feat(tmpl): {{domain_name}} placeholder — materialize on diff/apply, parameterize on snapshot

Adds internal/tmpl with Materialize (template placeholder -> zone name) and
Parameterize (zone name -> placeholder, the inverse used by the
template-from-zone snapshot). service.resolve now materializes the template
against DomainRef.ZoneName before diffing, so one template can be reused
across domains. LoadDomainFull (source query + hand-edited sqlc output, since
sqlc is not installed) now also selects zone_name to populate it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwxdSt4reTm7Dj1oxRvpP3

internal/tmpl/tmpl.go

@@ -0,0 +1,61 @@
+// Package tmpl renders reusable DNS templates for a concrete zone.
+//
+// A template stores records containing the {{domain_name}} placeholder; it is
+// materialised (placeholder -> zone name, without the trailing dot) just
+// before diff/apply against a specific domain, and parameterised (zone name
+// -> placeholder) when snapshotting a live zone into a reusable template.
+package tmpl
+
+import (
+	"strings"
+
+	"github.com/vasyakrg/dns-autoresolver/internal/model"
+	"github.com/vasyakrg/dns-autoresolver/internal/store/dto"
+)
+
+const Placeholder = "{{domain_name}}"
+
+func zoneName(z string) string { return strings.TrimSuffix(z, ".") }
+
+// Materialize renders a template's records for the given zone, substituting
+// {{domain_name}} with the zone name (without the trailing dot) in each
+// record's Name and every Value.
+func Materialize(doc dto.TemplateDoc, zone string) []model.Record {
+	z := zoneName(zone)
+	out := make([]model.Record, 0, len(doc.Records))
+	for _, r := range doc.Records {
+		vals := make([]string, len(r.Values))
+		for i, v := range r.Values {
+			vals[i] = strings.ReplaceAll(v, Placeholder, z)
+		}
+		out = append(out, model.Record{
+			Type:   model.RecordType(r.Type),
+			Name:   strings.ReplaceAll(r.Name, Placeholder, z),
+			TTL:    r.TTL,
+			Values: vals,
+		})
+	}
+	return out
+}
+
+// Parameterize replaces occurrences of the zone name with {{domain_name}} in
+// record names and values, so a snapshot of a live zone becomes portable.
+// Records with no zone-name occurrence (DKIM key, external CNAME target) are
+// left unchanged.
+func Parameterize(recs []model.Record, zone string) dto.TemplateDoc {
+	z := zoneName(zone)
+	out := dto.TemplateDoc{Records: make([]dto.RecordDTO, 0, len(recs))}
+	for _, r := range recs {
+		vals := make([]string, len(r.Values))
+		for i, v := range r.Values {
+			vals[i] = strings.ReplaceAll(v, z, Placeholder)
+		}
+		out.Records = append(out.Records, dto.RecordDTO{
+			Type:   string(r.Type),
+			Name:   strings.ReplaceAll(r.Name, z, Placeholder),
+			TTL:    r.TTL,
+			Values: vals,
+		})
+	}
+	return out
+}

internal/tmpl/tmpl_test.go

@@ -0,0 +1,45 @@
+package tmpl_test
+
+import (
+	"testing"
+
+	"github.com/vasyakrg/dns-autoresolver/internal/model"
+	"github.com/vasyakrg/dns-autoresolver/internal/store/dto"
+	"github.com/vasyakrg/dns-autoresolver/internal/tmpl"
+)
+
+func TestMaterializeReplacesInNameAndValues(t *testing.T) {
+	doc := dto.TemplateDoc{Records: []dto.RecordDTO{
+		{Type: "TXT", Name: "_dmarc.{{domain_name}}.", TTL: 600, Values: []string{"v=DMARC1; p=quarantine"}},
+		{Type: "MX", Name: "{{domain_name}}.", TTL: 600, Values: []string{"0 pmg2-mail.{{domain_name}}."}},
+		{Type: "TXT", Name: "{{domain_name}}.", TTL: 600, Values: []string{"v=spf1 a:mail.{{domain_name}} ~all"}},
+	}}
+	recs := tmpl.Materialize(doc, "reconops.ru.") // trailing dot stripped
+	if recs[0].Name != "_dmarc.reconops.ru." {
+		t.Fatalf("name: %q", recs[0].Name)
+	}
+	if recs[1].Values[0] != "0 pmg2-mail.reconops.ru." {
+		t.Fatalf("mx value: %q", recs[1].Values[0])
+	}
+	if recs[2].Values[0] != "v=spf1 a:mail.reconops.ru ~all" {
+		t.Fatalf("spf value: %q", recs[2].Values[0])
+	}
+}
+
+func TestParameterizeIsInverseForZoneOccurrences(t *testing.T) {
+	recs := []model.Record{
+		{Type: "TXT", Name: "_dmarc.reconops.ru.", TTL: 600, Values: []string{"v=DMARC1"}},
+		{Type: "TXT", Name: "reconops.ru.", TTL: 600, Values: []string{"v=spf1 a:mail.reconops.ru ~all"}},
+		{Type: "CNAME", Name: "mail.reconops.ru.", TTL: 600, Values: []string{"amail.amega.kz."}}, // external host untouched
+	}
+	doc := tmpl.Parameterize(recs, "reconops.ru.")
+	if doc.Records[0].Name != "_dmarc.{{domain_name}}." {
+		t.Fatalf("name: %q", doc.Records[0].Name)
+	}
+	if doc.Records[1].Values[0] != "v=spf1 a:mail.{{domain_name}} ~all" {
+		t.Fatalf("spf: %q", doc.Records[1].Values[0])
+	}
+	if doc.Records[2].Values[0] != "amail.amega.kz." {
+		t.Fatalf("external cname value must be untouched: %q", doc.Records[2].Values[0])
+	}
+}