package kvm2

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/xml"

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

// Volume names in the host's pool (spec entries 4 and 10). The per-VM
// volumes derive from the domain name; the base image from its catalogue
// key or, for a URL image, from a hash of the URL.
func overlayVolumeName(name string) string { return name + ".qcow2" }
func seedVolumeName(name string) string    { return name + "-seed.iso" }

// baseVolumeName carries the provider entry because the base is shared by
// every Proxy on a host but must not be shared by two entries: the kvm
// provider builds base-<key>.<format> in the same pool from the same
// catalogue shape, and two kvm2 entries pointing one key at different URLs
// would otherwise agree on the name and disagree on the contents.
func baseVolumeName(entry, key, format string) string {
	return "base-" + entry + "-" + key + "." + format
}
func markerVolumeName(baseName string) string { return baseName + ".sha256" }

// urlImageKey stands in for the catalogue key of an image given as a URL:
// the first 16 hex characters of sha256(url).
func urlImageKey(url string) string {
	sum := sha256.Sum256([]byte(url))
	return hex.EncodeToString(sum[:])[:16]
}

// volumeSpec is what StorageVolCreateXML needs. BackingPath and
// BackingFormat are set for an overlay only.
type volumeSpec struct {
	Name          string
	CapacityBytes int64
	Format        string
	BackingPath   string
	BackingFormat string
}

type volumeXML struct {
	XMLName      xml.Name          `xml:"volume"`
	Type         string            `xml:"type,attr"`
	Name         string            `xml:"name"`
	Capacity     volumeCapacityXML `xml:"capacity"`
	Target       volumeTargetXML   `xml:"target"`
	BackingStore *backingStoreXML  `xml:"backingStore"`
}

type volumeCapacityXML struct {
	Unit  string `xml:"unit,attr"`
	Value int64  `xml:",chardata"`
}

type volumeTargetXML struct {
	Format volumeFormatXML `xml:"format"`
}

type volumeFormatXML struct {
	Type string `xml:"type,attr"`
}

type backingStoreXML struct {
	Path   string          `xml:"path"`
	Format volumeFormatXML `xml:"format"`
}

func validVolumeFormat(f string) bool {
	return f == provider.KVMFormatQcow2 || f == provider.KVMFormatRaw
}

func buildVolumeXML(v volumeSpec) (string, error) {
	if v.Name == "" {
		return "", permanentf("volume XML: name is empty")
	}
	if v.CapacityBytes <= 0 {
		return "", permanentf("volume XML for %q: capacity must be positive, got %d", v.Name, v.CapacityBytes)
	}
	if !validVolumeFormat(v.Format) {
		return "", permanentf("volume XML for %q: unknown format %q (want %s or %s)", v.Name, v.Format, provider.KVMFormatQcow2, provider.KVMFormatRaw)
	}
	x := volumeXML{
		Type:     "file",
		Name:     v.Name,
		Capacity: volumeCapacityXML{Unit: "bytes", Value: v.CapacityBytes},
		Target:   volumeTargetXML{Format: volumeFormatXML{Type: v.Format}},
	}
	if v.BackingPath != "" {
		if !validVolumeFormat(v.BackingFormat) {
			return "", permanentf("volume XML for %q: unknown backing format %q (want %s or %s)", v.Name, v.BackingFormat, provider.KVMFormatQcow2, provider.KVMFormatRaw)
		}
		x.BackingStore = &backingStoreXML{Path: v.BackingPath, Format: volumeFormatXML{Type: v.BackingFormat}}
	}
	out, err := xml.MarshalIndent(x, "", "  ")
	if err != nil {
		return "", permanentf("volume XML for %q: %v", v.Name, err)
	}
	return string(out), nil
}