package kvm2

import (
	"encoding/xml"
	"strings"
	"time"

	"gitea.home.hrajfrisbee.cz/kacerr/egress-proxies-operator/internal/provider"
)

// The GC mark lives in the domain's <metadata> as one element in kvm2's own
// namespace (spec entry 8). The namespace is what selects it in
// DomainGetMetadata; libvirt 11.6 hands the element back without the xmlns
// declaration, so parsing matches on the local name only.
const (
	metadataURI       = "https://gitea.home.hrajfrisbee.cz/kacerr/egress-proxies-operator/kvm2"
	metadataLocalName = "instance"
)

// instanceMetadata is the mark as it is written and read back. The fields
// are the element's text as is; managed and createdAt interpret them.
type instanceMetadata struct {
	XMLName   xml.Name
	Managed   string `xml:"managed"`
	UID       string `xml:"uid"`
	CreatedAt string `xml:"createdAt"`
}

func newInstanceMetadata(uid string, createdAt time.Time) instanceMetadata {
	return instanceMetadata{
		XMLName:   xml.Name{Space: metadataURI, Local: metadataLocalName},
		Managed:   provider.LabelManagedYes,
		UID:       uid,
		CreatedAt: createdAt.UTC().Format(time.RFC3339),
	}
}

func (m instanceMetadata) managed() bool {
	return m.Managed == provider.LabelManagedYes
}

// createdAt returns the zero time when the element carries no parsable
// timestamp; GC treats that as old, which the spec accepts.
func (m instanceMetadata) createdAt() time.Time {
	t, err := time.Parse(time.RFC3339, m.CreatedAt)
	if err != nil {
		return time.Time{}
	}
	return t
}

// marshalInstanceMetadata renders the namespaced element that goes under
// the domain's <metadata>.
func marshalInstanceMetadata(m instanceMetadata) (string, error) {
	m.XMLName = xml.Name{Space: metadataURI, Local: metadataLocalName}
	out, err := xml.Marshal(m)
	if err != nil {
		return "", permanentf("marshalling instance metadata: %v", err)
	}
	return string(out), nil
}

// parseInstanceMetadata reads the element back, with or without its xmlns
// declaration. Anything that is not an <instance> element is ErrPermanent:
// the domain's metadata is corrupt and no retry fixes it.
func parseInstanceMetadata(s string) (instanceMetadata, error) {
	var m instanceMetadata
	if strings.TrimSpace(s) == "" {
		return instanceMetadata{}, permanentf("parsing instance metadata: empty document")
	}
	if err := xml.Unmarshal([]byte(s), &m); err != nil {
		return instanceMetadata{}, permanentf("parsing instance metadata: %v", err)
	}
	if m.XMLName.Local != metadataLocalName {
		return instanceMetadata{}, permanentf("parsing instance metadata: root element is <%s>, want <%s>", m.XMLName.Local, metadataLocalName)
	}
	return m, nil
}