Implement Browsing by Tags

[midwan]

Implement browsing by Tags, instead of only Folders.
This should also fix #34 as a workaround.

[tesshucom]

I'm also committed to Airsonic, and I'm familiar with Subsonic's API and implementation.

Care must be taken to completely replace the File structure and ID3 tags.
Many Subsonic clients are based on File structure because the situation where the file can not be found is avoided.

If you intend to take a general approach...

• Change the current directory list to getIndexes starting point. It is also important to keep in mind the Indexes#child (represents the music file that exists directly at the top of the music folder).
  This will ensure File structure based browsing.
• Support ID3 tags based songs search. The search results can be linked with File structure based browsing.

Most Subsonic clients have such data flow.
(So I asked # 50)

[midwan]

With v2.30, we are already using GetIndexes for the folders under the "Root" one.

The browsing by tags idea should allow you to see an Artists/Albums/Tracks structure instead, but I'm not sure if it's even worth implementing in MusicBee - there are too many limitations going through that, as it seems to expect a folder structure when browsing through the left pane.