evision-safe playlist timing

internal/playback/playlist_timing.go

@@ -0,0 +1,52 @@
+package playback
+
+import "time"
+
+type PlaylistTimingState struct {
+	Revision uint64
+	Duration time.Duration
+	Started  bool
+	Deadline time.Time
+}
+
+func NewPlaylistTiming(
+	revision uint64,
+	duration time.Duration,
+) PlaylistTimingState {
+	return PlaylistTimingState{
+		Revision: revision,
+		Duration: duration,
+	}
+}
+
+func StartPlaylistTiming(
+	current PlaylistTimingState,
+	revision uint64,
+	now time.Time,
+) (PlaylistTimingState, bool) {
+	if revision != current.Revision || current.Duration <= 0 || current.Started {
+		return current, false
+	}
+
+	next := current
+	next.Started = true
+	next.Deadline = now.Add(current.Duration)
+	return next, true
+}
+
+func ExpirePlaylistTiming(
+	current PlaylistTimingState,
+	revision uint64,
+	now time.Time,
+) (PlaylistTimingState, bool) {
+	if revision != current.Revision ||
+		!current.Started ||
+		now.Before(current.Deadline) {
+		return current, false
+	}
+
+	next := current
+	next.Started = false
+	next.Deadline = time.Time{}
+	return next, true
+}