#!/usr/bin/perl

# simple link shortner
# implemented as tied hash

use strict;
use warnings "all";
use Fcntl;
use Storable;
#use CGI::Carp qw/fatalsToBrowser/;

my $db = '/tmp/short.links.db';
my $str = '';
my $maxlinklength = 2048;
my %link;
my $name = '';
my $i;


if (defined($ARGV[0])){
# we got GET req. here, so let's redirect it.
	%link = %{retrieve("$db")};
	if (defined($link{$ARGV[0]})){
		$str = sprintf("Status: 302 Found
Location: %s

%s", $link{"$ARGV[0]"}, $link{"$ARGV[0]"});
	} else {
		$str = "Status: 200 OK
Content-type: text/plain

Link expired.
";
	}
}else{
# we got page/form request, or post link request

	if($ENV{'REQUEST_METHOD'} eq 'POST'){ # post link request
		# here we need to extract the link
		for($i = 0; $i < 5; $i++){
			$name .= ('a'..'z', 'A'..'Z')[int rand length(join('',('a'..'z', 'A'..'Z')))];
		}

		my $buf = '';
		if(defined($ENV{'CONTENT_LENGTH'})){
			if($ENV{'CONTENT_LENGTH'} < $maxlinklength) {
				sysread(STDIN, $buf, $ENV{'CONTENT_LENGTH'});

				if(substr($buf, 0, 3) eq 'exs'){
					if(($buf =~ /^exs=http%3A/) or
					  ($buf =~ /^exs=https%3A/) or
					  ($buf =~ /^exs=ftp%3A/) or
					  ($buf =~ /^exs=xmpp%3A/) or
					  ($buf =~ /^exs=ipp%3A/) or
					  ($buf =~ /^exs=ldap%3A/) or
					  ($buf =~ /^exs=ldaps%3A/) or
					  ($buf =~ /^exs=irc%3A/) or
					  ($buf =~ /^exs=ircs%3A/) or
					  ($buf =~ /^exs=ssh%3A/) or
					  ($buf =~ /^exs=svn%3A/) or
					  ($buf =~ /^exs=git%3A/) or
					  ($buf =~ /^exs=hg%3A/) or
					  ($buf =~ /^exs=rtmp%3A/) or
					  ($buf =~ /^exs=rtsp%3A/) or
					  ($buf =~ /^exs=rtp%3A/) or
					  ($buf =~ /^exs=shoutcast%3A/) or
					  ($buf =~ /^exs=icecast%3A/) or
					  ($buf =~ /^exs=mailto%3A/) or
					  ($buf =~ /^exs=smb%3A/) or
					  ($buf =~ /^exs=magnet%3A/) or
					  ($buf =~ /^exs=ed2k%3A/) or
					  ($buf =~ /^exs=skype%3A/) or
					  ($buf =~ /^exs=dav%3A/) or
					  ($buf =~ /^exs=h323%3A/) or
					  ($buf =~ /^exs=rsync%3A/) or
					  ($buf =~ /^exs=sftp%3A/)){
						$buf = substr($buf, 4);
					}else{
						syswrite STDOUT, "Status: 400 Bad Request
Content-type: text/plain

Invalid url.
";
						exit 0;
					}
				}else{
					syswrite STDOUT, 'Status: 400 Bad Request
Content-type: text/plain

Invalid parameter.
';
					exit 0;
				}

			}else{
				syswrite STDOUT, 'Status: 400 Bad Request
Content-type: text/plain

Link too long.';
				exit 0;
			}
		}else{
			syswrite STDOUT, 'Status: 400 Bad Request
Conten-type: text/plain

CONTENT_TYPE env. var. required
';
			exit 0;
		}

# create db file if it is absent
		unless( -f "$db"){
			sysopen(FILE, "$db", O_WRONLY|O_TRUNC|O_CREAT);
			close FILE;
			# save empty hash to init structure
			store \%link, $db;
		}

		# decode it :(
		$buf =~ s/\%([A-Fa-f0-9]{2})/pack('C', hex($1))/seg;
		%link = %{retrieve($db)};
		$link{$name} = $buf;
		store \%link, $db;
		# here we need to post form with extracted link or just string
		$str .= "Status: 200 OK
Content-type: text/plain

http://s.dafuq.ru/$name
";
	}else{	# we got form request with get/head method, so print it
          $str .= 'Pragma: no-cache
Cache-Control: no-cache
Content-Language: en, ru
Content-type: text/html

<!DOCTYPE html>
<html lang="ru">
	<head>
		<meta charset="UTF-8" />
		<style>
			* {
				margin: 10px;
				text-align: center;
				font-size: 14pt;
			}
			html, body {
				background-color: #adc0fc;
			}
		</style>
		<title>exs-elm.ru</title>
	</head>
	<body>
		<img src="http://img.dafuq.ru/logo.png" />

		<form method="post" action="/">
			Shorten this link:<br />
			<input type="text" size="30" maxlength="256" name="exs" style="font-size: 110%;"/></br />
			<input type="submit" value="Submit" style="font-size: 85%;" />
		</form>

	</body>
</html>
';

	}
}

syswrite STDOUT, $str;
exit 0;

__END__

всего 3 типа запросов
-на показ формы
-на аплод ссылки из формы/аплоад ссылки из ком.строки
-на редирект по ссылке





<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>Exs URL Shortner.</title>
</head>
<body>
	<form method="post" action="/s/">
		<p style="text-align: center;"><b>URL Shortner</b></p>
		<div style="text-align: center;"><input type="text" size="30" maxlength="256" name="exs" style="font-size:125%;"></div>
		<p style="text-align: center;"><input type="submit" value="Shorten!"></p>
	</form>
</body>
</html>