refactor: better tracker

Signed-off-by: Shiwei Zhang <[email protected]>

cmd/oras/internal/display/status/track/reader.go

@@ -46,13 +46,13 @@ func NewReader(r io.Reader, descriptor ocispec.Descriptor, actionPrompt string,
 }
 
 func managedReader(r io.Reader, descriptor ocispec.Descriptor, manager track.Manager) (*reader, error) {
-	tracker, err := track.NewReadTracker(manager, descriptor, r)
+	tracker, err := manager.Track(descriptor)
 	if err != nil {
 		return nil, err
 	}
 
 	return &reader{
-		ReadTracker: tracker,
+		ReadTracker: track.NewReadTracker(tracker, r),
 		manager:     manager,
 	}, nil
 }

internal/experimental/track/reader.go

@@ -2,8 +2,6 @@ package track
 
 import (
 	"io"
-
-	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
 // ReadTracker tracks the transmission based on the read operation.
@@ -13,16 +11,12 @@ type ReadTracker struct {
 	offset  int64
 }
 
-// NewReadTracker returns a new ReadTracker.
-func NewReadTracker(manager Manager, descriptor ocispec.Descriptor, r io.Reader) (*ReadTracker, error) {
-	tracker, err := manager.Track(descriptor)
-	if err != nil {
-		return nil, err
-	}
+// NewReadTracker attaches a tracker to a reader.
+func NewReadTracker(track Tracker, r io.Reader) *ReadTracker {
 	return &ReadTracker{
 		base:    r,
-		tracker: tracker,
-	}, nil
+		tracker: track,
+	}
 }
 
 // Read reads from the base reader and updates the status.