// NSRecords returns NS records from etcd.
func (s *server) NSRecords(q dns.Question, name string) (records []dns.RR, extra []dns.RR, err error) {
	services, err := s.backend.Records(name, false)
	if err != nil {
		return nil, nil, err
	}

	services = msg.Group(services)

	for _, serv := range services {
		ip := net.ParseIP(serv.Host)
		switch {
		case ip == nil:
			return nil, nil, fmt.Errorf("NS record must be an IP address")
		case ip.To4() != nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewNS(q.Name, serv.Host))
			extra = append(extra, serv.NewA(serv.Host, ip.To4()))
		case ip.To4() == nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewNS(q.Name, serv.Host))
			extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
		}
	}
	return records, extra, nil
}

func (s *server) TXTRecords(q dns.Question, name string) (records []dns.RR, err error) {
	services, err := s.backend.Records(name, false)
	if err != nil {
		return nil, err
	}

	services = msg.Group(services)

	for _, serv := range services {
		if serv.Text == "" {
			continue
		}
		records = append(records, serv.NewTXT(q.Name))
	}
	return records, nil
}

func (s *server) CNAMERecords(q dns.Question, name string) (records []dns.RR, err error) {
	services, err := s.backend.Records(name, true)
	if err != nil {
		return nil, err
	}

	services = msg.Group(services)

	if len(services) > 0 {
		serv := services[0]
		if ip := net.ParseIP(serv.Host); ip == nil {
			records = append(records, serv.NewCNAME(q.Name, dns.Fqdn(serv.Host)))
		}
	}
	return records, nil
}

// SRVRecords returns SRV records from etcd.
// If the Target is not a name but an IP address, a name is created.
func (s *server) SRVRecords(q dns.Question, name string, bufsize uint16, dnssec bool) (records []dns.RR, extra []dns.RR, err error) {
	services, err := s.backend.Records(name, false)
	if err != nil {
		return nil, nil, err
	}

	services = msg.Group(services)

	// Looping twice to get the right weight vs priority
	w := make(map[int]int)
	for _, serv := range services {
		weight := 100
		if serv.Weight != 0 {
			weight = serv.Weight
		}
		if _, ok := w[serv.Priority]; !ok {
			w[serv.Priority] = weight
			continue
		}
		w[serv.Priority] += weight
	}
	lookup := make(map[string]bool)
	for _, serv := range services {
		w1 := 100.0 / float64(w[serv.Priority])
		if serv.Weight == 0 {
			w1 *= 100
		} else {
			w1 *= float64(serv.Weight)
		}
		weight := uint16(math.Floor(w1))
		ip := net.ParseIP(serv.Host)
		switch {
		case ip == nil:
			srv := serv.NewSRV(q.Name, weight)
			records = append(records, srv)

			if _, ok := lookup[srv.Target]; ok {
				break
			}

			lookup[srv.Target] = true

			if !dns.IsSubDomain(s.config.Domain, srv.Target) {
				log.Printf("skydns: target %q is not sub of %q, looking up...", srv.Target, s.config.Domain)
				m1, e1 := s.Lookup(srv.Target, dns.TypeA, bufsize, dnssec)
				if e1 == nil {
					extra = append(extra, m1.Answer...)
				}
				m1, e1 = s.Lookup(srv.Target, dns.TypeAAAA, bufsize, dnssec)
				if e1 == nil {
					// If we have seen CNAME's we *assume* that they are already added.
					for _, a := range m1.Answer {
						if _, ok := a.(*dns.CNAME); !ok {
							extra = append(extra, a)
						}
					}
				}
				break
			}
			// Internal name, we should have some info on them, either v4 or v6
			// Clients expect a complete answer, because we are a recursor in their
			// view.
			addr, e1 := s.AddressRecords(dns.Question{srv.Target, dns.ClassINET, dns.TypeA},
				srv.Target, nil, bufsize, dnssec, true)
			if e1 == nil {
				extra = append(extra, addr...)
			}
		case ip.To4() != nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewSRV(q.Name, weight))
			extra = append(extra, serv.NewA(serv.Host, ip.To4()))
		case ip.To4() == nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewSRV(q.Name, weight))
			extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
		}
	}
	return records, extra, nil
}

func (s *server) AddressRecords(q dns.Question, name string, previousRecords []dns.RR, bufsize uint16, dnssec, both bool) (records []dns.RR, err error) {
	services, err := s.backend.Records(name, false)
	if err != nil {
		return nil, err
	}

	services = msg.Group(services)

	for _, serv := range services {
		ip := net.ParseIP(serv.Host)
		switch {
		case ip == nil:
			// Try to resolve as CNAME if it's not an IP, but only if we don't create loops.
			if q.Name == dns.Fqdn(serv.Host) {
				// x CNAME x is a direct loop, don't add those
				continue
			}

			newRecord := serv.NewCNAME(q.Name, dns.Fqdn(serv.Host))
			if len(previousRecords) > 7 {
				log.Printf("skydns: CNAME lookup limit of 8 exceeded for %s", newRecord)
				// don't add it, and just continue
				continue
			}
			if s.isDuplicateCNAME(newRecord, previousRecords) {
				log.Printf("skydns: CNAME loop detected for record %s", newRecord)
				continue
			}

			nextRecords, err := s.AddressRecords(dns.Question{Name: dns.Fqdn(serv.Host), Qtype: q.Qtype, Qclass: q.Qclass},
				strings.ToLower(dns.Fqdn(serv.Host)), append(previousRecords, newRecord), bufsize, dnssec, both)
			if err == nil {
				// Only have we found something we should add the CNAME and the IP addresses.
				if len(nextRecords) > 0 {
					records = append(records, newRecord)
					records = append(records, nextRecords...)
				}
				continue
			}
			// This means we can not complete the CNAME, try to look else where.
			target := newRecord.Target
			if dns.IsSubDomain(s.config.Domain, target) {
				// We should already have found it
				continue
			}
			m1, e1 := s.Lookup(target, q.Qtype, bufsize, dnssec)
			if e1 != nil {
				log.Printf("skydns: incomplete CNAME chain: %s", e1)
				continue
			}
			// Len(m1.Answer) > 0 here is well?
			records = append(records, newRecord)
			records = append(records, m1.Answer...)
			continue

			log.Printf("skydns: incomplete CNAME chain for %s", name)

		case ip.To4() != nil && (q.Qtype == dns.TypeA || both):
			records = append(records, serv.NewA(q.Name, ip.To4()))
		case ip.To4() == nil && (q.Qtype == dns.TypeAAAA || both):
			records = append(records, serv.NewAAAA(q.Name, ip.To16()))
		}
	}
	if s.config.RoundRobin {
		s.RoundRobin(records)
	}
	return records, nil
}