From 1a47985bd75d26178f86b1ba17f52a901066bab0 Mon Sep 17 00:00:00 2001
From: Alejandro Mery <amery@jpi.io>
Date: Tue, 12 Sep 2023 15:14:53 +0000
Subject: [PATCH] dns: Manager.WriteTo() generates BIND config, fully qualifies

Signed-off-by: Alejandro Mery <amery@jpi.io>
---
 pkg/dns/record.go | 17 +++++++++++++
 pkg/dns/write.go  | 62 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+)
 create mode 100644 pkg/dns/write.go

diff --git a/pkg/dns/record.go b/pkg/dns/record.go
index 407844f..be97701 100644
--- a/pkg/dns/record.go
+++ b/pkg/dns/record.go
@@ -12,6 +12,10 @@ import (
 	"github.com/libdns/libdns"
 )
 
+func (mgr *Manager) fqdn(name string) string {
+	return fmt.Sprintf("%s.%s.", name, mgr.domain)
+}
+
 // SortAddrSlice sorts a slice of [netip.Addr]
 func SortAddrSlice(s []netip.Addr) []netip.Addr {
 	sort.Slice(s, func(i, j int) bool {
@@ -193,3 +197,16 @@ func (mgr *Manager) genZoneHostRecords(z *Zone) []AddrRecord {
 	SortAddrRecords(out)
 	return out
 }
+
+func (mgr *Manager) genRegionAddressesCached(name string,
+	zones map[string][]netip.Addr) []netip.Addr {
+	//
+	var addrs []netip.Addr
+
+	for _, zoneName := range mgr.regions[name] {
+		addrs = append(addrs, zones[zoneName]...)
+	}
+
+	SortAddrSlice(addrs)
+	return addrs
+}
diff --git a/pkg/dns/write.go b/pkg/dns/write.go
new file mode 100644
index 0000000..5fdb05b
--- /dev/null
+++ b/pkg/dns/write.go
@@ -0,0 +1,62 @@
+package dns
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net/netip"
+)
+
+// WriteTo writes the DNS data for the cluster
+func (mgr *Manager) WriteTo(w io.Writer) (int64, error) {
+	var buf bytes.Buffer
+
+	cache := make(map[string][]netip.Addr)
+
+	// zones
+	for _, z := range mgr.zones {
+		mgr.writeZoneHosts(&buf, z)
+
+		// zone alias
+		addrs := mgr.genZoneAddresses(z)
+		zoneName := z.Name
+
+		rr := AddrRecord{
+			Name: mgr.fqdn(zoneName + mgr.suffix),
+			Addr: addrs,
+		}
+		_, _ = rr.WriteTo(&buf)
+
+		// and cache for regions
+		cache[zoneName] = addrs
+	}
+
+	// regions, sorted
+	for _, name := range mgr.genRegionsSorted() {
+		addrs := mgr.genRegionAddressesCached(name, cache)
+
+		mgr.writeRegionAddresses(&buf, name, addrs)
+	}
+
+	return buf.WriteTo(w)
+}
+
+func (mgr *Manager) writeZoneHosts(w io.Writer, z *Zone) {
+	_, _ = fmt.Fprintf(w, ";\n; %s\n;\n", z.Name)
+
+	for _, rr := range mgr.genZoneHostRecords(z) {
+		rr.Name = mgr.fqdn(rr.Name)
+		_, _ = rr.WriteTo(w)
+	}
+}
+
+func (mgr *Manager) writeRegionAddresses(w io.Writer, name string, addrs []netip.Addr) {
+	_, _ = fmt.Fprintf(w, "; %s\n", name)
+
+	rr := AddrRecord{
+		Name: mgr.fqdn(name + mgr.suffix),
+		Addr: addrs,
+	}
+
+	_, _ = rr.WriteTo(w)
+}