Implement Observer media and sample observables

Add an observable object that easily allows to track the current state of media and perform custom actions when that state changes.

Observable/Subject

An observable is a class responsible for receiving an ordinary object and emit personalized events that track the specific changes that occur to that object.

Examples

• ReceiverSubject
• MediaSubject
• LazyMediaObserver

Observers

An observer is an object that performs custom actions in response to events of an observable. For example, an observer that registers the watched state on a third-party service when the user watches something.

Examples

• Trakt - An observer that registers the watched state of media automatically in Trakt
• Playlist - A (default built-in) observer that waits for an item to stop playing to start the next one on the playlist.
• Kodi - An observer that registers the watched state of media automatically in Kodi
• PogDesignCat - An observer that registers the watched state of media automatically in PogDesignCat
• OpenSubtitles - An observer that marks a subtitle as compatible after viweing media with that subtitle

Tasks

• Create a state class
  • Extend the immutable map
  • Add a state watcher class
    • Matching Criteria
    • Notifier
    • Actions
      • Do
      • Emit
      • EmitWith
      • EmitState
• Allow predefined global media watchers