Explore dynamic pre-rolls and mid-rolls in HLS

class AVPlayerInterstitialEvent {
    var primaryItem: AVPlayerItem? { get }
    var identifier: String { get }
    var time: CMTime { get }
    var date: Date? { get }
    var templateItems: [AVPlayerItem] { get }
    var restrictions: AVPlayerInterstitialEvent.Restrictions { get }
    var resumptionOffset: CMTime { get }
    var playoutLimit: CMTime { get }
    var userDefinedAttributes: [AnyHashable : Any] { get }
}

// Client observes server-side interstitial playback
let player = AVPlayer(url: movieURL) // movieURL has EXT-X-DATERANGE ad tags
let observer = AVPlayerInterstitialEventMonitor(primaryPlayer: player)
NotificationCenter.default.addObserver(
  forName: AVPlayerInterstitialEventMonitor.currentEventDidChangeNotification,
  object: observer,
  queue: OperationQueue.main) {
      notification_ in
      self.updateUI(observer.currentEvent, observer.interstitialPlayer)
}

class AVPlayerInterstitialEventController : AVPlayerInterstitialEventMonitor {
    var events: [AVPlayerInterstitialEvent]!
    func cancelCurrentEvent(withResumptionOffset resumptionOffset: CMTime) 
}

// Client inserted events

// Client schedules an ad pod at 10s into primary asset
let player  = AVPlayer(url: movieURL)  // no ads in primary asset
let controller = AVPlayerInterstitialEventController(primaryPlayer: player)
let adPodTemplates = [AVPlayerItem(url: ad1URL), AVPlayerItem(url: ad2URL)]
let event = AVPlayerInterstitialEvent( 
  primaryItem: player.currentItem,
  time: CMTime(seconds: 10, preferredTimescale: 1),
  templateItems: adPodTemplates,
  restrictions: [],
  resumptionOffset: .zero,
  playoutLimit: .invalid)

 controller.events = [event]
 player.currentItem.translatesPlayerInterstitialEvents = true
 let vc = AVPlayerViewController()
 vc.player = player
 player.play()