client, err = ldap.DialURL(l.ldapURL)
	if err != nil {
		log.Fatal(err)
		return err
	}
	defer l.Client.Close()

	return nil
}

// SOA returns a syntetic SOA record for a zone.
func SOA(zone string) dns.RR {
	ttl := uint32(300)
	header := dns.RR_Header{Name: zone, Rrtype: dns.TypeSOA, Ttl: ttl, Class: dns.ClassINET}

	Mbox := hostmaster + "."
	Ns := "ns.dns."

	if zone[0] != '.' {
		Mbox += zone
		Ns += zone
	}

	return &dns.SOA{Hdr: header,
		Mbox:    Mbox,
		Ns:      Ns,
		Serial:  12345,
		Refresh: 7200,
		Retry:   1800,
		Expire:  86400,
		Minttl:  ttl,
	}
}

const hostmaster = "hostmaster"