#!/usr/bin/python
#
# mp3swapartist.py
#
# swap mp3 artist and album artist tags
#
# I set up my whole music collection using a directory structure
# based on artist/album/trackno - title. Now I realise that
# album artist is the proper tag to use for that structure.
#
# Copyright (C) 2013 Jeremy Tammik
#
import glob, os, re, sys
from mutagen.mp3 import MP3
from mutagen.id3 import TPE1, TPE2
import eyeD3

def swap_artist( filepath ):
  "Swap mp3 artist and album artist tags."

  assert filepath.lower().endswith( '.mp3' )

  try:

    audio = MP3( filepath )

    old_artist = unicode( audio['TPE1'] )

    assert 0 < len( old_artist )

    old_album_artist = ''

    if audio.has_key( 'TPE2' ):
      old_album_artist = unicode( audio['TPE2'] )

    s = "original artist '%s', album artist '%s'" % (old_artist, old_album_artist)

    if 0 == len( old_album_artist ):
      # copy artist to album artist
      s += ' - added album artist'
      audio.tags.add( TPE2( encoding=3, text=old_artist ) )
      audio.tags.save()

    elif old_artist != old_album_artist:
      # swap artist and album artist
      s += ' swapped'
      audio.tags.add( TPE2( encoding=3, text=old_artist ) )
      audio.tags.add( TPE1( encoding=3, text=old_album_artist ) )
      audio.tags.save()

    else:
      s += ' retained'

    print filepath + ':', s

  except StandardError, err:
    print 'Error:', str( err ), "in '%s'" % filepath


def main():
  "Walk a directory tree and swap all mp3 artist and album artist tags."

  #dir = '.'
  dir = '/$User/Music/lovers_rock/'

  for root, dirs, files in os.walk( dir ):
    for filename in files:
      if filename.lower().endswith( '.mp3' ):
        filepath = os.path.join( root, filename )
        swap_artist( filepath )


if __name__ == "__main__":
  main()