define playback worker status

internal/playback/state.go

@@ -1,5 +1,15 @@
 package playback
 
+import "time"
+
+type Unit uint8
+
+const (
+	UnitVideo Unit = iota
+	UnitAudio
+	UnitSync
+)
+
 type State uint8
 
 const (
@@ -10,3 +20,14 @@ const (
 	StateFailed
 	StateStopping
 )
+
+type Status struct {
+	Unit           Unit
+	State          State
+	Attempt        int
+	FailedAttempts int
+	RetryIn        time.Duration
+	Err            error
+}
+
+type StatusObserver func(Status)

internal/playback/state_test.go

@@ -0,0 +1,27 @@
+package playback
+
+import (
+	"errors"
+	"testing"
+	"time"
+)
+
+func TestStatusPreservesValues(t *testing.T) {
+	wantErr := errors.New("producer missing")
+	status := Status{
+		Unit:           UnitVideo,
+		State:          StateReconnecting,
+		Attempt:        2,
+		FailedAttempts: 1,
+		RetryIn:        time.Second,
+		Err:            wantErr,
+	}
+
+	if status.Unit != UnitVideo {
+		t.Errorf("Unit = %v, want %v", status.Unit, UnitVideo)
+	}
+	// Check the remaining fields similarly.
+	if !errors.Is(status.Err, wantErr) {
+		t.Errorf("Err = %v, want %v", status.Err, wantErr)
+	}
+}