// Package model defines Jarl's configuration objects and the in-memory
// State they live in.
//
// The State is the complete desired configuration of the name server. It is
// loaded from the database, modified by applying changeset operations to a
// copy, validated and rendered to BIND configuration files, and only then
// written back.
package model

import (
	"encoding/json"
	"slices"
	"sort"
	"strings"
	"time"

	"jarl/internal/dnsname"
)

// Meta holds bookkeeping fields shared by all objects.
type Meta struct {
	// Version is incremented on every change and used for optimistic
	// concurrency control.
	Version   int       `json:"version"`
	CreatedAt time.Time `json:"created_at"`
	UpdatedAt time.Time `json:"updated_at"`
	CreatedBy string    `json:"created_by,omitempty"`
	UpdatedBy string    `json:"updated_by,omitempty"`
}

// Touch updates the meta data for a modification by user at time now.
func (m *Meta) Touch(user string, now time.Time) {
	if m.Version == 0 {
		m.CreatedAt, m.CreatedBy = now, user
	}
	m.Version++
	m.UpdatedAt, m.UpdatedBy = now, user
}

// View is a BIND view.
// ViewColors are the colours the web UI can show a view in, besides the
// default (the link colour).
var ViewColors = []string{"green", "teal", "purple", "pink", "orange", "yellow", "red", "grey"}

type View struct {
	ID                 int64    `json:"id"`
	Name               string   `json:"name"`
	Position           int      `json:"position"`
	MatchClients       []string `json:"match_clients"`
	MatchDestinations  []string `json:"match_destinations"`
	MatchRecursiveOnly *bool    `json:"match_recursive_only,omitempty"`
	Comment            string   `json:"comment"`
	// Exposure overrides whether the view counts as reachable from the
	// internet (docs/exposure.md): "" works it out, ExposurePublic or
	// ExposurePrivate say so.
	Exposure string `json:"exposure,omitempty"`
	// ReverseSuggestionsOff stops suggesting reverse zones for the view's
	// addresses (docs/reverse.md), e.g. for a view only a few servers use;
	// DismissedReverse are the networks whose suggestion was dismissed.
	ReverseSuggestionsOff bool     `json:"reverse_suggestions_off,omitempty"`
	DismissedReverse      []string `json:"dismissed_reverse,omitempty"`
	// Acknowledged are exposure findings accepted on purpose; they are
	// shown as info instead of warnings.
	Acknowledged []Acknowledgement `json:"acknowledged,omitempty"`
	Meta
}

// Exposure overrides.
const (
	ExposureAuto    = ""
	ExposurePublic  = "public"
	ExposurePrivate = "private"
)

// Acknowledgement accepts one exposure finding (by its code) for a view,
// or for the server: the finding stays, as info, with who accepted it,
// when and why.
type Acknowledgement struct {
	Code   string    `json:"code"`
	Reason string    `json:"reason"`
	By     string    `json:"by"`
	At     time.Time `json:"at"`
}

// FindAck returns the acknowledgement of code in acks, if any.
func FindAck(acks []Acknowledgement, code string) *Acknowledgement {
	for i := range acks {
		if acks[i].Code == code {
			return &acks[i]
		}
	}
	return nil
}

// ACL is a named address match list.
type ACL struct {
	ID       int64    `json:"id"`
	Name     string   `json:"name"`
	Elements []string `json:"elements"`
	Comment  string   `json:"comment"`
	Meta
}

// TSIGKey is a shared secret key for TSIG.
type TSIGKey struct {
	ID        int64  `json:"id"`
	Name      string `json:"name"`
	Algorithm string `json:"algorithm"`
	Secret    string `json:"secret,omitempty"`
	Comment   string `json:"comment"`
	Meta
}

// Zone types.
const (
	ZonePrimary    = "primary"
	ZoneSecondary  = "secondary"
	ZoneMirror     = "mirror"
	ZoneStub       = "stub"
	ZoneStaticStub = "static-stub"
	ZoneForward    = "forward"
	ZoneHint       = "hint"
	ZoneRedirect   = "redirect"
	ZoneInView     = "in-view"
)

// ZoneTypes lists the supported zone types.
var ZoneTypes = []string{ZonePrimary, ZoneSecondary, ZoneMirror, ZoneStub, ZoneStaticStub, ZoneForward, ZoneHint, ZoneRedirect, ZoneInView}

// Serial policies.
const (
	SerialDate      = "date"
	SerialIncrement = "increment"
	SerialUnixtime  = "unixtime"
)

// SOA holds the SOA fields of a primary zone. The serial is maintained by
// Jarl and bumped automatically when the zone's data changes.
type SOA struct {
	MName   string `json:"mname"`
	RName   string `json:"rname"`
	Serial  uint32 `json:"serial"`
	Refresh uint32 `json:"refresh"`
	Retry   uint32 `json:"retry"`
	Expire  uint32 `json:"expire"`
	Minimum uint32 `json:"minimum"`
}

// Zone is a BIND zone.
type Zone struct {
	ID     int64  `json:"id"`
	Name   string `json:"name"`
	ViewID int64  `json:"view_id,omitempty"` // 0 when views are not used
	Type   string `json:"type"`
	// InView names the view whose zone of the same name this zone shares
	// (type in-view only).
	InView string `json:"in_view,omitempty"`
	// File is the zone file. It is generated for primary zones and for
	// zones named loads from transfers (secondary, mirror, stub), unless
	// set explicitly; hint and redirect zones must set it.
	File         string `json:"file,omitempty"`
	SOA          SOA    `json:"soa"`
	DefaultTTL   uint32 `json:"default_ttl"`
	SerialPolicy string `json:"serial_policy,omitempty"`
	// DNSSECPolicy is the dnssec-policy named signs the zone with (primary
	// zones only): "" for an unsigned zone, "default" (BIND's built-in
	// policy), the name of a dnssec-policy statement, or "insecure" while
	// signing is being removed safely (docs/dnssec.md).
	DNSSECPolicy string `json:"dnssec_policy,omitempty"`
	Comment      string `json:"comment"`
	// Disabled zones stay in Jarl, records and all, but named doesn't
	// load them: their zone statement is left out of named.conf.
	Disabled bool `json:"disabled,omitempty"`
	// LinkGroup links zones of the same name in different views: Jarl
	// keeps their shared records in step (docs/views.md#linked-zones). 0
	// for a zone that isn't linked; linked zones share the ID.
	LinkGroup int64 `json:"link_group,omitempty"`
	// AutoPTR keeps the PTR records of the zone's A and AAAA records in
	// step with them, in the reverse zones of the zone's views, as if every
	// change asked for it (docs/reverse.md).
	AutoPTR bool `json:"auto_ptr,omitempty"`
	Meta
}

// DNSSEC policies with a special meaning.
const (
	DNSSECDefault  = "default"  // BIND's built-in policy
	DNSSECInsecure = "insecure" // BIND's built-in policy for removing signing
)

// HasRecords reports whether Jarl manages the zone's records.
func (z *Zone) HasRecords() bool { return z.Type == ZonePrimary }

// Signed reports whether named signs the zone (or is still removing its
// signatures, under the insecure policy).
func (z *Zone) Signed() bool { return z.Type == ZonePrimary && z.DNSSECPolicy != "" }

// Record is a resource record in a primary zone.
type Record struct {
	ID     int64  `json:"id"`
	ZoneID int64  `json:"zone_id"`
	Name   string `json:"name"` // canonical FQDN
	Type   string `json:"type"`
	// TTL is nil when the record uses the zone's default TTL.
	TTL     *uint32 `json:"ttl,omitempty"`
	Data    string  `json:"data"` // canonical presentation format
	Comment string  `json:"comment"`
	// Disabled records stay in Jarl but are left out of the zone (the
	// zone file lists them as comments).
	Disabled bool `json:"disabled,omitempty"`
	// SharedID ties the copies of a shared record in linked zones
	// together (the same in every copy). 0 for a record of a zone that
	// isn't linked, and for a record local to its view in one that is.
	SharedID int64 `json:"shared_id,omitempty"`
	Meta
}

// EffectiveTTL returns the record's TTL, falling back to the zone default.
func (r *Record) EffectiveTTL(z *Zone) uint32 {
	if r.TTL != nil {
		return *r.TTL
	}
	return z.DefaultTTL
}

// Option scopes.
const (
	ScopeOptions  = "options"  // options { } block
	ScopeView     = "view"     // a view
	ScopeZone     = "zone"     // a zone
	ScopeTopLevel = "toplevel" // a free-form top-level statement
)

// Option is a configuration statement: a server option, a view or zone
// option, or a free-form top-level statement such as logging or controls.
// Value holds everything after the name, in named.conf syntax.
type Option struct {
	ID       int64  `json:"id"`
	Scope    string `json:"scope"`
	ScopeID  int64  `json:"scope_id,omitempty"`
	Name     string `json:"name"`
	Value    string `json:"value"`
	Position int    `json:"position"`
	Comment  string `json:"comment"`
	Meta
}

// Text returns the option as a single named.conf statement.
func (o *Option) Text() string {
	if o.Value == "" {
		return o.Name + ";"
	}
	return o.Name + " " + o.Value + ";"
}

// Settings are server-wide Jarl settings, mostly defaults for new zones.
type Settings struct {
	DefaultTTL   uint32   `json:"default_ttl"`
	Nameservers  []string `json:"nameservers"`
	RName        string   `json:"rname"`
	Refresh      uint32   `json:"refresh"`
	Retry        uint32   `json:"retry"`
	Expire       uint32   `json:"expire"`
	NegativeTTL  uint32   `json:"negative_ttl"`
	SerialPolicy string   `json:"serial_policy"`
	// BlockingPausedUntil, while set, lets every name through blocking
	// (docs/blocking.md); jarld clears it when the time is up.
	BlockingPausedUntil *time.Time `json:"blocking_paused_until,omitempty"`
	// BlockingPausedIndefinitely pauses blocking until someone resumes it.
	BlockingPausedIndefinitely bool `json:"blocking_paused_indefinitely,omitempty"`
	// Exposure and Acknowledged are the server's own (without views, and
	// for server-wide findings such as a visible version): see View.
	Exposure     string            `json:"exposure,omitempty"`
	Acknowledged []Acknowledgement `json:"acknowledged,omitempty"`
	// DismissedReverse are dismissed reverse zone suggestions (without
	// views; see View).
	DismissedReverse []string `json:"dismissed_reverse,omitempty"`
	// EncryptedDNSHosts are the host names clients use for DNS over TLS
	// and HTTPS (docs/encrypted-dns.md); the first is checked first.
	EncryptedDNSHosts []string `json:"encrypted_dns_hosts,omitempty"`
	Version           int      `json:"version"`
}

// BlockingPaused reports whether blocking is paused, for a time or until
// resumed.
func (s *Settings) BlockingPaused() bool {
	return s.BlockingPausedUntil != nil || s.BlockingPausedIndefinitely
}

// DefaultSettings returns the settings of a fresh installation.
func DefaultSettings() Settings {
	return Settings{
		DefaultTTL:   3600,
		Refresh:      3600,
		Retry:        900,
		Expire:       1209600,
		NegativeTTL:  300,
		SerialPolicy: SerialDate,
	}
}

// State is the complete desired configuration.
type State struct {
	Settings Settings
	Views    map[int64]*View
	ACLs     map[int64]*ACL
	Keys     map[int64]*TSIGKey
	Zones    map[int64]*Zone
	Records  map[int64]*Record
	Options  map[int64]*Option
	// Blocking (docs/blocking.md).
	Blocklists   map[int64]*Blocklist
	BlockRules   map[int64]*BlockRule
	BlockSteps   map[int64]*BlockStep
	ClientGroups map[int64]*ClientGroup
}

// NewState returns an empty state with default settings.
func NewState() *State {
	return &State{
		Settings: DefaultSettings(),
		Views:    map[int64]*View{},
		ACLs:     map[int64]*ACL{},
		Keys:     map[int64]*TSIGKey{},
		Zones:    map[int64]*Zone{},
		Records:  map[int64]*Record{},
		Options:  map[int64]*Option{},

		Blocklists:   map[int64]*Blocklist{},
		BlockRules:   map[int64]*BlockRule{},
		BlockSteps:   map[int64]*BlockStep{},
		ClientGroups: map[int64]*ClientGroup{},
	}
}

// Clone returns a deep copy of the state.
func (s *State) Clone() *State {
	c := &State{
		Settings: s.Settings,
		Views:    make(map[int64]*View, len(s.Views)),
		ACLs:     make(map[int64]*ACL, len(s.ACLs)),
		Keys:     make(map[int64]*TSIGKey, len(s.Keys)),
		Zones:    make(map[int64]*Zone, len(s.Zones)),
		Records:  make(map[int64]*Record, len(s.Records)),
		Options:  make(map[int64]*Option, len(s.Options)),

		Blocklists:   make(map[int64]*Blocklist, len(s.Blocklists)),
		BlockRules:   make(map[int64]*BlockRule, len(s.BlockRules)),
		BlockSteps:   make(map[int64]*BlockStep, len(s.BlockSteps)),
		ClientGroups: make(map[int64]*ClientGroup, len(s.ClientGroups)),
	}
	c.Settings.Nameservers = slices.Clone(s.Settings.Nameservers)
	c.Settings.Acknowledged = slices.Clone(s.Settings.Acknowledged)
	for id, v := range s.Views {
		n := *v
		n.MatchClients = slices.Clone(v.MatchClients)
		n.MatchDestinations = slices.Clone(v.MatchDestinations)
		n.Acknowledged = slices.Clone(v.Acknowledged)
		if v.MatchRecursiveOnly != nil {
			b := *v.MatchRecursiveOnly
			n.MatchRecursiveOnly = &b
		}
		c.Views[id] = &n
	}
	for id, a := range s.ACLs {
		n := *a
		n.Elements = slices.Clone(a.Elements)
		c.ACLs[id] = &n
	}
	for id, k := range s.Keys {
		n := *k
		c.Keys[id] = &n
	}
	for id, z := range s.Zones {
		n := *z
		c.Zones[id] = &n
	}
	for id, r := range s.Records {
		n := *r
		if r.TTL != nil {
			t := *r.TTL
			n.TTL = &t
		}
		c.Records[id] = &n
	}
	for id, o := range s.Options {
		n := *o
		c.Options[id] = &n
	}
	for id, b := range s.Blocklists {
		n := *b
		n.ViewIDs = slices.Clone(b.ViewIDs)
		c.Blocklists[id] = &n
	}
	for id, r := range s.BlockRules {
		n := *r
		n.ViewIDs = slices.Clone(r.ViewIDs)
		c.BlockRules[id] = &n
	}
	for id, st := range s.BlockSteps {
		n := *st
		c.BlockSteps[id] = &n
	}
	for id, g := range s.ClientGroups {
		n := *g
		n.Members = slices.Clone(g.Members)
		n.ViewIDs = slices.Clone(g.ViewIDs)
		c.ClientGroups[id] = &n
	}
	return c
}

// OrderedViews returns the views in match order.
func (s *State) OrderedViews() []*View {
	out := make([]*View, 0, len(s.Views))
	for _, v := range s.Views {
		out = append(out, v)
	}
	sort.Slice(out, func(i, j int) bool {
		if out[i].Position != out[j].Position {
			return out[i].Position < out[j].Position
		}
		return out[i].ID < out[j].ID
	})
	return out
}

// ViewByName finds a view by name (case-insensitive).
func (s *State) ViewByName(name string) *View {
	for _, v := range s.Views {
		if strings.EqualFold(v.Name, name) {
			return v
		}
	}
	return nil
}

// ViewName returns the name of the zone's view, or "" without views.
func (s *State) ViewName(z *Zone) string {
	if v := s.Views[z.ViewID]; v != nil {
		return v.Name
	}
	return ""
}

// ACLByName finds an ACL by name (case-insensitive, as BIND does).
func (s *State) ACLByName(name string) *ACL {
	for _, a := range s.ACLs {
		if strings.EqualFold(a.Name, name) {
			return a
		}
	}
	return nil
}

// KeyByName finds a TSIG key by name.
func (s *State) KeyByName(name string) *TSIGKey {
	n := NormalizeKeyName(name)
	for _, k := range s.Keys {
		if k.Name == n {
			return k
		}
	}
	return nil
}

// ViewKeyPrefix starts the names of the TSIG keys Jarl gives views
// (render/viewkeys.go); other keys can't use it.
const ViewKeyPrefix = "jarl-view-"

// ViewKeyName returns the name of a view's key.
func ViewKeyName(view string) string { return ViewKeyPrefix + view }

// NormalizeKeyName returns the canonical form of a key name: lowercase,
// without a trailing dot.
func NormalizeKeyName(name string) string {
	return strings.TrimSuffix(strings.ToLower(strings.TrimSpace(name)), ".")
}

// SortedACLs returns ACLs ordered by name.
func (s *State) SortedACLs() []*ACL {
	out := make([]*ACL, 0, len(s.ACLs))
	for _, a := range s.ACLs {
		out = append(out, a)
	}
	sort.Slice(out, func(i, j int) bool { return strings.ToLower(out[i].Name) < strings.ToLower(out[j].Name) })
	return out
}

// SortedKeys returns TSIG keys ordered by name.
func (s *State) SortedKeys() []*TSIGKey {
	out := make([]*TSIGKey, 0, len(s.Keys))
	for _, k := range s.Keys {
		out = append(out, k)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
	return out
}

// ZonesInView returns the zones of a view (viewID 0 for "no view"), sorted
// by name.
func (s *State) ZonesInView(viewID int64) []*Zone {
	var out []*Zone
	for _, z := range s.Zones {
		if z.ViewID == viewID {
			out = append(out, z)
		}
	}
	SortZones(out)
	return out
}

// SortedZones returns all zones ordered by view position and name.
func (s *State) SortedZones() []*Zone {
	out := make([]*Zone, 0, len(s.Zones))
	for _, z := range s.Zones {
		out = append(out, z)
	}
	pos := map[int64]int{}
	for i, v := range s.OrderedViews() {
		pos[v.ID] = i + 1
	}
	sort.Slice(out, func(i, j int) bool {
		if pi, pj := pos[out[i].ViewID], pos[out[j].ViewID]; pi != pj {
			return pi < pj
		}
		return CanonicalLess(out[i].Name, out[j].Name)
	})
	return out
}

// SortZones sorts zones by name in DNS canonical order.
func SortZones(zs []*Zone) {
	sort.Slice(zs, func(i, j int) bool { return CanonicalLess(zs[i].Name, zs[j].Name) })
}

// FindZone finds a zone by name within a view (viewID 0 for no view).
func (s *State) FindZone(name string, viewID int64) *Zone {
	name = dnsname.Fqdn(name)
	for _, z := range s.Zones {
		if z.Name == name && z.ViewID == viewID {
			return z
		}
	}
	return nil
}

// ZonesNamed returns all zones with the given name across views.
func (s *State) ZonesNamed(name string) []*Zone {
	name = dnsname.Fqdn(name)
	var out []*Zone
	for _, z := range s.Zones {
		if z.Name == name {
			out = append(out, z)
		}
	}
	return out
}

// ZoneRecords returns the records of a zone in display order.
func (s *State) ZoneRecords(zoneID int64) []*Record {
	var out []*Record
	for _, r := range s.Records {
		if r.ZoneID == zoneID {
			out = append(out, r)
		}
	}
	SortRecords(out, s.Zones[zoneID])
	return out
}

// ServedRecords returns the records of a zone that are in the zone file
// (not disabled), in display order.
func (s *State) ServedRecords(zoneID int64) []*Record {
	var out []*Record
	for _, r := range s.ZoneRecords(zoneID) {
		if !r.Disabled {
			out = append(out, r)
		}
	}
	return out
}

// RecordsByZone groups all records by zone ID (unsorted).
func (s *State) RecordsByZone() map[int64][]*Record {
	out := map[int64][]*Record{}
	for _, r := range s.Records {
		out[r.ZoneID] = append(out[r.ZoneID], r)
	}
	return out
}

// ServedRecordsByZone is RecordsByZone without disabled records.
func (s *State) ServedRecordsByZone() map[int64][]*Record {
	out := map[int64][]*Record{}
	for _, r := range s.Records {
		if !r.Disabled {
			out[r.ZoneID] = append(out[r.ZoneID], r)
		}
	}
	return out
}

// ScopedOptions returns the options of a scope: in a fixed order by name
// for a block (see optionLess), in the order they were added for
// top-level statements, which are written as entered.
func (s *State) ScopedOptions(scope string, scopeID int64) []*Option {
	var out []*Option
	for _, o := range s.Options {
		if o.Scope == scope && o.ScopeID == scopeID {
			out = append(out, o)
		}
	}
	if scope != ScopeTopLevel {
		sort.Slice(out, func(i, j int) bool { return optionLess(out[i], out[j]) })
		return out
	}
	sort.Slice(out, func(i, j int) bool {
		if out[i].Position != out[j].Position {
			return out[i].Position < out[j].Position
		}
		return out[i].ID < out[j].ID
	})
	return out
}

// FindOption returns the first option with the given name in a scope.
func (s *State) FindOption(scope string, scopeID int64, name string) *Option {
	for _, o := range s.ScopedOptions(scope, scopeID) {
		if o.Name == name {
			return o
		}
	}
	return nil
}

// typeOrder puts SOA and NS first when sorting records.
func typeOrder(t string) string {
	switch t {
	case "SOA":
		return "0"
	case "NS":
		return "1"
	}
	return "2" + t
}

// SortRecords sorts records in zone-file order: apex first, then names in
// DNS canonical order (so subdomains group together), then by type and
// data.
func SortRecords(rs []*Record, z *Zone) {
	apex := ""
	if z != nil {
		apex = z.Name
	}
	sort.SliceStable(rs, func(i, j int) bool {
		a, b := rs[i], rs[j]
		if a.Name != b.Name {
			if a.Name == apex {
				return true
			}
			if b.Name == apex {
				return false
			}
			return CanonicalLess(a.Name, b.Name)
		}
		if a.Type != b.Type {
			return typeOrder(a.Type) < typeOrder(b.Type)
		}
		if a.Data != b.Data {
			return a.Data < b.Data
		}
		return a.ID < b.ID
	})
}

// CanonicalLess compares names in DNS canonical order (RFC 4034 section
// 6.1): by label from the right.
func CanonicalLess(a, b string) bool {
	la := strings.Split(strings.TrimSuffix(a, "."), ".")
	lb := strings.Split(strings.TrimSuffix(b, "."), ".")
	for i, j := len(la)-1, len(lb)-1; i >= 0 && j >= 0; i, j = i-1, j-1 {
		if la[i] != lb[j] {
			return la[i] < lb[j]
		}
	}
	return len(la) < len(lb)
}

// RRSetKey identifies an RRset.
type RRSetKey struct {
	Name string
	Type string
}

// RRSets groups records into RRsets.
func RRSets(rs []*Record) map[RRSetKey][]*Record {
	out := map[RRSetKey][]*Record{}
	for _, r := range rs {
		k := RRSetKey{r.Name, r.Type}
		out[k] = append(out[k], r)
	}
	return out
}

// Ptr returns a pointer to v.
func Ptr[T any](v T) *T { return &v }

// Opt is an optional value for partial updates that distinguishes "not
// set" from "set to null".
type Opt[T any] struct {
	Set   bool
	Null  bool
	Value T
}

// Some returns an Opt holding v.
func Some[T any](v T) Opt[T] { return Opt[T]{Set: true, Value: v} }

// IsZero reports whether the option was not set (used by omitzero).
func (o Opt[T]) IsZero() bool { return !o.Set }

// UnmarshalJSON implements json.Unmarshaler.
func (o *Opt[T]) UnmarshalJSON(b []byte) error {
	o.Set = true
	if string(b) == "null" {
		o.Null = true
		return nil
	}
	return json.Unmarshal(b, &o.Value)
}

// MarshalJSON implements json.Marshaler.
func (o Opt[T]) MarshalJSON() ([]byte, error) {
	if !o.Set || o.Null {
		return []byte("null"), nil
	}
	return json.Marshal(o.Value)
}