#!/usr/bin/perl 

use strict;

use CGI;
use MD5;

my $EZproxyStartingPointURL = "";

sub EZproxyURLInit
{
  my ($EZproxyServerURL, $secret, $user, $groups) = @_;
  my ($packet, $EZproxyTicket);

  if ($secret eq "") {
    die "EZproxyURLInit secret missing";
  }

  $packet = '$u' . time();
  if ($groups ne "") {
    $packet .= '$g' . $groups;
  }
  $EZproxyTicket = CGI::escape(MD5->hexhash($secret . $user . $packet) . 
                               $packet);
  $EZproxyStartingPointURL = $EZproxyServerURL . "/login?user=" . 
    CGI::escape($user) . "&ticket=" . $EZproxyTicket;
}

sub EZproxyURL
{
  my ($url) = @_;

  if ($EZproxyStartingPointURL eq "") {
    die "EZproxyURLInit must be called before EZproxyURL";
  }

  return $EZproxyStartingPointURL . "&qurl=" . CGI::escape($url);
}

EZproxyURLInit("http://ezproxy.yourlib.org", "shhh", "someuser");

print "Content-Type: text/html\n\n";

print 
  "<a href=\"", EZproxyURL("http://www.somedb.com"), 
  "\">Some Database</a><br />\n", 

  "<a href=\"", EZproxyURL("http://www.otherdb.com"), 
  "\">Other Database</a><br />\n";