provide some logic for controlling creation of Track adapters

storage/message/message.go

@@ -10,7 +10,7 @@ type message struct {
 	*tracking.Track
 }
 
-func Message(tr *tracking.Track) *message {
+func Message(tr *tracking.Track) tracking.Adapted {
 	return &message{tr}
 }
 
@@ -19,7 +19,7 @@ func MakeMessage(c *tracking.Container, h ...string) *tracking.Track {
 	if h[0] == "" {
 		h[0] = "scopes"
 	}
-	return tracking.MakeTrack(c, h...)
+	return tracking.MakeTrack(c, h...).SetAdapterFactory(Message)
 }
 
 func (msg *message) Domain() string {
@@ -33,7 +33,7 @@ func Messages(db *sql.Storage) *tracking.Container {
 }
 
 func New(cont *tracking.Container, h ...string) *message {
-	return Message(cont.NewTrack(h, nil))
+	return tracking.Adapt[*message](cont.NewTrack(h, nil))
 }
 
 // message store action handler

storage/tracking/tracking.go

@@ -19,6 +19,9 @@ import (
 type ContFactory func(*sql.Storage) *Container
 type ItemFactory func(*Container, ...string) *Track
 
+type Adapted interface{}
+type AdapterFactory func(*Track) Adapted
+
 // basic track implementation
 
 type Track struct {
@@ -27,6 +30,7 @@ type Track struct {
 	TimeStamp *time.Time
 	Data      lib.Map
 	container *Container
+	adapter   AdapterFactory
 }
 
 func (tr *Track) TrackId() lib.Ident {
@@ -45,11 +49,21 @@ func MakeTrack(cont *Container, h ...string) *Track {
 	tr := Track{
 		Head:      lib.StrMap{},
 		container: cont,
+		adapter:   func(tr *Track) Adapted { return tr },
 	}
 	tr.SetHead(h...)
 	return &tr
 }
 
+func (tr *Track) SetAdapterFactory(af AdapterFactory) *Track {
+	tr.adapter = af
+	return tr
+}
+
+func Adapt[T Adapted](tr *Track) T {
+	return tr.adapter(tr).(T)
+}
+
 func (tr *Track) SetHead(h ...string) {
 	for i, k := range tr.container.HeadFields {
 		if i >= len(h) {