design.txt

Design document


available event listeners
* Device Announcement
* Beat
* Master
* Update <-- most information
* Media Details  <-- callback when requesting
* Mount
* Signature



CdjScrobbler.SongModel
* properties:
  which device 			<- CdjStatus.getTrackSourcePlayer()
  has metadata?     	<- true after our media query has finished
  song details  		<- set after ^
  total played time 	<- updated with each received message
  current state 		<- see below
  last update timestamp <- timestamp of last CdjStatus received. 
  						   Needed for incrementing played time,
* methods
  updatePlayTime()

CdjScrobbler.SongState
* states:
  Started 
  Ignored
  Cueing 
  Playing
  PlayingPaused
  Scrobbling
  ScrobblingPaused
  Stopped

Song Transitions
	Started -> Ignored (happens when no metadata available)
	Started -> Cueing
	Ignored -> Stopped    
	Cueing -> Started
	Cueing -> Playing               <- raise a now playing (get metadata now)
	Playing -> PlayingPaused
	Playing -> Stopped
	Playing -> Scrobbling           
	PlayingPaused -> Playing
	PlayingPaused -> Stopped
	Scrobbling -> ScrobblingPaused
	Scrobbling -> Stopped           <- raise a retire-scrobbling
	ScrobblingPaused -> Scrobbling
	ScrobblingPaused -> Stopped     <- raise a retire-scrobbling

CdjScrobbler.UpdateListener
* methods
  receive(DeviceUpdate update) https://deepsymmetry.org/beatlink/apidocs/org/deepsymmetry/beatlink/DeviceUpdateListener.html
  * either a MixerStatus or a CdjStatus (which is what we're interested in)
  * how do we use this to work out the play time of a track?

  General:
  * receive things which send us to stopped (such as change of track or eject)
  	isAtEnd() true
  	isTrackLoaded() false

  * receive things which increment play time by (timestamp - previous timestamp) x Util.pitchToPercentage(getPitch()), but only if isPlayingForward()
  	* if play time > 30s
  		transition Cueing -> Playing
  	* if scrobble point known && play time > scrobble point 
  		transition Playing -> Scrobbled


CdjScrobbler
* songscrobbler Map<int, CdjScrobblerSongModel>
  start a metadatafinder (see https://github.com/Deep-Symmetry/beat-link/#media-details)

* receive(DeviceUpdate)
	if isLinkMediaAvailable()
	  	send to the right cdjSongScrobbler
	  	add returned event (if any) to the queue of events to deal with TODO
	  		e.g now playing, retire scrobbling
	  	if the song scrobbler is now Stopped:
	  		recreate song scrobbler


thread design
* event update thread will notify UpdateListener on the event processing thread
  * this must then put song events on to the queue quickly and .notify the queue processor

Classes:
* CdjScrobbler.Application
* CdjScrobbler.UpdateListener
* CdjScrobbler.SongModel
* CdjScrobbler.SongState (enum)
* CdjScrobbler.QueueProcessor
* CdjScrobbler.SongEvent (abstract)
* CdjScrobbler.NowPlayingEvent
* CdjScrobbler.ScrobbleEvent
* CdjScrobbler.NowPlayingEventListener (interface)
* CdjScrobbler.ScrobbleEventListener (interface)
* CdjScrobbler.Scrobbler