Creating a Firestore Database from existing files

I have a few music albums - basically just files in folders - that I want to upload to Firebase Storage.

One would usually run a function after a file has been uploaded to create a Document containing the metadata about the Song but that's where Im stuck.

I can get most infos I need by reading the Tracks ID3 Tags but in a NoSql Database I think im supposed to not only create a Document for the Track but also a Document for each album with an array of all tracks - or at least an array with all track ids.

But when or how do I create the Album Document? Another example is the Album Cover.. I want to save the Url inside the Track Document as well as in the corresponding Album but that means that the Artwork is the first thing I need to upload because I can't add an URL because it doesn't exist yet.

I feel like I have to get this right before I start because updating everything afterwards is a pain.

Is using upload functions really the way to go here or is there really a tool or another way im missing.

thank you very much