package controller

import (
	"context"
	"fmt"
	"strings"

	"sigs.k8s.io/controller-runtime/pkg/client"

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

func isPrimaryType(t bindv1alpha1.ZoneType) bool {
	return t == bindv1alpha1.ZonePrimary || t == ""
}

// catalogEnabled reports whether a primary zone should be registered in the
// cluster catalog zone.
func catalogEnabled(zone *bindv1alpha1.BindZone) bool {
	if !isPrimaryType(zone.Spec.Type) {
		return false
	}
	if zone.Spec.Catalog == nil {
		return true
	}
	return *zone.Spec.Catalog
}

// fqdn resolves a record owner name relative to a zone origin.
func fqdn(name, zone string) string {
	zone = strings.TrimSuffix(zone, ".") + "."
	if name == "" || name == "@" {
		return zone
	}
	if strings.HasSuffix(name, ".") {
		return name
	}
	return name + "." + zone
}

func recordsToUpdates(zone string, records []bindv1alpha1.Record, defaultTTL int32) []bind.RecordUpdate {
	updates := make([]bind.RecordUpdate, 0, len(records))
	for _, rec := range records {
		ttl := defaultTTL
		if rec.TTL != nil {
			ttl = *rec.TTL
		}
		updates = append(updates, bind.RecordUpdate{
			FQDN:   fqdn(rec.Name, zone),
			Type:   rec.Type,
			TTL:    ttl,
			Values: rec.Values,
		})
	}
	return updates
}

// updateKeyName returns the TSIG key name (as used in named.conf) for a zone's
// update key, falling back to the object name.
func updateKeyName(ctx context.Context, c client.Client, zone *bindv1alpha1.BindZone) string {
	return tsigKeyName(ctx, c, zone.Namespace, zone.Spec.UpdateKeyRef)
}

// tsigKeyName resolves a BindTSIGKey object reference to the TSIG key name used
// in named.conf (the KeyName override when set, otherwise the object name).
// Returns "" for an empty ref, and falls back to the ref if the object cannot be
// read.
func tsigKeyName(ctx context.Context, c client.Client, namespace, ref string) string {
	if ref == "" {
		return ""
	}
	var key bindv1alpha1.BindTSIGKey
	if err := c.Get(ctx, client.ObjectKey{Namespace: namespace, Name: ref}, &key); err != nil {
		return ref
	}
	if key.Spec.KeyName != "" {
		return key.Spec.KeyName
	}
	return ref
}

// matchListInline renders address-match-list entries on one line.
func matchListInline(entries []string) string { return terminateInline(entries) }

func terminateInline(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, " ")
}

// alsoNotifyList renders also-notify entries, each optionally annotated with a
// TSIG key so the primary signs its NOTIFYs and secondaries can accept them by
// key (`allow-notify { key ... }`) rather than by pod IP. An entry that already
// carries a `key` clause is left untouched.
func alsoNotifyList(addrs []string, key string) string {
	key = strings.TrimSpace(key)
	var parts []string
	for _, a := range addrs {
		a = strings.TrimSpace(strings.TrimRight(a, ";"))
		if a == "" {
			continue
		}
		if key != "" && !strings.Contains(a, " key ") {
			a = fmt.Sprintf("%s key \"%s\"", a, key)
		}
		parts = append(parts, a+";")
	}
	return strings.Join(parts, " ")
}

// absolute qualifies a nameserver name. Unlike record owner names, a
// spec.nameservers entry is always a full domain name, never relative to the
// zone: an in-zone nameserver is spelled out in full.
func absolute(name string) string { return strings.TrimSuffix(name, ".") + "." }

// zoneNameservers resolves the names to publish in a zone's apex NS RRset: the
// declared nameservers, else the primary's stable in-cluster DNS name. The
// fallback is deliberately out-of-zone, so no pod IP is needed as glue.
func zoneNameservers(declared []string, cluster *bindv1alpha1.BindCluster) []string {
	if len(declared) > 0 {
		return declared
	}
	return []string{primaryAddress(cluster.Name, cluster.Namespace) + "."}
}

// apexNSUpdates returns the dynamic-update ops that keep a zone's apex NS RRset
// equal to nameservers, plus removal of the seed's ns1 glue once the zone
// declares its own nameservers. Ops colliding with a spec.records entry are
// dropped: records are applied afterwards and would re-add them, and the churn
// would bump the serial on every reconcile.
func apexNSUpdates(zone *bindv1alpha1.BindZone, nameservers []string) []bind.RecordUpdate {
	owns := func(name, typ string) bool {
		for _, rec := range zone.Spec.Records {
			if strings.EqualFold(rec.Type, typ) && fqdn(rec.Name, zone.Spec.ZoneName) == fqdn(name, zone.Spec.ZoneName) {
				return true
			}
		}
		return false
	}
	ttl := zone.Spec.DefaultTTL
	if ttl <= 0 {
		ttl = 3600
	}
	var updates []bind.RecordUpdate
	if !owns("@", "NS") {
		values := make([]string, 0, len(nameservers))
		for _, ns := range nameservers {
			values = append(values, absolute(ns))
		}
		updates = append(updates, bind.RecordUpdate{FQDN: fqdn("@", zone.Spec.ZoneName), Type: "NS", TTL: ttl, Values: values})
	}
	// The seed's placeholder glue pins a pod IP that goes stale on the first
	// reschedule; drop it once the zone names its real nameservers.
	if glue := fqdn("ns1", zone.Spec.ZoneName); len(zone.Spec.Nameservers) > 0 && !owns("ns1", "A") {
		published := false
		for _, ns := range nameservers {
			published = published || absolute(ns) == glue
		}
		if !published {
			updates = append(updates, bind.RecordUpdate{FQDN: glue, Type: "A", Delete: true})
		}
	}
	return updates
}