source: sipes/modules_contrib/link/link.module @ 6e81fb4

<?php

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

define('LINK_EXTERNAL', 'external');
define('LINK_INTERNAL', 'internal');
define('LINK_FRONT', 'front');
define('LINK_EMAIL', 'email');
define('LINK_NEWS', 'news');
define('LINK_DOMAINS', 'aero|arpa|asia|biz|com|cat|coop|edu|gov|info|int|jobs|mil|museum|name|nato|net|org|pro|travel|mobi|local');
// There are many other characters which are legal other than simply a-z - this includes them.
// html_entity_decode() is buggy in php 4 - we'll put it back here for D7 when 5.x is assumed.
/*define('LINK_ICHARS', (string) html_entity_decode(implode("", array(
    "&#x00E6;", // Ê
    "&#x00C6;", // Æ
    "&#x00F8;", // Þ
    "&#x00D8;", // Ø
    "&#x00E5;", // å
    "&#x00C5;", // Å
    "&#x00E4;", // À
    "&#x00C4;", // Ä
    "&#x00F6;", // ö
    "&#x00D6;", // Ö
    "&#x00FC;", // Ì
    "&#x00DC;", // Ü
  )), ENT_QUOTES, 'UTF-8'));*/

define('LINK_TARGET_DEFAULT', 'default');
define('LINK_TARGET_NEW_WINDOW', '_blank');
define('LINK_TARGET_TOP', '_top');
define('LINK_TARGET_USER', 'user');

/**
 * Maximum URLs length.
 */
define('LINK_URL_MAX_LENGTH', 2048);

/**
 * Implementation of hook_field_info().
 */
function link_field_info() {
  return array(
    'link' => array(
      'label' => t('Link'),
      'description' => t('Store a title, href, and attributes in the database to assemble a link.'),
    ),
  );
}

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

      $form['validate_url'] = array(
        '#type' => 'checkbox',
        '#title' => t('Validate URL'),
        '#default_value' => isset($field['validate_url']) && ($field['validate_url'] !== '') ? $field['validate_url'] : TRUE,
        '#description' => t('If checked, the URL field will be verified as a valid URL during validation.'),
      );

      $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 omitted, 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'] !== '') ? $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. Static and token-based titles may include most inline XHTML tags such as <em>strong</em>, <em>em</em>, <em>img</em>, <em>span</em>, etc.'),
      );

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

      $form['title_value_visibility'] = array(
        '#type' => 'checkbox',
        '#title' => t('Hide title if URL is empty'),
        '#default_value' => isset($field['title_value_visibility']) ? $field['title_value_visibility'] : 0,
        '#description' => t('Checking will hide the title when a URL is empty, leave un-checked to always display the title.'),
      );

      // 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'),
        );

        $form['enable_tokens'] = array(
          '#type' => 'checkbox',
          '#title' => t('Allow user-entered tokens'),
          '#default_value' => isset($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(
        LINK_TARGET_DEFAULT => t('Default (no target attribute)'),
        LINK_TARGET_TOP => t('Open link in window root'),
        LINK_TARGET_NEW_WINDOW => t('Open link in new window'),
        LINK_TARGET_USER => t('Allow the user to choose'),
      );
      $form['attributes'] = array(
        '#tree' => TRUE,
      );
      $form['attributes']['target'] = array(
        '#type' => 'radios',
        '#title' => t('Link Target'),
        '#default_value' => empty($field['attributes']['target']) ? LINK_TARGET_DEFAULT : $field['attributes']['target'],
        '#options' => $target_options,
      );
      $form['attributes']['rel'] = array(
        '#type' => 'textfield',
        '#title' => t('Rel Attribute'),
        '#description' => t('When output, this link will have this rel attribute. The most common usage is <a href="http://en.wikipedia.org/wiki/Nofollow">rel=&quot;nofollow&quot;</a> which prevents some search engines from spidering entered links.'),
        '#default_value' => empty($field['attributes']['rel']) ? '' : $field['attributes']['rel'],
        '#field_prefix' => 'rel = "',
        '#field_suffix' => '"',
        '#size' => 20,
      );
      $form['attributes']['class'] = array(
        '#type' => 'textfield',
        '#title' => t('Additional CSS Class'),
        '#description' => t('When output, this link will have this class attribute. Multiple classes should be separated by spaces.'),
        '#default_value' => empty($field['attributes']['class']) ? '' : $field['attributes']['class'],
      );
      $form['attributes']['title'] = array(
        '#title' => t("Link 'title' Attribute"),
        '#type' => 'textfield',
        '#field_prefix' => 'title = "',
        '#field_suffix' => '"',
        '#description' => t('When output, links will use this "title" attribute (when different from the link text). Read <a href="http://www.w3.org/TR/WCAG10-HTML-TECHS/#links">WCAG 1.0 Guidelines</a> for links comformances. Tokens values will be evaluated.'),
        '#default_value' => empty($field['attributes']['title']) ? '' : $field['attributes']['title'],
      );
      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', 'title_value_visibility', 'enable_tokens', 'validate_url');

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

    case 'views data':
      module_load_include('inc', 'link', 'views/link.views');
      return link_views_content_field_data($field);
  }
}

/**
 * Implementation of hook_content_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, $page) {
  module_load_include('inc', 'link');
  switch ($op) {
    case 'load':
      return _link_load($field, $items);

    case 'validate':
      $optional_field_found = FALSE;
      if ($field['validate_url'] !== 0 || is_null($field['validate_url']) || !isset($field['validate_url'])) {
        foreach ($items as $delta => $value) {
          _link_validate($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 'presave':
    case 'update':
      foreach ($items as $delta => $value) {
        _link_process($items[$delta], $delta, $field, $node);
      }
      break;

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

/**
 * Implementation of hook_widget_info().
 */
function link_widget_info() {
  return array(
    'link' => array(
      'label' => 'Link',
      '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] : '',
    '#title' => $field['widget']['label'],
    '#weight' => $field['widget']['weight'],
    '#description' => $field['widget']['description'],
    '#required' => $field['required'],
    '#field' => $field,
  );
  return $element;
}

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

/**
 * Implementation of hook_elements().
 */
function link_elements() {
  $elements = array();
  $elements['link'] =  array(
    '#input' => TRUE,
    '#process' => array('link_process'),
  );
  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) {
   module_load_include('inc', 'link');
   $field = $form['#field_info'][$element['#field_name']];
   $delta = $element['#delta'];
   $element['url'] = array(
     '#type' => 'textfield',
     '#maxlength' => LINK_URL_MAX_LENGTH,
     '#title' => t('URL'),
     '#description' => $element['#description'],
     '#required' => ($delta == 0 && $field['url'] !== 'optional') ? $element['#required'] : FALSE,
     '#default_value' => isset($element['#value']['url']) ? $element['#value']['url'] : NULL,
   );
   if ($field['title'] != 'none' && $field['title'] != 'value') {
     $element['title'] = array(
       '#type' => 'textfield',
       '#maxlength' => '255',
       '#title' => t('Title'),
       '#required' => ($delta == 0 && $field['title'] == 'required') ? $field['required'] : FALSE,
       '#default_value' => isset($element['#value']['title']) ? $element['#value']['title'] : NULL,
     );
   }

   // Initialize field attributes as an array if it is not an array yet.
   if (!is_array($field['attributes'])) {
     $field['attributes'] = array();
   }
   // Add default atrributes.
   $field['attributes'] += _link_default_attributes();
   $attributes = isset($element['#value']['attributes']) ? $element['#value']['attributes'] : $field['attributes'];
   if (!empty($field['attributes']['target']) && $field['attributes']['target'] == LINK_TARGET_USER) {
     $element['attributes']['target'] = array(
       '#type' => 'checkbox',
       '#title' => t('Open URL in a New Window'),
       '#return_value' => LINK_TARGET_NEW_WINDOW,
       '#default_value' => $attributes['target'],
     );
   }
   return $element;
}

/**
 * Implementation of hook_field_formatter_info().
 */
function link_field_formatter_info() {
  return array(
    'default' => array(
      'label' => t('Title, as link (default)'),
      'field types' => array('link'),
      'multiple values' => CONTENT_HANDLE_CORE,
    ),
    'title_plain' => array(
      'label' => t('Title, as plain text'),
      'field types' => array('link'),
      'multiple values' => CONTENT_HANDLE_CORE,
    ),
    'url' => array(
      'label' => t('URL, as link'),
      'field types' => array('link'),
      'multiple values' => CONTENT_HANDLE_CORE,
    ),
    'plain' => array(
      'label' => t('URL, as plain text'),
      'field types' => array('link'),
      'multiple values' => CONTENT_HANDLE_CORE,
    ),
    'absolute' => array(
      'label' => t('URL, as absolute 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,
    ),
    'separate' => array(
      'label' => t('Separate title and URL'),
      'field types' => array('link'),
      'multiple values' => CONTENT_HANDLE_CORE,
    ),
  );
}

function link_token_list($type = 'all') {
  if ($type == 'field' || $type == 'all') {
    $tokens = array();

    $tokens['link']['url'] = t("Link URL");
    $tokens['link']['title'] = t("Link title");
    $tokens['link']['view'] = t("Formatted html link");
    $tokens['link']['host'] = t("Link host");

    return $tokens;
  }
}

function link_token_values($type, $object = NULL) {
  if ($type == 'field') {
    $item = $object[0];

    $tokens['url'] = $item['url'];
    $tokens['title'] = $item['title'];
    $tokens['view'] = isset($item['view']) ? $item['view'] : '';
    $host = @parse_url($item['url']);
    $tokens['host'] = isset($host['host']) ? $host['host'] : '';

    return $tokens;
  }
}

/**
 * Implementation of hook_views_api().
 */
function link_views_api() {
  return array(
    'api' => 2,
    'path' => drupal_get_path('module', 'link') .'/views',
  );
}
/**
 * Implements hook_migrate_api().
 */
function link_migrate_api() {
  return array('api' => 2);
}

/**
 * Implements hook_content_generate().
 */
function link_content_generate($node, $field) {
  if (content_handle('widget', 'multiple values', $field) == CONTENT_HANDLE_MODULE) {
    return content_devel_multiple('_link_content_generate', $node, $field);
  }
  else {
    return _link_content_generate($node, $field);
  }
}

/**
 * Generates random link data for devel generate.
 */
function _link_content_generate($node, $field) {
  // Have to use title = true to get only one word, but then want to force it to lowercase.
  $url = url('http://www.example.com/' . drupal_strtolower(devel_create_greeking(1, TRUE)));
  $title = devel_create_greeking(mt_rand(1, 3), TRUE);

  return array(
    'url' => $url,
    'title' => $title,
    'attributes' => array(),
  );
}