#! /usr/bin/perl

# This file is maintained at http://git.mdcc.cx/draai
#	oggsymlinks - maintain a symlink forest
#	Copyright (C) 2008  Wessel Dankers <wsl@fruit.je>
#
#	This program is free software: you can redistribute it and/or modify
#	it under the terms of the GNU General Public License as published by
#	the Free Software Foundation, either version 3 of the License, or
#	(at your option) any later version.
#
#	This program is distributed in the hope that it will be useful,
#	but WITHOUT ANY WARRANTY; without even the implied warranty of
#	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#	GNU General Public License for more details.
#
#	You should have received a copy of the GNU General Public License
#	along with this program.  If not, see <http://www.gnu.org/licenses/>.

use strict;
use warnings;
use utf8;
use Carp;

my $dot = ord '.';
my $slash = ord '/';

my $verbose = $ENV{'DR_VERBOSE'};
my $debug = $ENV{'DR_DEBUG'};
my $dryrun = $ENV{'DR_DRYRUN'};

my $target = shift @ARGV;

my %target;

opendir TARGET, $target
	or croak "Can't open $target: $!";

while(my $artist = readdir TARGET) {
	next if ord($artist) == $dot;
	my $dir = "$target/$artist";
	my %albums;
	unless(opendir ARTIST, $dir) {
		my $err = $!;
		unless(-d $dir) {
			carp "$dir is not a directory, skipping";
			undef $target{$artist};
			next;
		}
		croak "Can't open $dir: $err";
	}
	while(my $album = readdir ARTIST) {
		next if ord($album) == $dot;
		my $link = "$dir/$album";
		my $dest = readlink $link;
		$albums{$album} = $dest;
		unless(defined $dest) {
			my $err = $!;
			if(!-l $link) {
				carp "$link is not a symlink, skipping";
			} else {
				carp "Can't read symlink $link: $err";
			}
			next;
		}
	}

	$target{$artist} = \%albums;
}

closedir TARGET;

sub path {
	my ($dir, $path) = @_;
	return $path if ord($path) == $slash;
	return "$dir/$path";
}

my %source;

foreach my $source (@ARGV) {
	# strip multiple/trailing slashes
	$source =~ s|//+|/|g;
	$source =~ s|(.)/$|$1|;

	my $psource = path($target, $source);
	opendir SOURCE, $psource
		or croak "Can't open $psource: $!";

	while(my $artist = readdir SOURCE) {
		next if ord($artist) == $dot;
		my $dir = "$source/$artist";
		my $pdir = "$psource/$artist";
		my $dude;
		$source{$artist} = {} unless exists $source{$artist};
		$dude = $source{$artist};
		my %albums;
		unless(opendir ARTIST, $pdir) {
			my $err = $!;
			unless(-d $pdir) {
				carp "$pdir is not a directory, skipping";
				next;
			}
			croak "Can't open $pdir: $!";
		}
		while(my $album = readdir ARTIST) {
			print "Inspecting $source, $artist, $album\n" if $debug;
			next if ord($album) == $dot;
			$dude->{$album} = $source;
		}
	}

	closedir SOURCE;
}

# remove redundant/bad symlinks and directories
while(my ($artist, $tartist) = each(%target)) {
	next unless defined $tartist;

	my $sartist = $source{$artist};

	while(my ($album, $link) = each(%$tartist)) {
		next unless defined $link;
		my $to = "$target/$artist/$album";
		if(defined $sartist) {
			my $src = $sartist->{$album};
			next if
				defined $src
				and $link eq path('..', "$src/$artist/$album");
		}
		if($verbose) {
			print "Would run: " if $dryrun;
			print "unlink $to\n";
		}
		unless($dryrun) {
			unlink $to or croak "Can't create remove $to: $!";
		}
		delete $tartist->{$album};
	}

	next if defined $sartist;
	next if keys %$tartist;
	my $dir = path($target, $artist);
	if($verbose) {
		print "Would run: " if $dryrun;
		print "rmdir $dir\n";
	}
	unless($dryrun) {
		rmdir $dir or warn "Can't rmdir $dir: $!";
	}
}

# create missing directories and symlinks
while(my ($artist, $sartist) = each(%source)) {
	my $tartist;

	if(exists $target{$artist}) {
		$tartist = $target{$artist};
		next unless defined $tartist;
	} else {
		my $dir = path($target, $artist);
		if($verbose) {
			print "Would run: " if $dryrun;
			print "mkdir $dir\n";
		}
		unless($dryrun) {
			mkdir $dir or croak "Can't mkdir $dir: $!";
		}
		$tartist = {};
	}

	while(my ($album, $src) = each(%$sartist)) {
		print "Checking for missing symlinks for $src, $artist, $album\n" if $debug;
		next if exists $tartist->{$album};
		my $from = path('..', "$src/$artist/$album");
		my $to = "$target/$artist/$album";
		if($verbose) {
			print "Would run: " if $dryrun;
			print "symlink $from, $to\n";
		}
		unless($dryrun) {
			symlink $from, $to
				or croak "Can't create symlink to $to at $from: $!";
		}
	}
}