package bind

/*

bind -
  Generate zonefiles suitiable for BIND.

	The zonefiles are read and written to the directory -bind_dir

	If the old zonefiles are readable, we read them to determine
	if an update is actually needed. The old zonefile is also used
	as the basis for generating the new SOA serial number.

*/

import (
	"bytes"
	"encoding/json"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"

	"github.com/miekg/dns"

	"github.com/StackExchange/dnscontrol/v2/models"
	"github.com/StackExchange/dnscontrol/v2/providers"
	"github.com/StackExchange/dnscontrol/v2/providers/diff"
)

var features = providers.DocumentationNotes{
	providers.CanUseCAA:              providers.Can(),
	providers.CanUsePTR:              providers.Can(),
	providers.CanUseNAPTR:            providers.Can(),
	providers.CanUseSRV:              providers.Can(),
	providers.CanUseSSHFP:            providers.Can(),
	providers.CanUseTLSA:             providers.Can(),
	providers.CanUseTXTMulti:         providers.Can(),
	providers.CantUseNOPURGE:         providers.Cannot(),
	providers.DocCreateDomains:       providers.Can("Driver just maintains list of zone files. It should automatically add missing ones."),
	providers.DocDualHost:            providers.Can(),
	providers.DocOfficiallySupported: providers.Can(),
}

func initBind(config map[string]string, providermeta json.RawMessage) (providers.DNSServiceProvider, error) {
	// config -- the key/values from creds.json
	// meta -- the json blob from NewReq('name', 'TYPE', meta)
	api := &Bind{
		directory: config["directory"],
	}
	if api.directory == "" {
		api.directory = "zones"
	}
	if len(providermeta) != 0 {
		err := json.Unmarshal(providermeta, api)
		if err != nil {
			return nil, err
		}
	}
	api.nameservers = models.StringsToNameservers(api.DefaultNS)
	return api, nil
}

func init() {
	providers.RegisterDomainServiceProviderType("BIND", initBind, features)
}

// SoaInfo contains the parts of a SOA rtype.
type SoaInfo struct {
	Ns      string `json:"master"`
	Mbox    string `json:"mbox"`
	Serial  uint32 `json:"serial"`
	Refresh uint32 `json:"refresh"`
	Retry   uint32 `json:"retry"`
	Expire  uint32 `json:"expire"`
	Minttl  uint32 `json:"minttl"`
}

func (s SoaInfo) String() string {
	return fmt.Sprintf("%s %s %d %d %d %d %d", s.Ns, s.Mbox, s.Serial, s.Refresh, s.Retry, s.Expire, s.Minttl)
}

// Bind is the provider handle for the Bind driver.
type Bind struct {
	DefaultNS   []string `json:"default_ns"`
	DefaultSoa  SoaInfo  `json:"default_soa"`
	nameservers []*models.Nameserver
	directory   string
}

// var bindSkeletin = flag.String("bind_skeletin", "skeletin/master/var/named/chroot/var/named/master", "")

func rrToRecord(rr dns.RR, origin string, replaceSerial uint32) (models.RecordConfig, uint32) {
	// Convert's dns.RR into our native data type (models.RecordConfig).
	// Records are translated directly with no changes.
	// If it is an SOA for the apex domain and
	// replaceSerial != 0, change the serial to replaceSerial.
	// WARNING(tlim): This assumes SOAs do not have serial=0.
	// If one is found, we replace it with serial=1.
	var oldSerial, newSerial uint32
	header := rr.Header()
	rc := models.RecordConfig{
		Type: dns.TypeToString[header.Rrtype],
		TTL:  header.Ttl,
	}
	rc.SetLabelFromFQDN(strings.TrimSuffix(header.Name, "."), origin)
	switch v := rr.(type) { // #rtype_variations
	case *dns.A:
		panicInvalid(rc.SetTarget(v.A.String()))
	case *dns.AAAA:
		panicInvalid(rc.SetTarget(v.AAAA.String()))
	case *dns.CAA:
		panicInvalid(rc.SetTargetCAA(v.Flag, v.Tag, v.Value))
	case *dns.CNAME:
		panicInvalid(rc.SetTarget(v.Target))
	case *dns.MX:
		panicInvalid(rc.SetTargetMX(v.Preference, v.Mx))
	case *dns.NS:
		panicInvalid(rc.SetTarget(v.Ns))
	case *dns.PTR:
		panicInvalid(rc.SetTarget(v.Ptr))
	case *dns.NAPTR:
		panicInvalid(rc.SetTargetNAPTR(v.Order, v.Preference, v.Flags, v.Service, v.Regexp, v.Replacement))
	case *dns.SOA:
		oldSerial = v.Serial
		if oldSerial == 0 {
			// For SOA records, we never return a 0 serial number.
			oldSerial = 1
		}
		newSerial = v.Serial
		//if (dnsutil.TrimDomainName(rc.Name, origin+".") == "@") && replaceSerial != 0 {
		if rc.GetLabel() == "@" && replaceSerial != 0 {
			newSerial = replaceSerial
		}
		panicInvalid(rc.SetTarget(
			fmt.Sprintf("%v %v %v %v %v %v %v",
				v.Ns, v.Mbox, newSerial, v.Refresh, v.Retry, v.Expire, v.Minttl),
		))
		// FIXME(tlim): SOA should be handled by splitting out the fields.
	case *dns.SRV:
		panicInvalid(rc.SetTargetSRV(v.Priority, v.Weight, v.Port, v.Target))
	case *dns.SSHFP:
		panicInvalid(rc.SetTargetSSHFP(v.Algorithm, v.Type, v.FingerPrint))
	case *dns.TLSA:
		panicInvalid(rc.SetTargetTLSA(v.Usage, v.Selector, v.MatchingType, v.Certificate))
	case *dns.TXT:
		panicInvalid(rc.SetTargetTXTs(v.Txt))
	default:
		log.Fatalf("rrToRecord: Unimplemented zone record type=%s (%v)\n", rc.Type, rr)
	}
	return rc, oldSerial
}

func panicInvalid(err error) {
	if err != nil {
		panic(fmt.Errorf("unparsable record received from BIND: %w", err))
	}
}

func makeDefaultSOA(info SoaInfo, origin string) *models.RecordConfig {
	// Make a default SOA record in case one isn't found:
	soaRec := models.RecordConfig{
		Type: "SOA",
	}
	soaRec.SetLabel("@", origin)
	if len(info.Ns) == 0 {
		info.Ns = "DEFAULT_NOT_SET."
	}
	if len(info.Mbox) == 0 {
		info.Mbox = "DEFAULT_NOT_SET."
	}
	if info.Serial == 0 {
		info.Serial = 1
	}
	if info.Refresh == 0 {
		info.Refresh = 3600
	}
	if info.Retry == 0 {
		info.Retry = 600
	}
	if info.Expire == 0 {
		info.Expire = 604800
	}
	if info.Minttl == 0 {
		info.Minttl = 1440
	}
	soaRec.SetTarget(info.String())

	return &soaRec
}

// GetNameservers returns the nameservers for a domain.
func (c *Bind) GetNameservers(string) ([]*models.Nameserver, error) {
	return c.nameservers, nil
}

// GetDomainCorrections returns a list of corrections to update a domain.
func (c *Bind) GetDomainCorrections(dc *models.DomainConfig) ([]*models.Correction, error) {
	dc.Punycode()
	// Phase 1: Copy everything to []*models.RecordConfig:
	//    expectedRecords < dc.Records[i]
	//    foundRecords < zonefile
	//
	// Phase 2: Do any manipulations:
	// add NS
	// manipulate SOA
	//
	// Phase 3: Convert to []diff.Records and compare:
	// expectedDiffRecords < expectedRecords
	// foundDiffRecords < foundRecords
	// diff.Inc...(foundDiffRecords, expectedDiffRecords )

	// Default SOA record.  If we see one in the zone, this will be replaced.
	soaRec := makeDefaultSOA(c.DefaultSoa, dc.Name)

	// Read foundRecords:
	foundRecords := make([]*models.RecordConfig, 0)
	var oldSerial, newSerial uint32

	if _, err := os.Stat(c.directory); os.IsNotExist(err) {
		fmt.Printf("\nWARNING: BIND directory %q does not exist!\n", c.directory)
	}

	zonefile := filepath.Join(c.directory, strings.Replace(strings.ToLower(dc.Name), "/", "_", -1)+".zone")
	foundFH, err := os.Open(zonefile)
	zoneFileFound := err == nil
	if err != nil && !os.IsNotExist(os.ErrNotExist) {
		// Don't whine if the file doesn't exist. However all other
		// errors will be reported.
		fmt.Printf("Could not read zonefile: %v\n", err)
	} else {
		for x := range dns.ParseZone(foundFH, dc.Name, zonefile) {
			if x.Error != nil {
				log.Println("Error in zonefile:", x.Error)
			} else {
				rec, serial := rrToRecord(x.RR, dc.Name, oldSerial)
				if serial != 0 && oldSerial != 0 {
					log.Fatalf("Multiple SOA records in zonefile: %v\n", zonefile)
				}
				if serial != 0 {
					// This was an SOA record. Update the serial.
					oldSerial = serial
					newSerial = generateSerial(oldSerial)
					// Regenerate with new serial:
					*soaRec, _ = rrToRecord(x.RR, dc.Name, newSerial)
					rec = *soaRec
				}
				foundRecords = append(foundRecords, &rec)
			}
		}
	}

	// Add SOA record to expected set:
	if !dc.HasRecordTypeName("SOA", "@") {
		dc.Records = append(dc.Records, soaRec)
	}

	// Normalize
	models.PostProcessRecords(foundRecords)

	differ := diff.New(dc)
	_, create, del, mod := differ.IncrementalDiff(foundRecords)

	buf := &bytes.Buffer{}
	// Print a list of changes. Generate an actual change that is the zone
	changes := false
	for _, i := range create {
		changes = true
		if zoneFileFound {
			fmt.Fprintln(buf, i)
		}
	}
	for _, i := range del {
		changes = true
		if zoneFileFound {
			fmt.Fprintln(buf, i)
		}
	}
	for _, i := range mod {
		changes = true
		if zoneFileFound {
			fmt.Fprintln(buf, i)
		}
	}
	msg := fmt.Sprintf("GENERATE_ZONEFILE: %s\n", dc.Name)
	if !zoneFileFound {
		msg = msg + fmt.Sprintf(" (%d records)\n", len(create))
	}
	msg += buf.String()
	corrections := []*models.Correction{}
	if changes {
		corrections = append(corrections,
			&models.Correction{
				Msg: msg,
				F: func() error {
					fmt.Printf("CREATING ZONEFILE: %v\n", zonefile)
					zf, err := os.Create(zonefile)
					if err != nil {
						log.Fatalf("Could not create zonefile: %v", err)
					}
					zonefilerecords := make([]dns.RR, 0, len(dc.Records))
					for _, r := range dc.Records {
						zonefilerecords = append(zonefilerecords, r.ToRR())
					}
					err = WriteZoneFile(zf, zonefilerecords, dc.Name)

					if err != nil {
						log.Fatalf("WriteZoneFile error: %v\n", err)
					}
					err = zf.Close()
					if err != nil {
						log.Fatalf("Closing: %v", err)
					}
					return nil
				},
			})
	}

	return corrections, nil
}