use strict;
use File::Find;
use MP3::Tag;

my $dir=$ARGV[0];

die "use mp3ren.pl directory_name" if (!$dir);

find (\&wanted, "$dir");

sub wanted {
	
	if (&match("$File::Find::name")) {

		&rename_MP3($File::Find::name);
	}
}

sub match {

	my $filename=$_[0];

	if (-d $filename) {
		return 0;
	}

	my $mp3 = MP3::Tag->new($filename);
	if (defined $mp3) {

		$mp3->get_tags;
		if (exists $mp3->{ID3v1}) {

			return 1;

		} else {

			print "$filename is not mp3 or no ID3v1 tag\n";
			return 0;
		}
	}
}

sub rename_MP3 {

  my $fullname_mp3=$_[0];
  my $mp3 = MP3::Tag->new($fullname_mp3);
  my $new_mp3_name;

  $mp3->get_tags;

  my $song=$mp3->{ID3v1}->song;
  my $artist=$mp3->{ID3v1}->artist;

  if ($artist && $song) {
	$new_mp3_name="$artist--$song";

  } elsif ($song) {
	$new_mp3_name="$song";

  } elsif ($artist) {
	$new_mp3_name="$artist--untitled";

  } else {
	$new_mp3_name="";
  }

  if ($new_mp3_name) {

	$new_mp3_name=~s#[\\|\?|\*|\||\:|"|<|>|/]+##g;
	$new_mp3_name.=".mp3";
	$new_mp3_name="$File::Find::dir/$new_mp3_name";

	if ($fullname_mp3 eq $new_mp3_name) {

		print "Error renaming $fullname_mp3 to $new_mp3_name: same name\n"

	} elsif (!rename("$fullname_mp3","$new_mp3_name")) {

		print "Error renaming $fullname_mp3 to $new_mp3_name: $!\n"

	} else {

		print "Renamed $fullname_mp3 to $new_mp3_name\n"
	}

  } else {

	print "Error renaming $fullname_mp3: no ID3v1 tag\n"
  }
}