I first tried using the modules Short URL and Shorten URLs but I believe the module Short URL is currently on its early stages.

I've decided to create a custom module for our project but basing it on the modules above. Unfortunately, the module isn't an API like Short URL. It was a combination of both in which it provides a UI for shortening URLs and records them.

I started with how the module redirects the URLs when it encounters one from the record. The Short URL implemented the hookinit() to do this. This is somewhat what I was able to come up with based on the _Short URL__ module:

<?php
/**
 * Implementation of hook_init().
 */
function url_shorten_init() {
  $token = arg(0); // Retrieve 1st segment of the URL.
  $long_url = NULL;

  if (!empty($token)) {
    $data = db_fetch_object(db_query("SELECT id, long_url FROM {url_shorten} WHERE short_url = '%s';", $token));

    if (!empty($data)) {
      $record = new stdClass();
      $record->sid = $data->id;
      $record->referer = (isset($_SERVER['HTTP_REFERER'])) ? $_SERVER['HTTP_REFERER'] : '';
      $record->date = time();
      $record->ip_address = ip2long(ip_address());

      drupal_write_record('url_shorten_stats', $record);
      drupal_goto($data->long_url, NULL, NULL, 301);
    }
  }
}

The code drupal_goto() is the one handling the redirect. I then did the UI for shortening URLs in which it makes use of a function for shortening. This was the function that I was able to copy from this page:

<?php
/**
 * Generate a string with url_shorten_maxlength alpha characters. Snippet was taken
 * from http://www.bytemycode.com/snippets/snippet/579/.
 */
function url_shorten_generate_code($length) {
  $code = '';

  // Recreate length to have different number of 
  // characters. 3 would be the minimum length.
  $new_length = rand(3, $length);

  for ($i = 0; $i < $new_length; $i++) {
    $code .= rand(0, 1) ? chr(rand(65, 90)) : chr(rand(97, 122));
  }

  // Check if the generated code already exists.
  db_query("SELECT id FROM {url_shorten} WHERE short_url = '%s'", $code);

  if (db_affected_rows() != 0) {
    url_shorten_generate_code($length);
  }
  else {
    return $code;
  }
}

It simply creates a string depending on the $length that is being generated randomly. The characters generated are being randomly picked from the ASCII table in which 65-90 are alpha characters in uppercase and 97-122 in lowercase. It then calls the function if the generated code already exists.

As for the UI, it simply provides a textfield for the Long URL and another textfield for the Short URL which is optional. I've also implemented the tagging feature taken from the Taxonomy core module. It was the taxonomy_autocomplete() that I made use of. I was able to come up (not really come up but copied :D) with this:

<?php
function url_shorten_autocomplete($string = '') {
  $arr = drupal_explode_tags($string);

  $last_string = trim(array_pop($arr));
  $matches = array();
  if ($last_string != '') {
    $result = db_query_range("SELECT tag FROM {url_shorten_tags} WHERE LOWER(tag) LIKE LOWER('%%%s%%')", $last_string, 0, 10);
    $prefix = count($arr) ? implode(', ', $arr) .', ' : '';

    while ($row = db_fetch_object($result)) {
      $matches[$prefix . $row->tag] = check_plain($row->tag);
    }
  }

  drupal_json($matches);
}

I've added some minor features e.g. records referrer and IP address for every redirect. Most are copied from other codes but I think their combination still provided a good URL Shortener. :bigsmile: