package checker

import (
	"encoding/json"

	"github.com/miekg/dns"
)

// Service type identifiers as exposed by happyDomain core.
const (
	serviceTypeOrigin       = "abstract.Origin"
	serviceTypeNSOnlyOrigin = "abstract.NSOnlyOrigin"
)

// nsPayload is a minimal local copy of services/abstract.Origin and
// services/abstract.NSOnlyOrigin keeping only the field this checker reads.
// The JSON tag matches the upstream wire format ("ns").
type nsPayload struct {
	NameServers []*dns.NS `json:"ns"`
}

// nsFromService extracts the list of NS records from an Origin or
// NSOnlyOrigin service payload.
func nsFromService(svc *serviceMessage) []*dns.NS {
	switch svc.Type {
	case serviceTypeOrigin, serviceTypeNSOnlyOrigin:
		var o nsPayload
		if err := json.Unmarshal(svc.Service, &o); err != nil {
			return nil
		}
		return o.NameServers
	}
	return nil
}