dns: introduce AddrRecord{} to abstract A/AAAA entries

Signed-off-by: Alejandro Mery <amery@jpi.io>

pkg/dns/dns.go

@@ -0,0 +1,2 @@
+// Package dns manages DNS entries for the cluster
+package dns

pkg/dns/record.go

@@ -0,0 +1,89 @@
+package dns
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net/netip"
+	"sort"
+	"time"
+
+	"darvaza.org/core"
+	"github.com/libdns/libdns"
+)
+
+// SortAddrSlice sorts a slice of [netip.Addr]
+func SortAddrSlice(s []netip.Addr) []netip.Addr {
+	sort.Slice(s, func(i, j int) bool {
+		return s[i].Less(s[j])
+	})
+	return s
+}
+
+// SortAddrRecords sorts a slice of [AddrRecord]
+// by Name and Address
+func SortAddrRecords(s []AddrRecord) []AddrRecord {
+	sort.Slice(s, func(i, j int) bool {
+		return s[i].Name < s[j].Name
+	})
+
+	for _, p := range s {
+		SortAddrSlice(p.Addr)
+	}
+
+	return s
+}
+
+// AddrRecord represents an A or AAAA record
+type AddrRecord struct {
+	Name string
+	Addr []netip.Addr
+}
+
+// Sort sorts the addresses of the record
+func (rr *AddrRecord) Sort() {
+	SortAddrSlice(rr.Addr)
+}
+
+// Export converts the record into libdns.Record
+func (rr *AddrRecord) Export() []libdns.Record {
+	out := make([]libdns.Record, len(rr.Addr))
+	for i, addr := range rr.Addr {
+		out[i] = libdns.Record{
+			Name:  rr.Name,
+			TTL:   time.Second * 1,
+			Type:  core.IIf(addr.Is6(), "AAAA", "A"),
+			Value: addr.String(),
+		}
+	}
+
+	return out
+}
+
+// WriteTo writes the record in BIND notation
+func (rr *AddrRecord) WriteTo(w io.Writer) (int64, error) {
+	var total int
+	for _, addr := range rr.Addr {
+		n, err := fmt.Fprint(w,
+			rr.Name, "\t",
+			1, "\t",
+			core.IIf(addr.Is6(), "AAAA", "A"), "\t",
+			addr.String(), "\n")
+
+		switch {
+		case err != nil:
+			return 0, err
+		case n > 0:
+			total += n
+		}
+	}
+
+	return int64(total), nil
+}
+
+// String converts the record into BIND entries
+func (rr *AddrRecord) String() string {
+	var buf bytes.Buffer
+	_, _ = rr.WriteTo(&buf)
+	return buf.String()
+}