flactag

#!/usr/bin/env perl
# modify FLAC tags using metaflac

use Getopt::Std;

$0 =~ s#.*/##;

# this array drives everything
%options = ('a', 'ARTIST',
	    'b', 'ALBUM',
	    'c', 'ALBUMARTIST',
	    'd', 'DISCNUMBER',
	    'e', 'DISCTOTAL',
	    'f', 'DISCSUBTITLE',
	    'g', 'GENRE',
	    'k', 'COMPOSER',
	    'l', 'TRACKTOTAL',
	    'n', 'TRACKNUMBER',
	    'p', 'PICTURE',
	    't', 'TITLE',
	    'y', 'DATE',
	    'z', 'MUSICBRAINZ'
);

# build USAGE
foreach $option (sort keys %options) {
	$usage .= " [-$option " . lc($options{$option}) . "]";
}
$USAGE = "USAGE: $0$usage files...\n";
$USAGE .= "\t- argument of 'nil' removes a tag, example: $0 -c nil\n";
$USAGE .= "\t- argument of PCRE search/replace will replace a value, example: $0 -b 's/foo/bar/'\n";
die "$USAGE" if !@ARGV || grep(/^--help$/, @ARGV);

# parse options and arguments
$optarg = join(':', keys(%options)) . ':'; # example:  a:m:g:t:d:
getopt($optarg, \%getopt); # pass reference to array

# show existing tags & exit if no arguments provided
grep(s/(\W)/\\\1/g, @ARGV); # escape non-word chars in filenames for shell
if (0 == %getopt) {
	foreach $file (@ARGV) {
		system("metaflac --list --block-type=VORBIS_COMMENT $file");
		system("metaflac --list --block-type=PICTURE $file | head -12");
	}
	exit;
}

# assemble the musicbrainz tags I can zap
@brainztags = qw(disc album artist albumartist track);
foreach my $string (@brainztags) {
	$string = uc("MUSICBRAINZ_" . $string . "ID");
}

# main loop
foreach $option (keys %getopt) {
	$tagname = $options{$option};
	$value = $getopt{$option};
	if ($value =~ m/^s\W/) {
		# it's a regex, read the existing tag
		foreach $filename (@ARGV) {
			# TODO: what if tag does not exist
			$existing_tag = `metaflac --show-tag=$tagname $filename` || die "could not process $filename";
			chomp $existing_tag;
			$existing_tag =~ s/^$tagname=//i; # a field consists of NAME=VALUE
			$_ = $existing_tag;
			eval $value;
			$new_tag = $_;
			#print "DEBUG: new $tagname is $new_tag\n";
			$metaflac_for_this{$filename} .= " --remove-first-tag=$tagname";
			$metaflac_for_this{$filename} .= " --set-tag=\"$tagname=$new_tag\"" unless 'nil' eq $value;
		}
	} else {
		# not a regex, no need to read existing tag
		if ($tagname eq 'PICTURE' && $value eq 'nil') {
			# special case: remove picture, must be run separately
			$metaflac_for_pics .= " --remove --block-type=PICTURE,PADDING --dont-use-padding";
		} elsif ($tagname eq 'MUSICBRAINZ' && $value eq 'nil') {
			# zap musicbrainz tags
			foreach my $tagname (@brainztags) {
				$metaflac_for_all .= " --remove-first-tag=$tagname";
			}
		} else {
			# set a tag to a value
			$metaflac_for_all .= " --remove-first-tag=$tagname";
			$metaflac_for_all .= " --set-tag=\"$tagname=$value\"" unless 'nil' eq $value;
		}
	}
}
# modify each file
foreach $filename (@ARGV) {
	$command = "metaflac $metaflac_for_this{$filename} $metaflac_for_all $filename";
	#print "DEBUG: $command\n";
	system($command);
	if ($metaflac_for_pics) {
		$command = "metaflac $metaflac_for_pics $filename";
		system($command);
	}
}