<?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|build|com|cat|ceo|coop|edu|gov|info|int|jobs|mil|museum|name|nato|net|org|post|pro|tel|travel|mobi|local|xxx');

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

/**
 * Maximum URLs length - needs to match value in link.install.
 */
define('LINK_URL_MAX_LENGTH', 2048);

/**
 * Implements hook_field_info().
 */
function link_field_info() {
  return array(
    'link_field' => array(
      'label' => t('Link'),
      'description' => t('Store a title, href, and attributes in the database to assemble a link.'),
      'settings' => array(
        'attributes' => _link_default_attributes(),
        'url' => 0,
        'title' => 'optional',
        'title_value' => '',
        'title_maxlength' => 128,
        'enable_tokens' => 1,
        'display' => array(
          'url_cutoff' => 80,
        ),
      ),
      'instance_settings' => array(
        'attributes' => _link_default_attributes(),
        'url' => 0,
        'title' => 'optional',
        'title_value' => '',
        'title_label_use_field_label' => FALSE,
        'title_maxlength' => 128,
        'enable_tokens' => 1,
        'display' => array(
          'url_cutoff' => 80,
        ),
        'validate_url' => 1,
        'absolute_url' => 1,
      ),
      'default_widget' => 'link_field',
      'default_formatter' => 'link_default',
      // Support hook_entity_property_info() from contrib "Entity API".
      'property_type' => 'field_item_link',
      'property_callbacks' => array('link_field_property_info_callback'),
    ),
  );
}

/**
 * Implements hook_field_instance_settings_form().
 */
function link_field_instance_settings_form($field, $instance) {
  $form = array(
    '#element_validate' => array('link_field_settings_form_validate'),
  );

  $form['absolute_url'] = array(
    '#type' => 'checkbox',
    '#title' => t('Absolute URL'),
    '#default_value' => isset($instance['settings']['absolute_url']) && ($instance['settings']['absolute_url'] !== '') ? $instance['settings']['absolute_url'] : TRUE,
    '#description' => t('If checked, the URL will always render as an absolute URL.'),
  );

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

  $form['url'] = array(
    '#type' => 'checkbox',
    '#title' => t('Optional URL'),
    '#default_value' => isset($instance['settings']['url']) ? $instance['settings']['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'),
  );

  $form['title'] = array(
    '#type' => 'radios',
    '#title' => t('Link Title'),
    '#default_value' => isset($instance['settings']['title']) ? $instance['settings']['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 entity 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.'),
  );

  $form['title_value'] = array(
    '#type' => 'textfield',
    '#title' => t('Static title'),
    '#default_value' => isset($instance['settings']['title_value']) ? $instance['settings']['title_value'] : '',
    '#description' => t('This title will always be used if &ldquo;Static Title&rdquo; is selected above.'),
  );

  $form['title_label_use_field_label'] = array(
    '#type' => 'checkbox',
    '#title' => t('Use field label as the label for the title field'),
    '#default_value' => isset($instance['settings']['title_label_use_field_label']) ? $instance['settings']['title_label_use_field_label'] : FALSE,
    '#description' => t('If this is checked the field label will be hidden.'),
  );

  $form['title_maxlength'] = array(
    '#type' => 'textfield',
    '#title' => t('Max length of title field'),
    '#default_value' => isset($instance['settings']['title_maxlength']) ? $instance['settings']['title_maxlength'] : '128',
    '#description' => t('Set a maximum length on the title field (applies only if Link Title is optional or required).  The maximum limit is 255 characters.'),
    '#maxlength' => 3,
    '#size' => 3,
  );

  if (module_exists('token')) {
    // Add token module replacements fields.
    $form['enable_tokens'] = array(
      '#type' => 'checkbox',
      '#title' => t('Allow user-entered tokens'),
      '#default_value' => isset($instance['settings']['enable_tokens']) ? $instance['settings']['enable_tokens'] : 1,
      '#description' => t('Checking will allow users to enter tokens in URLs and Titles on the entity edit form. This does not affect the field settings on this page.'),
    );

    $entity_info = entity_get_info($instance['entity_type']);
    $form['tokens_help'] = array(
      '#theme' => 'token_tree',
      '#token_types' => array($entity_info['token type']),
      '#global_types' => TRUE,
      '#click_insert' => TRUE,
      '#dialog' => TRUE,
    );
  }

  $form['display'] = array(
    '#tree' => TRUE,
  );
  $form['display']['url_cutoff'] = array(
    '#type' => 'textfield',
    '#title' => t('URL Display Cutoff'),
    '#default_value' => isset($instance['settings']['display']['url_cutoff']) ? $instance['settings']['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,
  );
  $form['attributes']['target'] = array(
    '#type' => 'radios',
    '#title' => t('Link Target'),
    '#default_value' => empty($instance['settings']['attributes']['target']) ? LINK_TARGET_DEFAULT : $instance['settings']['attributes']['target'],
    '#options' => $target_options,
  );
  $form['attributes']['rel'] = array(
    '#type' => 'textfield',
    '#title' => t('Rel Attribute'),
    '#description' => t('When output, this link will have this rel attribute. The most common usage is <a href="http://en.wikipedia.org/wiki/Nofollow">rel=&quot;nofollow&quot;</a> which prevents some search engines from spidering entered links.'),
    '#default_value' => empty($instance['settings']['attributes']['rel']) ? '' : $instance['settings']['attributes']['rel'],
    '#field_prefix' => 'rel = "',
    '#field_suffix' => '"',
    '#size' => 20,
  );
  $rel_remove_options = array(
    'default' => t('Keep rel as set up above (untouched/default)'),
    'rel_remove_external' => t('Remove rel if given link is external'),
    'rel_remove_internal' => t('Remove rel if given link is internal'),
  );
  $form['rel_remove'] = array(
    '#type' => 'radios',
    '#title' => t('Remove rel attribute automatically'),
    '#default_value' => !isset($instance['settings']['rel_remove']) ? 'default' : $instance['settings']['rel_remove'],
    '#description' => t('Turn on/off if rel attribute should be removed automatically, if user given link is internal/external'),
    '#options' => $rel_remove_options,
  );
  $form['attributes']['configurable_class'] = array(
    '#title' => t("Allow the user to enter a custom link class per link"),
    '#type' => 'checkbox',
    '#default_value' => empty($instance['settings']['attributes']['configurable_class']) ? '' : $instance['settings']['attributes']['configurable_class'],
  );
  $form['attributes']['class'] = array(
    '#type' => 'textfield',
    '#title' => t('Additional CSS Class'),
    '#description' => t('When output, this link will have this class attribute. Multiple classes should be separated by spaces.'),
    '#default_value' => empty($instance['settings']['attributes']['class']) ? '' : $instance['settings']['attributes']['class'],
  );
  $form['attributes']['configurable_title'] = array(
    '#title' => t("Allow the user to enter a link 'title' attribute"),
    '#type' => 'checkbox',
    '#default_value' => empty($instance['settings']['attributes']['configurable_title']) ? '' : $instance['settings']['attributes']['configurable_title'],
  );
  $form['attributes']['title'] = array(
    '#title' => t("Default link 'title' Attribute"),
    '#type' => 'textfield',
    '#description' => t('When output, links will use this "title" attribute if the user does not provide one and when different from the link text. Read <a href="http://www.w3.org/TR/WCAG10-HTML-TECHS/#links">WCAG 1.0 Guidelines</a> for links comformances. Tokens values will be evaluated.'),
    '#default_value' => empty($instance['settings']['attributes']['title']) ? '' : $instance['settings']['attributes']['title'],
    '#field_prefix' => 'title = "',
    '#field_suffix' => '"',
    '#size' => 20,
  );
  return $form;
}

/**
 * #element_validate handler for link_field_instance_settings_form().
 */
function link_field_settings_form_validate($element, &$form_state, $complete_form) {
  if ($form_state['values']['instance']['settings']['title'] === 'value' && empty($form_state['values']['instance']['settings']['title_value'])) {
    form_set_error('title_value', t('A default title must be provided if the title is a static value.'));
  }
  if (!empty($form_state['values']['instance']['settings']['display']['url_cutoff']) && !is_numeric($form_state['values']['instance']['settings']['display']['url_cutoff'])) {
    form_set_error('display', t('URL Display Cutoff value must be numeric.'));
  }
  if (empty($form_state['values']['instance']['settings']['title_maxlength'])) {
    form_set_value($element['title_maxlength'], '128', $form_state);
  }
  elseif (!is_numeric($form_state['values']['instance']['settings']['title_maxlength'])) {
    form_set_error('title_maxlength', t('The max length of the link title must be numeric.'));
  }
  elseif ($form_state['values']['instance']['settings']['title_maxlength'] > 255) {
    form_set_error('title_maxlength', t('The max length of the link title cannot be greater than 255 characters.'));
  }
}

/**
 * Implements hook_field_is_empty().
 */
function link_field_is_empty($item, $field) {
  return empty($item['title']) && empty($item['url']);
}

/**
 * Implements hook_field_load().
 */
function link_field_load($entity_type, $entities, $field, $instances, $langcode, &$items, $age) {
  foreach ($entities as $id => $entity) {
    foreach ($items[$id] as $delta => $item) {
      $items[$id][$delta]['attributes'] = _link_load($field, $item, $instances[$id]);
    }
  }
}

/**
 * Implements hook_field_validate().
 */
function link_field_validate($entity_type, $entity, $field, $instance, $langcode, $items, &$errors) {
  $optional_field_found = FALSE;
  if ($instance['settings']['validate_url'] !== 0 || is_null($instance['settings']['validate_url']) || !isset($instance['settings']['validate_url'])) {
    foreach ($items as $delta => $value) {
      _link_validate($items[$delta], $delta, $field, $entity, $instance, $langcode, $optional_field_found, $errors);
    }
  }

  if ($instance['settings']['url'] === 'optional' && $instance['settings']['title'] === 'optional' && $instance['required'] && !$optional_field_found) {
    $errors[$field['field_name']][$langcode][0][] = array(
      'error' => 'link_required',
      'message' => t('At least one title or URL must be entered.'),
      'error_element' => array('url' => FALSE, 'title' => TRUE),
    );
  }
}

/**
 * Implements hook_field_insert().
 */
function link_field_insert($entity_type, $entity, $field, $instance, $langcode, &$items) {
  foreach ($items as $delta => $value) {
    _link_process($items[$delta], $delta, $field, $entity);
  }
}

/**
 * Implements hook_field_update().
 */
function link_field_update($entity_type, $entity, $field, $instance, $langcode, &$items) {
  foreach ($items as $delta => $value) {
    _link_process($items[$delta], $delta, $field, $entity);
  }
}

/**
 * Implements hook_field_prepare_view().
 */
function link_field_prepare_view($entity_type, $entities, $field, $instances, $langcode, &$items) {
  foreach ($items as $entity_id => $entity_items) {
    foreach ($entity_items as $delta => $value) {
      _link_sanitize($items[$entity_id][$delta], $delta, $field, $instances[$entity_id], $entities[$entity_id]);
    }
  }
}

/**
 * Implements hook_field_widget_info().
 */
function link_field_widget_info() {
  return array(
    'link_field' => array(
      'label' => 'Link',
      'field types' => array('link_field'),
      'multiple values' => FIELD_BEHAVIOR_DEFAULT,
    ),
  );
}

/**
 * Implements hook_field_widget_form().
 */
function link_field_widget_form(&$form, &$form_state, $field, $instance, $langcode, $items, $delta, $element) {
  $element += array(
    '#type' => $instance['widget']['type'],
    '#default_value' => isset($items[$delta]) ? $items[$delta] : '',
  );
  return $element;
}

/**
 * Implements hook_field_widget_error().
 */
function link_field_widget_error($element, $error, $form, &$form_state) {
  if ($error['error_element']['title']) {
    form_error($element['title'], $error['message']);
  }
  elseif ($error['error_element']['url']) {
    form_error($element['url'], $error['message']);
  }
}

/**
 * Unpacks the item attributes for use.
 */
function _link_load($field, $item, $instance) {
  if (isset($item['attributes'])) {
    if (!is_array($item['attributes'])) {
      $item['attributes'] = unserialize($item['attributes']);
    }
    return $item['attributes'];
  }
  elseif (isset($instance['settings']['attributes'])) {
    return $instance['settings']['attributes'];
  }
  else {
    return $field['settings']['attributes'];
  }
}

/**
 * Prepares the item attributes and url for storage.
 */
function _link_process(&$item, $delta, $field, $entity) {
  // Trim whitespace from URL.
  if (!empty($item['url'])) {
    $item['url'] = trim($item['url']);
  }

  // If no attributes are set then make sure $item['attributes'] is an empty
  // array, so $field['attributes'] can override it.
  if (empty($item['attributes'])) {
    $item['attributes'] = array();
  }

  // Serialize the attributes array.
  if (!is_string($item['attributes'])) {
    $item['attributes'] = serialize($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($entity)) {
    if (!link_validate_url($item['url'])) {
      unset($item['url']);
    }
  }
}

/**
 * Validates that the link field has been entered properly.
 */
function _link_validate(&$item, $delta, $field, $entity, $instance, $langcode, &$optional_field_found, &$errors) {
  if ($item['url'] && !(isset($instance['default_value'][$delta]['url']) && $item['url'] === $instance['default_value'][$delta]['url'] && !$instance['required'])) {
    // Validate the link.
    if (link_validate_url(trim($item['url'])) == FALSE) {
      $errors[$field['field_name']][$langcode][$delta][] = array(
        'error' => 'link_required',
        'message' => t('The value %value provided for %field is not a valid URL.', array(
          '%value' => trim($item['url']),
          '%field' => $instance['label'],
        )),
        'error_element' => array('url' => TRUE, 'title' => FALSE),
      );
    }
    // Require a title for the link if necessary.
    if ($instance['settings']['title'] == 'required' && strlen(trim($item['title'])) == 0) {
      $errors[$field['field_name']][$langcode][$delta][] = array(
        'error' => 'link_required',
        'message' => t('Titles are required for all links.'),
        'error_element' => array('url' => FALSE, 'title' => TRUE),
      );
    }
  }
  // Require a link if we have a title.
  if ($instance['settings']['url'] !== 'optional' && strlen(isset($item['title']) ? $item['title'] : NULL) > 0 && strlen(trim($item['url'])) == 0) {
    $errors[$field['field_name']][$langcode][$delta][] = array(
      'error' => 'link_required',
      'message' => t('You cannot enter a title without a link url.'),
      'error_element' => array('url' => TRUE, 'title' => FALSE),
    );
  }
  // In a totally bizzaro case, where URLs and titles are optional but the field is required, ensure there is at least one link.
  if ($instance['settings']['url'] === 'optional' && $instance['settings']['title'] === 'optional'
      && (strlen(trim($item['url'])) !== 0 || strlen(trim($item['title'])) !== 0)) {
    $optional_field_found = TRUE;
  }
  // Require entire field.
  if ($instance['settings']['url'] === 'optional' && $instance['settings']['title'] === 'optional' && $instance['required'] == 1 && !$optional_field_found && isset($instance['id'])) {
    $errors[$field['field_name']][$langcode][$delta][] = array(
      'error' => 'link_required',
      'message' => t('At least one title or URL must be entered.'),
      'error_element' => array('url' => FALSE, 'title' => TRUE),
    );
  }
}

/**
 * Clean up user-entered values for a link field according to field settings.
 *
 * @param array $item 
 *   A single link item, usually containing url, title, and attributes.
 * @param int $delta 
 *   The delta value if this field is one of multiple fields.
 * @param array $field 
 *   The CCK field definition.
 * @param object $entity 
 *   The entity containing this link.
 */
function _link_sanitize(&$item, $delta, &$field, $instance, &$entity) {
  // Don't try to process empty links.
  if (empty($item['url']) && empty($item['title'])) {
    return;
  }
  if (empty($item['html'])) {
    $item['html'] = FALSE;
  }

  // Replace URL tokens.
  $entity_type = $instance['entity_type'];
  $entity_info = entity_get_info($entity_type);
  $property_id = $entity_info['entity keys']['id'];
  $entity_token_type = isset($entity_info['token type']) ? $entity_info['token type'] : (
    $entity_type == 'taxonomy_term' || $entity_type == 'taxonomy_vocabulary' ? str_replace('taxonomy_', '', $entity_type) : $entity_type
  );
  if (isset($instance['settings']['enable_tokens']) && $instance['settings']['enable_tokens']) {
    global $user;
    // Load the entity if necessary for entities in views.
    if (isset($entity->{$property_id})) {
      $entity_loaded = entity_load($entity_type, array($entity->{$property_id}));
      $entity_loaded = array_pop($entity_loaded);
    }
    else {
      $entity_loaded = $entity;
    }
    $item['url'] = token_replace($item['url'], array($entity_token_type => $entity_loaded));
  }

  $type = link_validate_url($item['url']);
  // If the type of the URL cannot be determined and URL validation is disabled,
  // then assume LINK_EXTERNAL for later processing.
  if ($type == FALSE && $instance['settings']['validate_url'] === 0) {
    $type = LINK_EXTERNAL;
  }
  $url = link_cleanup_url($item['url']);
  $url_parts = _link_parse_url($url);

  if (!empty($url_parts['url'])) {
    $item['url'] = $url_parts['url'];
    $item += array(
      'query' => isset($url_parts['query']) ? $url_parts['query'] : NULL,
      'fragment' => isset($url_parts['fragment']) ? $url_parts['fragment'] : NULL,
      'absolute' => !empty($instance['settings']['absolute_url']),
      'html' => TRUE,
    );
  }

  // Create a shortened URL for display.
  if ($type == LINK_EMAIL) {
    $display_url = str_replace('mailto:', '', $url);
  }
  else {
    $display_url = url($url_parts['url'],
      array(
        'query' => isset($url_parts['query']) ? $url_parts['query'] : NULL,
        'fragment' => isset($url_parts['fragment']) ? $url_parts['fragment'] : NULL,
        'absolute' => !empty($instance['settings']['absolute_url']),
      )
    );
  }
  if ($instance['settings']['display']['url_cutoff'] && strlen($display_url) > $instance['settings']['display']['url_cutoff']) {
    $display_url = substr($display_url, 0, $instance['settings']['display']['url_cutoff']) . "...";
  }
  $item['display_url'] = $display_url;

  // Use the title defined at the instance level.
  if ($instance['settings']['title'] == 'value' && strlen(trim($instance['settings']['title_value']))) {
    $title = $instance['settings']['title_value'];
    if (function_exists('i18n_string_translate')) {
      $i18n_string_name = "field:{$instance['field_name']}:{$instance['bundle']}:title_value";
      $title = i18n_string_translate($i18n_string_name, $title);
    }
  }
  // Use the title defined by the user at the widget level.
  elseif (isset($item['title'])) {
    $title = $item['title'];
  }
  else {
    $title = '';
  }

  // Replace title tokens.
  if ($title && ($instance['settings']['title'] == 'value' || $instance['settings']['enable_tokens'])) {
    // Load the entity if necessary for entities in views.
    if (isset($entity->{$property_id})) {
      $entity_loaded = entity_load($entity_type, array($entity->{$property_id}));
      $entity_loaded = array_pop($entity_loaded);
    }
    else {
      $entity_loaded = $entity;
    }
    $title = token_replace($title, array($entity_token_type => $entity_loaded));
    $title = filter_xss($title, array('b', 'br', 'code', 'em', 'i', 'img', 'span', 'strong', 'sub', 'sup', 'tt', 'u'));
    $item['html'] = TRUE;
  }
  $item['title'] = empty($title) ? $item['display_url'] : $title;

  if (!isset($item['attributes'])) {
    $item['attributes'] = array();
  }

  // Unserialize attributtes array if it has not been unserialized yet.
  if (!is_array($item['attributes'])) {
    $item['attributes'] = (array) unserialize($item['attributes']);
  }

  // Add default attributes.
  if (!is_array($instance['settings']['attributes'])) {
    $instance['settings']['attributes'] = _link_default_attributes();
  }
  else {
    $instance['settings']['attributes'] += _link_default_attributes();
  }

  // Merge item attributes with attributes defined at the field level.
  $item['attributes'] += $instance['settings']['attributes'];

  // If user is not allowed to choose target attribute, use default defined at
  // field level.
  if ($instance['settings']['attributes']['target'] != LINK_TARGET_USER) {
    $item['attributes']['target'] = $instance['settings']['attributes']['target'];
  }
  elseif ($item['attributes']['target'] == LINK_TARGET_USER) {
    $item['attributes']['target'] = LINK_TARGET_DEFAULT;
  }

  // Remove the target attribute if the default (no target) is selected.
  if (empty($item['attributes']) || (isset($item['attributes']['target']) && $item['attributes']['target'] == LINK_TARGET_DEFAULT)) {
    unset($item['attributes']['target']);
  }

  // Remove rel attribute for internal or external links if selected.
  if (isset($item['attributes']['rel']) && isset($instance['settings']['rel_remove']) && $instance['settings']['rel_remove'] != 'default') {
    if (($instance['settings']['rel_remove'] != 'rel_remove_internal' && $type != LINK_INTERNAL) ||
      ($instance['settings']['rel_remove'] != 'rel_remove_external' && $type != LINK_EXTERNAL)) {
      unset($item['attributes']['rel']);
    }
  }

  // Handle "title" link attribute.
  if (!empty($item['attributes']['title']) && module_exists('token')) {
    // Load the entity (necessary for entities in views).
    if (isset($entity->{$property_id})) {
      $entity_loaded = entity_load($entity_type, array($entity->{$property_id}));
      $entity_loaded = array_pop($entity_loaded);
    }
    else {
      $entity_loaded = $entity;
    }
    $item['attributes']['title'] = token_replace($item['attributes']['title'], array($entity_token_type => $entity_loaded));
    $item['attributes']['title'] = filter_xss($item['attributes']['title'], array('b', 'br', 'code', 'em', 'i', 'img', 'span', 'strong', 'sub', 'sup', 'tt', 'u'));
  }
  // Handle attribute classes.
  if (!empty($item['attributes']['class'])) {
    $classes = explode(' ', $item['attributes']['class']);
    foreach ($classes as &$class) {
      $class = drupal_html_class($class);
    }
    $item['attributes']['class'] = implode(' ', $classes);
  }
  unset($item['attributes']['configurable_class']);

  // Remove title attribute if it's equal to link text.
  if (isset($item['attributes']['title']) && $item['attributes']['title'] == $item['title']) {
    unset($item['attributes']['title']);
  }
  unset($item['attributes']['configurable_title']);

  // Remove empty attributes.
  $item['attributes'] = array_filter($item['attributes']);
}

/**
 * Because parse_url doesn't work with relative urls.
 *
 * @param string $url
 *   URL to parse.
 *
 * @return array
 *   Array of url pieces - only 'url', 'query', and 'fragment'.
 */
function _link_parse_url($url) {
  $url_parts = array();
  // Separate out the anchor, if any.
  if (strpos($url, '#') !== FALSE) {
    $url_parts['fragment'] = substr($url, strpos($url, '#') + 1);
    $url = substr($url, 0, strpos($url, '#'));
  }
  // Separate out the query string, if any.
  if (strpos($url, '?') !== FALSE) {
    $query = substr($url, strpos($url, '?') + 1);
    $url_parts['query'] = _link_parse_str($query);
    $url = substr($url, 0, strpos($url, '?'));
  }
  $url_parts['url'] = $url;
  return $url_parts;
}

/**
 * Replaces the PHP parse_str() function.
 *
 * Because parse_str replaces the following characters in query parameters name
 * in order to maintain compability with deprecated register_globals directive:
 *
 *   - chr(32) ( ) (space)
 *   - chr(46) (.) (dot)
 *   - chr(91) ([) (open square bracket)
 *   - chr(128) - chr(159) (various)
 *
 * @param string $query
 *   Query to parse.
 *
 * @return array
 *   Array of query parameters.
 *
 * @see http://php.net/manual/en/language.variables.external.php#81080
 */
function _link_parse_str($query) {
  $query_array = array();

  $pairs = explode('&', $query);
  foreach ($pairs as $pair) {
    $name_value = explode('=', $pair, 2);
    $name = urldecode($name_value[0]);
    $value = isset($name_value[1]) ? urldecode($name_value[1]) : NULL;
    $query_array[$name] = $value;
  }

  return $query_array;
}

/**
 * Implements hook_theme().
 */
function link_theme() {
  return array(
    'link_formatter_link_default' => array(
      'variables' => array('element' => NULL, 'field' => NULL),
    ),
    'link_formatter_link_plain' => array(
      'variables' => array('element' => NULL, 'field' => NULL),
    ),
    'link_formatter_link_absolute' => array(
      'variables' => array('element' => NULL, 'field' => NULL),
    ),
    'link_formatter_link_domain' => array(
      'variables' => array('element' => NULL, 'display' => NULL, 'field' => NULL),
    ),
    'link_formatter_link_title_plain' => array(
      'variables' => array('element' => NULL, 'field' => NULL),
    ),
    'link_formatter_link_url' => array(
      'variables' => array('element' => NULL, 'field' => NULL),
    ),
    'link_formatter_link_short' => array(
      'variables' => array('element' => NULL, 'field' => NULL),
    ),
    'link_formatter_link_label' => array(
      'variables' => array('element' => NULL, 'field' => NULL),
    ),
    'link_formatter_link_separate' => array(
      'variables' => array('element' => NULL, 'field' => NULL),
    ),
    'link_field' => array(
      'render element' => 'element',
    ),
  );
}

/**
 * Formats a link field widget.
 */
function theme_link_field($vars) {
  drupal_add_css(drupal_get_path('module', 'link') . '/link.css');
  $element = $vars['element'];
  // Prefix single value link fields with the name of the field.
  if (empty($element['#field']['multiple'])) {
    if (isset($element['url']) && !isset($element['title'])) {
      $element['url']['#title_display'] = 'invisible';
    }
  }

  $output = '';
  $output .= '<div class="link-field-subrow clearfix">';
  if (isset($element['title'])) {
    $output .= '<div class="link-field-title link-field-column">' . drupal_render($element['title']) . '</div>';
  }
  $output .= '<div class="link-field-url' . (isset($element['title']) ? ' link-field-column' : '') . '">' . drupal_render($element['url']) . '</div>';
  $output .= '</div>';
  if (!empty($element['attributes']['target'])) {
    $output .= '<div class="link-attributes">' . drupal_render($element['attributes']['target']) . '</div>';
  }
  if (!empty($element['attributes']['title'])) {
    $output .= '<div class="link-attributes">' . drupal_render($element['attributes']['title']) . '</div>';
  }
  if (!empty($element['attributes']['class'])) {
    $output .= '<div class="link-attributes">' . drupal_render($element['attributes']['class']) . '</div>';
  }
  $output .= drupal_render_children($element);
  return $output;
}

/**
 * Implements hook_element_info().
 */
function link_element_info() {
  $elements = array();
  $elements['link_field'] = array(
    '#input' => TRUE,
    '#process' => array('link_field_process'),
    '#theme' => 'link_field',
    '#theme_wrappers' => array('form_element'),
  );
  return $elements;
}

/**
 * Returns the default attributes and their values.
 */
function _link_default_attributes() {
  return array(
    'target' => LINK_TARGET_DEFAULT,
    'class' => '',
    'rel' => '',
  );
}

/**
 * Processes 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 $complete_form['#field_info'][$element['#field_name']].
 */
function link_field_process($element, $form_state, $complete_form) {
  $instance = field_widget_instance($element, $form_state);
  $settings = $instance['settings'];
  $element['url'] = array(
    '#type' => 'textfield',
    '#maxlength' => LINK_URL_MAX_LENGTH,
    '#title' => t('URL'),
    '#required' => ($element['#delta'] == 0 && $settings['url'] !== 'optional') ? $element['#required'] : FALSE,
    '#default_value' => isset($element['#value']['url']) ? $element['#value']['url'] : NULL,
  );
  if ($settings['title'] !== 'none' && $settings['title'] !== 'value') {
    // Figure out the label of the title field.
    if (!empty($settings['title_label_use_field_label'])) {
      // Use the element label as the title field label.
      $title_label = $element['#title'];
      // Hide the field label because there is no need for the duplicate labels.
      $element['#title_display'] = 'invisible';
    }
    else {
      $title_label = t('Title');
    }

    $element['title'] = array(
      '#type' => 'textfield',
      '#maxlength' => $settings['title_maxlength'],
      '#title' => $title_label,
      '#description' => t('The link title is limited to @maxlength characters maximum.', array('@maxlength' => $settings['title_maxlength'])),
      '#required' => ($settings['title'] == 'required' && (($element['#delta'] == 0 && $element['#required']) || !empty($element['#value']['url']))) ? TRUE : 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($settings['attributes'])) {
    $settings['attributes'] = array();
  }
  // Add default attributes.
  $settings['attributes'] += _link_default_attributes();
  $attributes = isset($element['#value']['attributes']) ? $element['#value']['attributes'] : $settings['attributes'];
  if (!empty($settings['attributes']['target']) && $settings['attributes']['target'] == LINK_TARGET_USER) {
    $element['attributes']['target'] = array(
      '#type' => 'checkbox',
      '#title' => t('Open URL in a New Window'),
      '#return_value' => LINK_TARGET_NEW_WINDOW,
      '#default_value' => isset($attributes['target']) ? $attributes['target'] : FALSE,
    );
  }
  if (!empty($settings['attributes']['configurable_title']) && $settings['attributes']['configurable_title'] == 1) {
    $element['attributes']['title'] = array(
      '#type' => 'textfield',
      '#title' => t('Link "title" attribute'),
      '#default_value' => isset($attributes['title']) ? $attributes['title'] : '',
      '#field_prefix' => 'title = "',
      '#field_suffix' => '"',
    );
  }
  if (!empty($settings['attributes']['configurable_class']) && $settings['attributes']['configurable_class'] == 1) {
    $element['attributes']['class'] = array(
      '#type' => 'textfield',
      '#title' => t('Custom link class'),
      '#default_value' => isset($attributes['class']) ? $attributes['class'] : '',
      '#field_prefix' => 'class = "',
      '#field_suffix' => '"',
    );
  }

  // If the title field is avaliable or there are field accepts multiple values
  // then allow the individual field items display the required asterisk if needed.
  if (isset($element['title']) || isset($element['_weight'])) {
    // To prevent an extra required indicator, disable the required flag on the
    // base element since all the sub-fields are already required if desired.
    $element['#required'] = FALSE;
  }

  return $element;
}

/**
 * Implements hook_field_formatter_info().
 */
function link_field_formatter_info() {
  return array(
    'link_default' => array(
      'label' => t('Title, as link (default)'),
      'field types' => array('link_field'),
      'multiple values' => FIELD_BEHAVIOR_DEFAULT,
    ),
    'link_title_plain' => array(
      'label' => t('Title, as plain text'),
      'field types' => array('link_field'),
      'multiple values' => FIELD_BEHAVIOR_DEFAULT,
    ),
    'link_url' => array(
      'label' => t('URL, as link'),
      'field types' => array('link_field'),
      'multiple values' => FIELD_BEHAVIOR_DEFAULT,
    ),
    'link_plain' => array(
      'label' => t('URL, as plain text'),
      'field types' => array('link_field'),
      'multiple values' => FIELD_BEHAVIOR_DEFAULT,
    ),
    'link_absolute' => array(
      'label' => t('URL, absolute'),
      'field types' => array('link_field'),
      'multiple values' => FIELD_BEHAVIOR_DEFAULT,
    ),
    'link_domain' => array(
      'label' => t('Domain, as link'),
      'field types' => array('link_field'),
      'multiple values' => FIELD_BEHAVIOR_DEFAULT,
      'settings' => array(
        'strip_www' => FALSE,
      ),
    ),
    'link_short' => array(
      'label' => t('Short, as link with title "Link"'),
      'field types' => array('link_field'),
      'multiple values' => FIELD_BEHAVIOR_DEFAULT,
    ),
    'link_label' => array(
      'label' => t('Label, as link with label as title'),
      'field types' => array('link_field'),
      'multiple values' => FIELD_BEHAVIOR_DEFAULT,
    ),
    'link_separate' => array(
      'label' => t('Separate title and URL'),
      'field types' => array('link_field'),
      'multiple values' => FIELD_BEHAVIOR_DEFAULT,
    ),
  );
}

/**
 * Implements hook_field_formatter_settings_form().
 */
function link_field_formatter_settings_form($field, $instance, $view_mode, $form, &$form_state) {
  $display = $instance['display'][$view_mode];
  $settings = $display['settings'];
  $element = array();
  if ($display['type'] == 'link_domain') {
    $element['strip_www'] = array(
      '#title' => t('Strip www. from domain'),
      '#type' => 'checkbox',
      '#default_value' => $settings['strip_www'],
    );
  }
  return $element;
}

/**
 * Implements hook_field_formatter_settings_summary().
 */
function link_field_formatter_settings_summary($field, $instance, $view_mode) {
  $display = $instance['display'][$view_mode];
  $settings = $display['settings'];
  if ($display['type'] == 'link_domain') {
    if ($display['settings']['strip_www']) {
      return t('Strip www. from domain');
    }
    else {
      return t('Leave www. in domain');
    }
  }
  return '';
}

/**
 * Implements hook_field_formatter_view().
 */
function link_field_formatter_view($entity_type, $entity, $field, $instance, $langcode, $items, $display) {
  $elements = array();
  foreach ($items as $delta => $item) {
    $elements[$delta] = array(
      '#theme' => 'link_formatter_' . $display['type'],
      '#element' => $item,
      '#field' => $instance,
      '#display' => $display,
    );
  }
  return $elements;
}

/**
 * Formats a link.
 */
function theme_link_formatter_link_default($vars) {
  $link_options = $vars['element'];
  unset($link_options['title']);
  unset($link_options['url']);

  if (isset($link_options['attributes']['class'])) {
    $link_options['attributes']['class'] = array($link_options['attributes']['class']);
  }
  // Display a normal link if both title and URL are available.
  if (!empty($vars['element']['title']) && !empty($vars['element']['url'])) {
    return l($vars['element']['title'], $vars['element']['url'], $link_options);
  }
  // If only a title, display the title.
  elseif (!empty($vars['element']['title'])) {
    return $link_options['html'] ? $vars['element']['title'] : check_plain($vars['element']['title']);
  }
  elseif (!empty($vars['element']['url'])) {
    return l($vars['element']['title'], $vars['element']['url'], $link_options);
  }
}

/**
 * Formats a link (or its title) as plain text.
 */
function theme_link_formatter_link_plain($vars) {
  $link_options = $vars['element'];
  if (isset($link_options['title'])) {
    unset($link_options['title']);
  }
  else {
    $vars['element']['title'] = '';
  }
  unset($link_options['url']);
  return empty($vars['element']['url']) ? check_plain($vars['element']['title']) : url($vars['element']['url'], $link_options);
}

/**
 * Formats a link as an absolute URL.
 */
function theme_link_formatter_link_absolute($vars) {
  $absolute = array('absolute' => TRUE);
  return empty($vars['element']['url']) ? '' : url($vars['element']['url'], $absolute + $vars['element']);
}

/**
 * Formats a link using the URL's domain for it's link text.
 */
function theme_link_formatter_link_domain($vars) {
  $link_options = $vars['element'];
  unset($link_options['title']);
  unset($link_options['url']);
  $domain = parse_url($vars['element']['display_url'], PHP_URL_HOST);
  if (!empty($vars['display']['settings']['strip_www'])) {
    $domain = str_replace('www.', '', $domain);
  }
  return $vars['element']['url'] ? l($domain, $vars['element']['url'], $link_options) : '';
}

/**
 * Formats a link's title as plain text.
 */
function theme_link_formatter_link_title_plain($vars) {
  return empty($vars['element']['title']) ? '' : check_plain($vars['element']['title']);
}

/**
 * Formats a link using an alternate display URL for its link text.
 */
function theme_link_formatter_link_url($vars) {
  $link_options = $vars['element'];
  unset($link_options['title']);
  unset($link_options['url']);
  return $vars['element']['url'] ? l($vars['element']['display_url'], $vars['element']['url'], $link_options) : '';
}

/**
 * Formats a link using "Link" as the link text.
 */
function theme_link_formatter_link_short($vars) {
  $link_options = $vars['element'];
  unset($link_options['title']);
  unset($link_options['url']);
  return $vars['element']['url'] ? l(t('Link'), $vars['element']['url'], $link_options) : '';
}

/**
 * Formats a link using the field's label as link text.
 */
function theme_link_formatter_link_label($vars) {
  $link_options = $vars['element'];
  unset($link_options['title']);
  unset($link_options['url']);
  return $vars['element']['url'] ? l($vars['field']['label'], $vars['element']['url'], $link_options) : '';
}

/**
 * Formats a link as separate title and URL elements.
 */
function theme_link_formatter_link_separate($vars) {
  $class = empty($vars['element']['attributes']['class']) ? '' : ' ' . $vars['element']['attributes']['class'];
  unset($vars['element']['attributes']['class']);
  $link_options = $vars['element'];
  unset($link_options['title']);
  unset($link_options['url']);
  $title = empty($vars['element']['title']) ? '' : check_plain($vars['element']['title']);

  // @TODO static html markup looks not very elegant
  // needs smarter output solution and an optional title/url seperator
  $url_parts = _link_parse_url($vars['element']['url']);
  $output = '';
  $output .= '<div class="link-item ' . $class . '">';
  if (!empty($title)) {
    $output .= '<div class="link-title">' . $title . '</div>';
  }
  $output .= '<div class="link-url">' . l($url_parts['url'], $vars['element']['url'], $link_options) . '</div>';
  $output .= '</div>';
  return $output;
}

/**
 * Implements hook_token_list().
 *
 * @TODO: hook_token_list no longer exists - this should change to hook_token_info().
 */
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");
    return $tokens;
  }
}

/**
 * Implements hook_token_values().
 *
 * @TODO: hook_token_values no longer exists - this should change to hook_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'] : '';

    return $tokens;
  }
}

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

/**
 * 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
 *   The url entered by the user.
 * @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.
      $LINK_DOMAINS = _link_domains();
      $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;
}

/**
 * Validates a URL.
 * 
 * Accepts all URLs following RFC 1738 standard for URL formation and all e-mail
 * addresses following the RFC 2368 standard for mailto address formation.
 *
 * @param string $text
 *   Url to be validated.
 * 
 * @return mixed
 *   Returns boolean FALSE if the URL is not valid. On success, returns one of
 *   the LINK_(linktype) constants.
 */
function link_validate_url($text) {
  // @TODO Complete letters.
  $LINK_ICHARS_DOMAIN = (string) html_entity_decode(implode("", array(
    "&#x00E6;", // æ
    "&#x00C6;", // Æ
    "&#x00C0;", // À
    "&#x00E0;", // à
    "&#x00C1;", // Á
    "&#x00E1;", // á
    "&#x00C2;", // Â
    "&#x00E2;", // â
    "&#x00E5;", // å
    "&#x00C5;", // Å
    "&#x00E4;", // ä
    "&#x00C4;", // Ä
    "&#x00C7;", // Ç
    "&#x00E7;", // ç
    "&#x00D0;", // Ð
    "&#x00F0;", // ð
    "&#x00C8;", // È
    "&#x00E8;", // è
    "&#x00C9;", // É
    "&#x00E9;", // é
    "&#x00CA;", // Ê
    "&#x00EA;", // ê
    "&#x00CB;", // Ë
    "&#x00EB;", // ë
    "&#x00CE;", // Î
    "&#x00EE;", // î
    "&#x00CF;", // Ï
    "&#x00EF;", // ï
    "&#x00F8;", // ø
    "&#x00D8;", // Ø
    "&#x00F6;", // ö
    "&#x00D6;", // Ö
    "&#x00D4;", // Ô
    "&#x00F4;", // ô
    "&#x00D5;", // Õ
    "&#x00F5;", // õ
    "&#x0152;", // Œ
    "&#x0153;", // œ
    "&#x00FC;", // ü
    "&#x00DC;", // Ü
    "&#x00D9;", // Ù
    "&#x00F9;", // ù
    "&#x00DB;", // Û
    "&#x00FB;", // û
    "&#x0178;", // Ÿ
    "&#x00FF;", // ÿ
    "&#x00D1;", // Ñ
    "&#x00F1;", // ñ
    "&#x00FE;", // þ
    "&#x00DE;", // Þ
    "&#x00FD;", // ý
    "&#x00DD;", // Ý
    "&#x00BF;", // ¿
  )), ENT_QUOTES, 'UTF-8');

  $LINK_ICHARS = $LINK_ICHARS_DOMAIN . (string) html_entity_decode(implode("", array(
    "&#x00DF;", // ß
  )), ENT_QUOTES, 'UTF-8');
  $allowed_protocols = variable_get('filter_allowed_protocols', array('http', 'https', 'ftp', 'news', 'nntp', 'telnet', 'mailto', 'irc', 'ssh', 'sftp', 'webcal'));
  $LINK_DOMAINS = _link_domains();

  // Starting a parenthesis group with (?: means that it is grouped, but is not captured.
  $protocol = '((?:' . implode("|", $allowed_protocols) . '):\/\/)';
  $authentication = "(?:(?:(?:[\w\.\-\+!$&'\(\)*\+,;=" . $LINK_ICHARS . "]|%[0-9a-f]{2})+(?::(?:[\w" . $LINK_ICHARS . "\.\-\+%!$&'\(\)*\+,;=]|%[0-9a-f]{2})*)?)?@)";
  $domain = '(?:(?:[a-z0-9' . $LINK_ICHARS_DOMAIN . ']([a-z0-9' . $LINK_ICHARS_DOMAIN . '\-_\[\]])*)(\.(([a-z0-9' . $LINK_ICHARS_DOMAIN . '\-_\[\]])+\.)*(' . $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 external links.
  $external_pattern = '/^' . $protocol . '?' . $authentication . '?(' . $domain . '|' . $ipv4 . '|' . $ipv6 . ' |localhost)' . $port . '?';

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

  $directories = "(?:\/[a-z0-9" . $LINK_ICHARS . "_\-\.~+%=&,$'#!():;*@\[\]]*)*";
  // Yes, four backslashes == a single backslash.
  $query = "(?:\/?\?([?a-z0-9" . $LINK_ICHARS . "+_|\-\.~\/\\\\%=&,$'!():;*@\[\]{} ]*))";
  $anchor = "(?:#[a-z0-9" . $LINK_ICHARS . "_\-\.~+%=&,$'():;*@\[\]\/\?]*)";

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

  $message_id = '[^@].*@' . $domain;
  $newsgroup_name = '(?:[0-9a-z+-]*\.)*[0-9a-z+-]*';
  $news_pattern = '/^news:(' . $newsgroup_name . '|' . $message_id . ')$/i';

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

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

  return FALSE;
}

/**
 * Returns the list of allowed domains, including domains added by admins via variable_set/$config.
 */
function _link_domains() {
  $link_extra_domains = variable_get('link_extra_domains', array());
  return empty($link_extra_domains) ? LINK_DOMAINS : LINK_DOMAINS . '|' . implode('|', $link_extra_domains);
}

/**
 * Implements hook_migrate_field_alter().
 */
function link_content_migrate_field_alter(&$field_value, $instance_value) {
  if ($field_value['type'] == 'link') {
    // Adjust the field type.
    $field_value['type'] = 'link_field';
    // Remove settings that are now on the instance.
    foreach (array('attributes', 'display', 'url', 'title', 'title_value', 'enable_tokens', 'validate_url') as $setting) {
      unset($field_value['settings'][$setting]);
    }
  }
}

/**
 * Implements hook_migrate_instance_alter().
 *
 * Widget type also changed to link_field.
 */
function link_content_migrate_instance_alter(&$instance_value, $field_value) {
  if ($field_value['type'] == 'link') {
    // Grab settings that were previously on the field.
    foreach (array('attributes', 'display', 'url', 'title', 'title_value', 'enable_tokens', 'validate_url') as $setting) {
      if (isset($field_value['settings'][$setting])) {
        $instance_value['settings'][$setting] = $field_value['settings'][$setting];
      }
    }
    // Adjust widget type.
    if ($instance_value['widget']['type'] == 'link') {
      $instance_value['widget']['type'] = 'link_field';
    }
    // Adjust formatter types.
    foreach ($instance_value['display'] as $context => $settings) {
      if (in_array($settings['type'], array('default', 'title_plain', 'url', 'plain', 'short', 'label', 'separate'))) {
        $instance_value['display'][$context]['type'] = 'link_' . $settings['type'];
      }
    }
  }
}

/**
 * Implements hook_field_settings_form().
 */
function link_field_settings_form() {
  return array();
}

/**
 * Additional callback to adapt the property info of link fields.
 * 
 * @see entity_metadata_field_entity_property_info()
 */
function link_field_property_info_callback(&$info, $entity_type, $field, $instance, $field_type) {
  $property = &$info[$entity_type]['bundles'][$instance['bundle']]['properties'][$field['field_name']];
  // Define a data structure so it's possible to deal with both the link title
  // and URL.
  $property['getter callback'] = 'entity_metadata_field_verbatim_get';
  $property['setter callback'] = 'entity_metadata_field_verbatim_set';

  // Auto-create the field item as soon as a property is set.
  $property['auto creation'] = 'link_field_item_create';

  $property['property info'] = link_field_item_property_info();
  $property['property info']['url']['required'] = !$instance['settings']['url'];
  $property['property info']['title']['required'] = ($instance['settings']['title'] == 'required');
  if ($instance['settings']['title'] == 'none') {
    unset($property['property info']['title']);
  }
  unset($property['query callback']);
}

/**
 * Callback for creating a new, empty link field item.
 *
 * @see link_field_property_info_callback()
 */
function link_field_item_create() {
  return array('title' => NULL, 'url' => NULL);
}

/**
 * Defines info for the properties of the link-field item data structure.
 */
function link_field_item_property_info() {
  $properties['title'] = array(
    'type' => 'text',
    'label' => t('The title of the link.'),
    'setter callback' => 'entity_property_verbatim_set',
  );
  $properties['url'] = array(
    'type' => 'uri',
    'label' => t('The URL of the link.'),
    'setter callback' => 'entity_property_verbatim_set',
  );
  $properties['attributes'] = array(
    'type' => 'struct',
    'label' => t('The attributes of the link.'),
    'setter callback' => 'entity_property_verbatim_set',
    'getter callback' => 'link_attribute_property_get',
  );
  return $properties;
}

/**
 * Entity property info getter callback for link attributes.
 */
function link_attribute_property_get($data, array $options, $name, $type, $info) {
  return isset($data[$name]) ? array_filter($data[$name]) : array();
}

/**
 * Implements hook_field_update_instance().
 */
function link_field_update_instance($instance, $prior_instance) {
  if (function_exists('i18n_string_update') && $instance['widget']['type'] == 'link_field' && $prior_instance['settings']['title_value'] != $instance['settings']['title_value']) {
    $i18n_string_name = "field:{$instance['field_name']}:{$instance['bundle']}:title_value";
    i18n_string_update($i18n_string_name, $instance['settings']['title_value']);
  }
}

/**
 * Implements hook_i18n_string_list_TEXTGROUP_alter().
 */
function link_i18n_string_list_field_alter(&$strings, $type = NULL, $object = NULL) {
  if ($type != 'field_instance' || !is_array($object) || !isset($object['widget']['type'])) {
    return;
  }
  if ($object['widget']['type'] == 'link_field' && isset($object['settings']['title_value'])) {
    $strings['field'][$object['field_name']][$object['bundle']]['title_value']['string'] = $object['settings']['title_value'];
  }
}
