package godns

import (
	"fmt"
	"net"
	"strings"

	"github.com/miekg/dns"
)

// Record is a single resource record with presentation-format rdata.
type Record struct {
	Owner string
	Class string
	Type  string
	TTL   uint32
	RData string
}

// RRSet groups records that share owner, class, and type.
type RRSet struct {
	Owner   string
	Class   string
	Type    string
	Records []Record
}

// Zone is a complete in-memory zone from AXFR (or assembled records).
type Zone struct {
	Origin  string
	Serial  uint32
	Records []Record
}

// RRSets groups Zone records by owner/class/type, preserving first-seen order.
func (z Zone) RRSets() []RRSet {
	type key struct{ owner, class, typ string }
	order := make([]key, 0)
	grouped := make(map[key][]Record)
	for _, rec := range z.Records {
		k := key{rec.Owner, rec.Class, rec.Type}
		if _, ok := grouped[k]; !ok {
			order = append(order, k)
		}
		grouped[k] = append(grouped[k], rec)
	}
	out := make([]RRSet, 0, len(order))
	for _, k := range order {
		out = append(out, RRSet{Owner: k.owner, Class: k.class, Type: k.typ, Records: grouped[k]})
	}
	return out
}

// A builds an IPv4 address record.
func A(owner string, ttl uint32, ip net.IP) (Record, error) {
	v4 := ip.To4()
	if v4 == nil {
		return Record{}, fmt.Errorf("A record requires an IPv4 address")
	}
	return fromRR(&dns.A{Hdr: rrHeader(owner, dns.TypeA, ttl), A: v4})
}

// AAAA builds an IPv6 address record.
func AAAA(owner string, ttl uint32, ip net.IP) (Record, error) {
	if ip == nil || ip.To16() == nil || ip.To4() != nil {
		return Record{}, fmt.Errorf("AAAA record requires an IPv6 address")
	}
	return fromRR(&dns.AAAA{Hdr: rrHeader(owner, dns.TypeAAAA, ttl), AAAA: ip.To16()})
}

// MX builds a mail-exchanger record.
func MX(owner string, ttl uint32, pref uint16, target string) (Record, error) {
	name, err := fqdnASCII(target)
	if err != nil {
		return Record{}, err
	}
	return fromRR(&dns.MX{Hdr: rrHeader(owner, dns.TypeMX, ttl), Preference: pref, Mx: name})
}

// TXT builds a text record.
func TXT(owner string, ttl uint32, text string) (Record, error) {
	return fromRR(&dns.TXT{Hdr: rrHeader(owner, dns.TypeTXT, ttl), Txt: []string{text}})
}

// CNAME builds a canonical-name record.
func CNAME(owner string, ttl uint32, target string) (Record, error) {
	name, err := fqdnASCII(target)
	if err != nil {
		return Record{}, err
	}
	return fromRR(&dns.CNAME{Hdr: rrHeader(owner, dns.TypeCNAME, ttl), Target: name})
}

// NS builds a nameserver record.
func NS(owner string, ttl uint32, target string) (Record, error) {
	name, err := fqdnASCII(target)
	if err != nil {
		return Record{}, err
	}
	return fromRR(&dns.NS{Hdr: rrHeader(owner, dns.TypeNS, ttl), Ns: name})
}

// SRV builds a service locator record.
func SRV(owner string, ttl uint32, prio, weight, port uint16, target string) (Record, error) {
	name, err := fqdnASCII(target)
	if err != nil {
		return Record{}, err
	}
	return fromRR(&dns.SRV{
		Hdr:      rrHeader(owner, dns.TypeSRV, ttl),
		Priority: prio,
		Weight:   weight,
		Port:     port,
		Target:   name,
	})
}

// PTR builds a pointer record.
func PTR(owner string, ttl uint32, target string) (Record, error) {
	name, err := fqdnASCII(target)
	if err != nil {
		return Record{}, err
	}
	return fromRR(&dns.PTR{Hdr: rrHeader(owner, dns.TypePTR, ttl), Ptr: name})
}

func rrHeader(owner string, typ uint16, ttl uint32) dns.RR_Header {
	name, err := fqdnASCII(owner)
	if err != nil {
		// fromRR is not called on this path; builders call fqdn via fromRR after Header is set.
		// Validate in fromRR instead so the error is returned to the caller.
		name = owner
	}
	return dns.RR_Header{Name: name, Rrtype: typ, Class: dns.ClassINET, Ttl: ttl}
}

func fromRR(rr dns.RR) (Record, error) {
	hdr := rr.Header()
	if err := asciiName("owner", strings.TrimSuffix(hdr.Name, ".")); err != nil {
		return Record{}, err
	}
	if hdr.Name == "" || !isASCII(hdr.Name) {
		return Record{}, fmt.Errorf("owner must be ASCII, got %q", hdr.Name)
	}
	return Record{
		Owner: dns.Fqdn(hdr.Name),
		Class: dns.ClassToString[hdr.Class],
		Type:  dns.TypeToString[hdr.Rrtype],
		TTL:   hdr.Ttl,
		RData: strings.TrimSpace(strings.TrimPrefix(rr.String(), hdr.String())),
	}, nil
}

func recordToRR(rec Record) (dns.RR, error) {
	if err := asciiName("owner", rec.Owner); err != nil {
		return nil, err
	}
	rr, err := dns.NewRR(fmt.Sprintf("%s %d %s %s %s", dns.Fqdn(rec.Owner), rec.TTL, rec.Class, rec.Type, rec.RData))
	if err != nil {
		return nil, fmt.Errorf("encode %s %s: %w", rec.Type, rec.Owner, err)
	}
	return rr, nil
}

func fqdnASCII(name string) (string, error) {
	if err := asciiName("name", name); err != nil {
		return "", err
	}
	return dns.Fqdn(strings.TrimSpace(name)), nil
}

func isASCII(s string) bool {
	for i := 0; i < len(s); i++ {
		if s[i] > 127 {
			return false
		}
	}
	return true
}