service.go

@@ -53,6 +53,37 @@ type ReverseLookupResult struct {
 	Names []string `json:"names"`
 }
 
+// ReverseIndex stores IP-to-name lookups in a dedicated semantic wrapper.
+//
+//	index := buildReverseIndex(records, 15*time.Second)
+//	names, ok := index.Lookup("10.10.10.10")
+type ReverseIndex struct {
+	cache *cache.Cache
+}
+
+func (index *ReverseIndex) Lookup(ip string) ([]string, bool) {
+	if index == nil || index.cache == nil {
+		return nil, false
+	}
+
+	normalizedIP := normalizeIP(ip)
+	if normalizedIP == "" {
+		return nil, false
+	}
+
+	rawNames, found := index.cache.Get(normalizedIP)
+	if !found {
+		return nil, false
+	}
+
+	names, ok := rawNames.([]string)
+	if !ok || len(names) == 0 {
+		return nil, false
+	}
+
+	return append([]string(nil), names...), true
+}
+
 // HealthResult is the typed payload returned by Health and dns.health.
 //
 //	health := service.Health()
@@ -67,7 +98,7 @@ type Service struct {
 	mu                           sync.RWMutex
 	records                      map[string]NameRecords
 	recordExpiry                 map[string]time.Time
-	reverseIndex                 *cache.Cache
+	reverseIndex                 *ReverseIndex
 	treeRoot                     string
 	zoneApex                     string
 	dnsPort                      int
@@ -180,7 +211,7 @@ func NewService(options ServiceOptions) *Service {
 	service := &Service{
 		records:                      cached,
 		recordExpiry:                 make(map[string]time.Time, len(cached)),
-		reverseIndex:                 buildReverseIndexCache(cached, options.RecordTTL),
+		reverseIndex:                 buildReverseIndex(cached, options.RecordTTL),
 		treeRoot:                     treeRoot,
 		zoneApex:                     computeZoneApex(cached),
 		dnsPort:                      options.DNSPort,
@@ -780,7 +811,7 @@ func (service *Service) pruneExpiredRecords() {
 }
 
 func (service *Service) refreshDerivedStateLocked() {
-	service.reverseIndex = buildReverseIndexCache(service.records, service.recordTTL)
+	service.reverseIndex = buildReverseIndex(service.records, service.recordTTL)
 	service.treeRoot = computeTreeRoot(service.records)
 	service.zoneApex = computeZoneApex(service.records)
 }
@@ -804,11 +835,6 @@ func (service *Service) ResolveAddress(name string) (ResolveAddressResult, bool)
 func (service *Service) ResolveReverse(ip string) ([]string, bool) {
 	service.pruneExpiredRecords()
 
-	normalizedIP := normalizeIP(ip)
-	if normalizedIP == "" {
-		return nil, false
-	}
-
 	service.mu.RLock()
 	reverseIndex := service.reverseIndex
 	service.mu.RUnlock()
@@ -817,16 +843,7 @@ func (service *Service) ResolveReverse(ip string) ([]string, bool) {
 		return nil, false
 	}
 
-	rawNames, found := reverseIndex.Get(normalizedIP)
-	if !found {
-		return nil, false
-	}
-
-	names, ok := rawNames.([]string)
-	if !ok || len(names) == 0 {
-		return nil, false
-	}
-	return append([]string(nil), names...), true
+	return reverseIndex.Lookup(ip)
 }
 
 // ResolveAll returns the full record set for a name, including synthesized apex NS data.
@@ -930,7 +947,7 @@ func resolveResult(record NameRecords) ResolveAllResult {
 	}
 }
 
-func buildReverseIndexCache(records map[string]NameRecords, ttl time.Duration) *cache.Cache {
+func buildReverseIndex(records map[string]NameRecords, ttl time.Duration) *ReverseIndex {
 	raw := map[string]map[string]struct{}{}
 	for name, record := range records {
 		for _, ip := range record.A {
@@ -976,7 +993,7 @@ func buildReverseIndexCache(records map[string]NameRecords, ttl time.Duration) *
 	for ip, names := range reverseIndex {
 		reverseIndexCache.Set(ip, names, cacheTTL)
 	}
-	return reverseIndexCache
+	return &ReverseIndex{cache: reverseIndexCache}
 }
 
 func normalizeIP(ip string) string {