<?php
// $Id: link.module,v 1.24 2008-03-31 06:50:42 quicksketch Exp $

/**
 * @file
 * Defines simple link field types.
 */

define('LINK_EXTERNAL', 'external');
define('LINK_INTERNAL', 'internal');
define('LINK_FRONT', 'front');
define('LINK_EMAIL', 'email');
define('LINK_DOMAINS', 'aero|arpa|biz|com|cat|coop|edu|gov|info|int|jobs|mil|museum|name|nato|net|org|pro|travel|mobi');

/**
 * Implementation of hook_field_info().
 */
function link_field_info() {
  return array(
    'link' => array('label' => 'Link'),
  );
}

/**
 * Implementation of hook_field_settings().
 */
function link_field_settings($op, $field) {
  switch ($op) {
    case 'form':
      $form = array(
        '#theme' => 'link_field_settings',
      );

      $form['url'] = array(
        '#type' => 'checkbox',
        '#title' => t('Optional URL'),
        '#default_value' => $field['url'],
        '#return_value' => 'optional',
        '#description' => t('If checked, the URL field is optional and submitting a title alone will be acceptable. If the URL is ommitted, the title will be displayed as plain text.'),
      );

      $title_options = array(
        'optional' => t('Optional Title'),
        'required' => t('Required Title'),
        'value' => t('Static Title: '),
        'none' => t('No Title'),
      );

      $form['title'] = array(
        '#type' => 'radios',
        '#title' => t('Link Title'),
        '#default_value' => isset($field['title']) ? $field['title'] : 'optional',
        '#options' => $title_options,
        '#description' => t('If the link title is optional or required, a field will be displayed to the end user. If the link title is static, the link will always use the same title. If <a href="http://drupal.org/project/token">token module</a> is installed, the static title value may use any other node field as its value.'),
      );

      $form['title_value'] = array(
        '#type' => 'textfield',
        '#default_value' => $field['title_value'],
        '#size' => '46',
      );

      // Add token module replacements if available
      if (module_exists('token')) {
        $form['tokens'] = array(
          '#type' => 'fieldset',
          '#collapsible' => TRUE,
          '#collapsed' => TRUE,
          '#title' => t('Placeholder tokens'),
          '#description' => t("The following placeholder tokens can be used in both paths and titles. When used in a path or title, they will be replaced with the appropriate values."),
        );
        $form['tokens']['help'] = array(
          '#value' => theme('token_help', 'node'),
        );

        $form['enable_tokens'] = array(
          '#type' => 'checkbox',
          '#title' => t('Allow tokens'),
          '#default_value' => isset($field['enable_tokens']) ? $field['enable_tokens'] : 1, 
          '#description' => t('Checking will allow users to enter tokens in URLs and Titles on the node edit form. This does not affect the field settings on this page.'),
        );
      }

      $form['display'] = array(
        '#tree' => true,
      );
      $form['display']['url_cutoff'] = array(
        '#type' => 'textfield',
        '#title' => t('URL Display Cutoff'),
        '#default_value' => isset($field['display']['url_cutoff']) ? $field['display']['url_cutoff'] : '80',
        '#description' => t('If the user does not include a title for this link, the URL will be used as the title. When should the link title be trimmed and finished with an elipsis (&hellip;)? Leave blank for no limit.'),
        '#maxlength' => 3,
        '#size' => 3,
      );

      $target_options = array(
        'default' => t('Default (no target attribute)'),
        '_top' => t('Open link in window root'),
        '_blank' => t('Open link in new window'),
        'user' => t('Allow the user to choose'),
      );
      $form['attributes'] = array(
        '#tree' => true,
      );
      $form['attributes']['target'] = array(
        '#type' => 'radios',
        '#title' => t('Link Target'),
        '#default_value' => $field['attributes']['target'] ? $field['attributes']['target'] : 'default',
        '#options' => $target_options,
      );
      $form['attributes']['rel'] = array(
        '#type' => 'textfield',
        '#title' => t('Rel Attribute'),
        '#description' => t('When output, this link will have this rel attribute. The most common usage is <a href="http://en.wikipedia.org/wiki/Nofollow">rel=&quot;nofollow&quot;</a> which prevents some search engines from spidering entered links.'),
        '#default_value' => $field['attributes']['rel'] ? $field['attributes']['rel'] : '',
      );
      $form['attributes']['class'] = array(
        '#type' => 'textfield',
        '#title' => t('Additional CSS Class'),
        '#description' => t('When output, this link will have have this class attribute. Multiple classes should be seperated by spaces.'),
        '#default_value' => isset($field['attributes']['class']) ? $field['attributes']['class'] : '',
      );
      return $form;

    case 'validate':
      if ($field['title'] == 'value' && empty($field['title_value'])) {
        form_set_error('title_value', t('A default title must be provided if the title is a static value'));
      }
      break;

    case 'save':
      return array('attributes', 'display', 'url', 'title', 'title_value', 'enable_tokens');

    case 'database columns':
      return array(
        'url' => array('type' => 'varchar', 'length' => 255, 'not null' => FALSE),
        'title' => array('type' => 'varchar', 'length' => 255, 'not null' => FALSE),
        'attributes' => array('type' => 'text', 'size' => 'medium', 'not null' => FALSE),
      );

    case 'filters':
      return array(
        'default' => array(
          'name' => t('URL'),
          'operator' => 'views_handler_operator_like',
          'handler' => 'views_handler_operator_like',
        ),
        'title' => array(
          'name' => t('Title'),
          'operator' => 'views_handler_operator_like',
          'handler' => 'views_handler_operator_like',
        ),
        'protocol' => array(
          'name' => t('Protocol'),
          'list' => drupal_map_assoc(variable_get('filter_allowed_protocols', array('http', 'https', 'ftp', 'news', 'nntp', 'telnet', 'mailto', 'irc', 'ssh', 'sftp', 'webcal'))),
          'operator' => 'views_handler_operator_or',
          'handler' => 'link_views_protocol_filter_handler',
        ),
      );

    case 'arguments':
      return array(
        'content: '. $field['field_name'] .'_url' => array(
          'name' => t('Link URL') .': '. t($field['widget']['label']) .' ('. $field['field_name'] .')',
          'handler' => 'link_views_argument_handler',
        ),
        'content: '. $field['field_name'] .'_title' => array(
          'name' => t('Link Title') .': '. t($field['widget']['label']) .' ('. $field['field_name'] .')',
          'handler' => 'link_views_argument_handler',
        ),
        'content: '. $field['field_name'] .'_target' => array(
          'name' => t('Link Target') .': '. t($field['widget']['label']) .' ('. $field['field_name'] .')',
          'handler' => 'link_views_argument_handler',
        ),
      );

  }
}

/**
 * Theme the settings form for the link field.
 */
function theme_link_field_settings($form) {
  $title_value = drupal_render($form['title_value']);
  $title_checkbox = drupal_render($form['title']['value']);

  // Set Static Title radio option to include the title_value textfield.
  $form['title']['value'] = array('#value' => '<div class="container-inline">'. $title_checkbox . $title_value .'</div>');

  // Reprint the title radio options with the included textfield.
  return drupal_render($form);
}

/**
 * Implementation of hook_field_is_empty().
 */
function link_content_is_empty($item, $field) {
  if (empty($item['title']) && empty($item['url'])) {
    return TRUE;
  }
  return FALSE;
}

/**
 * Implementation of hook_field().
 */
function link_field($op, &$node, $field, &$items, $teaser, $page) {
  switch ($op) {
    case 'load':
      foreach ($items as $delta => $item) {
        _link_load($items[$delta], $delta);
      }
      return $items;
      break;

    case 'validate':
      $optional_field_found = FALSE;
      foreach($items as $delta => $value) {
        _link_widget_validate($items[$delta],$delta, $field, $node, $optional_field_found);
      }

      if ($field['url'] == 'optional' && $field['title'] == 'optional' && $field['required'] && !$optional_field_found) {
        form_set_error($field['field_name'] .'][0][title', t('At least one title or URL must be entered.'));
      }
      break;

    case 'process form values':
      foreach($items as $delta => $value) {
        _link_widget_process($items[$delta],$delta, $field, $node);
      }
      break;

    case 'sanitize':
      foreach ($items as $delta => $value) {
        link_item_sanitize($items[$delta], $delta, $field, $node);
      }
      break;
  }
}

/**
 * Implementation of hook_widget_info().
 */
function link_widget_info() {
  return array(
    'link' => array(
      'label' => 'Text Fields for Title and URL',
      'field types' => array('link'),
      'multiple values' => CONTENT_HANDLE_CORE,
    ),
  );
}

/**
 * Implementation of hook_widget().
 */
function link_widget(&$form, &$form_state, $field, $items, $delta = 0) {
  $element = array(
    '#type' => $field['widget']['type'],
    '#default_value' => isset($items[$delta]) ? $items[$delta] : '',
  );
  return $element;
}


function _link_load(&$item, $delta = 0) {
  // Unserialize the attributes array.
  $item['attributes'] = unserialize($item['attributes']);
}

function _link_process(&$item, $delta = 0, $field, $node) {
  // Remove the target attribute if not selected.
  if (!$item['attributes']['target'] || $item['attributes']['target'] == "default") {
    unset($item['attributes']['target']);
  }
  // Trim whitespace from URL.
  $item['url'] = trim($item['url']);
  // Serialize the attributes array.
  $item['attributes'] = serialize($item['attributes']);

  // Don't save an invalid default value (e.g. 'http://').
  if ((isset($field['widget']['default_value'][$delta]['url']) && $item['url'] == $field['widget']['default_value'][$delta]['url']) && is_object($node)) {
    if (!link_validate_url($item['url'])) {
      unset($item['url']);
    }
  }
}

function _link_validate(&$item, $delta, $field, $node, &$optional_field_found) {
  if ($item['url'] && !(isset($field['widget']['default_value'][$delta]['url']) && $item['url'] == $field['widget']['default_value'][$delta]['url'] && !$field['required'])) {
    // Validate the link.
    if (link_validate_url(trim($item['url'])) == FALSE) {
      form_set_error($field['field_name'] .']['. $delta. '][url', t('Not a valid URL.'));
    }
    // Require a title for the link if necessary.
    if ($field['title'] == 'required' && strlen(trim($item['title'])) == 0) {
      form_set_error($field['field_name'] .']['. $delta. '][title', t('Titles are required for all links.'));
    }
  }
  // Require a link if we have a title.
  if ($field['url'] !== 'optional' && strlen($item['title']) > 0 && strlen(trim($item['url'])) == 0) {
    form_set_error($field['field_name'] .']['. $delta. '][url', t('You cannot enter a title without a link url.'));
  }
  // In a totally bizzaro case, where URLs and titles are optional but the field is required, ensure there is at least one link.
  if ($field['url'] == 'optional' && $field['title'] == 'optional' && (strlen(trim($item['url'])) != 0 || strlen(trim($item['title'])) != 0)) {
    $optional_field_found = TRUE;
  }
}

/**
 * Cleanup user-entered values for a link field according to field settings.
 * 
 * @param $item
 *   A single link item, usually containing url, title, and attributes.
 * @param $delta
 *   The delta value if this field is one of multiple fields.
 * @param $field
 *   The CCK field definition.
 * @param $node
 *   The node containing this link.
 */
function _link_sanitize(&$item, $delta, &$field, &$node) {
  // Replace URL tokens.
  if (module_exists('token') && $field['enable_tokens']) {
    $node = node_load($node->nid); // Necessary for nodes in views.
    $item['url'] = token_replace($item['url'], 'node', $node);
  }

  $type = link_validate_url($item['url']);
  $url = link_cleanup_url($item['url']);

  // Seperate out the anchor if any.
  if (strpos($url, '#') !== FALSE) {
    $item['fragment'] = substr($url, strpos($url, '#') + 1);
    $url = substr($url, 0, strpos($url, '#'));
  }
  // Seperate out the query string if any.
  if (strpos($url, '?') !== FALSE) {
    $item['query'] = substr($url, strpos($url, '?') + 1);
    $url = substr($url, 0, strpos($url, '?'));
  }
  // Save the new URL without the anchor or query.
  $item['url'] = $url;

  // Create a shortened URL for display.
  $display_url = $type == LINK_EMAIL ? str_replace('mailto:', '', $url) : url($url, array('query' => $item['query'], 'fragment' => $item['fragment'], 'absolute' => TRUE));
  if ($field['display']['url_cutoff'] && strlen($display_url) > $field['display']['url_cutoff']) {
    $display_url = substr($display_url, 0, $field['display']['url_cutoff']) . "...";
  }
  $item['display_url'] = $display_url;

  // Use the title defined at the field level.
  if ($field['title'] == 'value' && strlen(trim($field['title_value']))) {
    $title = $field['title_value'];
  }
  // Use the title defined by the user at the widget level.
  else {
    $title = $item['title'];
  }
  // Replace tokens.
  if (module_exists('token') && ($field['title'] == 'value' || $field['enable_tokens'])) {
    $node = node_load($node->nid); // Necessary for nodes in views.
    $title = token_replace($title, 'node', $node);
  }
  $item['display_title'] = empty($title) ? $item['display_url'] : $title;

  // Add attributes defined at the widget level
  $attributes = array();
  if (is_array($item['attributes'])) {
    foreach($item['attributes'] as $attribute => $attbvalue) {
      if (isset($item['attributes'][$attribute]) && $field['attributes'][$attribute] == 'user') {
        $attributes[$attribute] = $attbvalue;
       }
     }
   }
  // Add attributes defined at the field level
  if (is_array($field['attributes'])) {
    foreach($field['attributes'] as $attribute => $attbvalue) {
      if (!empty($attbvalue) && $attbvalue != 'default' && $attbvalue != 'user') {
        $attributes[$attribute] = $attbvalue;
      }
    }
  }
  $item['attributes'] = $attributes;

  // Add the widget label.
  $item['label'] = $field['widget']['label'];
}

/**
 * Implementation of hook_theme().
 */
function link_theme() {
  return array(
    'link_field_settings' => array(
      'arguments' => array('element' => NULL),
    ),
    'link_formatter_default' => array(
      'arguments' => array('element' => NULL),
    ),
    'link_formatter_plain' => array(
      'arguments' => array('element' => NULL),
    ),
    'link_formatter_short' => array(
      'arguments' => array('element' => NULL),
    ),
    'link_formatter_label' => array(
      'arguments' => array('element' => NULL),
    ),
    'link' => array(
      'arguments' => array('element' => NULL),
    ),
  );
}

/**
 * FAPI theme for an individual text elements.
 *
 * The textfield or textarea is already rendered by the
 * textfield or textarea themes and the html output
 * lives in $element['#children']. Override this theme to
 * make custom changes to the output.
 *
 * $element['#field_name'] contains the field name
 * $element['#delta']  is the position of this element in the group
 */
function theme_link($element) {
  drupal_add_css(drupal_get_path('module', 'link') .'/link.css');

  if ($element['#delta'] == 0) {

  }

  $output = '';
  $output .= '<div class="link-field-subrow clear-block">';
  if ($element['title']) {
    $output .= '<div class="link-field-title link-field-column">' . theme('textfield', $element['title']) . '</div>';
  }
  $output .= '<div class="link-field-url' . ($element['title'] ? ' link-field-column' : '') . '">' . theme('textfield', $element['url']) . '</div>';
  $output .= '</div>';
  if ($element['attributes']) {
    $output .= '<div class="link-attributes">' . theme('form_element', $element['attributes'], $element['attributes']['#value']) . '</div>';
  }
  return $output;
}

/*
 * Implementation of FAPI hook_elements().
 *
 * Any FAPI callbacks needed for individual widgets can be declared here,
 * and the element will be passed to those callbacks for processing.
 *
 * Drupal will automatically theme the element using a theme with
 * the same name as the hook_elements key.
 *
 * Autocomplete_path is not used by text_widget but other widgets can use it
 * (see nodereference and userreference).
 */
function link_elements() {
  $elements = array();
  $elements['link'] =  array(
    '#input' => TRUE,
    '#columns' => array('url', 'title'),
    '#delta' => 0,
    '#process' => array('link_process'),
    '#autocomplete_path' => FALSE,
    '#theme' => 'link_widget_form_row',
  );
  return $elements;
}

/**
 * Process the link type element before displaying the field.
 *
 * Build the form element. When creating a form using FAPI #process,
 * note that $element['#value'] is already set.
 *
 * The $fields array is in $form['#field_info'][$element['#field_name']].
 */
function link_process($element, $edit, $form_state, $form) {
   $field = $form['#field_info'][$element['#field_name']];
   $delta = $element['#delta'];
   $element['url'] = array(
     '#type' => 'textfield',
     '#maxlength' => '255',
     '#title' => t('URL'),
     '#description' => $element['#description'],
     '#required' => ($delta == 0 && $field['title'] != 'optional') ? $element['#required'] : FALSE,
     '#default_value' => isset($element['#value']['url']) ? $element['#value']['url'] : NULL,
   );
   if ($field['title'] != 'none') {
     $element['title'] = array(
       '#type' => 'textfield',
       '#maxlength' => '255',
       '#title' => t('Title'),
       '#required' => ($delta == 0 && $field['title'] == 'required') ? $field['required'] : FALSE,
       '#default_value' => isset($element['#value']['title']) ? $element['#value']['title'] : NULL,
     );

   }
   if ($field['attributes']['target'] == 'user') {
     $element['attributes']['target'] = array(
       '#type' => 'checkbox',
       '#title' => t('Open URL in a New Window'),
       '#return_value' => "_blank",
     );
   }
   return $element;
}

/**
 * Implementation of hook_field_formatter_info().
 */
function link_field_formatter_info() {
  return array(
    'default' => array(
      'label' => t('Default, as link with title'),
      'field types' => array('link'),
      'multiple values' => CONTENT_HANDLE_CORE,
    ),
    'plain' => array(
      'label' => t('Plain, as the text URL'),
      'field types' => array('link'),
      'multiple values' => CONTENT_HANDLE_CORE,
    ),
    'short' => array(
      'label' => t('Short, as link with title "Link"'),
      'field types' => array('link'),
      'multiple values' => CONTENT_HANDLE_CORE,
    ),
    'label' => array(
      'label' => t('Label, as link with label as title'),
      'field types' => array('link'),
      'multiple values' => CONTENT_HANDLE_CORE,
    ),
  );
}

/**
 * Theme function for 'default' text field formatter.
 */
function theme_link_formatter_default($element) {
  // Display a normal link if both title and URL are available.
  if (!empty($element['#item']['display_title']) && !empty($element['#item']['url'])) {
    return l($element['#item']['display_title'], $element['#item']['url'], $element['#item']);
  }
  // If only a title, display the title.
  else {
    return check_plain($element['#item']['display_title']);
  }
}

/**
 * Theme function for 'plain' text field formatter.
 */
function theme_link_formatter_plain($element) {
  return empty($element['#item']['url']) ? check_plain($element['#item']['title']) : check_plain($element['#item']['url']);
}

/**
 * Theme function for 'short' text field formatter.
 */
function theme_link_formatter_short($element) {
  return $element['#item']['url'] ? l(t('Link'), $element['#item']['url'], $element['#item']) : '';
}

/**
 * Theme function for 'short' text field formatter.
 */
function theme_link_formatter_label($element) {
  return $element['#item']['url'] ? l($element['#item']['label'], $element['#item']['url'], $element['#item']) : '';
}
/**
 * Views module argument handler for link fields
 */
function link_views_argument_handler($op, &$query, $argtype, $arg = '') {
  if ($op == 'filter') {
    $field_name = substr($argtype['type'], 9, strrpos($argtype['type'], '_') - 9);
    $column = substr($argtype['type'], strrpos($argtype['type'], '_') + 1);
  }
  else {
    $field_name = substr($argtype, 9, strrpos($argtype, '_') - 9);
    $column = substr($argtype, strrpos($argtype, '_') + 1);
  }

  // Right now the only attribute we support in views in 'target', but
  // other attributes of the href tag could be added later.
  if ($column == 'target') {
    $attribute = $column;
    $column = 'attributes';
  }

  $field = content_fields($field_name);
  $db_info = content_database_info($field);
  $main_column = $db_info['columns'][$column];

  // The table name used here is the Views alias for the table, not the actual
  // table name.
  $table = 'node_data_'. $field['field_name'];

  switch ($op) {
    case 'summary':
      $query->ensure_table($table);
      $query->add_field($main_column['column'], $table);
      return array('field' => $table .'.'. $main_column['column']);
      break;

    case 'filter':
      $query->ensure_table($table);
      if ($column == 'attributes') {
        // Because attributes are stored serialized, our only option is to also
        // serialize the data we're searching for and use LIKE to find similar data.
        $query->add_where($table .'.'. $main_column['column'] ." LIKE '%%%s%'", serialize($attribute) . serialize($arg));
      }
      else {
        $query->add_where($table .'.'. $main_column['column'] ." = '%s'", $arg);
      }
      break;

    case 'link':
      $item = array();
      foreach ($db_info['columns'] as $column => $attributes) {
        $view_column_name = $attributes['column'];
        $item[$column] = $query->$view_column_name;
      }

      return l(content_format($field, $item, 'plain'), $arg .'/'. $query->$main_column['column'], array(), NULL, NULL, FALSE, TRUE);

    case 'sort':
      break;

    case 'title':
      $item = array(key($db_info['columns']) => $query);
      return content_format($field, $item);
      break;
  }
}

/**
 * Views modules filter handler for link protocol filtering
 */
function link_views_protocol_filter_handler($op, $filter, $filterinfo, &$query) {
  global $db_type;

  $protocols = $filter['value'];
  $field = $filterinfo['field'];
  // $table is not the real table name but the views alias.
  $table = 'node_data_'. $filterinfo['content_field']['field_name'];

  foreach ($protocols as $protocol) {
    // Simple case, the URL begins with the specified protocol.
    $condition = $table .'.'. $field .' LIKE \''. $protocol .'%\'';

    // More complex case, no protocol specified but is automatically cleaned up
    // by link_cleanup_url(). RegEx is required for this search operation.
    if ($protocol == 'http') {
      if ($db_type == 'pgsql') {
        // PostGreSQL code has NOT been tested. Please report any problems to the link issue queue.
        // pgSQL requires all slashes to be double escaped in regular expressions.
        // See http://www.postgresql.org/docs/8.1/static/functions-matching.html#FUNCTIONS-POSIX-REGEXP
        $condition .= ' OR '. $table .'.'. $field .' ~* \''. '^(([a-z0-9]([a-z0-9\\-_]*\\.)+)('. LINK_DOMAINS .'|[a-z][a-z]))' .'\''; 
      }
      else {
        // mySQL requires backslashes to be double (triple?) escaped within character classes.
        // See http://dev.mysql.com/doc/refman/5.0/en/string-comparison-functions.html#operator_regexp
        $condition .= ' OR '. $table .'.'. $field .' REGEXP \''. '^(([a-z0-9]([a-z0-9\\\-_]*\.)+)('. LINK_DOMAINS .'|[a-z][a-z]))' .'\''; 
      }
    }

    $where_conditions[] = $condition;
  }

  $query->ensure_table($table);
  $query->add_where(implode(' '. $filter['operator'] .' ', $where_conditions));
}

/**
 * Forms a valid URL if possible from an entered address.
 * Trims whitespace and automatically adds an http:// to addresses without a protocol specified
 *
 * @param string $url
 * @param string $protocol The protocol to be prepended to the url if one is not specified
 */
function link_cleanup_url($url, $protocol = "http") {
  $url = trim($url);
  $type = link_validate_url($url);

  if ($type == LINK_EXTERNAL) {
    // Check if there is no protocol specified.
    $protocol_match = preg_match("/^([a-z0-9][a-z0-9\.\-_]*:\/\/)/i",$url);
    if (empty($protocol_match)) {
      // But should there be? Add an automatic http:// if it starts with a domain name.
      $domain_match = preg_match('/^(([a-z0-9]([a-z0-9\-_]*\.)+)('. LINK_DOMAINS .'|[a-z]{2}))/i',$url);
      if (!empty($domain_match)) {
        $url = $protocol."://".$url;
      }
    }
  }

  return $url;
}

/**
 * A lenient verification for URLs. Accepts all URLs following RFC 1738 standard
 * for URL formation and all email addresses following the RFC 2368 standard for
 * mailto address formation.
 *
 * @param string $text
 * @return mixed Returns boolean FALSE if the URL is not valid. On success, returns an object with
 * the following attributes: protocol, hostname, ip, and port.
 */
function link_validate_url($text) {

  $allowed_protocols = variable_get('filter_allowed_protocols', array('http', 'https', 'ftp', 'news', 'nntp', 'telnet', 'mailto', 'irc', 'ssh', 'sftp', 'webcal'));

  $protocol = '((' . implode("|", $allowed_protocols) . '):\/\/)';
  $authentication = '([a-z0-9]+(:[a-z0-9]+)?@)';
  $domain = '((([a-z0-9]([a-z0-9\-_\[\]]*\.))+)('. LINK_DOMAINS .'|[a-z]{2}))';
  $ipv4 = '([0-9]{1,3}(\.[0-9]{1,3}){3})'; 
  $ipv6 = '([0-9a-fA-F]{1,4}(\:[0-9a-fA-F]{1,4}){7})'; 
  $port = '(:([0-9]{1,5}))';

  // Pattern specific to eternal links.
  $external_pattern = '/^' . $protocol . '?'. $authentication . '?' . '(' . $domain . '|' . $ipv4 . '|' . $ipv6 . ' |localhost)' . $port . '?';

  // Pattern specific to internal links.
  $internal_pattern = "/^([a-z0-9_\-+\[\]]+)";

  $directories = "(\/[a-z0-9_\-\.~+%=&,$'():;*@\[\]]*)*";
  $query = "(\/?\?([?a-z0-9+_\-\.\/%=&,$'():;*@\[\]]*))";
  $anchor = "(#[a-z0-9_\-\.~+%=&,$'():;*@\[\]]*)";

  // The rest of the path for a standard URL.
  $end = $directories . '?' . $query . '?' .  $anchor . '?' . '$/i';

  $user = '[a-zA-Z0-9_\-\.\+\^!#\$%&*+\/\=\?\`\|\{\}~\'\[\]]+';
  $email_pattern = '/^mailto:' . $user . '@' . '(' . $domain . '|' . $ipv4 .'|'. $ipv6 . '|localhost)' . $query . '$/';

  if (preg_match($external_pattern . $end, $text)) {
    return LINK_EXTERNAL;
  }
  elseif (preg_match($internal_pattern . $end, $text)) {
    return LINK_INTERNAL;
  }
  elseif (in_array('mailto', $allowed_protocols) && preg_match($email_pattern, $text)) {
    return LINK_EMAIL;
  }
  elseif (strpos($text, '<front>') === 0) {
    return LINK_FRONT;
  }
  return FALSE;
}