// 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
}