#!/usr/bin/perl -w

use strict;
use CGI qw/header cookie start_html end_html url param/;
use Digest::MD5 qw(md5_hex);

my %login = (
test => 'test'
);

# this is just for demo
$login{$_} = md5_hex($login{$_}) foreach (keys %login);

sub checkSessionID {
  my $check = shift;
  my ($user,$pass) = split /:/,$check,2;
  return $login{$user} eq $pass ? 1:0;
}

sub checkUserPass {
  my $user = shift;
  my $pass = md5_hex(+shift);
  return $login{$user} eq $pass ? 1:0;
}

sub makeCookieValue {
  my $user = shift;
  my $pass = md5_hex(+shift);
  return "$user:$pass";
}

my %options;
my $cookie;

# yes, dirty and disgusting...but...oh well
if (param('clearCookie')) {
  $options{"-cookie"} = cookie(-name    => 'sessionID',
                   -value   => 'bye',
                   -expires => '-6M' # just in case
                  );
}
elsif (cookie('sessionID') && checkSessionID(cookie('sessionID'))) {
  $cookie = cookie(-name    => 'sessionID',
                   -value   => cookie('sessionID'),
                   -expires => '+1h'
                  );
}
elsif (param('username') && param('password') && checkUserPass(param('username'),param('password'))) {
  $cookie = cookie(-name    => 'sessionID',
                   -value   => makeCookieValue(param('username'),param('password')),
                   -expires => '+1h'
                  );
}

$options{"-cookie"} = $cookie if $cookie;
# if you wish, you can put more header options in %options
# if you wish to put more cookies, do: 
# $options{'-cookie'} = [ $options{'-cookie'} ];
# push @$options{'-cookie'}, $_ foreach (@more_cookies);
print header(%options),start_html;

# $cookie acts as our switch
if ($cookie) {
  print "Logged in and working! Cookie: ",cookie('sessionID') ? cookie('sessionID'):"You just logged in!";
  print "<br /><form action='",url(-absolute=>1),"' method='post'><input type='hidden' name='clearCookie' value='1'>
         <input type='Submit'></form>";
}
else {
  print "<form action='",url(-absolute=>1),"' method='post'>
  Login <input type='text' name='username' value='test'><br />
  Pass <input type='text' name='password' value='test'><br />
  <input type='Submit'></form>";
}
print end_html;