generation-aware playlist readiness

internal/playback/playlist_readiness.go

@@ -0,0 +1,52 @@
+package playback
+
+func IsSessionPlaying(
+	session SessionSnapshot,
+	statuses PlaybackStatusSnapshot,
+) bool {
+	if statuses.Generation != session.Generation {
+		return false
+	}
+
+	switch session.Plan.Topology {
+	case TopologyIndependent:
+		hasActiveFeed := session.Plan.Video.Active || session.Plan.Audio.Active
+		if !hasActiveFeed {
+			return false
+		}
+		if session.Plan.Video.Active && !statusIsPlaying(
+			statuses.Video,
+			statuses.HasVideo,
+			session.Generation,
+		) {
+			return false
+		}
+		if session.Plan.Audio.Active && !statusIsPlaying(
+			statuses.Audio,
+			statuses.HasAudio,
+			session.Generation,
+		) {
+			return false
+		}
+		return true
+
+	case TopologySynchronized:
+		return statusIsPlaying(
+			statuses.Sync,
+			statuses.HasSync,
+			session.Generation,
+		)
+
+	case TopologyIdle:
+		return false
+
+	default:
+		return false
+	}
+}
+
+func statusIsPlaying(status Status, present bool, generation uint64) bool {
+	return present &&
+		status.Generation == generation &&
+		status.State == StatePlaying
+}