package bind

import (
	"fmt"
	"sort"
	"strings"

	bindv1alpha1 "git.unkin.net/unkin/bind-operator/api/v1alpha1"
)

// RenderInput aggregates everything needed to render a cluster's named.conf.
type RenderInput struct {
	Cluster        *bindv1alpha1.BindCluster
	ACLs           []bindv1alpha1.BindACL
	Views          []bindv1alpha1.BindView
	Policies       []bindv1alpha1.BindPolicy
	DNSSECPolicies []bindv1alpha1.BindDNSSECPolicy
	Catalog        *bindv1alpha1.BindCatalogZone
	// Forwards are type:forward BindZones. They are pure configuration (no
	// replicated data), so they are rendered into named.conf on every pod
	// rather than added dynamically to the primary.
	Forwards []bindv1alpha1.BindZone
	// PrimaryAddress is the in-cluster address secondaries transfer from.
	PrimaryAddress string
	// NotifyKeyName is the TSIG key name secondaries accept intra-cluster NOTIFYs
	// under. The primary pod's NOTIFYs egress with its *pod* IP as the source — k8s
	// Services only NAT the inbound direction — so BIND, whose implicit
	// allow-notify is the zone's primaries list (the stable ClusterIP), REFUSES
	// them as "non-primary" and replication falls back to the SOA refresh timer.
	//
	// The primary signs its outgoing NOTIFYs with this key (the zone-scope
	// also-notify entries, applied via rndc, carry `key "<name>"`), and
	// secondaries render `allow-notify { key "<name>"; }` — an address-match-list
	// with a *key* element and NO IPs. Because it names only the key, this clause
	// is fully static: it never changes when a pod IP churns, so it cannot feed a
	// changed config-hash and cannot roll the StatefulSet (the v0.2.5 loop). Empty
	// leaves BIND's default behaviour unchanged.
	NotifyKeyName string
}

// RenderNamedConf returns the primary and secondary named.conf contents for a
// cluster. Both variants are shipped in the ConfigMap; the entrypoint selects
// one based on the pod ordinal.
func RenderNamedConf(in RenderInput) (primary string, secondary string) {
	// client.List returns cache-ordered (non-deterministic) results, so sort
	// every input slice before rendering. Otherwise the rendered config
	// reshuffles between reconciles, churning the ConfigMap — and with the
	// pod-template config hash that means an endless rolling restart.
	sortInput(&in)
	return render(in, true), render(in, false)
}

// sortInput orders every list rendered into named.conf deterministically.
func sortInput(in *RenderInput) {
	sort.Slice(in.ACLs, func(i, j int) bool { return in.ACLs[i].Name < in.ACLs[j].Name })
	sort.Slice(in.Views, func(i, j int) bool {
		if in.Views[i].Spec.Order != in.Views[j].Spec.Order {
			return in.Views[i].Spec.Order < in.Views[j].Spec.Order
		}
		return in.Views[i].Name < in.Views[j].Name
	})
	sort.Slice(in.Forwards, func(i, j int) bool { return in.Forwards[i].Spec.ZoneName < in.Forwards[j].Spec.ZoneName })
	sort.Slice(in.Policies, func(i, j int) bool { return in.Policies[i].Spec.ZoneName < in.Policies[j].Spec.ZoneName })
	sort.Slice(in.DNSSECPolicies, func(i, j int) bool { return in.DNSSECPolicies[i].Name < in.DNSSECPolicies[j].Name })
}

func render(in RenderInput, isPrimary bool) string {
	c := in.Cluster
	var b strings.Builder

	b.WriteString("// Managed by bind-operator. Do not edit.\n")
	b.WriteString(fmt.Sprintf("include \"%s\";\n", RndcKeyPath))
	b.WriteString(fmt.Sprintf("include \"%s\";\n\n", KeysConfPath))

	// Named ACLs (global scope).
	acls := append([]bindv1alpha1.BindACL(nil), in.ACLs...)
	sort.Slice(acls, func(i, j int) bool { return acls[i].Name < acls[j].Name })
	for _, a := range acls {
		b.WriteString(fmt.Sprintf("acl \"%s\" { %s };\n", a.Name, matchList(a.Spec.Entries)))
	}
	if len(acls) > 0 {
		b.WriteString("\n")
	}

	// DNSSEC policies (must precede zones that reference them).
	for _, p := range in.DNSSECPolicies {
		b.WriteString(renderDNSSECPolicy(p))
	}

	// options.
	b.WriteString("options {\n")
	b.WriteString(fmt.Sprintf("    directory \"%s\";\n", DataDir))
	b.WriteString("    listen-on port 53 { any; };\n")
	b.WriteString("    listen-on-v6 port 53 { any; };\n")
	b.WriteString(fmt.Sprintf("    recursion %s;\n", yesno(recursionFor(c))))
	if len(c.Spec.Forwarders) > 0 {
		b.WriteString(fmt.Sprintf("    forwarders { %s };\n", terminate(c.Spec.Forwarders)))
	}
	if allowNewZones(c) {
		b.WriteString("    allow-new-zones yes;\n")
	}
	b.WriteString("    dnssec-validation auto;\n")
	// Secondaries accept NOTIFY authenticated by the cluster's NOTIFY TSIG key.
	// Catalog member and plain secondary zones take their implicit allow-notify
	// from their primaries (the primary Service ClusterIP), but the primary's
	// NOTIFYs are sourced from its pod IP, so they are refused as "non-primary"
	// unless an explicit allow-notify covers them. Rather than enumerate pod IPs
	// (restart-scoped config that depends on pod IPs — the v0.2.5 roll loop), we
	// accept any NOTIFY signed with the cluster key: `allow-notify { key "X"; }`.
	b.WriteString(allowNotifyClause(in, isPrimary, "    "))
	for _, o := range c.Spec.ExtraOptions {
		b.WriteString("    " + strings.TrimRight(o, ";") + ";\n")
	}
	// When there are no views, response-policy and catalog-zones live in options.
	if len(in.Views) == 0 {
		b.WriteString(responsePolicyClause(in.Policies, "    "))
		b.WriteString(catalogZonesClause(in, isPrimary, "    "))
	}
	b.WriteString("};\n\n")

	// controls (rndc).
	b.WriteString("controls {\n")
	b.WriteString("    inet 127.0.0.1 port 953 allow { 127.0.0.1; } keys { \"rndc-key\"; };\n")
	b.WriteString("};\n\n")

	// Views, if any.
	views := append([]bindv1alpha1.BindView(nil), in.Views...)
	sort.Slice(views, func(i, j int) bool { return views[i].Spec.Order < views[j].Spec.Order })
	for _, v := range views {
		b.WriteString(renderView(v, in, isPrimary))
	}

	// Catalog zone declaration lives at top level when there are no views.
	if in.Catalog != nil && len(in.Views) == 0 {
		b.WriteString(renderCatalogZoneDecl(in, isPrimary, ""))
	}

	// Top-level forward zones (BIND only allows top-level zones when no views
	// are defined; in-view forward zones are rendered inside renderView).
	if len(in.Views) == 0 {
		for _, z := range in.Forwards {
			if z.Spec.ViewRef == "" {
				b.WriteString(renderForwardZone(z, ""))
			}
		}
	}

	return b.String()
}

// renderForwardZone renders a type:forward zone clause.
func renderForwardZone(z bindv1alpha1.BindZone, indent string) string {
	var b strings.Builder
	b.WriteString(fmt.Sprintf("%szone \"%s\" {\n", indent, z.Spec.ZoneName))
	b.WriteString(indent + "    type forward;\n")
	b.WriteString(indent + "    forward only;\n")
	if len(z.Spec.Forwarders) > 0 {
		b.WriteString(fmt.Sprintf("%s    forwarders { %s };\n", indent, terminate(z.Spec.Forwarders)))
	}
	b.WriteString(indent + "};\n")
	return b.String()
}

func renderView(v bindv1alpha1.BindView, in RenderInput, isPrimary bool) string {
	var b strings.Builder
	b.WriteString(fmt.Sprintf("view \"%s\" {\n", v.Name))
	mc := v.Spec.MatchClients
	if len(mc) == 0 {
		mc = []string{"any"}
	}
	b.WriteString(fmt.Sprintf("    match-clients { %s };\n", matchList(mc)))
	if len(v.Spec.MatchDestinations) > 0 {
		b.WriteString(fmt.Sprintf("    match-destinations { %s };\n", matchList(v.Spec.MatchDestinations)))
	}
	rec := recursionFor(in.Cluster)
	if v.Spec.Recursion != nil {
		rec = *v.Spec.Recursion
	}
	b.WriteString(fmt.Sprintf("    recursion %s;\n", yesno(rec)))
	if len(v.Spec.AllowQuery) > 0 {
		b.WriteString(fmt.Sprintf("    allow-query { %s };\n", matchList(v.Spec.AllowQuery)))
	}
	for _, o := range v.Spec.ExtraOptions {
		b.WriteString("    " + strings.TrimRight(o, ";") + ";\n")
	}
	// Policies and catalog scoped to this view.
	viewPolicies := filterPoliciesForView(in.Policies, v.Name)
	b.WriteString(responsePolicyClause(viewPolicies, "    "))
	b.WriteString(catalogZonesClause(in, isPrimary, "    "))
	if in.Catalog != nil {
		b.WriteString(renderCatalogZoneDecl(in, isPrimary, "    "))
	}
	// Forward zones bound to this view.
	for _, z := range in.Forwards {
		if z.Spec.ViewRef == v.Name {
			b.WriteString(renderForwardZone(z, "    "))
		}
	}
	b.WriteString("};\n\n")
	return b.String()
}

func renderDNSSECPolicy(p bindv1alpha1.BindDNSSECPolicy) string {
	name := p.Spec.PolicyName
	if name == "" {
		name = p.Name
	}
	var b strings.Builder
	b.WriteString(fmt.Sprintf("dnssec-policy \"%s\" {\n", name))
	if p.Spec.NSEC3 {
		b.WriteString("    nsec3param;\n")
	}
	if p.Spec.MaxZoneTTL != "" {
		b.WriteString(fmt.Sprintf("    max-zone-ttl %s;\n", p.Spec.MaxZoneTTL))
	}
	if p.Spec.SignaturesValidity != "" {
		b.WriteString(fmt.Sprintf("    signatures-validity %s;\n", p.Spec.SignaturesValidity))
	}
	alg := p.Spec.Algorithm
	if alg == "" {
		alg = "ecdsap256sha256"
	}
	if p.Spec.CSK != nil {
		b.WriteString("    keys {\n")
		b.WriteString("        csk " + keyLine(p.Spec.CSK, alg) + ";\n")
		b.WriteString("    };\n")
	} else {
		b.WriteString("    keys {\n")
		if p.Spec.KSK != nil {
			b.WriteString("        ksk " + keyLine(p.Spec.KSK, alg) + ";\n")
		}
		if p.Spec.ZSK != nil {
			b.WriteString("        zsk " + keyLine(p.Spec.ZSK, alg) + ";\n")
		}
		b.WriteString("    };\n")
	}
	for _, o := range p.Spec.ExtraOptions {
		b.WriteString("    " + strings.TrimRight(o, ";") + ";\n")
	}
	b.WriteString("};\n\n")
	return b.String()
}

func keyLine(k *bindv1alpha1.DNSSECKey, defaultAlg string) string {
	lifetime := k.Lifetime
	if lifetime == "" {
		lifetime = "unlimited"
	}
	alg := k.Algorithm
	if alg == "" {
		alg = defaultAlg
	}
	if k.KeySize > 0 {
		return fmt.Sprintf("lifetime %s algorithm %s %d", lifetime, alg, k.KeySize)
	}
	return fmt.Sprintf("lifetime %s algorithm %s", lifetime, alg)
}

func responsePolicyClause(policies []bindv1alpha1.BindPolicy, indent string) string {
	if len(policies) == 0 {
		return ""
	}
	sorted := append([]bindv1alpha1.BindPolicy(nil), policies...)
	sort.Slice(sorted, func(i, j int) bool { return sorted[i].Spec.Order < sorted[j].Spec.Order })
	var b strings.Builder
	b.WriteString(indent + "response-policy {\n")
	for _, p := range sorted {
		b.WriteString(fmt.Sprintf("%s    zone \"%s\";\n", indent, p.Spec.ZoneName))
	}
	b.WriteString(indent + "};\n")
	return b.String()
}

// transferPrimaries returns the primaries list secondaries use to AXFR the
// catalog (and, by inheritance, its member zones), each annotated with the
// catalog transfer TSIG key. The primary requires key-authenticated transfers
// (allow-transfer { key ... }), so an unkeyed primaries list is REFUSED.
func transferPrimaries(in RenderInput) []string {
	primaries := in.Catalog.Spec.DefaultPrimaries
	if len(primaries) == 0 && in.PrimaryAddress != "" {
		primaries = []string{in.PrimaryAddress}
	}
	key := in.Catalog.Spec.TransferKeyRef
	if key == "" {
		return primaries
	}
	out := make([]string, 0, len(primaries))
	for _, p := range primaries {
		p = strings.TrimSpace(strings.TrimRight(p, ";"))
		if p == "" {
			continue
		}
		if strings.Contains(p, " key ") {
			out = append(out, p)
		} else {
			out = append(out, fmt.Sprintf("%s key \"%s\"", p, key))
		}
	}
	return out
}

// allowNotifyClause renders an options-scope allow-notify on secondaries that
// accepts intra-cluster NOTIFYs authenticated by the cluster's NOTIFY TSIG key.
// Zones (catalog members and plain secondaries) point their primaries at the
// primary Service ClusterIP for stable AXFR, which also becomes their implicit
// allow-notify — but NOTIFYs leave the primary pod with its *pod* IP as source,
// so without this they are refused as "non-primary". The primary signs those
// NOTIFYs with NotifyKeyName (see the also-notify entries applied via rndc), and
// this clause admits them by key.
//
// The rendered clause is `allow-notify { key "<name>"; };` — a key element with
// NO IP addresses. It is therefore fully static: it depends only on the key
// name, never on any pod IP, so it can never change the config-hash and can
// never trigger a rolling restart. This is the fix for the v0.2.5 loop, where an
// options-scope allow-notify enumerating the primary pod IP re-rendered on every
// pod churn, flipped the hash, rolled the pods, changed the IP, and looped.
//
// Emitted only on secondaries and only when the NOTIFY key name is known.
func allowNotifyClause(in RenderInput, isPrimary bool, indent string) string {
	if isPrimary {
		return ""
	}
	key := strings.TrimSpace(in.NotifyKeyName)
	if key == "" {
		return ""
	}
	return fmt.Sprintf("%sallow-notify { key \"%s\"; };\n", indent, key)
}

func catalogZonesClause(in RenderInput, isPrimary bool, indent string) string {
	// Only secondaries consume the catalog to auto-provision member zones.
	if in.Catalog == nil || isPrimary {
		return ""
	}
	primaries := transferPrimaries(in)
	if len(primaries) == 0 {
		return ""
	}
	var b strings.Builder
	b.WriteString(indent + "catalog-zones {\n")
	b.WriteString(fmt.Sprintf("%s    zone \"%s\" default-primaries { %s };\n", indent, in.Catalog.Spec.ZoneName, terminate(primaries)))
	b.WriteString(indent + "};\n")
	return b.String()
}

// renderCatalogZoneDecl declares the catalog zone as a secondary on consumer
// pods. The primary hosts the catalog zone dynamically (created by the
// BindCatalogZone controller via rndc addzone), so nothing is emitted here for
// the primary.
func renderCatalogZoneDecl(in RenderInput, isPrimary bool, indent string) string {
	if isPrimary {
		return ""
	}
	cat := in.Catalog
	file := CatalogFilePath(cat.Spec.ZoneName)
	primaries := transferPrimaries(in)
	if len(primaries) == 0 {
		// Primary IP not known yet; omit the secondary catalog zone rather than
		// emit an invalid empty primaries list. A Pod-triggered reconcile renders
		// it once the primary pod has an IP.
		return ""
	}
	var b strings.Builder
	b.WriteString(fmt.Sprintf("%szone \"%s\" {\n", indent, cat.Spec.ZoneName))
	b.WriteString(indent + "    type secondary;\n")
	b.WriteString(fmt.Sprintf("%s    file \"%s\";\n", indent, file))
	b.WriteString(fmt.Sprintf("%s    primaries { %s };\n", indent, terminate(primaries)))
	b.WriteString(indent + "};\n\n")
	return b.String()
}

func filterPoliciesForView(policies []bindv1alpha1.BindPolicy, view string) []bindv1alpha1.BindPolicy {
	var out []bindv1alpha1.BindPolicy
	for _, p := range policies {
		if p.Spec.ViewRef == view || p.Spec.ViewRef == "" {
			out = append(out, p)
		}
	}
	return out
}

// matchList renders address-match-list elements, each terminated with a
// semicolon: `10.0.0.0/8; key foo;`.
func matchList(entries []string) string {
	return terminate(entries)
}

// terminate joins elements each followed by "; ".
func terminate(entries []string) string {
	var parts []string
	for _, e := range entries {
		e = strings.TrimSpace(strings.TrimRight(e, ";"))
		if e == "" {
			continue
		}
		parts = append(parts, e+";")
	}
	return strings.Join(parts, " ")
}

func yesno(b bool) string {
	if b {
		return "yes"
	}
	return "no"
}

func recursionFor(c *bindv1alpha1.BindCluster) bool {
	if c.Spec.Recursion != nil {
		return *c.Spec.Recursion
	}
	return c.Spec.Mode == bindv1alpha1.ModeResolver
}

func allowNewZones(c *bindv1alpha1.BindCluster) bool {
	if c.Spec.AllowNewZones != nil {
		return *c.Spec.AllowNewZones
	}
	return true
}