metatag.module

<?php

/**
 * @file
 * Primary hook implementations for Metatag.
 */

/**
 * Implements hook_help().
 */
function metatag_help($path, $arg) {
  if ($path == 'admin/config/search/metatags') {
    return '<p>' . t('Configure global meta tag default values below. Meta tags may be left as the default.') . '</p>'
      . '<p>' . t('Meta tag patterns are passed down from one level to the next unless they are overridden. To view a summary of the individual meta tags and the pattern for a specific configuration, click on its name below.') . '</p>'
      . '<p>' . t('If the top-level configuration is not specific enough, additional default meta tag configurations can be added for a specific entity type or entity bundle, e.g. for a specific content type, using the "Add default meta tags" form.') . '</p>'
      . '<p>' . t('Meta tags can be further refined on a per-entity basis, e.g. for individual nodes, from the "Meta tags" fields that show on those edit forms.')
      . '<p>' . t('To view a summary of the default meta tags and the inheritance, click on a meta tag type.') . '</p>';
  }
  elseif ($path == 'admin/config/search/metatags/config/add') {
    return '<p>' . t('Use the following form to override the global default meta tags for a specific entity type or entity bundle. In practical terms, this allows the meta tags to be customized for a specific content type or taxonomy vocabulary, so that its content will have different meta tags <em>default values</em> than others.') . '</p>'
      . '<p>' . t('As a reminder, the meta tags can be further refined on a per entity basis using the "Meta tags" field, but it is recommended to set reasonable defaults for each entity type or bundle (e.g. content types).') . '</p>';
  }
  elseif ($path == 'admin/help#metatag') {
    return '<p>' . t('The Metatag module provides a options to let each page have customized meta data added to the "meta" tags in the HEAD section of the document.') . '</p>';
  }
  elseif ($path == 'admin/config/search/metatags/bulk-revert') {
    return '<p>' . t('This form <strong>will wipe out</strong> all custom meta tags for the selected entities, reverting them to the default configuration assigned at the <a href="@url">Defaults tab</a>. For example, if the meta tags are changed for an article they will be removed if the "Node: Article" checkbox is selected.', array('@url' => url('admin/config/search/metatags'))) . '</p>';
  }
}

/**
 * Implements hook_theme().
 */
function metatag_theme() {
  $info['metatag'] = array(
    'render element' => 'element',
    'file' => 'metatag.theme.inc',
  );
  $info['metatag_http_equiv'] = array(
    'render element' => 'element',
    'file' => 'metatag.theme.inc',
  );
  $info['metatag_link_rel'] = array(
    'render element' => 'element',
    'file' => 'metatag.theme.inc',
  );
  $info['metatag_link_rev'] = array(
    'render element' => 'element',
    'file' => 'metatag.theme.inc',
  );
  $info['metatag_property'] = array(
    'render element' => 'element',
    'file' => 'metatag.theme.inc',
  );

  return $info;
}

/**
 * Implements hook_ctools_plugin_api().
 */
function metatag_ctools_plugin_api($owner, $api) {
  if ($owner == 'metatag' && $api == 'metatag') {
    return array('version' => 1);
  }
}

/**
 * Implements hook_ctools_plugin_directory().
 */
function metatag_ctools_plugin_directory($owner, $plugin_type) {
  if ($owner == 'ctools' && $plugin_type == 'content_types') {
    return "plugins/$plugin_type";
  }
}

/**
 * Implements hook_hook_info().
 */
function metatag_hook_info() {
  $hooks = array(
    'metatag_config_default',
    'metatag_config_default_alter',
    'metatag_config_delete',
    'metatag_config_insert',
    'metatag_config_instance_info',
    'metatag_config_instance_info_alter',
    'metatag_config_load',
    'metatag_config_load_presave',
    'metatag_config_update',
    'metatag_info',
    'metatag_info_alter',
  );

  return array_fill_keys($hooks, array('group' => 'metatag'));
}

/**
 * Implements hook_permission().
 */
function metatag_permission() {
  $permissions['administer meta tags'] = array(
    'title' => t('Administer meta tags'),
    'restrict access' => TRUE,
    'description' => t('Control the main settings pages and modify per-object meta tags.'),
  );
  $permissions['edit meta tags'] = array(
    'title' => t('Edit meta tags'),
    'description' => t('Modify meta tags on individual entity records (nodes, terms, users, etc).'),
  );

  // Optional extended edit permissions.
  if (variable_get('metatag_extended_permissions', FALSE)) {
    $permissions['edit meta tags']['description'] .= '<br />' . t('<em>Extended Permissions</em> has been enabled. Roles have the :admin permission will see all meta tags on edit forms, otherwise the permissions below will control which meta tags are available and are needed in addition to <em>Edit meta tags</em>.', array(':admin' => t('Administer meta tags')));
    $metatags = metatag_get_info();
    foreach ($metatags['tags'] as $metatag_name => $metatag) {
      $permissions['edit meta tag: ' . $metatag_name] = array(
        'title' => t('Extended permission: Edit :tag meta tag', array(':tag' => $metatag['label'])),
        'description' => t('Customize the :tag meta tag on individual forms.', array(':tag' => $metatag['label'])),
      );
    }
  }

  return $permissions;
}

/**
 * Implements hook_menu().
 */
function metatag_menu() {
  $items['admin/config/search/metatags'] = array(
    'title' => 'Metatag',
    'description' => 'Configure Metatag defaults.',
    'page callback' => 'metatag_config_overview',
    'access arguments' => array('administer meta tags'),
    'file' => 'metatag.admin.inc',
  );
  $items['admin/config/search/metatags/config'] = array(
    'title' => 'Defaults',
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'weight' => -10,
  );
  $items['admin/config/search/metatags/config/add'] = array(
    'title' => 'Add default meta tags',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('metatag_config_add_form'),
    'access arguments' => array('administer meta tags'),
    'file' => 'metatag.admin.inc',
    'type' => MENU_LOCAL_ACTION,
  );
  $items['admin/config/search/metatags/config/%metatag_config'] = array(
    'title callback' => 'metatag_config_title',
    'title arguments' => array(5),
    'page callback' => 'drupal_get_form',
    'page arguments' => array('metatag_config_edit_form', 5),
    'access arguments' => array('administer meta tags'),
    'file' => 'metatag.admin.inc',
  );
  $items['admin/config/search/metatags/config/%metatag_config/edit'] = array(
    'title' => 'Edit',
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'weight' => -10,
  );
  $items['admin/config/search/metatags/config/%metatag_config/enable'] = array(
    'title' => 'Enable',
    'page callback' => 'metatag_config_enable',
    'page arguments' => array(5),
    'access callback' => 'metatag_config_access',
    'access arguments' => array('enable', 5),
    'file' => 'metatag.admin.inc',
  );
  $items['admin/config/search/metatags/config/%metatag_config/disable'] = array(
    'title' => 'Disable',
    'page callback' => 'metatag_config_disable',
    'page arguments' => array(5),
    'access callback' => 'metatag_config_access',
    'access arguments' => array('disable', 5),
    'file' => 'metatag.admin.inc',
  );
  $items['admin/config/search/metatags/config/%metatag_config/revert'] = array(
    'title' => 'Revert',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('metatag_config_delete_form', 5),
    'access callback' => 'metatag_config_access',
    'access arguments' => array('revert', 5),
    'file' => 'metatag.admin.inc',
    'type' => MENU_LOCAL_TASK,
  );
  $items['admin/config/search/metatags/config/%metatag_config/delete'] = array(
    'title' => 'Delete',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('metatag_config_delete_form', 5),
    'access callback' => 'metatag_config_access',
    'access arguments' => array('delete', 5),
    'file' => 'metatag.admin.inc',
  );
  $items['admin/config/search/metatags/config/%metatag_config/export'] = array(
    'title' => 'Export',
    'page callback' => 'metatag_config_export_form',
    'page arguments' => array(5),
    'access arguments' => array('administer meta tags'),
    'file' => 'metatag.admin.inc',
    'type' => MENU_LOCAL_TASK,
    'weight' => 10,
  );
  $items['admin/config/search/metatags/settings'] = array(
    'title' => 'Settings',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('metatag_admin_settings_form'),
    'access arguments' => array('administer meta tags'),
    'type' => MENU_LOCAL_TASK,
    'weight' => 30,
    'file' => 'metatag.admin.inc',
  );
  $items['admin/config/search/metatags/bulk-revert'] = array(
    'title' => 'Bulk revert',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('metatag_bulk_revert_form'),
    'access arguments' => array('administer meta tags'),
    'type' => MENU_LOCAL_TASK,
    'weight' => 40,
    'file' => 'metatag.admin.inc',
  );

  // Optional integration with the i18n_string module for translating the
  // configurations. Note: this should also check for 'metatag_i18n_disabled'
  // but doing so would require rebuilding the menu cache every time the Metatag
  // settings page was saved, which may not be advised. Instead the links to
  // these pages on the config pages *do* check the variable, which is close
  // enough.
  if (module_exists('i18n_string')) {
    $items['admin/config/search/metatags/config/%metatag_config/translate'] = array(
      'title' => 'Translate',
      'access arguments' => array('administer meta tags'),
      'page callback' => 'i18n_string_object_translate_page',
      'page arguments' => array('metatag_config', 5),
      'type' => MENU_LOCAL_TASK,
    );
    $items['admin/config/search/metatags/config/%metatag_config/translate/%i18n_language'] = array(
      'title' => 'Translate',
      'access arguments' => array('administer meta tags'),
      'page callback' => 'i18n_string_object_translate_page',
      'page arguments' => array('metatag_config', 5, 7),
      'type' => MENU_CALLBACK,
    );
  }

  return $items;
}

/**
 * Implements hook_flush_caches().
 */
function metatag_flush_caches() {
  return array('cache_metatag');
}

/**
 * Implements hook_action_info().
 * Provides integration with Views bulk operations.
 */
function metatag_action_info() {
  return array(
    'metatag_modify_metatags_action' => array(
      'type' => 'entity',
      'label' => t('Modify entity metatags'),
      'configurable' => FALSE,
      'vbo_configurable' => TRUE,
      'behavior' => array('changes_property'),
      'triggers' => array('any'),
      'permissions' => array('edit meta tags'),
    ),
  );
}

/**
 * Updates entity metatags with values from the action form.
 *
 * @param  object $entity
 *   The entity housing the metatags to modify.
 * @param  array $context
 *   Contextual information passed from the View bulk operation configuration
 *   form. The updated metatag values for the entity are stored in
 *   $context['updates'].
 */
function metatag_modify_metatags_action($entity, $context) {
  if (empty($entity)) {
    drupal_set_message(t("Error while trying to update an entity's metatags."),
      'warning', FALSE);
    return;
  }

  $updates = $context['updates'];
  $language = $entity->language;

  // Reset metatags to the entity default configs.
  if ($context['reset_default']) {
    $instance = $context['entity_type'] . ':' . $entity->type;
    $entity_defaults = metatag_config_load_with_defaults($instance);

    // Clean up empty values.
    foreach ($entity_defaults as $name => $tag) {
      if (empty($tag['value'])) {
        unset($entity_defaults[$name]);
      }
    }

    $entity->metatags[$language] = $entity_defaults;
  }
  // Otherwise, we're updating existing values. Ensure that the entity has any
  // metatags already set. If so then merge the updates to avoid overwriting
  // existing values that may exist as an array. E.g. robots.
  elseif (!empty($entity->metatags) && !empty($entity->metatags[$language])) {
    foreach ($updates as $tag => $value_array) {
      if (is_array($updates[$tag]['value']) && !empty($entity->metatags[$language][$tag]['value'])) {
        $entity->metatags[$language][$tag]['value'] = array_merge($entity->metatags[$language][$tag]['value'],
          array_filter($updates[$tag]['value']));
      }
      elseif (!empty($updates[$tag]['value'])) {
        $entity->metatags[$language][$tag]['value'] = $updates[$tag]['value'];
      }
    }
  }
  // Otherwise just set the net new tags.
  else {
    $entity->metatags[$language] = $updates;
  }

  entity_save($context['entity_type'], $entity);
}

/**
 * The Views bulk operation configuration form for modifying metatags.
 *
 * @param  array $context
 *   Contextual information passed from the View bulk operation configuration
 *   form.
 *
 * @return array
 *   A form API compatible array.
 */
function metatag_modify_metatags_action_form($context) {
  $form = array(
    '#entity_type' => $context['entity_type'],
  );

  // There can be multiple instances being edited here. So the 2nd param passed
  // here is as generic as possible.
  metatag_metatags_form($form, 'global');

  // Force the metatags tab to be fully visible and save a click from the user.
  $form['metatags']['#collapsed'] = FALSE;
  $form['metatags']['#collapsible'] = FALSE;

  // If we're reseting to the entity default, then we don't need to show the
  // form fields.
  $form['metatags']['#states'] = array(
    'visible' => array(
      ':input[name="reset_default"]' => array('checked' => FALSE),
    ),
  );

  // Add an option to reset selected entities to the default configuration.
  $form['reset_default'] = array(
    '#type' => 'checkbox',
    '#title' => t('Reset to metatag defaults'),
    '#default_value' => FALSE,
    '#description' => t('Check to <strong>fully reset all metatags</strong> on
      the entities being modified to their <a href="@settings">default
      configuration</a>.', array(
      '@settings' => url('admin/config/search/metatags'),
    )),
  );

  return $form;
}

/**
 * Submit handler for metatag_modify_metatags_action_form(). Filters out
 * the user entered values from the defaults and returns the updated values to
 * the $context array.
 *
 * @return array
 *   The updated metatag values that is ultimately keyed at $context['updates'].
 */
function metatag_modify_metatags_action_submit($form, &$form_state) {
  $updates = $form_state['values']['metatags'][LANGUAGE_NONE];
  $defaults = metatag_config_load_with_defaults($form['#entity_type']);

  // Filter out the true updates.
  metatag_filter_values_from_defaults($updates, $defaults);

  return array(
    'updates' => $updates,
    'reset_default' => $form_state['values']['reset_default'],
  );
}

/**
 * Load a metatag configuration record with all the defaults merged in.
 *
 * For example, given the configuration instance 'node:article', this function
 * will load the configuration records for 'node:article', then 'node', and
 * then finally 'global', with each attempt using an array merge.
 *
 * The levels of defaults is arranged by splitting the $instance variable by
 * the colon character, and always using a 'global' instance at the end.
 */
function metatag_config_load_with_defaults($instance, $include_global = TRUE) {
  $defaults = &drupal_static(__FUNCTION__, array());

  // Use the current page's locale.
  $langcode = $GLOBALS['language_content']->language;

  // Statically cache defaults since they can include multiple levels.
  $cid = "config:{$instance}:{$langcode}" . ($include_global ? ':withglobal' : ':withoutglobal');

  if (!isset($defaults[$cid])) {
    if ($cache = metatag_cache_get($cid)) {
      $defaults[$cid] = $cache->data;
    }
    else {
      $defaults[$cid] = array();
      $instances = metatag_config_get_parent_instances($instance, $include_global);
      $configs = metatag_config_load_multiple($instances);
      foreach ($instances as $key) {
        // Ignore disabled configurations.
        if (!isset($configs[$key]) || !empty($configs[$key]->disabled)) {
          continue;
        }

        // Add config to the defaults array.
        if (!empty($configs[$key]->config)) {
          $defaults[$cid] += $configs[$key]->config;
        }
      }

      metatag_cache_set($cid, $defaults[$cid]);
    }
  }

  return $defaults[$cid];
}

/**
 * Load a metatag configuration record.
 */
function metatag_config_load($instance) {
  $results = metatag_config_load_multiple(array($instance));
  return !empty($results[$instance]) ? $results[$instance] : FALSE;
}

/**
 * Load multiple metatag configuration records.
 */
function metatag_config_load_multiple(array $instances) {
  // Load the data.
  ctools_include('export');
  $configs = ctools_export_load_object('metatag_config', 'names', $instances);

  // "Fix" any records that might be using old values. Ideally these will be
  // permanently fixed by being re-saved or re-exported.
  foreach (metatag_config_get_replacements() as $old_tag => $new_tag) {
    foreach ($configs as $instance => $config) {
      if (isset($config->config[$old_tag])) {
        $config->config[$new_tag] = $config->config[$old_tag];
        unset($config->config[$old_tag]);
      }
    }
  }

  // Translate the configuration.
  if (module_exists('i18n_string') && !variable_get('metatag_i18n_disabled', FALSE)) {
    $options = array();

    // By default disable the watchdog logging of translation messages.
    $options['watchdog'] = variable_get('metatag_i18n_enable_watchdog', FALSE);

    foreach ($configs as $instance => &$config) {
      foreach ($config->config as $tag => &$value) {
        if (isset($value['value']) && is_string($value['value'])) {
          $value['value'] = i18n_string_translate(array(
            'metatag',
            'metatag_config',
            $instance,
            $tag,
          ),
          $value['value'],
          $options);
        }
      }
    }
  }

  return $configs;
}

/**
 * Identify the meta tags that have been deprecated and replaced by others.
 */
function metatag_config_get_replacements() {
  $replacements = &drupal_static(__FUNCTION__);

  if (!isset($replacements)) {
    $replacements = array();

    foreach (metatag_get_info('tags') as $tag_name => $tag_info) {
      if (!empty($tag_info['replaces'])) {
        if (!is_array($tag_info['replaces'])) {
          $tag_info['replaces'] = array($tag_info['replaces']);
        }
        foreach ($tag_info['replaces'] as $replaces) {
          $replacements[$replaces] = $tag_name;
        }
      }
    }
  }

  return $replacements;
}

/**
 * Save a metatag configuration record to the database.
 */
function metatag_config_save($config) {
  $config->is_new = empty($config->cid);

  // Allow modules to alter the configuration before it is saved using
  // hook_metatag_config_presave().
  module_invoke_all('metatag_config_presave', $config);

  if ($config->is_new) {
    drupal_write_record('metatag_config', $config);

    // Allow modules to act upon the record insertion using
    // hook_metatag_config_insert().
    module_invoke_all('metatag_config_insert', $config);
  }
  else {
    drupal_write_record('metatag_config', $config, array('cid'));

    // Allow modules to act upon the record update using
    // hook_metatag_config_insert().
    module_invoke_all('metatag_config_update', $config);
  }

  unset($config->is_new);

  // Clear any caches.
  metatag_config_cache_clear();
}

/**
 * Delete a metatag configuration record.
 */
function metatag_config_delete($config) {
  db_delete('metatag_config')
    ->condition('instance', $config->instance)
    ->execute();

  // Allow modules to act upon the record deletion using
  // hook_metatag_config_delete().
  module_invoke_all('metatag_config_delete', $config);

  // Clear any caches.
  metatag_config_cache_clear();
}

/**
 * Clear the metatag configuration cache.
 */
function metatag_config_cache_clear() {
  cache_clear_all('*', 'cache_metatag', TRUE);
  drupal_static_reset('metatag_config_load_with_defaults');
  drupal_static_reset('metatag_entity_supports_metatags');
  drupal_static_reset('metatag_config_instance_info');
  drupal_static_reset('metatag_get_info');
  ctools_include('export');
  ctools_export_load_object_reset('metatag_config');
}

/**
 * Load an entity's tags.
 *
 * @param string $entity_type
 *   The entity type to load.
 * @param int $entity_id
 *   The ID of the entity to load.
 * @param mixed $revision_id
 *   Optional revision ID to load instead of the entity ID.
 *
 * @return array
 *   An array of tag data keyed by language for the entity's current active
 *   revision.
 */
function metatag_metatags_load($entity_type, $entity_id, $revision_id = NULL) {
  // A specific revision ID was not requested, so get the active revision ID.
  if (is_null($revision_id)) {
    // Unfortunately, the only way of getting the active revision ID is to
    // first load the entity, and then extract the ID. This is a bit
    // performance intensive, but it seems to be the only way of doing it.
    $entities = entity_load($entity_type, array($entity_id));
    if (!empty($entities[$entity_id])) {
      // We only care about the revision_id.
      list(, $revision_id,) = entity_extract_ids($entity_type, $entities[$entity_id]);
    }
  }

  // This returns an array nested by the entity ID, the revision ID and the
  // langcode.
  $metatags = metatag_metatags_load_multiple($entity_type, array($entity_id), array($revision_id));

  // Look for records for the requested revision ID.
  if (isset($metatags[$entity_id][$revision_id])) {
    return $metatags[$entity_id][$revision_id];
  }

  // Getting to this point means that no meta tags were identified earlier, so
  // return an empty array.
  return array();
}

/**
 * Load tags for multiple entities.
 *
 * @param string $entity_type
 *   The entity type to load.
 * @param array $entity_ids
 *   The list of entity IDs.
 * @param array $revision_ids
 *   Optional revision ID to load instead of the entity ID.
 *
 * @return array
 *   An array of tag data, keyed by entity ID, revision ID and language.
 */
function metatag_metatags_load_multiple($entity_type, array $entity_ids, array $revision_ids = array()) {
  // Double check entity IDs are all numeric.
  $entity_ids = array_filter($entity_ids, 'is_numeric');
  if (empty($entity_ids)) {
    return array();
  }

  // Ensure that the revision IDs are all numeric too.
  $revision_ids = array_filter($revision_ids, 'is_numeric');

  // Verify that there aren't any empty values copied in from
  // metatag_metatags_load(). Note: a zero indicates that the entity record does
  // not support revisions, so this is ok to do.
  $revision_ids = array_filter($revision_ids);

  // Also need to check if the metatag table exists since this condition could
  // fire before the table has been installed yet.
  if (!variable_get('metatag_schema_installed', FALSE)) {
    if (db_table_exists('metatag')) {
      variable_set('metatag_schema_installed', TRUE);
    }
    else {
      watchdog('metatag', 'The system tried to load metatag data before the schema was fully loaded.', array(), WATCHDOG_WARNING);
      return array();
    }
  }

  // Verify that the metatag.revision_id field has been added to the {metatag}
  // table schema.
  if (!variable_get('metatag_has_revision_id', FALSE)) {
    if (db_field_exists('metatag', 'revision_id')) {
      variable_set('metatag_has_revision_id', TRUE);
    }
    else {
      watchdog('metatag', 'The database updates need to be ran.', array(), WATCHDOG_WARNING);
      return array();
    }
  }

  // Get all translations of tag data for this entity.
  $query = db_select('metatag', 'm')
    ->fields('m', array('entity_id', 'revision_id', 'language', 'data'))
    ->condition('m.entity_type', $entity_type);
  // Filter by revision_ids if they are available. If not, filter by entity_ids.
  if (!empty($revision_ids)) {
    $query->condition('m.revision_id', $revision_ids, 'IN');
  }
  else {
    $query->condition('m.entity_id', $entity_ids, 'IN');
  }
  $result = $query->execute();

  // Marshal it into an array keyed by entity ID. Each value is an array of
  // translations keyed by language code.
  $metatags = array();
  while ($record = $result->fetchObject()) {
    $data = unserialize($record->data);

    // "Fix" any records that might be using old values. Ideally these will be
    // permanently fixed by being re-saved or re-exported.
    foreach (metatag_config_get_replacements() as $old_tag => $new_tag) {
      if (isset($data[$old_tag])) {
        $data[$new_tag] = $data[$old_tag];
        unset($data[$old_tag]);
      }
    }

    $metatags[$record->entity_id][$record->revision_id][$record->language] = $data;
  }

  return $metatags;
}

/**
 * Save an entity's tags.
 *
 * @param string $entity_type
 *   The entity type to load.
 * @param int $entity_id
 *   The entity's primary ID.
 * @param int $revision_id
 *   The entity's revision ID.
 * @param array $metatags
 *   All of the tag information, keyed by the language code. Most meta tags use
 *   the 'value' element, so the structure should look like:
 *   array(
 *     LANGUAGE_NONE => array(
 *       'title' => array(
 *         'value' => "This node's title!",
 *       ),
 *       'og:title' => array(
 *         'value' => "This node's title for Open Graph!",
 *       ),
 *       'og:image' => array(
 *         'value' => "[node:field_thumbnail]",
 *       ),
 *     ),
 *   );
 * @param string|null $bundle
 *   The bundle of the entity that is being saved. Optional.
 */
function metatag_metatags_save($entity_type, $entity_id, $revision_id, $metatags, $bundle = NULL) {
  // Check that $entity_id is numeric because of Entity API and string IDs.
  if (!is_numeric($entity_id)) {
    return;
  }

  // Don't do anything if the entity type is not supported.
  if (!metatag_entity_supports_metatags($entity_type)) {
    return;
  }

  // Verify the entity bundle is supported, if not available just check the
  // entity type.
  if (!empty($bundle)) {
    if (!metatag_entity_supports_metatags($entity_type, $bundle)) {
      return;
    }
  }
  else {
    if (!metatag_entity_supports_metatags($entity_type)) {
      return;
    }
  }

  // The revision_id must be a numeric value; some entities use NULL for the
  // revision so change that to a zero.
  if (is_null($revision_id)) {
    $revision_id = 0;
  }

  // Handle scenarios where the metatags are completely empty, this will have
  // the effect of erasing the meta tags for those this entity.
  if (empty($metatags)) {
    $metatags = array();
    // Add an empty array record for each language.
    $languages = db_query("SELECT language
        FROM {metatag}
        WHERE (entity_type = :type)
        AND (entity_id = :id)
        AND (revision_id = :revision)",
      array(
        ':type'     => $entity_type,
        ':id'       => $entity_id,
        ':revision' => $revision_id,
      ))->fetchCol();
    foreach ($languages as $oldlang) {
      $metatags[$oldlang] = array();
    }
  }

  // Update each of the per-language metatag configurations in turn.
  foreach ($metatags as $langcode => $new_metatags) {
    // Allow other modules to alter the meta tags prior to saving using
    // hook_metatag_presave().
    foreach (module_implements('metatag_presave') as $module) {
      $function = "{$module}_metatag_presave";
      $function($new_metatags, $entity_type, $entity_id, $revision_id, $langcode);
    }

    // If the data array is empty, there is no data to actually save, so just
    // delete the record from the database.
    if (empty($new_metatags)) {
      db_delete('metatag')
        ->condition('entity_type', $entity_type)
        ->condition('entity_id', $entity_id)
        ->condition('revision_id', $revision_id)
        ->condition('language', $langcode)
        ->execute();
    }
    // Otherwise save the data for this entity.
    else {
      db_merge('metatag')
        ->key(array(
          'entity_type' => $entity_type,
          'entity_id' => $entity_id,
          'language' => $langcode,
          'revision_id' => $revision_id,
        ))
        ->fields(array(
          'data' => serialize($new_metatags),
        ))
        ->execute();
    }
  }

  // Clear cached data.
  metatag_metatags_cache_clear($entity_type, $entity_id);

  // Clear the entity cache.
  entity_get_controller($entity_type)->resetCache(array($entity_id));
}

/**
 * Delete an entity's tags.
 *
 * @param string $entity_type
 *   The entity type.
 * @param int $entity_id
 *   The entity's ID.
 * @param int $revision_id
 *   The entity's VID.
 * @param string $langcode
 *   The language ID of the entry to delete. If left blank, all language
 *   entries for this entity will be deleted.
 */
function metatag_metatags_delete($entity_type, $entity_id, $revision_id = NULL, $langcode = NULL) {
  $revision_ids = array();
  if (!empty($revision_id)) {
    $revision_ids[] = $revision_id;
  }
  return metatag_metatags_delete_multiple($entity_type, array($entity_id), $revision_ids, $langcode);
}

/**
 * Delete multiple entities' tags.
 *
 * @param string $entity_type
 *   The entity type.
 * @param array $entity_ids
 *   The list of IDs.
 * @param array $revision_ids
 *   An optional list of revision IDs; if omitted all revisions will be deleted.
 * @param string $langcode
 *   The language ID of the entities to delete. If left blank, all language
 *   entries for the enities will be deleted.
 *
 * @return bool
 *   If any problems were encountered will return FALSE, otherwise TRUE.
 */
function metatag_metatags_delete_multiple($entity_type, array $entity_ids, array $revision_ids = array(), $langcode = NULL) {
  // Double check entity IDs and revision IDs are numeric.
  $entity_ids = array_filter($entity_ids, 'is_numeric');
  $revision_ids = array_filter($revision_ids, 'is_numeric');

  if (!empty($entity_ids) || !empty($revision_ids)) {
    $transaction = db_transaction();
    try {
      // Let other modules know about the records being deleted using
      // hook_metatag_metatags_delete().
      module_invoke_all('metatag_metatags_delete', $entity_type, $entity_ids, $revision_ids, $langcode);

      // Set the entity to delete.
      $query = db_delete('metatag')
        ->condition('entity_type', $entity_type);

      // If revision IDs were specified then just use those in the query.
      if (!empty($revision_ids)) {
        $query->condition('revision_id', $revision_ids, 'IN');
      }
      // No revision IDs were specified, so work from the entity IDs.
      else {
        $query->condition('entity_id', $entity_ids, 'IN');
      }

      // Limit to a language if one was specified.
      if (!empty($langcode)) {
        $query->condition('language', $langcode);
      }

      // Perform the deletion(s).
      $query->execute();

      // Clear cached data.
      metatag_metatags_cache_clear($entity_type, $entity_ids);

      // Clear the caches for these entities.
      entity_get_controller($entity_type)->resetCache($entity_ids);

      return TRUE;
    }
    catch (Exception $e) {
      $transaction->rollback();
      watchdog_exception('metatag', $e);
      throw $e;
    }
  }
  else {
    watchdog('metatag', 'No entity IDs or revision IDs were submitted to metatag_metatags_delete_multiple().');
  }

  return FALSE;
}

/**
 * Clear the cached records for a given entity type or entity ID.
 *
 * @param string $entity_type
 *   The entity type to clear.
 */
function metatag_metatags_cache_clear($entity_type, $entity_ids = NULL) {
  if (empty($entity_ids)) {
    cache_clear_all("output:$entity_type", 'cache_metatag', TRUE);
  }
  else {
    if (!is_array($entity_ids)) {
      $entity_ids = array($entity_ids);
    }
    foreach ($entity_ids as $entity_id) {
      cache_clear_all("output:$entity_type:$entity_id", 'cache_metatag');
    }
  }
}

/**
 * Implements hook_entity_load().
 */
function metatag_entity_load($entities, $entity_type) {
  // Wrap this in a try-catch block to work around occasions when the schema
  // hasn't been updated yet.
  try {
    if (metatag_entity_supports_metatags($entity_type)) {
      // Get the revision_ids.
      $revision_ids = array();

      // Track the entity IDs for values to load.
      $entity_ids = array();

      // Some entities don't support revisions.
      $supports_revisions = TRUE;

      // Extract the revision ID and verify the entity's bundle is supported.
      foreach ($entities as $key => $entity) {
        list($entity_id, $revision_id, $bundle) = entity_extract_ids($entity_type, $entity);

        // Verify that each entity bundle supports Metatag.
        if (metatag_entity_supports_metatags($entity_type, $bundle)) {
          $entity_ids[] = $entity_id;

          if (!empty($revision_id)) {
            $revision_ids[] = $revision_id;
          }
        }
      }

      // Only proceed if either there were revision IDs identified, or the
      // entity doesn't support revisions anyway.
      if (!empty($entity_ids)) {
        // Load all meta tags for these entities.
        $metatags = metatag_metatags_load_multiple($entity_type, $entity_ids, $revision_ids);

        // Assign the metatag records for the correct revision ID.
        if (!empty($metatags)) {
          foreach ($entities as $entity_id => $entity) {
            list($entity_id, $revision_id) = entity_extract_ids($entity_type, $entity);
            $revision_id = intval($revision_id);
            $entities[$entity_id]->metatags = isset($metatags[$entity_id][$revision_id]) ? $metatags[$entity_id][$revision_id] : array();
          }
        }
      }
    }
  }
  catch (Exception $e) {
    watchdog('metatag', 'Error loading meta tag data, do the <a href="@update">database updates</a> need to be run? The error occurred when loading record(s) %ids for the %type entity type. The error message was: %error',
      array(
        '@update' => base_path() . 'update.php',
        '%ids' => implode(', ', array_keys($entities)),
        '%type' => $entity_type,
        '%error' => $e->getMessage(),
      ),
    WATCHDOG_WARNING);

    // Don't display the same message twice for Drush.
    if (drupal_is_cli()) {
      drupal_set_message(t('Run your updates, like drush updb.'));
    }
    // Only message people who can see it in watchdog and can likely fix it.
    elseif (user_access('access site reports')) {
      drupal_set_message(t('Error loading meta tag data, do the <a href="@update">database updates</a> need to be run?', array('@update' => base_path() . 'update.php')), 'error');
    }
  }
}

/**
 * Implements hook_entity_insert().
 */
function metatag_entity_insert($entity, $entity_type) {
  if (isset($entity->metatags)) {
    list($entity_id, $revision_id, $bundle) = entity_extract_ids($entity_type, $entity);

    // Verify that this entity type / bundle is supported.
    if (!metatag_entity_supports_metatags($entity_type, $bundle)) {
      return;
    }

    $revision_id = intval($revision_id);

    // Determine the entity's language.
    $langcode = entity_language($entity_type, $entity);

    // Unfortunately due to how core works, the normal entity_language()
    // function returns 'und' instead of the node's language during node
    // creation.
    if ((empty($langcode) || $langcode == LANGUAGE_NONE) && !empty($entity->language)) {
      $langcode = $entity->language;
    }

    // If no language was still found, use the 'no language' value.
    if (empty($langcode)) {
      $langcode = LANGUAGE_NONE;
    }

    // Work-around for initial entity creation where a language was selection
    // but where it's different to the form's value.
    if (!isset($entity->metatags[$langcode]) && isset($entity->metatags[LANGUAGE_NONE])) {
      $entity->metatags[$langcode] = $entity->metatags[LANGUAGE_NONE];
      unset($entity->metatags[LANGUAGE_NONE]);
    }

    // Support for Workbench Moderation.
    if ($entity_type == 'node' && _metatag_isdefaultrevision($entity)) {
      return;
    }

    metatag_metatags_save($entity_type, $entity_id, $revision_id, $entity->metatags, $bundle);
  }
}

/**
 * Implements hook_entity_update().
 */
function metatag_entity_update($entity, $entity_type) {
  list($entity_id, $revision_id, $bundle) = entity_extract_ids($entity_type, $entity);

  // If this entity object isn't allowed meta tags, don't continue.
  if (!metatag_entity_supports_metatags($entity_type, $bundle)) {
    return;
  }

  $revision_id = intval($revision_id);

  if (isset($entity->metatags)) {
    // Determine the entity's new language. This will always be accurate as the
    // language value will already have been updated by the time this function
    // executes, and it will be loaded for the correct edit process.
    $new_language = metatag_entity_get_language($entity_type, $entity);

    // If applicable, determine the entity's original language. This cannot be
    // obtained via the normal API as that data will already have been updated,
    // instead check to see if the entity has an old-fasioned 'language' value.
    if (isset($entity->original) && isset($entity->language) && isset($entity->original->language)) {
      $old_language = $entity->original->language;

      // If the language has changed then additional checking needs to be done.
      // Need to compare against the entity's raw language value as they will
      // be different when updating a translated entity, versus an untranslated
      // entity or a source entity for translation, and give a false positive.
      if ($new_language == $entity->language && $new_language != $old_language) {
        // If this entity is not translated, or if it is translated but the
        // translation was previously created, then some language cleanup needs
        // to be done.
        if (!isset($entity->translation) || (isset($entity->translation) && !empty($entity->translation['created']))) {
          // Delete the old language record. This will not affect old revisions.
          db_delete('metatag')
            ->condition('entity_type', $entity_type)
            ->condition('entity_id', $entity_id)
            ->condition('revision_id', $revision_id)
            ->condition('language', $old_language)
            ->execute();

          // Swap out the metatag values for the two languages.
          if (isset($entity->metatags[$old_language])) {
            $entity->metatags[$new_language] = $entity->metatags[$old_language];
            unset($entity->metatags[$old_language]);
          }
        }
      }
    }

    // Support for Workbench Moderation.
    if ($entity_type == 'node' && _metatag_isdefaultrevision($entity)) {
      return;
    }

    // Save the record.
    metatag_metatags_save($entity_type, $entity_id, $revision_id, $entity->metatags, $bundle);
  }
  else {
    // Still ensure the meta tag output is cached.
    metatag_metatags_cache_clear($entity_type, $entity_id);
  }
}

/**
 * Implements hook_entity_delete().
 */
function metatag_entity_delete($entity, $entity_type) {
  list($entity_id) = entity_extract_ids($entity_type, $entity);
  metatag_metatags_delete($entity_type, $entity_id);
}

/**
 * Implements hook_field_attach_delete_revision().
 */
function metatag_field_attach_delete_revision($entity_type, $entity) {
  list($entity_id, $revision_id) = entity_extract_ids($entity_type, $entity);
  $revision_id = intval($revision_id);
  metatag_metatags_delete($entity_type, $entity_id, $revision_id);
}

/**
 * Build and alter metatag instance name.
 *
 * @param object $entity
 *   The entity object to generate the metatags instance name for.
 * @param string $entity_type
 *   The entity type of the entity.
 * @param string $bundle
 *   The bundle of the entity.
 *
 * @return string
 *   The resulting name of the config instance.
 */
function metatag_get_entity_metatags_instance($entity, $entity_type, $bundle) {
  $instance = "{$entity_type}:{$bundle}";
  drupal_alter('metatag_get_entity_metatags_instance', $instance, $entity, $entity_type, $bundle);
  return $instance;
}

/**
 * Implements hook_entity_view().
 *
 * Provides additional argument to allow the display to be forced, to work
 * around problems elsewhere in the APIs.
 */
function metatag_entity_view($entity, $entity_type, $view_mode, $langcode, $force = FALSE) {
  // Only run this function once per page load, for an entity which is allowed
  // metatags.
  static $i_will_say_this_only_once = FALSE;

  // Only proceed if this entity object is the page being viewed.
  if (_metatag_entity_is_page($entity_type, $entity)) {
    // Get the entity's extra information.
    list($entity_id, $revision_id, $bundle) = entity_extract_ids($entity_type, $entity);

    // If this entity object isn't allowed meta tags, don't continue.
    if (!metatag_entity_supports_metatags($entity_type, $bundle)) {
      return;
    }

    // Some API calls need to force the data loading.
    if (!$force) {
      // Only run this function once per page load.
      if ($i_will_say_this_only_once) {
        return;
      }
      $i_will_say_this_only_once = TRUE;
    }

    // CTools uses 'page_manager' view mode to indicate the full entity display
    // page rather than 'full', so streamline the internal processes.
    if ($view_mode == 'page_manager') {
      $view_mode = 'full';
    }

    // Generate metatags output.
    if ($output = metatag_generate_entity_metatags($entity, $entity_type, $langcode, $view_mode)) {
      $instance = metatag_get_entity_metatags_instance($entity, $entity_type, $bundle);
      // We need to register the term's metatags, so we can later fetch them.
      // @see metatag_page_build().
      metatag_page_set_metatags($instance, $output);
    }
  }
}

/**
 * Generate the metatags for a given entity.
 *
 * @param object $entity
 *   The entity object to generate the metatags for.
 * @param string $entity_type
 *   The entity type of the entity.
 * @param string $langcode
 *   The language code used for rendering the entity.
 * @param string $view_mode
 *   The view mode the entity is rendered in.
 * @param bool $cached
 *   TRUE if metatags can be loaded from and saved to the cache. FALSE if the
 *   cache should be bypassed.
 *
 * @return mixed
 *   A renderable array of metatags for the given entity.
 *   If this entity object isn't allowed meta tags, return FALSE (empty).
 */
function metatag_generate_entity_metatags($entity, $entity_type, $langcode = NULL, $view_mode = 'full', $cached = TRUE) {
  // Obtain some details of the entity that are needed elsewhere.
  list($entity_id, $revision_id, $bundle) = entity_extract_ids($entity_type, $entity);

  // If this entity object isn't allowed meta tags, don't continue.
  if (!metatag_entity_supports_metatags($entity_type, $bundle)) {
    return;
  }

  $revision_id = intval($revision_id);

  // Check if a specific metatag config exists, otherwise just use the global
  // one, stripping out the bundle.
  $instance = metatag_get_entity_metatags_instance($entity, $entity_type, $bundle);
  if (!metatag_config_load_with_defaults($instance, FALSE)) {
    $instance = "{$entity_type}";
  }

  // Determine the language this entity actually uses.
  $entity_language = metatag_entity_get_language($entity_type, $entity);

  // If no language was requested, try the language defined for this page
  // request.
  if (empty($langcode)) {
    $langcode = $GLOBALS['language_content']->language;
  }

  // This entity doesn't have any languages defined, i.e. it uses 'und'. This
  // can't conflict with loading the wrong language as entities either have no
  // language or they have specific one(s), they can't have both.
  if ($entity_language == LANGUAGE_NONE) {
    $langcode = LANGUAGE_NONE;
  }

  // If there are no meta tags for the currently identified language, and there
  // *are* meta tags defined for the entity's default language, use the entity's
  // default language's values, unless the "Don't load entity's default
  // language values if no languages match" option is enabled on the advanced
  // settings page.
  elseif (empty($entity->metatags[$langcode]) && !empty($entity->metatags[$entity_language]) && !variable_get('metatag_entity_no_lang_default', FALSE)) {
    $langcode = $entity_language;
  }

  // Other scenarios.
  else {
    // There's no need to do anything else - either there are meta tag values
    // created for the requested language or there aren't.
  }

  $cid = FALSE;
  $key = FALSE;
  $metatag_variants = array();

  // Caching is enabled.
  if ($cached && variable_get('metatag_cache_output', FALSE)) {
    // All possible variants of the metatags for this entity are stored in a
    // single cache entry.
    $cid = "output:$entity_type:$entity_id";

    // All applicable pieces for this current page.
    $key_parts = array(
      'entity_type' => $entity_type,
      'bundle' => $bundle,
      'entity_id' => $entity_id,
      'revision_id' => $revision_id,
      // Cache separately based on the language of the passed-in entity and the
      // overall active language of the page.
      'langcode' => $langcode,
      'language_content' => $GLOBALS['language_content']->language,
      'view_mode' => $view_mode,
    );
    $key = metatag_cache_default_cid_parts($key_parts);

    if ($cache = metatag_cache_get($cid)) {
      $metatag_variants = $cache->data;
    }
  }

  // If a cached object exists for this key, return it.
  if (!empty($key) && isset($metatag_variants[$key])) {
    $output = $metatag_variants[$key];
  }

  // Otherwise, generate the output tags.
  else {
    // Separate the meta tags.
    $metatags = isset($entity->metatags) ? $entity->metatags : array();

    // Build options for meta tag rendering.
    $options = array(
      'entity' => $entity,
      'entity_type' => $entity_type,
      'view_mode' => $view_mode,
    );

    // Ensure we actually pass a language object rather than language code.
    $languages = language_list();
    if (isset($languages[$langcode])) {
      $options['language'] = $languages[$langcode];
    }

    // Include token replacement data. Don't reload the entity object as doing
    // so would conflict with content editorial workflows.
    if (!empty($entity_id)) {
      $token_type = token_get_entity_mapping('entity', $entity_type);
      $options['token data'][$token_type] = $entity;
    }

    // Render the metatags and save to the cache.
    $output = metatag_metatags_view($instance, $metatags, $options);

    // If output caching is enabled, store the data for later.
    if (!empty($key) && !empty($cid)) {
      $metatag_variants[$key] = $output;
      metatag_cache_set($cid, $metatag_variants);
    }
  }

  return $output;
}

/**
 * Generate the metatags for a given entity.
 *
 * @param object $entity_id
 *   The entity id of the entity to generate the metatags for.
 * @param string $entity_type
 *   The entity type of the entity to generate the metatags for.
 * @param string $langcode
 *   The language code used for rendering the entity.
 *
 * @return array
 *   A renderable array of metatags for the given entity.
 */
function metatags_get_entity_metatags($entity_id, $entity_type, $langcode = NULL) {
  $entities = entity_load($entity_type, array($entity_id));
  $entity = reset($entities);
  return !empty($entity) ? metatag_generate_entity_metatags($entity, $entity_type, $langcode) : array();
}

/**
 * Build a renderable array of meta tag output.
 *
 * @param string $instance
 *   The configuration instance key of the meta tags to use, e.g.
 *   "node:article".
 * @param array $metatags
 *   An array of meta tag data.
 * @param array $options
 *   (optional) An array of options including the following keys and values:
 *   - language: A language object.
 *   - token data: An array of data to pass into token_replace() during
 *                 meta tag value generation.
 */
function metatag_metatags_view($instance, array $metatags = array(), array $options = array()) {
  $output = array();

  // Convert language codes to a language object.
  if (isset($options['language']) && is_string($options['language'])) {
    $languages = language_list();
    $options['language'] = isset($languages[$options['language']]) ? $languages[$options['language']] : NULL;
  }

  if (empty($options['language'])) {
    $options['language'] = $GLOBALS['language_content'];
  }

  // If there are any tags, determine the translation to display.
  if (!empty($metatags)) {
    // Get the display language; default to the entity's language.
    if (isset($options['language']) && isset($options['language']->language) && isset($metatags[$options['language']->language])) {
      $metatags = $metatags[$options['language']->language];
    }
    // If no language requested, use the no-language value.
    elseif (!empty($metatags[LANGUAGE_NONE])) {
      $metatags = $metatags[LANGUAGE_NONE];
    }
    else {
      $metatags = array();
    }
  }

  // Add any default tags to the mix.
  $metatags += metatag_config_load_with_defaults($instance);

  $options['instance'] = $instance;

  // Trigger hook_metatag_metatags_alter(). Allow the raw meta tags to be
  // modified prior to rendering.
  drupal_alter('metatag_metatags', $metatags, $instance, $options);

  // Don't output meta tags that only contain the pager.
  $current_pager = metatag_get_current_pager();

  foreach ($metatags as $metatag => $data) {
    if ((!empty($data['value']) || (isset($data['value']) && is_numeric($data['value'])))
      && $metatag_instance = metatag_get_instance($metatag, $data)) {
      $tag_output = $metatag_instance->getElement($options);
      // Don't output the pager if that's all there is.
      if ($tag_output != $current_pager) {
        $output[$metatag] = $tag_output;
      }
    }
  }

  // Allow the output meta tags to be modified using
  // hook_metatag_metatags_view_alter().
  drupal_alter('metatag_metatags_view', $output, $instance, $options);

  return $output;
}

/**
 * Get the pager string for the current page.
 *
 * @return string
 *   Returns a string based upon the 'metatag_pager_string' variable and the
 *   current page number.
 */
function metatag_get_current_pager() {
  if (isset($_GET['page']) && !empty($_GET['page']) && is_numeric($_GET['page'])) {
    $page = intval($_GET['page']) + 1;
    if ($page > 1) {
      $pager = variable_get('metatag_pager_string', 'Page PAGER | ');
      return str_replace('PAGER', $page, $pager);
    }
  }
}

/**
 * Returns metatags values.
 */
function metatag_metatags_values($instance, array $metatags = array(), array $options = array()) {
  $values = array();

  // Apply defaults to the data for each language.
  foreach ($metatags as $language => $metatag) {
    $metatags[$language] += metatag_config_load_with_defaults($instance);
  }

  // Generate output only if we have a valid language.
  if (isset($options['language']) && is_string($options['language']) && isset($metatags[$options['language']])) {
    $language = $options['language'];

    // Convert language codes to a language object.
    $languages = language_list();
    $options['language'] = isset($languages[$language]) ? $languages[$language] : NULL;
    $options['instance'] = $instance;
    // Get output elements.
    foreach ($metatags[$language] as $metatag => $data) {
      if ($metatag_instance = metatag_get_instance($metatag, $data)) {
        $values[$metatag] = $metatag_instance->getValue($options);
      }
    }
  }

  return array_filter($values, 'drupal_strlen');
}

/**
 * Build a FAPI array for editing meta tags.
 *
 * @param array $form
 *   The current FAPI array.
 * @param string $instance
 *   The configuration instance key of the metatags to use, e.g. "node:article".
 * @param array $metatags
 *   An array of metatag data.
 * @param array $options
 *   (optional) An array of options including the following keys and values:
 *   - token types: An array of token types to be passed to theme_token_tree().
 */
function metatag_metatags_form(array &$form, $instance, array $metatags = array(), array $options = array()) {
  $info = metatag_get_info();
  if (empty($info['tags'])) {
    return;
  }

  // Work out the language code to use, default to NONE.
  $langcode = LANGUAGE_NONE;
  if (!empty($form['#entity_type'])) {
    if (!empty($form['#entity'])) {
      $langcode = metatag_entity_get_language($form['#entity_type'], $form['#entity']);
    }
    else {
      $entity_info = entity_get_info($form['#entity_type']);
      if (!empty($entity_info['token type'])) {
        $entity_key = '#' . $entity_info['token type'];
        if (!empty($form[$entity_key])) {
          $langcode = metatag_entity_get_language($form['#entity_type'], $form[$entity_key]);
        }
      }
    }
  }

  // Merge in the default options.
  $options += array(
    'token types' => array(),
    'defaults' => metatag_config_load_with_defaults($instance),
    'instance' => $instance,
  );

  // Trigger hook_metatag_token_types_alter().
  // Allow the defined tokens to be modified.
  drupal_alter('metatag_token_types', $options);

  $form['metatags'] = array(
    '#type' => 'fieldset',
    '#title' => t('Meta tags'),
    '#collapsible' => TRUE,
    '#collapsed' => TRUE,
    '#multilingual' => TRUE,
    '#tree' => TRUE,
    '#access' => user_access('edit meta tags') || user_access('administer meta tags'),
    '#weight' => 40,
    '#language' => $langcode,
    '#attributes' => array(
      'class' => array('metatags-form'),
    ),
  );
  $form['metatags'][$langcode] = array(
    '#metatag_defaults' => $options['defaults'],
    '#type' => 'container',
    '#multilingual' => TRUE,
    '#tree' => TRUE,
  );
  // Show a different intro message for entity pages vs config pages.
  if (isset($form['#entity'])) {
    $form['metatags']['intro_text'] = array(
      '#markup' => '<p>' . t('Configure the meta tags below. Tokens, e.g. "[node:summary]", automatically insert the corresponding information from that field or value, which helps to avoid redundant meta data and possible search engine penalization; see the "Browse available tokens" popup for more details.') . '</p>',
      '#weight' => -10,
    );
  }
  else {
    $form['metatags']['intro_text'] = array(
      '#markup' => '<p>' . t('Configure the meta tags below. Use tokens (see the "Browse available tokens" popup) to avoid redundant meta data and search engine penalization. For example, a \'keyword\' value of "example" will be shown on all content using this configuration, whereas using the [node:field_keywords] automatically inserts the "keywords" values from the current entity (node, term, etc).') . '</p>',
      '#weight' => -10,
    );
  }

  // Only support vertical tabs if there is a vertical tab element.
  foreach (element_children($form) as $key) {
    if (isset($form[$key]['#type']) && $form[$key]['#type'] == 'vertical_tabs') {
      $form['metatags']['#group'] = $key;
      $form['metatags']['#attached']['js']['vertical-tabs'] = drupal_get_path('module', 'metatag') . '/metatag.vertical-tabs.js';
      break;
    }
  }

  // Merge in the default meta tag configurations.
  $metatags += $options['defaults'];

  // This will be used later.
  $group_metatag_access = array();

  // Build the form for each metatag.
  foreach ($info['tags'] as $metatag => $metatag_info) {
    // @todo Replace context matching with hook_metatag_access().
    if (isset($options['context']) && isset($metatag_info['context'])) {
      if (!in_array($options['context'], $metatag_info['context'])) {
        continue;
      }
    }

    $metatag_instance = metatag_get_instance($metatag, isset($metatags[$metatag]) ? $metatags[$metatag] : array());
    if (empty($metatag_instance)) {
      continue;
    }

    // Get the form element from the meta tag class.
    $metatag_form = $metatag_instance->getForm($options);
    if (isset($metatag_form['value']['#default_value']) && is_array($metatag_form['value']['#default_value'])) {
      $metatag_form['value']['#default_value'] = array_filter($metatag_form['value']['#default_value']);
    }

    // Add a default value form element.
    if (isset($options['defaults'][$metatag]['value'])) {
      if (is_array($options['defaults'][$metatag]['value'])) {
        $options['defaults'][$metatag]['value'] = array_filter($options['defaults'][$metatag]['value']);
      }

      $metatag_form['default'] = array(
        '#type' => 'hidden',
        '#value' => $options['defaults'][$metatag]['value'],
      );
    }

    // Optional extended edit permissions.
    if (variable_get('metatag_extended_permissions', FALSE)) {
      $metatag_form['#access'] = user_access('edit meta tag: ' . $metatag) || user_access('administer meta tags');
    }
    else {
      $metatag_form['#access'] = $form['metatags']['#access'];
    }

    if (!empty($metatag_info['group'])) {
      $group_key = $metatag_info['group'];
      if (isset($info['groups'][$group_key]['label']) && !isset($form['metatags'][$langcode][$group_key])) {
        $group = $info['groups'][$group_key] + array('form' => array(), 'description' => NULL);
        $form['metatags'][$langcode][$group_key] = $group['form'] + array(
          '#type' => 'fieldset',
          '#title' => $group['label'],
          '#description' => !empty($group['description']) ? $group['description'] : '',
          '#collapsible' => TRUE,
          '#collapsed' => TRUE,
        );
      }
      $form['metatags'][$langcode][$group_key][$metatag] = $metatag_form + array(
        '#parents' => array('metatags', $langcode, $metatag),
      );

      // Hide the fieldset itself if there is not at least one of the meta tag
      // fields visible.
      if (variable_get('metatag_extended_permissions', FALSE)) {
        $form['metatags'][$langcode][$group_key]['#access'] = count(element_get_visible_children($form['metatags'][$langcode][$group_key])) > 0;
      }
      else {
        $form['metatags'][$langcode][$group_key]['#access'] = $form['metatags']['#access'];
      }
      // Structure the access parameter into this array, and make use of it
      // later when we move on. Besides, this foreach is getting heavy.
      $group_metatag_access[$group_key] = $form['metatags'][$langcode][$group_key]['#access'];
    }
    else {
      $form['metatags'][$langcode][$metatag] = $metatag_form;
    }
  }

  // Hide the fieldset itself if there is not at least one of the meta tag
  // fields visible; only bother checking this if the user had edit access in
  // the first place.
  if ($form['metatags']['#access'] && variable_get('metatag_extended_permissions', FALSE)) {
    $form['metatags']['#access'] = count(element_get_visible_children($form['metatags'][$langcode])) > 0;
  }

  // Check the #access of each group. If it passed, we display options for
  // tokens. By this we update the #description of each group.
  if ($form['metatags']['#access']) {
    // Check if each meta tag group is being displayed.
    if (!empty($group_metatag_access)) {
      // Built the token browser link. For value "all" theme_token_tree()
      // compares with string, not array.
      if (in_array('all', $options['token types'])) {
        $options['token types'] = 'all';
      }
      $token_listing_link = theme('token_tree',
        array(
          'token_types' => $options['token types'],
          'dialog' => TRUE,
        )
      );

      foreach ($group_metatag_access as $group_key => $token_access) {
        if ($token_access) {
          // Update the description.
          if (isset($form['metatags'][$langcode][$group_key]['#description'])) {
            $form['metatags'][$langcode][$group_key]['#description'] .= '<br />';
          }
          else {
            $form['metatags'][$langcode][$group_key]['#description'] = '';
          }

          // Add the token browser popup link.
          $form['metatags'][$langcode][$group_key]['#description'] .= $token_listing_link;
        }
      }
    }
  }

  // Add a submit handler to compare the submitted values against the default
  // values.
  $form += array('#submit' => array());
  if (module_exists('commerce') && isset($form['#entity_type']) && $form['#entity_type'] == 'commerce_product') {
    $form['actions']['submit']['#submit'][] = 'metatag_commerce_product_form_submit';
  }
  else {
    array_unshift($form['#submit'], 'metatag_metatags_form_submit');
  }
}

/**
 * Form API submission callback.
 *
 * Unset meta tag values that equal their default values, and load any
 * additional meta tag values for other languages so that they can be properly
 * saved later on.
 *
 * @see metatag_metatags_save()
 */
function metatag_metatags_form_submit($form, &$form_state) {
  if (!empty($form_state['values']['metatags'])) {
    // Unset meta tag values that equal their default values.
    foreach ($form_state['values']['metatags'] as $langcode => $values) {
      if (!empty($form['metatags'][$langcode]['#metatag_defaults'])) {
        metatag_filter_values_from_defaults($form_state['values']['metatags'][$langcode], $form['metatags'][$langcode]['#metatag_defaults']);
      }
    }

    // Need to load the entity's values for other languages, otherwise they will
    // be incorrectly deleted later on.
    if (isset($form['#entity']) && !empty($form['#entity']->metatags)) {
      foreach ($form['#entity']->metatags as $langcode => $values) {
        if (!isset($form_state['values']['metatags'][$langcode])) {
          $form_state['values']['metatags'][$langcode] = $values;
        }
      }
    }
  }
}

/**
 * Form API submission callback for Commerce product.
 *
 * Unlike metatag_metatags_form_submit.
 *
 * @see metatag_metatags_save()
 */
function metatag_commerce_product_form_submit($form, &$form_state) {
  // Trigger the normal meta tag form submission.
  metatag_metatags_form_submit($form, $form_state);

  // The entity being saved.
  $entity_type = 'commerce_product';
  $product = $form_state[$entity_type];
  $entity_id = $product->product_id;
  $revision_id = $product->revision_id;

  // Get the full entity details.
  list(, , $bundle) = entity_extract_ids($entity_type, $product);

  // Update the meta tags for this entity type.
  metatag_metatags_save($entity_type, $entity_id, $revision_id, $form_state['values']['metatags'], $bundle);
}

/**
 * Implements hook_field_extra_fields().
 */
function metatag_field_extra_fields() {
  $extra = array();
  foreach (entity_get_info() as $entity_type => $entity_info) {
    if (!empty($entity_info['bundles'])) {
      foreach (array_keys($entity_info['bundles']) as $bundle) {
        if (metatag_entity_supports_metatags($entity_type, $bundle)) {
          $extra[$entity_type][$bundle]['form']['metatags'] = array(
            'label' => t('Meta tags'),
            'description' => t('Meta tag module form elements.'),
            'weight' => 40,
          );
        }
      }
    }
  }
  return $extra;
}

/**
 * Check whether the requested entity type (and bundle) support metatag.
 *
 * By default the entities are disabled, only certain entities will have been
 * enabled during installation. If an entity type is enabled it is assumed that
 * the entity bundles will also be enabled by default.
 *
 * @see metatag_entity_type_is_suitable()
 */
function metatag_entity_supports_metatags($entity_type = NULL, $bundle = NULL) {
  $entity_types = &drupal_static(__FUNCTION__);

  // Identify which entities & bundles are supported the first time the
  // function is called.
  if (!isset($entity_types)) {
    foreach (entity_get_info() as $entity_name => $entity_info) {
      // Verify that this entity type is suitable.
      $entity_types[$entity_name] = metatag_entity_type_is_suitable($entity_name, $entity_info);

      // The entity type technically supports entities.
      if (!empty($entity_types[$entity_name])) {
        // Entiy types are enabled by default.
        // Allow entities to be disabled by assigning a variable
        // 'metatag_enable_{$entity_type}' the value FALSE, e.g.:
        //
        // // Disable metatags for file_entity.
        // $conf['metatag_enable_file'] = FALSE;
        //
        // @see Settings page.
        if (variable_get('metatag_enable_' . $entity_name, FALSE) == FALSE) {
          $entity_types[$entity_name] = FALSE;
        }

        // Check each bundle.
        else {
          $entity_types[$entity_name] = array();
          foreach ($entity_info['bundles'] as $bundle_name => $bundle_info) {
            // If only one bundle exists, take configuration for entity, to
            // reflect options as they are available in the UI.
            if (count($entity_info['bundles']) === 1) {
              $entity_types[$entity_name][$bundle_name] = variable_get('metatag_enable_' . $entity_name, FALSE) == TRUE;
              continue;
            }

            // Allow bundles to be disabled by assigning a variable
            // 'metatag_enable_{$entity_type}__{$bundle}' the value FALSE, e.g.:
            //
            // // Disable metatags for carousel nodes.
            // $conf['metatag_enable_node__carousel'] = FALSE;
            //
            // @see Settings page.
            if (variable_get('metatag_enable_' . $entity_name . '__' . $bundle_name, TRUE) == FALSE) {
              $entity_types[$entity_name][$bundle_name] = FALSE;
            }
            else {
              $entity_types[$entity_name][$bundle_name] = TRUE;
            }
          }
        }
      }
    }
  }

  // It was requested to check a specific entity.
  if (isset($entity_type)) {
    // It was also requested to check a specific bundle for this entity.
    if (isset($bundle)) {
      $supported = !empty($entity_types[$entity_type][$bundle]);
    }

    // Check the entity.
    else {
      $supported = !empty($entity_types[$entity_type]);
    }

    return $supported;
  }

  // If nothing specific was requested, return the complete list of supported
  // entities & bundles.
  return $entity_types;
}

/**
 * Enable support for a specific entity type if setting does not exist.
 *
 * @param string $entity_type
 *    The entity type.
 * @param string $bundle
 *    The bundle of the entity.
 * @param bool $force_enable
 *   If TRUE, then the type is enabled regardless of any stored variables.
 *
 * @return bool
 *   TRUE if either the bundle or entity type was enabled by this function.
 */
function metatag_entity_type_enable($entity_type, $bundle = NULL, $force_enable = FALSE) {
  // The bundle was defined.
  $bundle_set = FALSE;
  if (isset($bundle)) {
    $stored_bundle = variable_get('metatag_enable_' . $entity_type . '__' . $bundle, NULL);
    if ($force_enable || !isset($stored_bundle)) {
      variable_set('metatag_enable_' . $entity_type . '__' . $bundle, TRUE);
      $bundle_set = TRUE;
    }
  }

  // Always enable the entity type, because otherwise there's no point in
  // enabling the bundle.
  $entity_type_set = FALSE;
  $stored_entity_type = variable_get('metatag_enable_' . $entity_type, NULL);
  if ($force_enable || !isset($stored_entity_type)) {
    variable_set('metatag_enable_' . $entity_type, TRUE);
    $entity_type_set = TRUE;
  }

  // Clear the static cache so that the entity type / bundle will work.
  drupal_static_reset('metatag_entity_supports_metatags');

  return $bundle_set || $entity_type_set;
}

/**
 * Disable support for a specific entity type.
 *
 * @param string $entity_type
 *    The entity type.
 * @param string $bundle
 *    The bundle of the entity.
 */
function metatag_entity_type_disable($entity_type, $bundle = NULL) {
  // The bundle was defined.
  if (isset($bundle)) {
    variable_set('metatag_enable_' . $entity_type . '__' . $bundle, FALSE);
  }
  // The bundle was not defined.
  else {
    variable_set('metatag_enable_' . $entity_type, FALSE);
  }

  // Clear the static cache so that the entity type / bundle will work.
  drupal_static_reset('metatag_entity_supports_metatags');
}

/**
 * Add meta tags to be added later with metatag_page_build().
 *
 * @param string $instance
 *   The configuration instance key of the meta tags, e.g. "node:article".
 * @param array $metatags
 *   An array of meta tags from metatag_metatags_view().
 */
function metatag_page_set_metatags($instance, $metatags) {
  $page_metatags = &drupal_static(__FUNCTION__, array());
  $page_metatags[$instance] = $metatags;
}

/**
 * Retrieve the array of meta tags to be added with metatag_page_build().
 */
function metatag_page_get_metatags() {
  // @todo Add alter to this result?
  return drupal_static('metatag_page_set_metatags', array());
}

/**
 * Implements hook_page_build().
 */
function metatag_page_build(&$page) {
  // By default do not add meta tags to admin pages. To enable meta tags on
  // admin pages set the 'metatag_tag_admin_pages' variable to TRUE.
  if (path_is_admin(current_path()) && !variable_get('metatag_tag_admin_pages', FALSE)) {
    return;
  }

  // Special consideration for the Me module, which uses the "user/me" path and
  // will cause problems.
  if (arg(0) == 'user' && arg(1) == 'me' && function_exists('me_menu_alter')) {
    return;
  }

  // The page region can be changed.
  $region = variable_get('metatag_page_region', 'content');

  // Ensure these arrays exist, otherwise several use cases will fail.
  if (!isset($page[$region]) || !is_array($page[$region])) {
    $page[$region] = array();
  }
  if (!isset($page[$region]['metatags']) || !is_array($page[$region]['metatags'])) {
    $page[$region]['metatags'] = array();
  }

  // The front page has special consideration. Also, check if this is an error
  // (403/404) page, those also require separate handling.
  $instance = 'global:frontpage';
  if ((drupal_is_front_page() && metatag_config_is_enabled($instance))
    || ($instance = metatag_is_error_page())) {

    // Generate the cache ID.
    $cid_parts = array(
      'instance' => $instance,
    );
    $cid = metatag_cache_default_cid_parts($cid_parts);

    if (variable_get('metatag_cache_output', FALSE)) {
      if ($cache = metatag_cache_get($cid)) {
        $metatags = $cache->data;
      }
      else {
        $metatags = metatag_metatags_view($instance, array());
        metatag_cache_set($cid, $metatags);
      }
    }
    else {
      $metatags = metatag_metatags_view($instance, array());
    }

    $page[$region]['metatags'][$instance] = $metatags;
  }

  // Load any meta tags assigned via metatag_page_set_metatags(). Note: this
  // must include the necessary defaults.
  else {
    $page[$region]['metatags'] += metatag_page_get_metatags();
  }

  // If no meta tags were loaded at least load the global defaults. This may be
  // disabled, see README.txt for details.
  if (empty($page[$region]['metatags']) && variable_get('metatag_load_all_pages', TRUE)) {
    $instance = 'global';

    // Generate the cache ID.
    $cid_parts = array(
      'instance' => $instance,
      'path' => request_path(),
    );
    $cid = metatag_cache_default_cid_parts($cid_parts);

    if ($cache = metatag_cache_get($cid)) {
      $metatags = $cache->data;
    }
    else {
      $metatags = metatag_metatags_view($instance, array());
      // If output caching is enabled, save this for later.
      if (variable_get('metatag_cache_output', FALSE)) {
        metatag_cache_set($cid, $metatags);
      }
    }
    $page[$region]['metatags'][$instance] = $metatags;
  }
}

/**
 * Returns whether the current page is the page of the passed in entity.
 *
 * @param string $entity_type
 *    The entity type; e.g. 'node' or 'user'.
 * @param object $entity
 *    The entity object.
 *
 * @return mixed
 *   TRUE if the current page is the page of the specified entity, or FALSE
 *   otherwise. If $entity_type == 'comment' return empty (FALSE).
 */
function _metatag_entity_is_page($entity_type, $entity) {
  // Exclude comment entities as this conflicts with comment_fragment.module.
  if ($entity_type == 'comment') {
    return;
  }

  $uri = entity_uri($entity_type, $entity);
  $current_path = current_path();

  // Support for Workbench Moderation - if this is a node, check if the content
  // type supports moderation.
  if ($entity_type == 'node' && function_exists('workbench_moderation_node_type_moderated') && workbench_moderation_node_type_moderated($entity->type) === TRUE) {
    return !empty($uri['path']) && ($current_path == $uri['path'] || $current_path == $uri['path'] . '/draft');
  }

  // Support for core node revisions.
  elseif (!empty($uri['path']) && strpos($current_path, $uri['path']) === 0 && strpos($current_path, '/revisions/') && strpos($current_path, '/view')) {
    return TRUE;
  }

  // Support for Views' taxonomy_term pages with depth specifier, e.g.
  // "taxonomy_term/123/1/all".
  elseif ($entity_type == 'taxonomy_term' && strpos($current_path, $uri['path']) === 0 && count(explode('/', $current_path)) == 4) {
    return TRUE;
  }

  // Any other page.
  else {
    return !empty($uri['path']) && $current_path == $uri['path'];
  }
}

/**
 * Implements hook_field_attach_rename_bundle().
 */
function metatag_field_attach_rename_bundle($entity_type, $bundle_old, $bundle_new) {
  $instance_old = $entity_type . ':' . $bundle_old;
  $instance_new = $entity_type . ':' . $bundle_new;
  if ($config = metatag_config_load($instance_old)) {
    $config->instance = $instance_new;
    metatag_config_save($config);
    $config->instance = $instance_old;
    metatag_config_delete($config);
  }
}

/**
 * Implements hook_field_attach_delete_bundle().
 */
function metatag_field_attach_delete_bundle($entity_type, $bundle) {
  $instance = $entity_type . ':' . $bundle;
  if ($config = metatag_config_load($instance)) {
    metatag_config_delete($config);
  }
}

/**
 * Implements hook_field_attach_form().
 */
function metatag_field_attach_form($entity_type, $entity, &$form, &$form_state, $langcode) {
  // Entity_Translation will trigger this hook again, skip it.
  if (!empty($form_state['entity_translation']['is_translation'])) {
    return;
  }

  list($entity_id, $revision_id, $bundle) = entity_extract_ids($entity_type, $entity);

  if (!metatag_entity_supports_metatags($entity_type, $bundle)) {
    return;
  }

  $instance = metatag_get_entity_metatags_instance($entity, $entity_type, $bundle);

  // Grab the meta tags for display in the form if there are any.
  if (!empty($entity->metatags)) {
    // Identify the language to use with this entity.
    $entity_language = metatag_entity_get_language($entity_type, $entity);

    // If this is a new translation using Entity Translation, load the meta
    // tags from the entity's original language.
    if (module_exists('entity_translation') && empty($form['#entity_translation_source_form']) && ($handler = entity_translation_entity_form_get_handler($form, $form_state)) && isset($entity->metatags[$handler->getSourceLanguage()])) {
      $metatags = $entity->metatags[$handler->getSourceLanguage()];
    }
    // Determine from where we should get the tags.
    elseif (isset($entity->metatags[$langcode])) {
      // Set the tags to the translation set matching that of the form.
      $metatags = $entity->metatags[$langcode];
    }
    // There is no translation for this entity's tags in the current
    // language. Instead, display tags in the language of the entity, the
    // source language of translations. The will provide translators with the
    // original text to translate.
    elseif (isset($entity->metatags[$entity_language])) {
      $metatags = $entity->metatags[$entity_language];
    }
    // This is a preview so set the tags to the raw submission data.  No
    // language has been set.
    else {
      $metatags = $entity->metatags;
    }
  }
  else {
    $metatags = array();
  }

  // Certain circumstances can result in $metatags not being an array.
  if (!is_array($metatags)) {
    $metatags = array();
  }

  $options['token types'] = array(
    token_get_entity_mapping('entity', $entity_type),
  );
  $options['context'] = $entity_type;

  // @todo Remove metatag_form_alter() when https://www.drupal.org/node/1284642 is fixed in core.
  // metatag_metatags_form($form, $instance, $metatags, $options);
  $form['#metatags'] = array(
    'instance' => $instance,
    'metatags' => $metatags,
    'options' => $options,
  );
}

/**
 * Implements hook_form_alter().
 *
 * @todo Remove this when https://www.drupal.org/node/1284642 is fixed in core.
 */
function metatag_form_alter(&$form, $form_state, $form_id) {
  if (!empty($form['#metatags']) && !isset($form['metatags'])) {
    extract($form['#metatags']);
    metatag_metatags_form($form, $instance, $metatags, $options);
    unset($form['#metatags']);
  }
}

/**
 * Get the meta tag information array of a meta tag.
 *
 * @param string $name
 *   The meta tag name, e.g. description, for which the info shall be returned,
 *   or NULL to return an array with info about all meta tags.
 */
function metatag_get_info($type = NULL, $name = NULL) {
  // Use the advanced drupal_static() pattern, since this is called very often.
  static $drupal_static_fast;
  if (!isset($drupal_static_fast)) {
    $drupal_static_fast['metatag_info'] = &drupal_static(__FUNCTION__);
  }
  $info = &$drupal_static_fast['metatag_info'];

  global $language;
  if (!isset($info)) {
    // hook_metatag_info() includes translated strings, so each language is
    // cached separately.
    $cid = 'info:' . $language->language;

    if ($cache = metatag_cache_get($cid)) {
      $info = $cache->data;
    }
    else {
      // Obtain all metatag specs defined in other modules using
      // hook_metatag_info().
      $info = module_invoke_all('metatag_info');
      $info += array('tags' => array(), 'groups' => array());

      // Merge in default values.
      foreach ($info['tags'] as $key => $data) {
        $info['tags'][$key] += array(
          // Merge in default values.
          'name' => $key,
          'class' => 'DrupalTextMetaTag',
        );
      }

      // Let other modules alter the entity info using
      // hook_metatag_info_alter().
      drupal_alter('metatag_info', $info);

      metatag_cache_set($cid, $info);
    }
  }

  if (isset($type) && isset($name)) {
    return isset($info[$type][$name]) ? $info[$type][$name] : FALSE;
  }
  elseif (isset($type)) {
    return isset($info[$type]) ? $info[$type] : array();
  }
  else {
    return $info;
  }
}

/**
 * Return instance of metatag.
 */
function metatag_get_instance($metatag, array $data = array()) {
  $info = metatag_get_info('tags', $metatag);
  if (!empty($info['class']) && class_exists($info['class'])) {
    $class = $info['class'];
    return new $class($info, $data);
  }
}

/**
 * Return the string value of a meta tag.
 *
 * @param string $metatag
 *   The meta tag string.
 * @param array $data
 *   The array of data for the meta tag class instance.
 * @param array $options
 *   An optional array of additional options to pass to the getValue() method
 *   of the meta tag class instance.
 *   - raw: A boolean if TRUE will not perform token replacement.
 *
 * @return string
 *   A string value.
 */
function metatag_get_value($metatag, array $data, array $options = array()) {
  $value = '';
  if ($metatag_instance = metatag_get_instance($metatag, $data)) {
    $options["instance"] = $metatag;
    $value = $metatag_instance->getValue($options);
    if (is_array($value)) {
      $value = implode(', ', $value);
    }
  }
  return $value;
}

/**
 * Set a variable to be altered in metatag_preprocess_html().
 *
 * @see metatag_get_preprocess_variables()
 * @see metatag_preprocess_html()
 * @see metatag_preprocess_maintenance_page()
 */
function metatag_set_preprocess_variable($hook, $variable, $value) {
  $variables = &drupal_static(__FUNCTION__, array());
  $variables[$hook][$variable] = $value;
}

/**
 * Return an array of variables to be altered in preprocess functions.
 *
 * @see metatag_set_preprocess_variable()
 * @see metatag_preprocess_html()
 * @see metatag_preprocess_maintenance_page()
 */
function metatag_get_preprocess_variables($hook) {
  $variables = drupal_static('metatag_set_preprocess_variable', array());
  return isset($variables[$hook]) ? $variables[$hook] : array();
}

/**
 * Implements hook_preprocess_html().
 */
function metatag_preprocess_html(&$variables) {
  foreach (metatag_get_preprocess_variables('html') as $variable => $value) {
    $variables[$variable] = $value;
  }
}

/**
 * Implements hook_preprocess_maintenance_page().
 */
function metatag_preprocess_maintenance_page(&$variables) {
  foreach (metatag_get_preprocess_variables('html') as $variable => $value) {
    $variables[$variable] = $value;
  }
}

/**
 * Implements hook_html_head_alter().
 *
 * Hide tags added by core that are now handled by metatag.
 */
function metatag_html_head_alter(&$elements) {
  $metatags = array();
  $other_tags = array();
  foreach ($elements as $key => $data) {
    // Identify meta tags added by the Metatag module.
    if (strpos($key, 'metatag_') === 0) {
      $metatags[] = $key;
    }
    // Identify meta tags added by other modules.
    else {
      $other_tags[] = $key;
    }
  }

  // The meta tag keys to look for.
  $metatag_keys = array('name', 'property');

  // Attributes to look for.
  $attributes = array('name', 'rel');

  // Look for meta tags that were added by other modules and hide them.
  foreach ($metatags as $metatag_name) {
    $metatag = &$elements[$metatag_name];

    // Setting the #access attribute to these will stop them from being output
    // but still leave the tags present for other modules to interact with.
    foreach ($other_tags as $other_tag) {
      $other = &$elements[$other_tag];

      // Look for other meta tags that have one of the defined attributes which
      // matches one of the values from Metatag's tag.
      foreach ($attributes as $attribute) {
        if (isset($other['#attributes'], $other['#attributes'][$attribute]) && is_string($other['#attributes'][$attribute])) {
          foreach ($metatag_keys as $metatag_key) {
            if (isset($metatag[$metatag_key])) {
              if (strtolower($other['#attributes'][$attribute]) == $metatag[$metatag_key]) {
                $other['#access'] = FALSE;
              }
            }
          }
        }
      }
    }
  }

  // If the 'leave core tags' option is disabled then the following meta tags
  // will be removed if they're provided by core.
  if (!variable_get('metatag_leave_core_tags', FALSE)) {
    $core_tags = array(
      'generator',
      'canonical',
      'shortlink',
      // Leave the shortcut icon, that's more of a theming thing.
      // 'shortcut icon',.
    );
    foreach ($elements as $name => &$element) {
      // Ignore meta tags provided by Metatag.
      if (strpos($name, 'metatag_') === 0) {
        continue;
      }

      // Setting the #access attribute to these will stop them from being output
      // but still leave the tags present for other modules to interact with.
      foreach ($core_tags as $tag) {
        if (!empty($element['#attributes']['rel']) && $element['#attributes']['rel'] == $tag) {
          $element['#access'] = FALSE;
        }
        elseif (!empty($element['#attributes']['name']) && strtolower($element['#attributes']['name']) == $tag) {
          $element['#access'] = FALSE;
        }
      }
    }
  }
}

/**
 * Implements hook_get_form().
 */
function metatag_metatag_get_form($metatag, array $data = array(), array $options = array()) {
  $instance = metatag_get_instance($metatag, $data);
  return $instance->getForm($options);
}

/**
 * Returns Instance info if exists otherwise return FALSE.
 */
function metatag_config_instance_info($instance = NULL) {
  global $language;

  $info = &drupal_static(__FUNCTION__);

  // hook_metatag_info() includes translated strings, so each language is cached
  // separately.
  $cid = 'metatag:config:instance:info:' . $language->language;

  if (!isset($info)) {
    if ($cache = metatag_cache_get($cid)) {
      $info = $cache->data;
    }
    else {
      // Allow modules to act upon the record insertion using
      // hook_metatag_config_instance_info().
      $info = module_invoke_all('metatag_config_instance_info');

      // Allow other modules to customize the data using
      // hook_metatag_config_instance_info_alter().
      drupal_alter('metatag_config_instance_info', $info);

      metatag_cache_set($cid, $info);
    }
  }

  if (isset($instance)) {
    return isset($info[$instance]) ? $info[$instance] : FALSE;
  }
  else {
    return $info;
  }
}

/**
 * Filter out meta tag values that equal the default values.
 *
 * @todo Use information in $values[$metatag]['default'] rather than a $defaults parameter.
 */
function metatag_filter_values_from_defaults(array &$values, array $defaults = array()) {
  foreach ($values as $metatag => $data) {
    $default = isset($data['default']) ? $data['default'] : (isset($defaults[$metatag]['value']) ? $defaults[$metatag]['value'] : NULL);
    if (isset($default) && isset($data['value']) && $default === $data['value']) {
      // Meta tag has a default, and it matches user-submitted value.
      unset($values[$metatag]);
    }
    elseif (!isset($default) && (is_string($data['value']) && !drupal_strlen($data['value']) || (is_array($data['value']) && !array_filter($data['value'])))) {
      // Metatag does not have a default, and user did not submit a value.
      unset($values[$metatag]);
    }
    if (isset($values[$metatag]['default'])) {
      // Unset the default hidden value.
      unset($values[$metatag]['default']);
    }
  }
}

/**
 * Return all the parents of a given configuration instance.
 *
 * @param string $instance
 *   A meta tag configuration instance.
 *
 * @return array
 *   An array of instances starting with the $instance parameter, with the end
 *   of the array being the global instance.
 */
function metatag_config_get_parent_instances($instance, $include_global = TRUE) {
  $parents = array();
  $segments = explode(':', $instance);
  while (count($segments) > 0) {
    $parents[] = implode(':', $segments);
    array_pop($segments);
  }
  if ($include_global && end($parents) !== 'global') {
    $parents[] = 'global';
  }
  reset($parents);
  return $parents;
}

/**
 * Get the proper label of a configuration instance.
 *
 * @param string $instance
 *   A meta tag configuration instance.
 */
function metatag_config_instance_label($instance) {
  $labels = &drupal_static(__FUNCTION__, array());

  if (!isset($labels[$instance])) {
    $instance_parts = explode(':', $instance);
    $instance_part = array_pop($instance_parts);
    if ($context = metatag_config_instance_info($instance)) {
      $labels[$instance] = $context['label'];
    }
    else {
      $labels[$instance] = t('Unknown (@instance)', array('@instance' => $instance_part));
    }
    // Normally the following would use metatag_config_get_parent_instances()
    // but since we already sliced the instance by separator and removed the
    // last segment, putting the array back together gives us this instance's
    // parent.
    if (!empty($instance_parts)) {
      $labels[$instance] = metatag_config_instance_label(implode(':', $instance_parts)) . ': ' . $labels[$instance];
    }
  }

  return $labels[$instance];
}

/**
 * Title callback for meta tag configuration instances.
 */
function metatag_config_title($config) {
  return metatag_config_instance_label($config->instance);
}

/**
 * Access callback for meta tag configuration instances.
 */
function metatag_config_access($op, $config = NULL) {
  if (!user_access('administer meta tags')) {
    return FALSE;
  }

  if ($op == 'enable') {
    return !empty($config->disabled);
  }
  elseif ($op == 'disable') {
    return empty($config->disabled);
  }
  elseif ($op == 'delete') {
    return ($config->export_type & EXPORT_IN_DATABASE) && !($config->export_type & EXPORT_IN_CODE);
  }
  elseif ($op == 'revert') {
    return ($config->export_type & EXPORT_IN_DATABASE) && ($config->export_type & EXPORT_IN_CODE);
  }

  return FALSE;
}

/**
 * Checks if a metatag configuration record is enabled.
 *
 * @param string $instance
 *   The configuration instance machine name.
 *
 * @return bool
 *   TRUE if the configuration is enabled, or FALSE otherwise.
 */
function metatag_config_is_enabled($instance, $include_defaults = FALSE, $include_global = TRUE) {
  if ($include_defaults) {
    $instances = metatag_config_get_parent_instances($instance, $include_global);
    $configs = metatag_config_load_multiple($instances);

    // Check if one of the configs is enabled.
    foreach ($configs as $config) {
      if (empty($config->disabled)) {
        return TRUE;
      }
    }

    // No enabled configs found.
    return FALSE;
  }
  else {
    $config = metatag_config_load($instance);
    return !empty($config) && empty($config->disabled);
  }
}

/**
 * Wrapper around entity_language().
 *
 * @param mixed $entity_type
 *   An entity type's machine name.
 * @param object $entity
 *   The entity to review; will be typecast to an object if an array is passed.
 *
 * @return string
 *   A string indicating the language code to be used; returns LANGUAGE_NONE if
 *   the entity does not have a language assigned.
 */
function metatag_entity_get_language($entity_type, $entity) {
  // Determine the entity's language, af.
  $langcode = entity_language($entity_type, (object) $entity);

  // If no matching language was found, which will happen for e.g. terms and
  // users, it is normally recommended to use the system default language.
  // However, as the system default language can change, this could potentially
  // cause data loss / confusion problems; as a result use the system "no
  // language" value to avoid any potential problems.
  if (empty($langcode)) {
    $langcode = LANGUAGE_NONE;
  }

  return $langcode;
}

/**
 * Implements hook_features_api().
 */
function metatag_features_api() {
  $components = array(
    'metatag' => array(
      'name' => t('Metatag'),
      'feature_source' => TRUE,
      'default_hook' => 'metatag_export_default',
      'default_file' => FEATURES_DEFAULTS_INCLUDED,
      'file' => drupal_get_path('module', 'metatag') . '/metatag.features.inc',
    ),
  );
  return $components;
}

/**
 * Implements hook_views_post_render().
 *
 * Try loading meta tags from a Views page display.
 */
function metatag_views_post_render(&$view, &$output, &$cache) {
  // By default do not add meta tags to admin pages. To enable meta tags on
  // admin pages set the 'metatag_tag_admin_pages' variable to TRUE.
  if (path_is_admin(current_path()) && !variable_get('metatag_tag_admin_pages', FALSE)) {
    return;
  }

  // If display is not set for some reason, get out to prevent PHP notices.
  if (!isset($view->display[$view->current_display])) {
    return;
  }

  // Build a shortcut to the current display object.
  $display = $view->display[$view->current_display];

  // Only proceed if this view is a full page and has a valid path, don't
  // process block or other Views display objects.
  if ($display->display_plugin == 'page' && !empty($display->display_options['path'])) {
    // Try to work out what entity type this is.
    $entity_type = '';

    // All paths must have a placeholder.
    $placeholder_pos = strpos($display->display_options['path'], '%');
    if ($placeholder_pos !== FALSE) {
      // The first argument must be a numeric entity ID.
      if (!empty($view->args) && is_numeric($view->args[0])) {
        // The first argument should be an entity ID.
        $id = $view->args[0];

        // Taxonomy terms are the most commonly used item, so check that first.
        if ($display->display_options['path'] == 'taxonomy/term/%' || $display->display_options['path'] == 'taxonomy/term/%/%') {
          $entity_type = 'taxonomy_term';
        }
        // Node pages.
        elseif ($display->display_options['path'] == 'node/%') {
          $entity_type = 'node';
        }
        // User pages.
        elseif ($display->display_options['path'] == 'user/%') {
          $entity_type = 'user';
        }
      }
    }

    // Check for other types of entities.
    if (empty($entity_type)) {
      // Trigger hook_metatag_views_post_render_get_entity().
      $hook = 'metatag_views_post_render_get_entity';
      foreach (module_implements($hook) as $module) {
        $function = $module . '_' . $hook;
        if (function_exists($function)) {
          $entity_type = call_user_func($function, $view);
          // If an entity type was identified, stop checking.
          if (!empty($entity_type)) {
            break;
          }
        }
      }
    }

    // If an entity type was identified, try loading the entity.
    if (!empty($entity_type)) {
      // Try loading the requested entity.
      $entities = entity_load($entity_type, array($id));
      if (!empty($entities)) {
        $entity = array_pop($entities);

        // Trigger our hook_entity_view().
        metatag_entity_view($entity, $entity_type, 'full', NULL, TRUE);
      }
    }
  }
}

/**
 * Implements hook_ctools_render_alter().
 *
 * Temporary solution to load meta tags on entity pages that are driven by
 * CTools display handlers.
 */
function metatag_ctools_render_alter(&$info, $page, $context) {
  // By default do not add meta tags to admin pages. To enable meta tags on
  // admin pages set the 'metatag_tag_admin_pages' variable to TRUE.
  if (path_is_admin(current_path()) && !variable_get('metatag_tag_admin_pages', FALSE)) {
    return;
  }

  // Only proceed if this is a full page (don't process individual panes) and
  // there's an 'admin path' for the current task.
  if ($page && !empty($context['task']['admin path'])) {
    // Loop over each context.
    foreach ($context['contexts'] as $context_argument) {
      if (is_array($context_argument->type) && !empty($context_argument->data)) {
        if (in_array('entity', $context_argument->type)) {
          $entity = $context_argument->data;
          $entity_type = str_replace('entity:', '', $context_argument->plugin);

          // Verify this is an appropriate entity.
          $entity_info = entity_get_info($entity_type);
          if (!empty($entity_info) && _metatag_entity_is_page($entity_type, $entity)) {
            // Load the meta tags for this entity.
            global $language;
            metatag_entity_view($entity, $entity_type, 'full', $language->language, TRUE);

            // Don't bother looping over any more contexts, an entity has been
            // found.
            break;
          }
        }
      }
    }
  }
}

/**
 * Checks if this entity is the default revision (published).
 *
 * Only needed when running Workbench Moderation v1; v3 is skipped.
 *
 * @param object $entity
 *   The entity object, e.g., $node.
 *
 * @return bool
 *   TRUE if the entity is the default revision, FALSE otherwise.
 */
function _metatag_isdefaultrevision($entity) {
  // D7 "Forward revisioning" is complex and causes a node_save() with the
  // future node in node table. This fires hook_node_update() twice and cause
  // abnormal behaviour in metatag.
  //
  // The steps taken by Workbench Moderation is to save the forward revision
  // first and overwrite this with the live version in a shutdown function in
  // a second step. This will confuse metatag. D7 has no generic property
  // in the node object, if the node that is updated is the 'published' version
  // or only a draft of a future version.
  //
  // This behaviour will change in D8 where $node->isDefaultRevision has been
  // introduced. See below links for more details.
  // - https://www.drupal.org/node/1879482
  // - https://www.drupal.org/node/218755
  // - https://www.drupal.org/node/1522154
  //
  // Every moderation module saving a forward revision needs to return FALSE.
  // @todo: Refactor this workaround under D8.
  // Workbench Moderation v1 uses the hook_node_presave() for some custom logic.
  // This was replaced with hook_entity_presave() in v3, so only proceed if the
  // old hook implementation is present.
  if (function_exists('workbench_moderation_node_presave')) {
    // If this is a node, check if the content type supports moderation.
    if (function_exists('workbench_moderation_node_type_moderated') && workbench_moderation_node_type_moderated($entity->type) === TRUE) {
      return !empty($entity->workbench_moderation['updating_live_revision']);
    }
  }

  return FALSE;
}

/**
 * Generate the cache ID to use with metatag_cache_get/metatag_cache_set calls.
 *
 * @param array $cid_parts
 *   A list of values to be used.
 *
 * @return string
 *   The cache ID string.
 */
function metatag_cache_default_cid_parts(array $cid_parts = array()) {
  // The initial parts, control the order of the parts.
  $cid_part_defaults = array(
    'cache_type' => 'output',
    'instance' => '',
    'entity_type' => '',
    'entity_id' => '',
    'bundle' => '',
    'langcode' => $GLOBALS['language_content']->language,
    'revision_id' => '',
    'view_mode' => '',
    'status' => 200,
    'protocol' => $GLOBALS['is_https'] ? 'https' : 'http',
    'hostname' => $_SERVER['HTTP_HOST'],
    'base_path' => base_path(),
  );
  $cid_parts = array_merge($cid_part_defaults, $cid_parts);

  // Add the HTTP status code.
  $headers = drupal_get_http_header();
  if (isset($headers['status'])) {
    $cid_parts['status'] = intval($headers['status']);
  }

  // Allow each page in a sequence to have different values.
  if (isset($_GET['page']) && is_numeric($_GET['page'])) {
    $cid_parts['page'] = intval($_GET['page']);
  }

  // Allow other modules to customize the data using
  // hook_metatag_page_cache_cid_parts_alter().
  drupal_alter('metatag_page_cache_cid_parts', $cid_parts);

  // Remove empty parts.
  $cid_parts = array_filter($cid_parts);

  // Concatenate the cache ID parts, trim the results to 255 chars.
  return substr(implode(':', $cid_parts), 0, 255);
}

/**
 * Wrapper for cache_set.
 *
 * @see cache_set()
 */
function metatag_cache_set($cid, $data) {
  // By default the cached data will not expire.
  $expire = CACHE_PERMANENT;

  // Triggers hook_metatag_cache_set_expire_alter().
  drupal_alter("metatag_cache_set_expire", $expire, $cid, $data);
  return cache_set($cid, $data, 'cache_metatag', $expire);
}

/**
 * Wrapper for cache_get.
 *
 * @see cache_get()
 */
function metatag_cache_get($cid) {
  // Try to load the object.
  return cache_get($cid, 'cache_metatag');
}

/**
 * Determines if we are in an error page and return the appropriate instance.
 *
 * @return string
 *   String of error.
 */
function metatag_is_error_page() {
  $known_errors = array(
    'global:403' => '403 Forbidden',
    'global:404' => '404 Not Found',
  );
  $headers = drupal_get_http_header();
  if (isset($headers['status'])) {
    foreach ($known_errors as $error => $status) {
      if ($status == $headers['status']) {
        return $error;
      }
    }
  }
  return '';
}

/**
 * Implements hook_admin_menu_cache_info().
 */
function metatag_admin_menu_cache_info() {
  $caches['metatag'] = array(
    'title' => t('Metatag'),
    'callback' => 'metatag_config_cache_clear',
  );
  return $caches;
}

/**
 * Identify whether an entity type is technically capable of having meta tags.
 *
 * In order to be capable of having meta tags, an entity type must have view
 * modes, must be fieldable, and may not be a configuration entity.
 *
 * @param string $entity_type
 *    The entity type.
 * @param array $entity_info
 *    Entity information.
 *
 * @return bool
 *    Return TRUE if suitable.
 */
function metatag_entity_type_is_suitable($entity_type, $entity_info = array()) {
  $suitable = TRUE;

  // If the entity info was not passed along, load it.
  if (empty($entity_info)) {
    $entity_info = entity_get_info($entity_type);
  }

  // Configuration entities may not have meta tags.
  if (isset($entity_info['configuration']) && $entity_info['configuration'] == TRUE) {
    $suitable = FALSE;
  }

  // Entities must have bundles.
  elseif (empty($entity_info['bundles'])) {
    $suitable = FALSE;
  }

  // The entity type must be fieldable.
  elseif (empty($entity_info['fieldable'])) {
    $suitable = FALSE;
  }

  else {
    // Ignore some view modes that are automatically added by certain modules.
    unset($entity_info['view modes']['ical']);
    unset($entity_info['view modes']['diff_standard']);
    unset($entity_info['view modes']['token']);

    // There must be view modes.
    if (empty($entity_info['view modes'])) {
      $suitable = FALSE;
    }

    else {
      // Specifically disable some entity types.
      $excluded = array(
        // Comment module.
        'comment',
        // Field Collection module.
        'field_collection_item',
        // Paragraphs module.
        'paragraphs_item',
      );
      if (in_array($entity_type, $excluded)) {
        $suitable = FALSE;
      }
    }
  }

  // Trigger hook_metatag_entity_type_is_supported_alter() to allow other
  // modules to either enable or disable certain entity types.
  drupal_alter('metatag_entity_type_is_supported', $suitable, $entity_type, $entity_info);

  return $suitable;
}

/**
 * Implements hook_node_type_insert().
 *
 * When a content type is created, enable it for use with Metatag.
 */
function metatag_node_type_insert($info) {
  if (metatag_entity_supports_metatags('node')) {
    if (metatag_entity_type_enable('node', $info->type)) {
      drupal_set_message(t('Metatag support has been enabled for the @label content type.', array('@label' => $info->name)));
    }
  }
}

/**
 * Implements hook_node_type_delete().
 *
 * When a content type is deleted, remove the corresponding Metatag variable.
 */
function metatag_node_type_delete($info) {
  variable_del('metatag_enable_node__' . $info->type);
}

/**
 * Implements hook_taxonomy_vocabulary_insert().
 *
 * When a vocabulary is created, enable it for use with Metatag.
 */
function metatag_taxonomy_vocabulary_insert($vocabulary) {
  if (metatag_entity_supports_metatags('taxonomy_term')) {
    if (metatag_entity_type_enable('taxonomy_term', $vocabulary->machine_name)) {
      drupal_set_message(t('Metatag support has been enabled for the @label vocabulary.', array('@label' => $vocabulary->name)));
    }
  }
}

/**
 * Implements hook_taxonomy_vocabulary_delete().
 *
 * When a vocabulary is deleted, remove the corresponding Metatag variable.
 */
function metatag_taxonomy_vocabulary_delete($info) {
  variable_del('metatag_enable_taxonomy_term__' . $info->machine_name);
}

/**
 * Implements hook_workbench_moderation_transition().
 *
 * Clear a node's caches when its Workbench Moderation state is changed.
 */
function metatag_workbench_moderation_transition($node, $previous_state, $new_state) {
  metatag_metatags_cache_clear('node', array($node->nid));
}

/**
 * Sort callback for sorting by metatag instance string values.
 */
function _metatag_config_instance_sort($a, $b) {
  $a_contexts = explode(':', $a);
  $b_contexts = explode(':', $b);

  // Global config always comes first.
  if ($a_contexts[0] == 'global' && $b_contexts[0] != 'global') {
    return -1;
  }
  elseif ($b_contexts[0] == 'global' && $a_contexts[0] != 'global') {
    return 1;
  }

  for ($i = 0; $i < max(count($a_contexts), count($b_contexts)); $i++) {
    $a_context = isset($a_contexts[$i]) ? $a_contexts[$i] : '';
    $b_context = isset($b_contexts[$i]) ? $b_contexts[$i] : '';
    if ($a_context == $b_context) {
      continue;
    }
    else {
      return strcmp($a_context, $b_context);
    }
  }
}

/**
 * Translations & internationalization (i18n).
 */

/**
 * Implements hook_entity_translation_delete().
 *
 * Required for content translations being handled via Entity_Translation to
 * remove the appropriate record when a translation is removed without the
 * corresponding entity record also being removed.
 */
function metatag_entity_translation_delete($entity_type, $entity, $langcode) {
  // Get the entity's ID.
  list($entity_id, $revision_id) = entity_extract_ids($entity_type, $entity);
  $revision_id = intval($revision_id);

  // Delete the translation.
  metatag_metatags_delete($entity_type, $entity_id, $revision_id, $langcode);
}

/**
 * Translates the metatag if i18n_string integration is enabled.
 *
 * @param string $string
 *   String in default language or array of strings to be translated.
 * @param string $tag_name
 *   The internal name of the meta tag being translated.
 * @param mixed $context
 *   A context string to use with i18n, or the $options array from a Metatag::
 *   getValue() method; if the latter it will be used to generate the full
 *   context.
 * @param string $langcode
 *   The language code to submit instead of the current page's language.
 * @param bool $update
 *   Whether or not to create/update records in {locales_source}.
 *
 * @return string
 *   The translated string if i18n_string is enabled, otherwise just returns the
 *   original string.
 *
 * @see i18n_string_translate()
 */
function metatag_translate_metatag($string, $tag_name, $context, $langcode = NULL, $update = TRUE) {
  if (module_exists('i18n_string') && !variable_get('metatag_i18n_disabled', FALSE)) {
    // By default do not add meta tags to admin pages. To enable meta tags on
    // admin pages set the 'metatag_tag_admin_pages' variable to TRUE.
    static $page_is_admin;
    if (is_null($page_is_admin)) {
      $page_is_admin = FALSE;
      if (path_is_admin(current_path()) && !variable_get('metatag_tag_admin_pages', FALSE)) {
        $page_is_admin = TRUE;
      }
    }
    if ($page_is_admin) {
      return $string;
    }

    // If the context is an array then it is the $options from the meta tag
    // generator and needs some custom tailoring. Doing it this way to avoid an
    // unnecessary entity_extract_ids() call when i18n isn't being used.
    if (is_array($context)) {
      // Optionally disable output generation.
      if (!variable_get('metatag_i18n_translate_output', FALSE)) {
        return $string;
      }

      // Output generation was enabled, so continue as normal.
      $new_context = 'output:';
      if (drupal_is_front_page()) {
        $new_context .= 'frontpage';
      }
      // If this is an entity page, use the entity as the context.
      elseif (!empty($context['entity_type']) && !empty($context['entity'])) {
        list($entity_id, $revision_id, $bundle) = entity_extract_ids($context['entity_type'], $context['entity']);
        $new_context .= $context['entity_type'] . ':' . $entity_id;
      }
      // Otherwise, use the page URL.
      else {
        // Trim this to avoid SQL errors on the {locales_source} table.
        // length = 255 - strlen('metatag:output:page:') - strlen(metatag);
        $strlen = 255 - strlen('metatag:output:page:' . $tag_name);
        $new_context .= 'page:' . drupal_substr(current_path(), 0, $strlen);
      }
      $context = $new_context;
    }

    $options = array(
      // Automatically create/update the {locales_source} record if one wasn't
      // found.
      'update' => $update,
      // Translate the string.
      'translate' => TRUE,
    );

    // If the langcode was passed in, add it to the options passed to i18n.
    if (!empty($langcode)) {
      $options['langcode'] = $langcode;
    }

    // By default disable the watchdog logging of translation messages.
    $options['watchdog'] = variable_get('metatag_i18n_enable_watchdog', FALSE);

    // Triggers hook_metatag_i18n_context_alter() - allows the i18n string to
    // be altered before being used.
    drupal_alter('metatag_i18n_context', $context, $tag_name);

    // If the context was erased just send back the original string - it's
    // unlikely, but it could happen.
    if (empty($context)) {
      return $string;
    }

    // The 'name' is split up by i18n_string into two components - the textgroup
    // is the first item, the others are joined together with a ':' separator
    // to make the context. In order to have the contexts show with "metatag" as
    // the first part of the context, it has to be added twice to the name.
    $name = array(
      'metatag',
      $context,
      $tag_name,
    );

    // Notify i18n of the string, and obtain a translation if one is available.
    return i18n_string($name, $string, $options);
  }

  // If the i18n_string module isn't enabled then just pass back the string
  // as-is.
  else {
    return $string;
  }
}

/**
 * Translate a set of metatags to the current language.
 *
 * @param array $metatags
 *   List of meta tags to be translated.
 * @param string $context
 *   An optional context to use with i18n.
 * @param string $langcode
 *   The language code to submit instead of the current page's language.
 * @param bool $update
 *   Whether or not to create/update records in {locales_source}.
 */
function metatag_translate_metatags(&$metatags, $context = NULL, $langcode = NULL, $update = TRUE) {
  if (!empty($metatags)) {
    foreach ($metatags as $key => $data) {
      if (!empty($data['value']) && is_string($data['value'])) {
        $metatags[$key] = array(
          'value' => metatag_translate_metatag($data['value'], $key, $context, $langcode, $update),
        );
      }
    }
  }
}

/**
 * Update the translated definitions of meta tags.
 *
 * @param array $metatags
 *   List of meta tags to have their translations updated.
 * @param string $context
 *   The string that will be used to group strings in the translation UI.
 */
function metatag_translations_update($metatags, $context) {
  // Store the context as it was originally provided.
  $original_context = $context;

  // Update the i18n string.
  if (module_exists('i18n_string') && !variable_get('metatag_i18n_disabled', FALSE)) {
    $options = array();

    // By default disable the watchdog logging of translation messages.
    $options['watchdog'] = variable_get('metatag_i18n_enable_watchdog', FALSE);

    foreach ($metatags as $tag_name => $data) {
      // Revert the context, so that it can be changed if needed.
      $context = $original_context;

      if (!empty($data['value']) && is_string($data['value'])) {
        // Triggers hook_metatag_i18n_context_alter() - allows the i18n string
        // to be altered before being used.
        drupal_alter('metatag_i18n_context', $context, $tag_name);

        // Don't do anything if the context was erased - it's unlikely, but it
        // could happen.
        if (empty($context)) {
          continue;
        }

        // The textgroup is the first part of the string.
        i18n_string_update("metatag:{$context}:{$tag_name}", $data['value'], $options);
      }
    }
  }
}

/**
 * Remove the translated definitions of meta tags.
 *
 * @param array $metatags
 *   List of meta tags to have their translations updated.
 * @param string $context
 *   The string that will be used to group strings in the translation UI.
 */
function metatag_translations_delete($metatags, $context) {
  // Store the context as it was originally provided.
  $original_context = $context;

  // Update the i18n string.
  if (module_exists('i18n_string') && !variable_get('metatag_i18n_disabled', FALSE)) {
    $options = array();

    // By default disable the watchdog logging of translation messages.
    $options['watchdog'] = variable_get('metatag_i18n_enable_watchdog', FALSE);

    foreach ($metatags as $tag_name => $data) {
      // Revert the context, so that it can be changed if needed.
      $context = $original_context;

      if (!empty($data['value']) && is_string($data['value'])) {
        // Triggers hook_metatag_i18n_context_alter() - allows the i18n string
        // to be altered before being used.
        drupal_alter('metatag_i18n_context', $context, $tag_name);

        // Don't do anything if the context was erased - it's unlikely, but it
        // could happen.
        if (empty($context)) {
          continue;
        }

        // The textgroup is the first part of the string.
        i18n_string_remove("metatag:{$context}:{$tag_name}", $data['value'], $options);
      }
    }
  }
}

/**
 * Implements hook_config_insert().
 *
 * Implements hook_metatag_config_insert() on behalf of i18n_string.
 */
function i18n_string_metatag_config_insert($config) {
  $context = 'metatag_config:' . $config->instance;
  metatag_translations_update($config->config, $context);
}

/**
 * Implements hook_config_update().
 *
 * Implements hook_metatag_config_update() on behalf of i18n_string.
 */
function i18n_string_metatag_config_update($config) {
  // Defer to the 'insert' function.
  i18n_string_metatag_config_insert($config);
}

/**
 * Implements hook_config_delete().
 *
 * Implements hook_metatag_config_delete() on behalf of i18n_string.
 */
function i18n_string_metatag_config_delete($config) {
  $context = 'metatag_config:' . $config->instance;
  metatag_translations_delete($config->config, $context);
}