package localzone

import (
	"fmt"
	"strings"
)

// RenderZone renders a complete zone from declared records, for sources that
// own a zone outright (a Kubernetes DNSZone) rather than editing a file in
// place. It runs the same checks the console writer does: every record goes
// through newRecord, a delegation may not shadow data, and the rendering is
// re-parsed and compared with the records before it is returned, so a renderer
// bug surfaces as an error here and not as a zone that silently stopped
// answering.
//
// serial is the SOA serial; 0 means the writer's default. A declarative source
// should pass something that changes exactly when the spec does, so two
// replicas rendering the same object produce the same bytes.
func RenderZone(origin string, def ZoneDefaults, recs []Record, serial uint32) (string, error) {
	origin, err := NormalizeOrigin(origin)
	if err != nil {
		return "", fmt.Errorf("zone name: %w", err)
	}
	f, err := newFileState(origin, def)
	if err != nil {
		return "", err
	}
	for _, in := range recs {
		rec, err := newRecord(origin, in.Name, in.Type, ttlOr(in.TTL, f.ttl), in.Value)
		if err != nil {
			return "", err
		}
		for _, have := range f.recs {
			if have.Key() == rec.Key() && have.Value == rec.Value {
				return "", fmt.Errorf("%s %s is declared twice", rec.Name, rec.Type)
			}
		}
		f.recs = append(f.recs, rec)
	}
	if err := f.finish(); err != nil {
		return "", err
	}
	if serial != 0 {
		f.soa.Serial = serial
	}
	text := f.render()
	check, err := parseFileState(origin, text)
	if err != nil {
		return "", fmt.Errorf("the zone file for %s did not render correctly: %w", origin, err)
	}
	if err := sameRecords(check.recs, f.recs); err != nil {
		return "", fmt.Errorf("the zone file for %s did not render correctly: %w", origin, err)
	}
	return strings.Replace(text, FileHeader, ZoneSourceHeader, 1), nil
}

// ZoneSourceHeader tops a rendered zone that an external object owns.
const ZoneSourceHeader = `; fancy-dns zone rendered from a Kubernetes DNSZone object.
;
; Regenerated whenever the object changes; edit the DNSZone, not this file.
`