#!/opt/local/bin/perl

use 5.010;
use strict;
use warnings;
use File::Find qw(find);

my $library = "F:/Music";
#$library = "F:/FLAC/Downloaded/New";
my %files;

find({ wanted => \&action, no_chdir => 1 }, $library);

sub action {
	if (-d) {
		my $dn = $File::Find::name;
		%files = getfiles($dn);
		my $fc = keys %files;
#		say $fc;
		unless ($fc == 0) {
			replaygain($dn);
			foreach my $fn (sort(keys %files)) {
				rmtag($fn, 'discnumber', 'disctotal', 'rating', 'comment');
				albumartist($fn, $fc);
				track($fn);
				totaltracks($fn, $fc);
#				empty($fn);
#				duplicate($fn);
			}
		}


		undef %files;
	}
}
# Make this subroutine and the whole script so that each file name is stored in a hash and that each member contains an anonymous hash with the tags (the alltags hash).
# This means it won't have to look up the tags again for the albumartist subroutine.

sub gettags {
	my $fn = shift;
	my %alltags;
	open(OUTPUT, '-|', qq{metaflac --no-utf8-convert --export-tags-to=- "$fn"}) || die "can\'t run metaflac: $!";
	local $_;
	while (<OUTPUT>) {
		chomp;
		my @tag = split('=');
		my $tagname = lc($tag[0]);
		if ($tag[1]) {
			push @{$alltags{$tagname}}, $tag[1];
		} else {
			push @{$alltags{$tagname}}, 'null';
		}
	}
	close(OUTPUT) || die "couldn\'t close metaflac: $!";
	return %alltags;
}

sub getfiles {
	my $dn = shift;
	my %files;
	opendir(my $dh, $dn) or die "Can\'t open directory '$dn': $!";
	foreach (readdir $dh) {
		my $fn = "$dn/$_";
		if (/.flac$/ && -f $fn) {
			$files{$fn} = { gettags($fn) };
		}
	}
	closedir $dh or die "Can\'t close directory '$dn': $!";
	return %files;
}

sub replaygain {
	my $dn = shift;
	my %replaygain;

	foreach my $fn (sort(keys %files)) {
		if ($files{$fn}{replaygain_album_gain}) {
			$replaygain{$files{$fn}{replaygain_album_gain}->[0]}++;
		}
	}
	if (keys(%replaygain) != 1) {
		print "$dn: adding ReplayGain...";
		system('metaflac', '--add-replay-gain', keys(%files));
		say " done";
	}
}

sub albumartist {
	my $fn = shift;
	my $tracks = shift;
	if (!$files{$fn}{albumartist}) {
		my $albumartist = 'Various Artists';
		my %artist;
		my $max;
		if ($tracks == 1) {
			$max = $tracks;
		}
		else {
			$max = $tracks / 2;
		}
		foreach my $fn (keys %files) {
			$artist{$files{$fn}{artist}->[0]}++
		}
		if (keys(%artist) <= $max) {
			my $ac = 0;
			foreach my $a (keys %artist) {
				if ($artist{$a} > $ac) {
					$ac = $artist{$a};
					$albumartist = $a;
				}
			}
		}
		say "$fn: adding albumartist tag";
		system('metaflac', "--set-tag=ALBUMARTIST=$albumartist", $fn);
	}
}

sub empty {
	my $fn = shift;
	foreach my $k (keys %{$files{$fn}}) {
		foreach (@{$files{$fn}{$k}}) {
			if ($_ eq 'null') {
				say "$fn: WARNING: empty $k tag";
			}
		}
	}
}

sub duplicate {
	my $fn = shift;
	my %exists;
	foreach my $k (keys %{$files{$fn}}) {
		foreach (@{$files{$fn}{$k}}) {
			my $tag = quotemeta($k . '=' . $_);
			if ($exists{$tag}) {
				say "$fn: WARNING: duplicate $k tag";
			} else {
				$exists{$tag} = 1;
			}
		}
	}
}

sub track {
	my $fn = shift;
	my $track = $files{$fn}{tracknumber}->[0];
	if ($track =~ m/^0/ && $track != 0) {
		say "$fn: fixing tracknumber tag";
		$track =~ s/^0+//;
		system('metaflac', '--remove-tag=TRACKNUMBER', "--set-tag=TRACKNUMBER=$track", $fn);
	}
}

sub totaltracks {
	my $fn = shift;
	my $tracks = shift;
	if (
	!$files{$fn}{totaltracks} &&
	!$files{$fn}{tracktotal}
	) {
		say "$fn: adding totaltracks tag";
		system('metaflac', "--set-tag=TOTALTRACKS=$tracks", $fn);
	}
	elsif (
	$files{$fn}{tracktotal} &&
	!$files{$fn}{totaltracks}
	) {
		say "$fn: replacing tracktotal tag with totaltracks";
		system('metaflac', '--remove-tag=TRACKTOTAL', "--set-tag=TOTALTRACKS=$files{$fn}{tracktotal}->[0]", $fn);
	}	
}

sub rmtag {
	my $fn = shift;
	foreach (@_) {
		if ($files{$fn}{$_}) {
			say "$fn: removing $_ tag";
			system('metaflac', "--remove-tag=$_", $fn);
		}
	}
}