Box    BaseBox
	Reason UpdateReason
	Zid    id.Zid
}

// UpdateFunc is a function to be called when a change is detected.
type UpdateFunc func(UpdateInfo)

// UpdateNotifier is an UpdateFunc, but with separate values.
type UpdateNotifier func(BaseBox, id.Zid, UpdateReason)

// Subject is a box that notifies observers about changes.
type Subject interface {
	// RegisterObserver registers an observer that will be notified
	// if one or all zettel are found to be changed.
	RegisterObserver(UpdateFunc)
}

func (dp *dirBox) stopFileServices() {
	for _, c := range dp.fCmds {
		close(c)
	}
}

func (dp *dirBox) notifyChanged(zid id.Zid, reason box.UpdateReason) {
	if notify := dp.cdata.Notify; notify != nil {
		dp.log.Trace().Zid(zid).Uint("reason", uint64(reason)).Msg("notifyChanged")
		notify(dp, zid, reason)
	}
}

func (dp *dirBox) getFileChan(zid id.Zid) chan fileCmd {
	// Based on https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
	sum := 2166136261 ^ uint32(zid)
	sum *= 16777619

)

type zipBox struct {
	log      *logger.Logger
	number   int
	name     string
	enricher box.Enricher
	notify   box.UpdateNotifier
	dirSrv   *notify.DirService
}

func (zb *zipBox) Location() string {
	if strings.HasPrefix(zb.name, "/") {
		return "file://" + zb.name
	}

)

// ConnectData contains all administration related values.
type ConnectData struct {
	Number   int // number of the box, starting with 1.
	Config   config.Config
	Enricher box.Enricher
	Notify   box.UpdateNotifier
	Mapper   Mapper
}

// Mapper allows to inspect the mapping between old-style and new-style zettel identifier.
type Mapper interface {
	Warnings(context.Context) (*id.Set, error) // Fetch problematic zettel identifier

			propertyKeys.Set(kd.Name)
		}
	}
	boxLog := kernel.Main.GetLogger(kernel.BoxService)
	mgr := &Manager{
		mgrLog:       boxLog.Clone().Str("box", "manager").Child(),
		rtConfig:     rtConfig,
		infos:        make(chan box.UpdateInfo, len(boxURIs)*10),
		propertyKeys: propertyKeys,

		idxLog:   boxLog.Clone().Str("box", "index").Child(),
		idxStore: createIdxStore(rtConfig),
		idxAr:    newAnteroomQueue(1000),
		idxReady: make(chan struct{}, 1),
	}
	mgr.zidMapper = NewZidMapper(mgr)

	cdata := ConnectData{Number: 1, Config: rtConfig, Enricher: mgr, Notify: mgr.notifyChanged, Mapper: mgr.zidMapper}
	boxes := make([]box.ManagedBox, 0, len(boxURIs)+2)
	for _, uri := range boxURIs {
		p, err := Connect(uri, authManager, &cdata)
		if err != nil {
			return nil, err
		}
		if p != nil {

func (mgr *Manager) checkContinue(ctx context.Context) error {
	if mgr.State() != box.StartStateStarted {
		return box.ErrStopped
	}
	return ctx.Err()
}

func (mgr *Manager) notifyChanged(bbox box.BaseBox, zid id.Zid, reason box.UpdateReason) {
	if infos := mgr.infos; infos != nil && zid != id.MappingZid {
		mgr.infos <- box.UpdateInfo{Box: bbox, Reason: reason, Zid: zid}
	}
}

	maxBytes  int
	mx        sync.RWMutex // Protects the following fields
	zettel    map[id.Zid]zettel.Zettel
	curBytes  int
}

func (mb *memBox) notifyChanged(zid id.Zid, reason box.UpdateReason) {
	if notify := mb.cdata.Notify; notify != nil {
		notify(mb, zid, reason)
	}
}

func (mb *memBox) Location() string {
	return mb.u.String()
}

// DirService specifies a directory service for file based zettel.
type DirService struct {
	box      box.ManagedBox
	log      *logger.Logger
	dirPath  string
	notifier Notifier
	infos    box.UpdateNotifier
	mx       sync.RWMutex // protects status, entries
	state    DirServiceState
	entries  entrySet
}

// ErrNoDirectory signals missing directory data.
var ErrNoDirectory = errors.New("unable to retrieve zettel directory information")

// NewDirService creates a new directory service.
func NewDirService(box box.ManagedBox, log *logger.Logger, notifier Notifier, notify box.UpdateNotifier) *DirService {
	return &DirService{
		box:      box,
		log:      log,
		notifier: notifier,
		infos:    notify,
		state:    DsCreated,
	}
}

// State the current service state.
func (ds *DirService) State() DirServiceState {
	ds.mx.RLock()

	if oldLen != newLen {
		return newLen < oldLen
	}
	return newExt < oldExt
}

func (ds *DirService) notifyChange(zid id.Zid, reason box.UpdateReason) {
	if notify := ds.infos; notify != nil {
		ds.log.Trace().Zid(zid).Uint("reason", uint64(reason)).Msg("notifyChange")
		notify(ds.box, zid, reason)
	}
}