func (a *ACBuild) writeEmptyManifest() error {
	acid, err := types.NewACIdentifier("acbuild-unnamed")
	if err != nil {
		return err
	}

	archlabel, err := types.NewACIdentifier("arch")
	if err != nil {
		return err
	}

	oslabel, err := types.NewACIdentifier("os")
	if err != nil {
		return err
	}

	manifest := &schema.ImageManifest{
		ACKind:    schema.ImageManifestKind,
		ACVersion: schema.AppContainerVersion,
		Name:      *acid,
		Labels: types.Labels{
			types.Label{
				*archlabel,
				runtime.GOARCH,
			},
			types.Label{
				*oslabel,
				runtime.GOOS,
			},
		},
	}

	manblob, err := manifest.MarshalJSON()
	if err != nil {
		return err
	}

	manfile, err := os.Create(path.Join(a.CurrentACIPath, aci.ManifestFile))
	if err != nil {
		return err
	}

	_, err = manfile.Write(manblob)
	if err != nil {
		return err
	}

	err = manfile.Close()
	if err != nil {
		return err
	}

	return nil
}

func WriteImageManifest(m *spec.AciManifest, targetFile string, projectName string, cntVersion string) {
	name, err := types.NewACIdentifier(m.NameAndVersion.Name())
	if err != nil {
		panic(err)
	}

	version := m.NameAndVersion.Version()
	if version == "" {
		version = GenerateVersion()
	}

	labels := types.Labels{}
	labels = append(labels, types.Label{Name: "version", Value: version})
	labels = append(labels, types.Label{Name: "os", Value: "linux"})
	labels = append(labels, types.Label{Name: "arch", Value: "amd64"})

	if m.Aci.App.User == "" {
		m.Aci.App.User = "0"
	}
	if m.Aci.App.Group == "" {
		m.Aci.App.Group = "0"
	}

	im := schema.BlankImageManifest()
	im.Annotations = m.Aci.Annotations

	cntVersionIdentifier, _ := types.NewACIdentifier("cnt-version")
	im.Annotations.Set(*cntVersionIdentifier, cntVersion)
	im.Dependencies = toAppcDependencies(m.Aci.Dependencies)
	im.Name = *name
	im.Labels = labels

	im.App = &types.App{
		Exec:             m.Aci.App.Exec,
		EventHandlers:    []types.EventHandler{{Name: "pre-start", Exec: []string{"/cnt/bin/prestart"}}},
		User:             m.Aci.App.User,
		Group:            m.Aci.App.Group,
		WorkingDirectory: m.Aci.App.WorkingDirectory,
		Environment:      m.Aci.App.Environment,
		MountPoints:      m.Aci.App.MountPoints,
		Ports:            m.Aci.App.Ports,
		Isolators:        m.Aci.App.Isolators,
	}

	buff, err := im.MarshalJSON()
	if err != nil {
		panic(err)
	}
	err = ioutil.WriteFile(targetFile, buff, 0644)
	if err != nil {
		panic(err)
	}
}

// StoreTrustedKeyPrefix stores the contents of public key r as a prefix trusted key.
func (ks *Keystore) StoreTrustedKeyPrefix(prefix string, r io.Reader) (string, error) {
	acidentifier, err := types.NewACIdentifier(prefix)
	if err != nil {
		return "", err
	}
	return storeTrustedKey(path.Join(ks.LocalPrefixPath, acidentifier.String()), r)
}

func handleAppAnnotation(w http.ResponseWriter, r *http.Request, pm *schema.PodManifest, im *schema.ImageManifest) {
	defer r.Body.Close()

	n := mux.Vars(r)["name"]
	k, err := types.NewACIdentifier(n)
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		fmt.Fprintf(w, "App annotation name %q is not a valid AC Identifier", n)
		return
	}

	n = mux.Vars(r)["app"]
	an, err := types.NewACName(n)
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		fmt.Fprintf(w, "App name %q is not a valid AC Name", n)
		return
	}

	merged := mergeAppAnnotations(im, pm, an)

	v, ok := merged.Get(k.String())
	if !ok {
		w.WriteHeader(http.StatusNotFound)
		fmt.Fprintf(w, "App annotation %q not found", k)
		return
	}

	w.Header().Add("Content-Type", "text/plain")
	w.WriteHeader(http.StatusOK)
	w.Write([]byte(v))
}

// NewAppFromString takes a command line app parameter and returns a map of labels.
//
// Example app parameters:
// 	example.com/reduce-worker:1.0.0
// 	example.com/reduce-worker,channel=alpha,label=value
// 	example.com/reduce-worker:1.0.0,label=value
//
// As can be seen in above examples - colon, comma and equal sign have
// special meaning. If any of them has to be a part of a label's value
// then consider writing your own string to App parser.
func NewAppFromString(app string) (*App, error) {
	var (
		name   string
		labels map[types.ACIdentifier]string
	)

	preparedApp, err := prepareAppString(app)
	if err != nil {
		return nil, err
	}
	v, err := url.ParseQuery(preparedApp)
	if err != nil {
		return nil, err
	}
	labels = make(map[types.ACIdentifier]string, 0)
	for key, val := range v {
		if len(val) > 1 {
			return nil, fmt.Errorf("label %s with multiple values %q", key, val)
		}
		if key == "name" {
			name = val[0]
			continue
		}
		labelName, err := types.NewACIdentifier(key)
		if err != nil {
			return nil, err
		}
		labels[*labelName] = val[0]
	}
	a, err := NewApp(name, labels)
	if err != nil {
		return nil, err
	}
	return a, nil
}

// NewAppFromString takes a command line app parameter and returns a map of labels.
//
// Example app parameters:
// 	example.com/reduce-worker:1.0.0
// 	example.com/reduce-worker,channel=alpha,label=value
func NewAppFromString(app string) (*App, error) {
	var (
		name   string
		labels map[types.ACIdentifier]string
	)

	app = strings.Replace(app, ":", ",version=", -1)
	app = "name=" + app
	v, err := url.ParseQuery(strings.Replace(app, ",", "&", -1))
	if err != nil {
		return nil, err
	}
	labels = make(map[types.ACIdentifier]string, 0)
	for key, val := range v {
		if len(val) > 1 {
			return nil, fmt.Errorf("label %s with multiple values %q", key, val)
		}
		if key == "name" {
			name = val[0]
			continue
		}
		labelName, err := types.NewACIdentifier(key)
		if err != nil {
			return nil, err
		}
		labels[*labelName] = val[0]
	}
	a, err := NewApp(name, labels)
	if err != nil {
		return nil, err
	}
	return a, nil
}

func isolatorStrFromString(is string) (types.ACIdentifier, string, error) {
	is = "name=" + is
	v, err := url.ParseQuery(strings.Replace(is, ",", "&", -1))
	if err != nil {
		return "", "", err
	}

	var name string
	var values []string
	var acn *types.ACIdentifier

	for key, val := range v {
		if len(val) > 1 {
			return "", "", fmt.Errorf("label %s with multiple values %q", key, val)
		}

		switch key {
		case "name":
			acn, err = types.NewACIdentifier(val[0])
			if err != nil {
				return "", "", err
			}
			name = val[0]
		default:
			// (TODO)yifan: Not support the default boolean yet.
			values = append(values, fmt.Sprintf(`"%s": "%s"`, key, val[0]))
		}
	}
	return *acn, getIsolatorStr(name, strings.Join(values, ", ")), nil
}

// DeleteTrustedKeyPrefix deletes the prefix trusted key identified by fingerprint.
func (ks *Keystore) DeleteTrustedKeyPrefix(prefix, fingerprint string) error {
	acidentifier, err := types.NewACIdentifier(prefix)
	if err != nil {
		return err
	}
	return os.Remove(path.Join(ks.LocalPrefixPath, acidentifier.String(), fingerprint))
}

// AddLabel will add a label with the given name and value to the untarred ACI
// stored at a.CurrentACIPath. If the label already exists its value will be updated to
// the new value.
func (a *ACBuild) AddLabel(name, value string) (err error) {
	if err = a.lock(); err != nil {
		return err
	}
	defer func() {
		if err1 := a.unlock(); err == nil {
			err = err1
		}
	}()

	acid, err := types.NewACIdentifier(name)
	if err != nil {
		return err
	}

	fn := func(s *schema.ImageManifest) error {
		removeLabelFromMan(*acid)(s)
		s.Labels = append(s.Labels,
			types.Label{
				Name:  *acid,
				Value: value,
			})
		return nil
	}
	return util.ModifyManifest(fn, a.CurrentACIPath)
}

func validatePodAnnotations(metadataURL string, pm *schema.PodManifest) results {
	r := results{}

	var actualAnnots types.Annotations

	annots, err := metadataGet(metadataURL, "/pod/annotations/")
	if err != nil {
		return append(r, err)
	}

	for _, key := range strings.Split(string(annots), "\n") {
		if key == "" {
			continue
		}

		val, err := metadataGet(metadataURL, "/pod/annotations/"+key)
		if err != nil {
			r = append(r, err)
		}

		name, err := types.NewACIdentifier(key)
		if err != nil {
			r = append(r, fmt.Errorf("invalid annotation name: %v", err))
			continue
		}

		actualAnnots.Set(*name, string(val))
	}

	if !reflect.DeepEqual(actualAnnots, pm.Annotations) {
		r = append(r, fmt.Errorf("pod annotations mismatch: %v vs %v", actualAnnots, pm.Annotations))
	}

	return r
}

func checkSignature(ks *Keystore, prefix string, signed, signature io.ReadSeeker) (*openpgp.Entity, error) {
	acidentifier, err := types.NewACIdentifier(prefix)
	if err != nil {
		return nil, err
	}
	keyring, err := ks.loadKeyring(acidentifier.String())
	if err != nil {
		return nil, errwrap.Wrap(errors.New("keystore: error loading keyring"), err)
	}
	entities, err := openpgp.CheckArmoredDetachedSignature(keyring, signed, signature)
	if err == io.EOF {
		// When the signature is binary instead of armored, the error is io.EOF.
		// Let's try with binary signatures as well
		if _, err := signed.Seek(0, 0); err != nil {
			return nil, errwrap.Wrap(errors.New("error seeking ACI file"), err)
		}
		if _, err := signature.Seek(0, 0); err != nil {
			return nil, errwrap.Wrap(errors.New("error seeking signature file"), err)
		}
		entities, err = openpgp.CheckDetachedSignature(keyring, signed, signature)
	}
	if err == io.EOF {
		// otherwise, the client failure is just "EOF", which is not helpful
		return nil, fmt.Errorf("keystore: no valid signatures found in signature file")
	}
	return entities, err
}

// MaskTrustedKeySystemPrefix masks the system prefix trusted key identified by fingerprint.
func (ks *Keystore) MaskTrustedKeySystemPrefix(prefix, fingerprint string) (string, error) {
	acidentifier, err := types.NewACIdentifier(prefix)
	if err != nil {
		return "", err
	}
	dst := path.Join(ks.LocalPrefixPath, acidentifier.String(), fingerprint)
	return dst, ioutil.WriteFile(dst, []byte(""), 0644)
}

func pathToACIdentifier(path string) (types.ACIdentifier, error) {
	if dirname := filepath.Base(filepath.Dir(path)); dirname == "@" {
		return Root, nil
	} else if prefix, err := types.NewACIdentifier(strings.Replace(dirname, ",", "/", -1)); err != nil {
		return "", err
	} else {
		return *prefix, nil
	}
}

func (ks *Keystore) loadKeyring(prefix string) (openpgp.KeyRing, error) {
	acidentifier, err := types.NewACIdentifier(prefix)
	if err != nil {
		return nil, err
	}
	var keyring openpgp.EntityList
	trustedKeys := make(map[string]*openpgp.Entity)

	prefixRoot := strings.Split(acidentifier.String(), "/")[0]
	paths := []struct {
		root     string
		fullPath string
	}{
		{ks.SystemRootPath, ks.SystemRootPath},
		{ks.LocalRootPath, ks.LocalRootPath},
		{path.Join(ks.SystemPrefixPath, prefixRoot), path.Join(ks.SystemPrefixPath, acidentifier.String())},
		{path.Join(ks.LocalPrefixPath, prefixRoot), path.Join(ks.LocalPrefixPath, acidentifier.String())},
	}
	for _, p := range paths {
		err := filepath.Walk(p.root, func(path string, info os.FileInfo, err error) error {
			if err != nil && !os.IsNotExist(err) {
				return err
			}
			if info == nil {
				return nil
			}
			if info.IsDir() {
				switch {
				case strings.HasPrefix(p.fullPath, path):
					return nil
				default:
					return filepath.SkipDir
				}
			}
			// Remove trust for default keys.
			if info.Size() == 0 {
				delete(trustedKeys, info.Name())
				return nil
			}
			entity, err := entityFromFile(path)
			if err != nil {
				return err
			}
			trustedKeys[fingerprintToFilename(entity.PrimaryKey.Fingerprint)] = entity
			return nil
		})
		if err != nil {
			return nil, err
		}
	}

	for _, v := range trustedKeys {
		keyring = append(keyring, v)
	}
	return keyring, nil
}

func (custom *CmakeCustomizations) GetImageName() (*types.ACIdentifier, error) {
	imageName := custom.Configuration.Project
	if filepath.Base(imageName) == "..." {
		imageName = filepath.Dir(imageName)
		if custom.Configuration.UseBinary != "" {
			imageName += "-" + custom.Configuration.UseBinary
		}
	}
	return types.NewACIdentifier(strings.ToLower(imageName))
}

func newLabel(name, value string) (*types.Label, error) {
	acName, err := types.NewACIdentifier(name)
	if err != nil {
		return nil, err
	}
	return &types.Label{
		Name:  *acName,
		Value: value,
	}, nil
}

func (p *Pod) processAci(e common.RuntimeApp) (*schema.RuntimeApp, error) {
	aci, err := p.buildAci(e)
	if err != nil {
		return nil, err
	}

	name, err := types.NewACName(e.Name)
	if err != nil {
		return nil, errs.WithEF(err, p.fields.WithField("name", e.Name), "Invalid name format")
	}

	sum, err := Sha512sum(aci.target + pathImageAci)
	if err != nil {
		return nil, errs.WithEF(err, p.fields.WithField("file", aci.target+pathImageAci), "Failed to calculate sha512 of aci")
	}

	tmp, _ := types.NewHash("sha512-" + sum)

	labels := types.Labels{}
	labels = append(labels, types.Label{Name: "version", Value: aci.manifest.NameAndVersion.Version()})
	identifier, _ := types.NewACIdentifier(aci.manifest.NameAndVersion.Name())
	ttmp := schema.RuntimeImage{Name: identifier, ID: *tmp, Labels: labels}

	e.App.Group = aci.manifest.Aci.App.Group
	e.App.User = aci.manifest.Aci.App.User
	if e.App.User == "" {
		e.App.User = "0"
	}
	if e.App.Group == "" {
		e.App.Group = "0"
	}

	isolators, err := common.ToAppcIsolators(e.App.Isolators)
	if err != nil {
		return nil, errs.WithEF(err, p.fields, "Failed to prepare isolators")
	}

	return &schema.RuntimeApp{
		Name:  *name,
		Image: ttmp,
		App: &types.App{
			Exec:              e.App.Exec,
			User:              e.App.User,
			Group:             e.App.Group,
			WorkingDirectory:  e.App.WorkingDirectory,
			SupplementaryGIDs: e.App.SupplementaryGIDs,
			Environment:       e.App.Environment,
			MountPoints:       e.App.MountPoints,
			Ports:             e.App.Ports,
			Isolators:         isolators,
		},
		Mounts:      e.Mounts,
		Annotations: e.Annotations}, nil
}

func (afl *AnnotationsFlag) Set(val string) error {
	pieces := strings.SplitN(val, "=", 2)
	if len(pieces) != 2 {
		return errors.New("Annotations must be provided in NAME=VALUE format")
	} else if name, err := types.NewACIdentifier(pieces[0]); err != nil {
		return err
	} else {
		(*types.Annotations)(afl).Set(*name, pieces[1])
		return nil
	}
}

func (p *Pod) processAci() []schema.RuntimeApp {
	apps := []schema.RuntimeApp{}
	for _, e := range p.manifest.Pod.Apps {

		aciName := p.buildAciIfNeeded(e)
		// TODO: support not FS override by only storing info pod manifest
		//		if aciName == nil {
		//			aciName = &e.Image
		//		}

		name, _ := types.NewACName(e.Name)

		sum, err := utils.Sha512sum(p.path + "/" + e.Name + "/target/image.aci")
		if err != nil {
			log.Get().Panic(err)
		}

		tmp, _ := types.NewHash("sha512-" + sum)

		labels := types.Labels{}
		labels = append(labels, types.Label{Name: "version", Value: aciName.Version()})
		identifier, _ := types.NewACIdentifier(aciName.Name())
		ttmp := schema.RuntimeImage{Name: identifier, ID: *tmp, Labels: labels}

		if e.App.User == "" {
			e.App.User = "0"
		}
		if e.App.Group == "" {
			e.App.Group = "0"
		}

		apps = append(apps, schema.RuntimeApp{
			Name:  *name,
			Image: ttmp,
			App: &types.App{
				Exec:             e.App.Exec,
				EventHandlers:    e.App.EventHandlers,
				User:             e.App.User,
				Group:            e.App.Group,
				WorkingDirectory: e.App.WorkingDirectory,
				Environment:      e.App.Environment,
				MountPoints:      e.App.MountPoints,
				Ports:            e.App.Ports,
				Isolators:        e.App.Isolators,
			},
			Mounts:      e.Mounts,
			Annotations: e.Annotations})

	}

	return apps
}

func NewApp(name string, labels map[types.ACIdentifier]string) (*App, error) {
	if labels == nil {
		labels = make(map[types.ACIdentifier]string, 0)
	}
	acn, err := types.NewACIdentifier(name)
	if err != nil {
		return nil, err
	}
	return &App{
		Name:   *acn,
		Labels: labels,
	}, nil
}