Running firebase functions on trigger and schedule

• AddUser() -> triggered on spotify user access approval (playlist read/write): adds user profileId:token to firestore
• CombinePlaylists () -> Triggered on user request to combine two or more playlists, add list of source playlists anbd destination playlist ids to firebase
• Scheduler() -> runs 1x a day to go through user profiles / playlists and runs CombinePlaylists

Storing user data

• Profile: Spotify.profileId:userToken
• CombinedPlaylists: Spotify.profileId:JSON.stringify({source.playlistId:destination.playlistId[]})

1. User Access
   • User will need to approve app to access their playlists (read/write)
     • add user's token to firestore: profileId:token
2. If user is approved they need to provide:
   • source playlist Ids array
   • destination playlist name
3. Firebase combine playlists function will ^ Fetch profileId:token from firestore
   • Fetch songs in source playlists array
   • Create destination playlist (if name doesnt exists)
   • Add source playlist songs to destination (shuffle?)
4. Setup recurring tasks to trigger firebase function (will require story spotify access token for refresh)
   • For each profileId:token in fire store: Run combine function

[ ] Optimize combining playlists so that (possibly some sort of playlist or song 'lastModified') [ ] On first user req to combine playlist Error out on destination playlist already exists [ ]