generation-aware playback statuses

internal/playback/state.go

@@ -1,6 +1,7 @@
 package playback
 
 import (
+	"context"
 	"fmt"
 	"time"
 )
@@ -27,6 +28,7 @@ const (
 type Status struct {
 	Unit           Unit
 	State          State
+	Generation     uint64
 	Attempt        int
 	FailedAttempts int
 	RetryIn        time.Duration
@@ -35,6 +37,17 @@ type Status struct {
 
 type StatusObserver func(Status)
 
+type generationContextKey struct{}
+
+func withGeneration(ctx context.Context, generation uint64) context.Context {
+	return context.WithValue(ctx, generationContextKey{}, generation)
+}
+
+func generationFromContext(ctx context.Context) uint64 {
+	generation, _ := ctx.Value(generationContextKey{}).(uint64)
+	return generation
+}
+
 func (u Unit) String() string {
 	switch u {
 	case UnitVideo: