#! /bin/sh -e

case $# in 0) set -- . ;; esac

parse_vorbis_comment () {
  tag=$1
  
  while read value; do
  case "$value" in
    artist=* | album=* | musicbrainz_albumid=*)
      label=${value%%=*}
      eval $label=\${value#*=}
      eval have_$label=t
      ;;
  esac
  done <<TAG
$tag
TAG
}

find "$@" \( -name '*.flac' -o -name '*.ogg' -o -name '*.mp3' \) -print | \
while read file; do
  have_artist=nil
  have_album=nil
  have_musicbrainz_albumid=nil
  case "$file" in
    "$skip"/*)
      continue
      ;;
    *.flac)
      parse_vorbis_comment "$(
	metaflac --list --block-type=VORBIS_COMMENT "$file" |
	sed -n '/^.*comment\[[0-9]*\]: /s///p')"
      ;;
    *.ogg)
      parse_vorbis_comment "$(vorbiscomment "$file")"
      ;;
    *.mp3)
      tag="$(id3v2 --list "$file")"
      while read fourcc rest; do
	rest=${rest#*): }
	case "$fourcc,$rest" in
	  TPE1,*) artist=$rest have_artist=t ;;
	  TALB,*) album=$rest have_album=t ;;
	  TXXX,"(MusicBrainz Album Id): "*)
	    musicbrainz_albumid=${rest#*): }
	    have_musicbrainz_albumid=t
	    ;;
	esac
      done <<TAG
$tag
TAG
  esac
  case $have_artist,$have_album,$have_musicbrainz_albumid in
    t,t,t)
      echo "$musicbrainz_albumid $artist | $album"
      skip=${file%/*}
      ;;
  esac
done