jarl/internal/engine/ops.go

package engine

import (
	"bytes"
	"encoding/json"
	"fmt"
	"net/netip"
	"strings"
	"time"

	"jarl/internal/auth"
	"jarl/internal/catalog"
	"jarl/internal/dnsname"
	"jarl/internal/model"
	"jarl/internal/namedconf"
	"jarl/internal/rr"
	"jarl/internal/validate"
)

const maxTTL = 2147483647

// applyCtx carries what applying an operation needs.
type applyCtx struct {
	p        *auth.Principal
	now      time.Time
	warnings []string
}

func (c *applyCtx) user() string { return c.p.Name() }

func (c *applyCtx) require(a auth.Action) error {
	if c.p.Can(a) {
		return nil
	}
	return errf(KindForbidden, "permission denied: this needs %s", a)
}

func (c *applyCtx) warn(format string, args ...any) {
	c.warnings = append(c.warnings, fmt.Sprintf(format, args...))
}

func decode(data json.RawMessage, v any) error {
	if len(data) == 0 {
		return nil
	}
	dec := json.NewDecoder(bytes.NewReader(data))
	dec.DisallowUnknownFields()
	if err := dec.Decode(v); err != nil {
		return errf(KindBadRequest, "invalid operation data: %v", err)
	}
	return nil
}

func checkVersion(op model.Op, current int, what string) error {
	if op.BaseVersion != 0 && op.BaseVersion != current {
		return errf(KindConflict, "%s was changed by someone else after this change was staged (version %d, now %d); review it and stage the change again", what, op.BaseVersion, current)
	}
	return nil
}

// applyOp applies one stored operation to st.
func applyOp(st *model.State, op model.Op, c *applyCtx) error {
	var err error
	switch op.Kind {
	case OpZoneCreate:
		err = applyZoneCreate(st, op, c)
	case OpZoneUpdate:
		err = applyZoneUpdate(st, op, c)
	case OpZoneDelete:
		err = applyZoneDelete(st, op, c)
	case OpRecordCreate:
		err = applyRecordCreate(st, op, c)
	case OpRecordUpdate:
		err = applyRecordUpdate(st, op, c)
	case OpRecordDelete:
		err = applyRecordDelete(st, op, c)
	case OpRRSetReplace:
		err = applyRRSetReplace(st, op, c)
	case OpViewCreate:
		err = applyViewCreate(st, op, c)
	case OpViewUpdate:
		err = applyViewUpdate(st, op, c)
	case OpViewDelete:
		err = applyViewDelete(st, op, c)
	case OpViewReorder:
		err = applyViewReorder(st, op, c)
	case OpACLCreate, OpACLUpdate:
		err = applyACLPut(st, op, c)
	case OpACLDelete:
		err = applyACLDelete(st, op, c)
	case OpTSIGCreate, OpTSIGUpdate:
		err = applyTSIGPut(st, op, c)
	case OpTSIGDelete:
		err = applyTSIGDelete(st, op, c)
	case OpOptionCreate, OpOptionUpdate:
		err = applyOptionPut(st, op, c)
	case OpOptionDelete:
		err = applyOptionDelete(st, op, c)
	case OpSettingsUpdate:
		err = applySettings(st, op, c)
	default:
		err = errf(KindBadRequest, "unknown operation %q", op.Kind)
	}
	if e, ok := AsError(err); ok && e.OpSeq == 0 {
		e.OpSeq = op.Seq
	}
	return err
}

// ---- zones

func zoneAction(st *model.State, z *model.Zone, write bool) auth.Action {
	return auth.Action{Resource: auth.ResZones, Write: write, Zone: z.Name, View: st.ViewName(z)}
}

// ParseZoneName accepts a zone name or a CIDR prefix (for reverse zones).
func ParseZoneName(s string) (string, error) {
	s = strings.TrimSpace(s)
	if strings.Contains(s, "/") {
		if p, err := netip.ParsePrefix(s); err == nil {
			return dnsname.ReverseZone(p)
		}
	}
	a, err := dnsname.ToASCII(s)
	if err != nil {
		return "", err
	}
	name := dnsname.Fqdn(a)
	if err := dnsname.CheckZoneName(name); err != nil {
		return "", fmt.Errorf("invalid zone name %q: %v", s, err)
	}
	return name, nil
}

func normalizeZoneType(t string) (string, error) {
	t = strings.ToLower(strings.TrimSpace(t))
	if s, ok := catalog.ZoneTypeSynonyms[t]; ok {
		t = s
	}
	for _, zt := range model.ZoneTypes {
		if t == zt {
			return t, nil
		}
	}
	return "", fmt.Errorf("unknown zone type %q (use one of %s)", t, strings.Join(model.ZoneTypes, ", "))
}

func setZoneFields(st *model.State, z *model.Zone, in *ZoneInput, creating bool) error {
	if in.Name != nil {
		name, err := ParseZoneName(*in.Name)
		if err != nil {
			return errf(KindBadRequest, "%v", err)
		}
		if !creating && name != z.Name {
			return errf(KindBadRequest, "zones can't be renamed; create a new zone (it can copy the records with clone_from) and delete the old one")
		}
		z.Name = name
	}
	if in.ViewID != nil {
		if *in.ViewID != 0 && st.Views[*in.ViewID] == nil {
			return errf(KindNotFound, "view %d does not exist", *in.ViewID)
		}
		z.ViewID = *in.ViewID
	} else if in.View != nil {
		if *in.View == "" {
			z.ViewID = 0
		} else if v := st.ViewByName(*in.View); v != nil {
			z.ViewID = v.ID
		} else {
			return errf(KindNotFound, "view %q does not exist", *in.View)
		}
	}
	if in.Type != nil {
		t, err := normalizeZoneType(*in.Type)
		if err != nil {
			return errf(KindBadRequest, "%v", err)
		}
		z.Type = t
	}
	if in.InView != nil {
		z.InView = strings.TrimSpace(*in.InView)
	}
	if in.File != nil {
		z.File = strings.TrimSpace(*in.File)
	}
	if s := in.SOA; s != nil {
		if s.MName != nil {
			n, err := dnsname.Owner(*s.MName, z.Name)
			if err != nil {
				return errf(KindBadRequest, "SOA mname: %v", err)
			}
			z.SOA.MName = n
		}
		if s.RName != nil {
			mb, err := dnsname.MailboxFromEmail(*s.RName)
			if err != nil {
				return errf(KindBadRequest, "SOA rname: %v", err)
			}
			z.SOA.RName = mb
		}
		if s.Serial != nil {
			z.SOA.Serial = *s.Serial
		}
		set := func(dst *uint32, v *uint32, name string) error {
			if v == nil {
				return nil
			}
			if *v > maxTTL {
				return errf(KindBadRequest, "SOA %s must be at most 2147483647", name)
			}
			*dst = *v
			return nil
		}
		for _, f := range []struct {
			dst  *uint32
			v    *uint32
			name string
		}{{&z.SOA.Refresh, s.Refresh, "refresh"}, {&z.SOA.Retry, s.Retry, "retry"}, {&z.SOA.Expire, s.Expire, "expire"}, {&z.SOA.Minimum, s.Minimum, "minimum"}} {
			if err := set(f.dst, f.v, f.name); err != nil {
				return err
			}
		}
	}
	if in.DefaultTTL != nil {
		if *in.DefaultTTL > maxTTL {
			return errf(KindBadRequest, "default TTL must be at most 2147483647")
		}
		z.DefaultTTL = *in.DefaultTTL
	}
	if in.SerialPolicy != nil {
		z.SerialPolicy = strings.ToLower(strings.TrimSpace(*in.SerialPolicy))
	}
	if in.DNSSECPolicy != nil {
		p := strings.Trim(strings.TrimSpace(*in.DNSSECPolicy), `"`)
		switch strings.ToLower(p) {
		case "none", "off":
			p = ""
		case model.DNSSECDefault, model.DNSSECInsecure:
			p = strings.ToLower(p)
		}
		z.DNSSECPolicy = p
	}
	if in.Comment != nil {
		z.Comment = *in.Comment
	}
	return nil
}

func applyZoneCreate(st *model.State, op model.Op, c *applyCtx) error {
	var in ZoneInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	if op.ID == 0 || st.Zones[op.ID] != nil {
		return errf(KindConflict, "zone ID %d is already in use", op.ID)
	}
	if in.Name == nil || in.Type == nil {
		return errf(KindBadRequest, "a new zone needs a name and a type")
	}
	z := &model.Zone{ID: op.ID}
	if err := setZoneFields(st, z, &in, true); err != nil {
		return err
	}
	if err := c.require(zoneAction(st, z, true)); err != nil {
		return err
	}
	if existing := st.FindZone(z.Name, z.ViewID); existing != nil {
		where := ""
		if v := st.ViewName(z); v != "" {
			where = " in view " + v
		}
		return errf(KindConflict, "zone %s already exists%s", dnsname.Display(z.Name), where)
	}
	z.Touch(c.user(), c.now)
	st.Zones[z.ID] = z
	return nil
}

func applyZoneUpdate(st *model.State, op model.Op, c *applyCtx) error {
	z := st.Zones[op.ID]
	if z == nil {
		return errf(KindNotFound, "zone %d does not exist", op.ID)
	}
	if err := checkVersion(op, z.Version, "zone "+dnsname.Display(z.Name)); err != nil {
		return err
	}
	if err := c.require(zoneAction(st, z, true)); err != nil {
		return err
	}
	var in ZoneInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	if len(in.Nameservers) > 0 || len(in.Records) > 0 || in.CloneFrom != 0 || len(in.Options) > 0 {
		return errf(KindBadRequest, "nameservers, records, options and clone_from can only be used when creating a zone")
	}
	oldView := z.ViewID
	if err := setZoneFields(st, z, &in, false); err != nil {
		return err
	}
	if z.ViewID != oldView {
		if other := st.FindZone(z.Name, z.ViewID); other != nil && other.ID != z.ID {
			return errf(KindConflict, "the target view already has a zone %s", dnsname.Display(z.Name))
		}
		if err := c.require(zoneAction(st, z, true)); err != nil {
			return err
		}
	}
	z.Touch(c.user(), c.now)
	return nil
}

func applyZoneDelete(st *model.State, op model.Op, c *applyCtx) error {
	z := st.Zones[op.ID]
	if z == nil {
		return errf(KindNotFound, "zone %d does not exist", op.ID)
	}
	if err := checkVersion(op, z.Version, "zone "+dnsname.Display(z.Name)); err != nil {
		return err
	}
	if err := c.require(zoneAction(st, z, true)); err != nil {
		return err
	}
	deleteZone(st, z.ID)
	return nil
}

func deleteZone(st *model.State, id int64) {
	for rid, r := range st.Records {
		if r.ZoneID == id {
			delete(st.Records, rid)
		}
	}
	for oid, o := range st.Options {
		if o.Scope == model.ScopeZone && o.ScopeID == id {
			delete(st.Options, oid)
		}
	}
	delete(st.Zones, id)
}

// ---- records

func recordAction(st *model.State, z *model.Zone, name, typ string, write bool) auth.Action {
	return auth.Action{Resource: auth.ResRecords, Write: write, Zone: z.Name, View: st.ViewName(z), Name: name, Type: typ}
}

func recordLabel(r *model.Record) string {
	return fmt.Sprintf("record %s %s %s", r.Name, r.Type, r.Data)
}

// parseRecord resolves and validates name, type and data for zone z.
func parseRecord(z *model.Zone, name, typ, data string) (string, *rr.Parsed, error) {
	if !z.HasRecords() {
		return "", nil, errf(KindBadRequest, "zone %s is a %s zone; records can only be managed in primary zones", dnsname.Display(z.Name), z.Type)
	}
	owner, err := dnsname.Owner(name, z.Name)
	if err != nil {
		return "", nil, errf(KindBadRequest, "%v", err)
	}
	if err := dnsname.CheckOwner(owner); err != nil {
		return "", nil, errf(KindBadRequest, "invalid name %q: %v", name, err)
	}
	if !dnsname.IsSubdomain(owner, z.Name) {
		return "", nil, errf(KindBadRequest, "%s is not inside zone %s", dnsname.Display(owner), dnsname.Display(z.Name))
	}
	p, err := rr.Parse(z.Name, owner, typ, data)
	if err != nil {
		return "", nil, errf(KindBadRequest, "%s %s: %v", dnsname.Display(owner), strings.ToUpper(typ), err)
	}
	return owner, p, nil
}

func rrsetTTL(st *model.State, zoneID int64, name, typ string, exceptID int64) (*uint32, bool) {
	for _, r := range st.Records {
		if r.ZoneID == zoneID && r.Name == name && r.Type == typ && r.ID != exceptID && !r.Disabled {
			if r.TTL == nil {
				return nil, true
			}
			t := *r.TTL
			return &t, true
		}
	}
	return nil, false
}

func applyRecordCreate(st *model.State, op model.Op, c *applyCtx) error {
	var in RecordInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	if op.ID == 0 || st.Records[op.ID] != nil {
		return errf(KindConflict, "record ID %d is already in use", op.ID)
	}
	z := st.Zones[in.ZoneID]
	if z == nil {
		return errf(KindNotFound, "zone %d does not exist", in.ZoneID)
	}
	if in.Name == nil || in.Type == nil || in.Data == nil {
		return errf(KindBadRequest, "a record needs a name, a type and data")
	}
	owner, p, err := parseRecord(z, *in.Name, *in.Type, *in.Data)
	if err != nil {
		return err
	}
	if err := c.require(recordAction(st, z, owner, p.Type, true)); err != nil {
		return err
	}
	r := &model.Record{ID: op.ID, ZoneID: z.ID, Name: owner, Type: p.Type, Data: p.Data}
	switch {
	case in.TTL.Set && !in.TTL.Null:
		if in.TTL.Value > maxTTL {
			return errf(KindBadRequest, "TTL must be at most 2147483647")
		}
		r.TTL = model.Ptr(in.TTL.Value)
	case !in.TTL.Set:
		// Join an existing RRset with its TTL.
		if ttl, ok := rrsetTTL(st, z.ID, owner, p.Type, 0); ok {
			r.TTL = ttl
		}
	}
	if in.Comment != nil {
		r.Comment = *in.Comment
	}
	if in.Disabled != nil {
		r.Disabled = *in.Disabled
	}
	for _, w := range p.Warnings {
		c.warn("%s %s: %s", dnsname.Display(owner), p.Type, w)
	}
	r.Touch(c.user(), c.now)
	st.Records[r.ID] = r
	return nil
}

func applyRecordUpdate(st *model.State, op model.Op, c *applyCtx) error {
	r := st.Records[op.ID]
	if r == nil {
		return errf(KindNotFound, "record %d does not exist", op.ID)
	}
	if err := checkVersion(op, r.Version, recordLabel(r)); err != nil {
		return err
	}
	z := st.Zones[r.ZoneID]
	if z == nil {
		return errf(KindNotFound, "the record's zone does not exist")
	}
	if err := c.require(recordAction(st, z, r.Name, r.Type, true)); err != nil {
		return err
	}
	var in RecordInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	if in.ZoneID != 0 && in.ZoneID != r.ZoneID {
		return errf(KindBadRequest, "records can't be moved to another zone; delete and re-create them")
	}
	name, typ, data := r.Name, r.Type, r.Data
	if in.Name != nil {
		name = *in.Name
	}
	if in.Type != nil {
		typ = *in.Type
	}
	if in.Data != nil {
		data = *in.Data
	} else if in.Type != nil && !strings.EqualFold(*in.Type, r.Type) {
		return errf(KindBadRequest, "changing the type of a record needs new data too")
	}
	if in.Name != nil || in.Type != nil || in.Data != nil {
		owner, p, err := parseRecord(z, name, typ, data)
		if err != nil {
			return err
		}
		if owner != r.Name || p.Type != r.Type {
			if err := c.require(recordAction(st, z, owner, p.Type, true)); err != nil {
				return err
			}
		}
		for _, w := range p.Warnings {
			c.warn("%s %s: %s", dnsname.Display(owner), p.Type, w)
		}
		moved := owner != r.Name || p.Type != r.Type
		r.Name, r.Type, r.Data = owner, p.Type, p.Data
		if moved && !in.TTL.Set {
			if ttl, ok := rrsetTTL(st, z.ID, owner, p.Type, r.ID); ok {
				r.TTL = ttl
			}
		}
	}
	if in.TTL.Set {
		if in.TTL.Null {
			r.TTL = nil
		} else {
			if in.TTL.Value > maxTTL {
				return errf(KindBadRequest, "TTL must be at most 2147483647")
			}
			r.TTL = model.Ptr(in.TTL.Value)
		}
	}
	if in.Comment != nil {
		r.Comment = *in.Comment
	}
	if in.Disabled != nil {
		r.Disabled = *in.Disabled
	}
	r.Touch(c.user(), c.now)
	return nil
}

func applyRecordDelete(st *model.State, op model.Op, c *applyCtx) error {
	if op.ID != 0 {
		r := st.Records[op.ID]
		if r == nil {
			return errf(KindNotFound, "record %d does not exist", op.ID)
		}
		if err := checkVersion(op, r.Version, recordLabel(r)); err != nil {
			return err
		}
		z := st.Zones[r.ZoneID]
		if z != nil {
			if err := c.require(recordAction(st, z, r.Name, r.Type, true)); err != nil {
				return err
			}
		}
		delete(st.Records, r.ID)
		return nil
	}
	// Delete by match.
	var in RecordInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	z := st.Zones[in.ZoneID]
	if z == nil {
		return errf(KindNotFound, "zone %d does not exist", in.ZoneID)
	}
	if in.Name == nil || in.Type == nil {
		return errf(KindBadRequest, "deleting records by match needs a name and a type")
	}
	owner, err := dnsname.Owner(*in.Name, z.Name)
	if err != nil {
		return errf(KindBadRequest, "%v", err)
	}
	typ, _, err := rr.NormalizeType(*in.Type)
	if err != nil {
		return errf(KindBadRequest, "%v", err)
	}
	if err := c.require(recordAction(st, z, owner, typ, true)); err != nil {
		return err
	}
	data := ""
	if in.Data != nil && strings.TrimSpace(*in.Data) != "" {
		_, p, err := parseRecord(z, owner, typ, *in.Data)
		if err != nil {
			return err
		}
		data = p.Data
	}
	n := 0
	for id, r := range st.Records {
		if r.ZoneID == z.ID && r.Name == owner && r.Type == typ && (data == "" || strings.EqualFold(r.Data, data)) {
			delete(st.Records, id)
			n++
		}
	}
	if n == 0 && !in.MissingOK {
		what := dnsname.Display(owner) + " " + typ
		if data != "" {
			what += " " + data
		}
		return errf(KindNotFound, "no record %s in zone %s", what, dnsname.Display(z.Name))
	}
	return nil
}

func applyRRSetReplace(st *model.State, op model.Op, c *applyCtx) error {
	var in RRSetInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	z := st.Zones[in.ZoneID]
	if z == nil {
		return errf(KindNotFound, "zone %d does not exist", in.ZoneID)
	}
	owner, err := dnsname.Owner(in.Name, z.Name)
	if err != nil {
		return errf(KindBadRequest, "%v", err)
	}
	typ, _, err := rr.NormalizeType(in.Type)
	if err != nil {
		return errf(KindBadRequest, "%v", err)
	}
	if err := c.require(recordAction(st, z, owner, typ, true)); err != nil {
		return err
	}
	var desired []string
	seen := map[string]bool{}
	for _, d := range in.Data {
		_, p, err := parseRecord(z, owner, typ, d)
		if err != nil {
			return err
		}
		for _, w := range p.Warnings {
			c.warn("%s %s: %s", dnsname.Display(owner), typ, w)
		}
		k := strings.ToLower(p.Data)
		if !seen[k] {
			seen[k] = true
			desired = append(desired, p.Data)
		}
	}
	var ttl *uint32
	ttlKnown := false
	if in.TTL.Set {
		ttlKnown = true
		if !in.TTL.Null {
			if in.TTL.Value > maxTTL {
				return errf(KindBadRequest, "TTL must be at most 2147483647")
			}
			ttl = model.Ptr(in.TTL.Value)
		}
	} else if t, ok := rrsetTTL(st, z.ID, owner, typ, 0); ok {
		ttl, ttlKnown = t, true
	}
	// The RRset becomes exactly the given data. A disabled record with
	// one of the values is enabled again; other disabled records are left
	// alone.
	keep := map[string]bool{}
	// (In ID order, so which of two identical records is kept doesn't
	// depend on map order.)
	for _, id := range sortedKeys(st.Records) {
		r := st.Records[id]
		if r.ZoneID != z.ID || r.Name != owner || r.Type != typ {
			continue
		}
		k := strings.ToLower(r.Data)
		if seen[k] && !keep[k] {
			keep[k] = true
			if (ttlKnown && !sameTTL(r.TTL, ttl)) || r.Disabled {
				if ttlKnown {
					r.TTL = copyTTL(ttl)
				}
				r.Disabled = false
				r.Touch(c.user(), c.now)
			}
			continue
		}
		if r.Disabled {
			continue
		}
		delete(st.Records, id)
	}
	ids := in.NewIDs
	for _, d := range desired {
		if keep[strings.ToLower(d)] {
			continue
		}
		if len(ids) == 0 {
			return errf(KindBadRequest, "internal error: no IDs allocated for new records")
		}
		r := &model.Record{ID: ids[0], ZoneID: z.ID, Name: owner, Type: typ, Data: d, TTL: copyTTL(ttl)}
		ids = ids[1:]
		if st.Records[r.ID] != nil {
			return errf(KindConflict, "record ID %d is already in use", r.ID)
		}
		if in.Comment != nil {
			r.Comment = *in.Comment
		}
		r.Touch(c.user(), c.now)
		st.Records[r.ID] = r
	}
	return nil
}

func sameTTL(a, b *uint32) bool {
	if a == nil || b == nil {
		return a == nil && b == nil
	}
	return *a == *b
}

func copyTTL(t *uint32) *uint32 {
	if t == nil {
		return nil
	}
	v := *t
	return &v
}

// ---- views

func viewAction(name string) auth.Action {
	return auth.Action{Resource: auth.ResViews, Write: true, View: name}
}

func normalizeElements(list []string, field string) ([]string, error) {
	out := []string{}
	for _, s := range list {
		if strings.TrimSpace(s) == "" {
			continue
		}
		e, err := namedconf.ParseAMElement(s)
		if err != nil {
			return nil, errf(KindBadRequest, "%s element %q: %v", field, s, err)
		}
		out = append(out, e.String())
	}
	return out, nil
}

func setViewFields(v *model.View, in *ViewInput) error {
	if in.Name != nil {
		v.Name = strings.TrimSpace(*in.Name)
	}
	if in.MatchClients != nil {
		l, err := normalizeElements(*in.MatchClients, "match-clients")
		if err != nil {
			return err
		}
		v.MatchClients = l
	}
	if in.MatchDestinations != nil {
		l, err := normalizeElements(*in.MatchDestinations, "match-destinations")
		if err != nil {
			return err
		}
		v.MatchDestinations = l
	}
	if in.MatchRecursiveOnly.Set {
		if in.MatchRecursiveOnly.Null {
			v.MatchRecursiveOnly = nil
		} else {
			v.MatchRecursiveOnly = model.Ptr(in.MatchRecursiveOnly.Value)
		}
	}
	if in.Comment != nil {
		v.Comment = *in.Comment
	}
	if in.Position != nil {
		v.Position = *in.Position
	}
	return nil
}

func applyViewCreate(st *model.State, op model.Op, c *applyCtx) error {
	var in ViewInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	if op.ID == 0 || st.Views[op.ID] != nil {
		return errf(KindConflict, "view ID %d is already in use", op.ID)
	}
	if in.Name == nil || strings.TrimSpace(*in.Name) == "" {
		return errf(KindBadRequest, "a view needs a name")
	}
	v := &model.View{ID: op.ID, Position: len(st.Views), MatchClients: []string{}, MatchDestinations: []string{}}
	if err := setViewFields(v, &in); err != nil {
		return err
	}
	if err := c.require(viewAction(v.Name)); err != nil {
		return err
	}
	if st.ViewByName(v.Name) != nil {
		return errf(KindConflict, "view %s already exists", v.Name)
	}
	v.Touch(c.user(), c.now)
	st.Views[v.ID] = v
	renumberViews(st)
	return nil
}

// renumberViews makes positions 0..n-1 in the current order.
func renumberViews(st *model.State) {
	for i, v := range st.OrderedViews() {
		v.Position = i
	}
}

func applyViewUpdate(st *model.State, op model.Op, c *applyCtx) error {
	v := st.Views[op.ID]
	if v == nil {
		return errf(KindNotFound, "view %d does not exist", op.ID)
	}
	if err := checkVersion(op, v.Version, "view "+v.Name); err != nil {
		return err
	}
	if err := c.require(viewAction(v.Name)); err != nil {
		return err
	}
	var in ViewInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	oldName := v.Name
	if err := setViewFields(v, &in); err != nil {
		return err
	}
	if v.Name != oldName {
		if other := st.ViewByName(v.Name); other != nil && other.ID != v.ID {
			return errf(KindConflict, "view %s already exists", v.Name)
		}
		if err := c.require(viewAction(v.Name)); err != nil {
			return err
		}
		// Keep in-view references working.
		for _, z := range st.Zones {
			if z.Type == model.ZoneInView && strings.EqualFold(z.InView, oldName) {
				z.InView = v.Name
				z.Touch(c.user(), c.now)
			}
		}
	}
	v.Touch(c.user(), c.now)
	renumberViews(st)
	return nil
}

func applyViewDelete(st *model.State, op model.Op, c *applyCtx) error {
	v := st.Views[op.ID]
	if v == nil {
		return errf(KindNotFound, "view %d does not exist", op.ID)
	}
	if err := checkVersion(op, v.Version, "view "+v.Name); err != nil {
		return err
	}
	if err := c.require(viewAction(v.Name)); err != nil {
		return err
	}
	var in DeleteInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	zones := st.ZonesInView(v.ID)
	if len(zones) > 0 && !in.Cascade {
		var names []string
		for _, z := range zones {
			names = append(names, dnsname.Display(z.Name))
		}
		return errf(KindConflict, "view %s still has %d zone(s) (%s); move or delete them first, or delete the view with cascade", v.Name, len(zones), strings.Join(names, ", "))
	}
	for _, z := range zones {
		if err := c.require(zoneAction(st, z, true)); err != nil {
			return err
		}
		deleteZone(st, z.ID)
	}
	for oid, o := range st.Options {
		if o.Scope == model.ScopeView && o.ScopeID == v.ID {
			delete(st.Options, oid)
		}
	}
	delete(st.Views, v.ID)
	renumberViews(st)
	return nil
}

func applyViewReorder(st *model.State, op model.Op, c *applyCtx) error {
	var in ReorderInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	if len(in.IDs) != len(st.Views) {
		return errf(KindConflict, "the new order lists %d views, but there are %d", len(in.IDs), len(st.Views))
	}
	seen := map[int64]bool{}
	for _, id := range in.IDs {
		v := st.Views[id]
		if v == nil || seen[id] {
			return errf(KindBadRequest, "the new order must list every view exactly once")
		}
		seen[id] = true
		if err := c.require(viewAction(v.Name)); err != nil {
			return err
		}
	}
	for i, id := range in.IDs {
		v := st.Views[id]
		if v.Position != i {
			v.Position = i
			v.Touch(c.user(), c.now)
		}
	}
	return nil
}

// ---- ACLs

func applyACLPut(st *model.State, op model.Op, c *applyCtx) error {
	if err := c.require(auth.Action{Resource: auth.ResACLs, Write: true}); err != nil {
		return err
	}
	var in ACLInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	var a *model.ACL
	if op.Kind == OpACLCreate {
		if op.ID == 0 || st.ACLs[op.ID] != nil {
			return errf(KindConflict, "ACL ID %d is already in use", op.ID)
		}
		if in.Name == nil {
			return errf(KindBadRequest, "an ACL needs a name")
		}
		a = &model.ACL{ID: op.ID, Elements: []string{}}
	} else {
		a = st.ACLs[op.ID]
		if a == nil {
			return errf(KindNotFound, "ACL %d does not exist", op.ID)
		}
		if err := checkVersion(op, a.Version, "ACL "+a.Name); err != nil {
			return err
		}
	}
	oldName := a.Name
	if in.Name != nil {
		name := strings.TrimSpace(*in.Name)
		if namedconf.BuiltinACLs[strings.ToLower(name)] {
			return errf(KindBadRequest, "%q is a built-in ACL name", name)
		}
		if err := namedconf.CheckACLName(name); err != nil {
			return errf(KindBadRequest, "%v", err)
		}
		if other := st.ACLByName(name); other != nil && other.ID != a.ID {
			return errf(KindConflict, "ACL %s already exists", name)
		}
		a.Name = name
	}
	if in.Elements != nil {
		l, err := normalizeElements(*in.Elements, "ACL")
		if err != nil {
			return err
		}
		a.Elements = l
	}
	if in.Comment != nil {
		a.Comment = *in.Comment
	}
	a.Touch(c.user(), c.now)
	st.ACLs[a.ID] = a
	if op.Kind == OpACLUpdate && oldName != a.Name {
		renameRefs(st, refACL, oldName, a.Name, c)
	}
	return nil
}

func applyACLDelete(st *model.State, op model.Op, c *applyCtx) error {
	if err := c.require(auth.Action{Resource: auth.ResACLs, Write: true}); err != nil {
		return err
	}
	a := st.ACLs[op.ID]
	if a == nil {
		return errf(KindNotFound, "ACL %d does not exist", op.ID)
	}
	if err := checkVersion(op, a.Version, "ACL "+a.Name); err != nil {
		return err
	}
	if users := FindRefs(st, refACL, a.Name); len(users) > 0 {
		return errf(KindConflict, "ACL %s is still used by %s", a.Name, strings.Join(users, ", "))
	}
	delete(st.ACLs, a.ID)
	return nil
}

// ---- TSIG keys

func applyTSIGPut(st *model.State, op model.Op, c *applyCtx) error {
	if err := c.require(auth.Action{Resource: auth.ResTSIG, Write: true}); err != nil {
		return err
	}
	var in TSIGInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	var k *model.TSIGKey
	if op.Kind == OpTSIGCreate {
		if op.ID == 0 || st.Keys[op.ID] != nil {
			return errf(KindConflict, "key ID %d is already in use", op.ID)
		}
		if in.Name == nil || in.Secret == nil {
			return errf(KindBadRequest, "a TSIG key needs a name and a secret")
		}
		k = &model.TSIGKey{ID: op.ID, Algorithm: "hmac-sha256"}
	} else {
		k = st.Keys[op.ID]
		if k == nil {
			return errf(KindNotFound, "TSIG key %d does not exist", op.ID)
		}
		if err := checkVersion(op, k.Version, "TSIG key "+k.Name); err != nil {
			return err
		}
	}
	oldName := k.Name
	if in.Name != nil {
		name := model.NormalizeKeyName(*in.Name)
		if err := dnsname.CheckZoneName(dnsname.Fqdn(name)); err != nil || name == "" || name == "." {
			return errf(KindBadRequest, "invalid key name %q (use letters, digits, hyphens and dots, e.g. xfer-key or ns2-xfer.example.com)", *in.Name)
		}
		if other := st.KeyByName(name); other != nil && other.ID != k.ID {
			return errf(KindConflict, "TSIG key %s already exists", name)
		}
		k.Name = name
	}
	if in.Algorithm != nil {
		alg := strings.ToLower(strings.TrimSpace(*in.Algorithm))
		if _, ok := validate.TSIGAlgorithms[alg]; !ok {
			return errf(KindBadRequest, "unsupported TSIG algorithm %q", alg)
		}
		k.Algorithm = alg
	}
	if in.Secret != nil {
		k.Secret = strings.TrimSpace(*in.Secret)
	}
	if in.Comment != nil {
		k.Comment = *in.Comment
	}
	k.Touch(c.user(), c.now)
	st.Keys[k.ID] = k
	if op.Kind == OpTSIGUpdate && oldName != k.Name {
		renameRefs(st, refKey, oldName, k.Name, c)
	}
	return nil
}

func applyTSIGDelete(st *model.State, op model.Op, c *applyCtx) error {
	if err := c.require(auth.Action{Resource: auth.ResTSIG, Write: true}); err != nil {
		return err
	}
	k := st.Keys[op.ID]
	if k == nil {
		return errf(KindNotFound, "TSIG key %d does not exist", op.ID)
	}
	if err := checkVersion(op, k.Version, "TSIG key "+k.Name); err != nil {
		return err
	}
	if users := FindRefs(st, refKey, k.Name); len(users) > 0 {
		return errf(KindConflict, "TSIG key %s is still used by %s", k.Name, strings.Join(users, ", "))
	}
	delete(st.Keys, k.ID)
	return nil
}

// ---- options

func optionAction(st *model.State, scope string, scopeID int64) (auth.Action, error) {
	switch scope {
	case model.ScopeOptions, model.ScopeTopLevel:
		return auth.Action{Resource: auth.ResOptions, Write: true}, nil
	case model.ScopeView:
		v := st.Views[scopeID]
		if v == nil {
			return auth.Action{}, errf(KindNotFound, "view %d does not exist", scopeID)
		}
		return viewAction(v.Name), nil
	case model.ScopeZone:
		z := st.Zones[scopeID]
		if z == nil {
			return auth.Action{}, errf(KindNotFound, "zone %d does not exist", scopeID)
		}
		return zoneAction(st, z, true), nil
	}
	return auth.Action{}, errf(KindBadRequest, "unknown option scope %q (use options, view, zone or toplevel)", scope)
}

// catalogScope returns the catalog scope for an option scope.
func catalogScope(st *model.State, scope string, scopeID int64) string {
	switch scope {
	case model.ScopeOptions:
		return catalog.ScopeOptions
	case model.ScopeTopLevel:
		return catalog.ScopeTop
	case model.ScopeView:
		return catalog.ScopeView
	case model.ScopeZone:
		if z := st.Zones[scopeID]; z != nil {
			return catalog.ZoneScope(z.Type)
		}
	}
	return ""
}

// NormalizeOption checks an option name for its scope and returns the
// canonical name and value.
func NormalizeOption(st *model.State, scope string, scopeID int64, name, value string) (string, string, error) {
	cs := catalogScope(st, scope, scopeID)
	n := strings.ToLower(strings.TrimSpace(name))
	if canon, syn := catalog.Canonical(cs, n); syn {
		n = canon
	}
	stmt, ok := catalog.Default().Lookup(cs, n)
	if !ok {
		hint := ""
		if scope == model.ScopeZone {
			if z := st.Zones[scopeID]; z != nil {
				hint = " for " + z.Type + " zones"
			}
		}
		return "", "", errf(KindBadRequest, "%q is not a valid option%s in this scope", name, hint)
	}
	if stmt.Managed {
		return "", "", errf(KindBadRequest, "%q can't be set as an option; it is managed through %s", n, stmt.ManagedBy)
	}
	v := strings.TrimSpace(strings.TrimSuffix(strings.TrimSpace(value), ";"))
	if v == "" {
		if n == "include" {
			return "", "", errf(KindBadRequest, "include needs a file name")
		}
		return n, "", nil
	}
	// Quote plain strings for options that take a quoted string.
	if (stmt.Kind == catalog.KindString) && !strings.HasPrefix(v, `"`) && !strings.ContainsAny(v, " \t{};") {
		v = namedconf.QuoteString(v)
	}
	parsed, err := namedconf.ParseOptionValue(n, v)
	if err != nil {
		return "", "", errf(KindBadRequest, "option %s: %v", n, err)
	}
	return n, namedconf.Compact(parsed.Items[1:]), nil
}

func applyOptionPut(st *model.State, op model.Op, c *applyCtx) error {
	var in OptionInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	var o *model.Option
	if op.Kind == OpOptionCreate {
		if op.ID == 0 || st.Options[op.ID] != nil {
			return errf(KindConflict, "option ID %d is already in use", op.ID)
		}
		if in.Scope == nil || in.Name == nil {
			return errf(KindBadRequest, "an option needs a scope and a name")
		}
		o = &model.Option{ID: op.ID, Scope: *in.Scope}
		if in.ScopeID != nil {
			o.ScopeID = *in.ScopeID
		}
		if o.Scope == model.ScopeOptions || o.Scope == model.ScopeTopLevel {
			o.ScopeID = 0
		}
		o.Position = maxPosition(st, o.Scope, o.ScopeID) + 1
	} else {
		o = st.Options[op.ID]
		if o == nil {
			return errf(KindNotFound, "option %d does not exist", op.ID)
		}
		if err := checkVersion(op, o.Version, "option "+o.Name); err != nil {
			return err
		}
		if in.Scope != nil && *in.Scope != o.Scope || in.ScopeID != nil && *in.ScopeID != o.ScopeID {
			return errf(KindBadRequest, "options can't be moved to another scope; delete and re-create them")
		}
	}
	act, err := optionAction(st, o.Scope, o.ScopeID)
	if err != nil {
		return err
	}
	if err := c.require(act); err != nil {
		return err
	}
	name, value := o.Name, o.Value
	if in.Name != nil {
		name = *in.Name
	}
	if in.Value != nil {
		value = *in.Value
	}
	n, v, err := NormalizeOption(st, o.Scope, o.ScopeID, name, value)
	if err != nil {
		return err
	}
	o.Name, o.Value = n, v
	if in.Comment != nil {
		o.Comment = *in.Comment
	}
	if in.Position != nil {
		o.Position = *in.Position
	}
	o.Touch(c.user(), c.now)
	st.Options[o.ID] = o
	return nil
}

func maxPosition(st *model.State, scope string, scopeID int64) int {
	m := 0
	for _, o := range st.Options {
		if o.Scope == scope && o.ScopeID == scopeID && o.Position > m {
			m = o.Position
		}
	}
	return m
}

func applyOptionDelete(st *model.State, op model.Op, c *applyCtx) error {
	o := st.Options[op.ID]
	if o == nil {
		return errf(KindNotFound, "option %d does not exist", op.ID)
	}
	if err := checkVersion(op, o.Version, "option "+o.Name); err != nil {
		return err
	}
	act, err := optionAction(st, o.Scope, o.ScopeID)
	if err != nil {
		return err
	}
	if err := c.require(act); err != nil {
		return err
	}
	delete(st.Options, o.ID)
	return nil
}

// ---- settings

func applySettings(st *model.State, op model.Op, c *applyCtx) error {
	if err := c.require(auth.Action{Resource: auth.ResOptions, Write: true}); err != nil {
		return err
	}
	var in SettingsInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	s := &st.Settings
	if in.DefaultTTL != nil {
		s.DefaultTTL = *in.DefaultTTL
	}
	if in.Nameservers != nil {
		var ns []string
		for _, n := range *in.Nameservers {
			if strings.TrimSpace(n) == "" {
				continue
			}
			a, err := dnsname.ToASCII(strings.TrimSpace(n))
			if err != nil {
				return errf(KindBadRequest, "%v", err)
			}
			ns = append(ns, dnsname.Fqdn(a))
		}
		s.Nameservers = ns
	}
	if in.RName != nil {
		if strings.TrimSpace(*in.RName) == "" {
			s.RName = ""
		} else {
			mb, err := dnsname.MailboxFromEmail(*in.RName)
			if err != nil {
				return errf(KindBadRequest, "%v", err)
			}
			s.RName = mb
		}
	}
	if in.Refresh != nil {
		s.Refresh = *in.Refresh
	}
	if in.Retry != nil {
		s.Retry = *in.Retry
	}
	if in.Expire != nil {
		s.Expire = *in.Expire
	}
	if in.NegativeTTL != nil {
		s.NegativeTTL = *in.NegativeTTL
	}
	if in.SerialPolicy != nil {
		s.SerialPolicy = strings.ToLower(*in.SerialPolicy)
	}
	s.Version++
	return nil
}