Danbooru downloader with pools

#!/usr/bin/perl

use strict;
use LWP::UserAgent;
use HTTP::Response;
use threads;
use threads::shared;
use File::Basename;
use Digest::SHA1 qw(sha1_hex);
use URI::Escape;
use Cwd;

my $stop = 0;
$SIG{'INT'} = 'SIGINT_handler';

$| = 1; #flush stdout immediately

my $user;
my $pass;
my $directory :shared;
$directory = 'images';
my @tags;
my $tags;
my $pool;
my $url_tags = 'http://danbooru.donmai.us/post/index.xml';
my $url_pool = 'http://danbooru.donmai.us/pool/show.xml';
my $limit = 1000;
my $threads = 5;

$_ = join ' ', @ARGV;
if (/--help|-h/i)
{
    show_help();
    exit;
}

if (s/-(-user|u) (\S+)//)
{
    $user = $2;
}

if (s/-(-pass|p) (\S+)//)
{
    $pass = $2;
}

if (s/-(-limit|l) (\d+)//)
{
    $limit = $2;
}

if (s/-(-threads|t) (\d+)//)
{
    $threads = $2;
}

if (s/-(-pool|p) (\d+)//)
{
    $pool = $2;
}

if (s/-(-dir|d) (\S+)//)
{
    $directory = $2;
}

@tags = split / /, $_;

map { s/[^A-Za-z0-9_]//g; chomp; } @tags;
$tags = join '+', @tags;
my @tags;

if (($tags eq '' and $pool eq '') or ($user eq '' or $pass eq ''))
{
    show_help();
    exit;
}

my $url;
if ($pool eq '') { $url = $url_tags; }
else             { $url = $url_pool; }

my $hashed_pass = sha1_hex("choujin-steiner--$pass--");
$hashed_pass = uri_escape($hashed_pass);
$user = uri_escape($user);
$url .= "?login=$user&password_hash=$hashed_pass";

$directory =~ s/\/|\\$//;

if (!-d $directory)
{
    mkdir $directory;
}

chdir $directory;

fetch_site(1) =~ /<posts count="(\d+)"/;
if ($1)
{
    print "Total count match: $1, per page: $limit\n";
}
else
{
    print "ERROR: can't get total count match\n";
    exit;
}

my @files :shared;
my $max = int $1/$limit + 1;

for (1..$max)
{
    if ($stop)
    {
        print "Interruped by SIGINT\n";
        exit(0);
    }

    my $data = fetch_site($_);
    while ($data =~ /file_url="([^"]+)"/g)
    {
        push @files, $1;
    }
}

my @thr;
my $file;
if ($#files+1 < $threads) { $threads = $#files+1; };

print "THREADS: $threads, FILES ".($#files+1)."\n";

for (1..$threads)
{
    if ($file = shift @files)
    {
        $thr[$_] = threads->create(\&save_file, $file);
    }
}

while (sleep 1)
{
    for (1..$threads)
    {
        if ($thr[$_]->is_joinable)
        {
            $thr[$_]->join;
            if ($file = shift @files)
            {
                $thr[$_] = threads->create(\&save_file, $file);
            }
        }
    }
    last if ($#files == -1 && threads->list == 0);
}

sub fetch_site
{
    my $page = shift;
    my $ua = LWP::UserAgent->new;
    print "Getting [$url] page $page... ";
    my $local_url = $url;
    if ($pool eq '') { $local_url .= "&tags=$tags&page=$page&limit=$limit"; }
    else             { $local_url .= "&id=$pool&page=$page&limit=$limit"; }
    my $responce = $ua->get($local_url);
    if ($responce->is_success)
    {
        print "OK\n";
        return $responce->content;
    }
    else
    {
        print 'ERROR ' . $responce->code . ' ' . $responce->message . "\n";
        return undef;
    }
}

sub save_file
{
    my $name = shift;
    my $ua = LWP::UserAgent->new;
    my $filename;
    #print cwd()."\n";
    $name =~ /([^\/\\]+?)$/;
    $filename = $1;
    print ''.($#files+1)." files left, saving $filename\n";
    $ua->get($name, ':content_file' => $filename);
    threads->exit;
}

sub show_help
{
    print "Danbooru download script.
Usage: ".basename($0)." -u <username> -p <pass> <options> {--pool <pool_name>|space_separated_tag_list}
Options:
    --limit(-l)     files PER PAGE (defaut $limit)
    --threads(-t)       number of threads (default $threads)
    --dir(-d)       dir to save images (default `$directory')";
}

sub SIGINT_handler
{
    @files = ();
    $stop = 1;
}