refactor: Isolate progress channel in Messenger

cmd/oras/internal/display/status/progress/manager.go

@@ -34,12 +34,9 @@ const (
 
 var errManagerStopped = errors.New("progress output manager has already been stopped")
 
-// Status is print message channel
-type Status chan *status
-
 // Manager is progress view master
 type Manager interface {
-	Add() (Status, error)
+	Add() (*Messenger, error)
 	SendAndStop(desc ocispec.Descriptor, prompt string) error
 	Close() error
 }
@@ -107,7 +104,7 @@ func (m *manager) render() {
 }
 
 // Add appends a new status with 2-line space for rendering.
-func (m *manager) Add() (Status, error) {
+func (m *manager) Add() (*Messenger, error) {
 	if m.closed() {
 		return nil, errManagerStopped
 	}
@@ -124,26 +121,25 @@ func (m *manager) Add() (Status, error) {
 
 // SendAndStop send message for descriptor and stop timing.
 func (m *manager) SendAndStop(desc ocispec.Descriptor, prompt string) error {
-	status, err := m.Add()
+	messenger, err := m.Add()
 	if err != nil {
 		return err
 	}
-	defer close(status)
-	status <- NewStatusMessage(prompt, desc, desc.Size)
-	status <- EndTiming()
+	messenger.Send(prompt, desc, desc.Size)
+	messenger.Stop()
 	return nil
 }
 
-func (m *manager) statusChan(s *status) Status {
+func (m *manager) statusChan(s *status) *Messenger {
 	ch := make(chan *status, BufferSize)
 	m.updating.Add(1)
 	go func() {
 		defer m.updating.Done()
 		for newStatus := range ch {
-			s.Update(newStatus)
+			s.update(newStatus)
 		}
 	}()
-	return ch
+	return &Messenger{ch: ch}
 }
 
 // Close stops all status and waits for updating and rendering.

cmd/oras/internal/display/status/progress/messenger.go

@@ -0,0 +1,95 @@
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package progress
+
+import (
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"oras.land/oras/cmd/oras/internal/display/status/progress/humanize"
+	"time"
+)
+
+// Messenger is progress message channel.
+type Messenger struct {
+	ch     chan *status
+	closed bool
+}
+
+// Start initializes the messenger.
+func (sm *Messenger) Start() {
+	if sm.ch == nil {
+		return
+	}
+	sm.ch <- startTiming()
+}
+
+// Send a status message for the specified descriptor.
+func (sm *Messenger) Send(prompt string, descriptor ocispec.Descriptor, offset int64) {
+	for {
+		select {
+		case sm.ch <- newStatusMessage(prompt, descriptor, offset):
+			return
+		case <-sm.ch:
+			// purge the channel until successfully pushed
+		default:
+			// ch is nil
+			return
+		}
+	}
+}
+
+// Stop the messenger after sending a end message.
+func (sm *Messenger) Stop() {
+	if sm.closed {
+		return
+	}
+	sm.ch <- endTiming()
+	close(sm.ch)
+	sm.closed = true
+}
+
+// newStatus generates a base empty status.
+func newStatus() *status {
+	return &status{
+		offset:      -1,
+		total:       humanize.ToBytes(0),
+		speedWindow: newSpeedWindow(framePerSecond),
+	}
+}
+
+// newStatusMessage generates a status for messaging.
+func newStatusMessage(prompt string, descriptor ocispec.Descriptor, offset int64) *status {
+	return &status{
+		prompt:     prompt,
+		descriptor: descriptor,
+		offset:     offset,
+	}
+}
+
+// startTiming creates start timing message.
+func startTiming() *status {
+	return &status{
+		offset:    -1,
+		startTime: time.Now(),
+	}
+}
+
+// endTiming creates end timing message.
+func endTiming() *status {
+	return &status{
+		offset:  -1,
+		endTime: time.Now(),
+	}
+}

cmd/oras/internal/display/status/progress/messenger_test.go

@@ -0,0 +1,94 @@
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package progress
+
+import (
+	v1 "github.com/opencontainers/image-spec/specs-go/v1"
+	"testing"
+)
+
+func Test_Messenger(t *testing.T) {
+	var msg *status
+	ch := make(chan *status, BufferSize)
+	messenger := &Messenger{ch: ch}
+
+	messenger.Start()
+	select {
+	case msg = <-ch:
+		if msg.offset != -1 {
+			t.Errorf("Expected start message with offset -1, got %d", msg.offset)
+		}
+	default:
+		t.Error("Expected start message")
+	}
+
+	desc := v1.Descriptor{
+		Digest: "mouse",
+		Size:   100,
+	}
+	expected := int64(50)
+	messenger.Send("Reading", desc, expected)
+	select {
+	case msg = <-ch:
+		if msg.offset != expected {
+			t.Errorf("Expected status message with offset %d, got %d", expected, msg.offset)
+		}
+		if msg.prompt != "Reading" {
+			t.Errorf("Expected status message prompt Reading, got %s", msg.prompt)
+		}
+	default:
+		t.Error("Expected status message")
+	}
+
+	messenger.Send("Reading", desc, expected)
+	messenger.Send("Read", desc, desc.Size)
+	select {
+	case msg = <-ch:
+		if msg.offset != desc.Size {
+			t.Errorf("Expected status message with offset %d, got %d", expected, msg.offset)
+		}
+		if msg.prompt != "Read" {
+			t.Errorf("Expected status message prompt Read, got %s", msg.prompt)
+		}
+	default:
+		t.Error("Expected status message")
+	}
+	select {
+	case msg = <-ch:
+		t.Errorf("Unexpected status message %v", msg)
+	default:
+	}
+
+	expected = int64(-1)
+	messenger.Stop()
+	select {
+	case msg = <-ch:
+		if msg.offset != expected {
+			t.Errorf("Expected END status message with offset %d, got %d", expected, msg.offset)
+		}
+	default:
+		t.Error("Expected END status message")
+	}
+
+	messenger.Stop()
+	select {
+	case msg = <-ch:
+		if msg != nil {
+			t.Errorf("Unexpected status message %v", msg)
+		}
+	default:
+	}
+}

cmd/oras/internal/display/status/progress/status.go

@@ -56,40 +56,6 @@ type status struct {
 	lock      sync.Mutex
 }
 
-// newStatus generates a base empty status.
-func newStatus() *status {
-	return &status{
-		offset:      -1,
-		total:       humanize.ToBytes(0),
-		speedWindow: newSpeedWindow(framePerSecond),
-	}
-}
-
-// NewStatusMessage generates a status for messaging.
-func NewStatusMessage(prompt string, descriptor ocispec.Descriptor, offset int64) *status {
-	return &status{
-		prompt:     prompt,
-		descriptor: descriptor,
-		offset:     offset,
-	}
-}
-
-// StartTiming starts timing.
-func StartTiming() *status {
-	return &status{
-		offset:    -1,
-		startTime: time.Now(),
-	}
-}
-
-// EndTiming ends timing and set status to done.
-func EndTiming() *status {
-	return &status{
-		offset:  -1,
-		endTime: time.Now(),
-	}
-}
-
 func (s *status) isZero() bool {
 	return s.offset < 0 && s.startTime.IsZero() && s.endTime.IsZero()
 }
@@ -121,7 +87,7 @@ func (s *status) String(width int) (string, string) {
 		percent = 1
 	default: // 0% ~ 99%, show 2-digit precision
 		if total != 0 && s.offset >= 0 {
-			// percentage calculatable
+			// calculate percentage
 			percent = float64(s.offset) / float64(total)
 		}
 		offset = fmt.Sprintf("%.2f", humanize.RoundTo(s.total.Size*percent))
@@ -190,8 +156,7 @@ func (s *status) durationString() string {
 	return d.String()
 }
 
-// Update updates a status.
-func (s *status) Update(n *status) {
+func (s *status) update(n *status) {
 	s.lock.Lock()
 	defer s.lock.Unlock()
 

cmd/oras/internal/display/status/progress/status_test.go

@@ -35,7 +35,7 @@ func Test_status_String(t *testing.T) {
 	}
 
 	// not done
-	s.Update(&status{
+	s.update(&status{
 		prompt: "test",
 		descriptor: ocispec.Descriptor{
 			MediaType: "application/vnd.oci.empty.oras.test.v1+json",
@@ -57,7 +57,7 @@ func Test_status_String(t *testing.T) {
 		t.Error(err)
 	}
 	// done
-	s.Update(&status{
+	s.update(&status{
 		endTime:    time.Now(),
 		offset:     s.descriptor.Size,
 		descriptor: s.descriptor,
@@ -76,7 +76,7 @@ func Test_status_String_zeroWidth(t *testing.T) {
 	}
 
 	// not done
-	s.Update(&status{
+	s.update(&status{
 		prompt: "test",
 		descriptor: ocispec.Descriptor{
 			MediaType: "application/vnd.oci.empty.oras.test.v1+json",
@@ -93,7 +93,7 @@ func Test_status_String_zeroWidth(t *testing.T) {
 		t.Error(err)
 	}
 	// done
-	s.Update(&status{
+	s.update(&status{
 		endTime:    time.Now(),
 		offset:     s.descriptor.Size,
 		descriptor: s.descriptor,