<?
/* ==========================================================
 * URLLog PHP-script for redirecting ShortURLs
 * (C) Copyright 2006-2015 Tecnic Software productions (TNSP)
 * ==========================================================
 * How to set up short URL redirection:
 *
 * 1) Set up URLLog database (see urllog.tcl for more information)
 *
 * 2) In this example we assume that your short URL prefix is:
 *    http://example.com/u/
 *    This setting is called urllog_shorturl_prefix in urllog.tcl
 *
 * 3) Place this PHP script under your www-server root. In this
 *    example we will use "/var/www/urlredirect.php" that is
 *    visible as http://example.com/urlredirect.php
 *
 *    Edit script dbFilename setting below to point to correct
 *    URLLog SQLite database file location.
 *
 * 4) Create or edit /var/www/.htaccess and add following:
 *    RewriteEngine on
 *    RewriteRule ^u/([^\?\&]+)$ /urlredirect.php?u=$1
 *
 * 5) You may need to restart/reload your www-server.
 *
 * 6) Profit.
 */
try {
  // You need to uncomment and configure one of the PDO object
  // initialization lines below, depending on what kind of SQL
  // database you are using.

  // If using SQLite3, set the filename / path there:
  //$db = new PDO("sqlite:/path/to/urllog.sqlite");
}
catch (PDOException $e) {
  myerr("Could not connect to URL database: ".$e->getMessage().".");
}


// ==========================================================
// Helper functions
function urlToID($url)
{
  $idCodes = "ABCDEFGHIJKLNMOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
  $idNumCodes = strlen($idCodes);

  $len = strlen($url);
  if ($len < 1)
    return -1;

  for ($id = 0, $i = 0; $i < $len; $i++)
  {
    $id *= $idNumCodes;
    $n = strpos($idCodes, $url[$i]);
    if ($n !== FALSE)
      $id += $n;
    else
      return -2;
  }
  return $id;
}

function myerr($str = "")
{
  header("Status: 404 Not Found");
  echo "404 Not Found - ".$str;
  exit;
}

// Check arguments
if (isset($_GET["u"]))
  $urlStr = $_GET["u"];
else
  myerr("No ID given.");

// Calculate urlID
$urlID = urlToID($urlStr);
if ($urlID < 0)
  myerr("Invalid ID.");


// Find the matching URL, if any
foreach ($db->query("SELECT url FROM urls WHERE id=".$urlID) as $row)
{
  header("Location: ".$row["url"]);
  exit;
}

$db = null;
// Output result
myerr("No such ID in database.");
?>