<?php

/**
 * @file
 * Replaces entity legacy fields with regular fields.
 *
 * Provides an API and a basic UI to replace legacy pseudo-fields with regular
 * fields. The API only offers synchronization between the two data storage
 * systems and data replacement on entity load/save. Field definitions have to
 * be provided by the modules exploiting the API.
 *
 * Title implements its own entity description API to describe core legacy
 * pseudo-fields:
 * - Node: title
 * - Taxonomy Term: name, description
 * - Comment: subject
 *
 * @todo: API PHPdocs
 */

module_load_include('inc', 'title', 'title.core');
module_load_include('inc', 'title', 'title.field');

/**
 * Implements hook_module_implements_alter().
 */
function title_module_implements_alter(&$implementations, $hook) {
  if (isset($implementations['title'])) {
    $group = $implementations['title'];
    unset($implementations['title']);

    switch ($hook) {
      // The following hook implementations should be executed as last ones.
      case 'entity_info_alter':
      case 'entity_presave':
      case 'field_attach_presave':
        $implementations['title'] = $group;
        break;

      // The following hook implementations should be executed after
      // entity_translation.
      case 'entity_load':
        if (isset($implementations['entity_translation'])) {
          $length = array_search('entity_translation', array_keys($implementations)) + 1;
          $implementations = array_merge(array_slice($implementations, 0, $length, TRUE), array('title' => $group), array_slice($implementations, $length, count($implementations) - 1, TRUE));
        }
        break;

      // Normally Title needs to act as first module to perform synchronization.
      default:
        $implementations = array('title' => $group) + $implementations;
    }
  }
}

/**
 * Implements hook_entity_info_alter().
 */
function title_entity_info_alter(&$info) {
  foreach ($info as $entity_type => $entity_info) {
    if (!empty($entity_info['fieldable']) && !empty($info[$entity_type]['field replacement'])) {
      foreach ($info[$entity_type]['field replacement'] as $legacy_field => $data) {
        // Provide defaults for the replacing field name.
        $fr_info = &$info[$entity_type]['field replacement'][$legacy_field];
        if (empty($fr_info['field']['field_name'])) {
          $fr_info['field']['field_name'] = $legacy_field . '_field';
        }
        $fr_info['instance']['field_name'] = $fr_info['field']['field_name'];

        // Provide defaults for the sync callbacks.
        $type = $fr_info['field']['type'];
        if (empty($fr_info['callbacks'])) {
          $fr_info['callbacks'] = array();
        }
        $fr_info['callbacks'] += array(
          'sync_get' => "title_field_{$type}_sync_get",
          'sync_set' => "title_field_{$type}_sync_set",
        );

        // Support add explicit support for entity_label().
        if (isset($entity_info['entity keys']['label']) && $entity_info['entity keys']['label'] == $legacy_field) {
          // Store the original label callback for compatibility reasons.
          if (isset($info[$entity_type]['label callback'])) {
            $info[$entity_type]['label fallback']['title'] = $info[$entity_type]['label callback'];
          }
          $info[$entity_type]['label callback'] = 'title_entity_label';
          $fr_info += array('preprocess_key' => $info[$entity_type]['entity keys']['label']);
        }
      }
    }
  }
}

/**
 * Return field replacement specific information.
 *
 * @param $entity_type
 *   The name of the entity type.
 * @param $legacy_field
 *   (Optional) The legacy field name to be replaced.
 */
function title_field_replacement_info($entity_type, $legacy_field = NULL) {
  $info = entity_get_info($entity_type);
  if (empty($info['field replacement'])) {
    return FALSE;
  }

  if (isset($legacy_field)) {
    return isset($info['field replacement'][$legacy_field]) ? $info['field replacement'][$legacy_field] : FALSE;
  }

  return $info['field replacement'];
}

/**
 * Implements callback_entity_info_label().
 */
function title_entity_label($entity, $type, $langcode = NULL) {
  $entity_info = entity_get_info($type);
  $legacy_field = $entity_info['entity keys']['label'];
  $info = $entity_info['field replacement'][$legacy_field];
  list(, , $bundle) = entity_extract_ids($type, $entity);

  // If field replacement is enabled we use the replacing field value.
  if (title_field_replacement_enabled($type, $bundle, $legacy_field)) {
    $langcode = field_language($type, $entity, $info['field']['field_name'], $langcode);
    $values = $info['callbacks']['sync_get']($type, $entity, $legacy_field, $info, $langcode);
    return isset($values[$legacy_field]) ? $values[$legacy_field] : $entity->{$legacy_field};
  }

  if (isset($entity_info['label fallback']['title']) && function_exists($entity_info['label fallback']['title'])) {
    $label = $entity_info['label fallback']['title']($entity, $type, $langcode);
    return isset($label) ? $label : $entity->{$legacy_field};
  }
  // Otherwise if we have a fallback defined we use the original label callback.
  return property_exists($entity, $legacy_field) ? $entity->{$legacy_field} : NULL;
}

/**
 * Implements hook_entity_presave().
 */
function title_entity_presave($entity, $entity_type) {
  $entity_langcode = title_entity_language($entity_type, $entity);
  $langcode = $entity_langcode;

  // If Entity Translation is enabled and the entity type is transltable,we need
  // to check if we have a translation for the current active language. If so we
  // need to synchronize the legacy field values into the replacing field
  // translations in the active language.
  if (module_invoke('entity_translation', 'enabled', $entity_type)) {
    $langcode = title_active_language();
    $translations = entity_translation_get_handler($entity_type, $entity)->getTranslations();
    // If we are removing a translation for the active language we need to skip
    // reverse synchronization, as we would store empty values in the original
    // replacing fields immediately afterwards.
    if (!isset($translations->data[$langcode])) {
      $langcode = isset($translations->hook[$langcode]['hook']) && $translations->hook[$langcode]['hook'] == 'delete' ? FALSE : $entity_langcode;
    }
  }

  // Perform reverse synchronization to retain any change in the legacy field
  // values. We must avoid doing this twice as we might overwrite the already
  // synchronized values, if we are updating an existing entity.
  if ($langcode) {
    title_entity_sync($entity_type, $entity, $langcode, TRUE);
  }

  // If we are not dealing with the entity language, we need to synchronize the
  // original values into the legacy fields to ensure they are always stored in
  // the entity table.
  if ($entity_langcode != $langcode) {
    list($id, , ) = entity_extract_ids($entity_type, $entity);
    $sync = &drupal_static('title_entity_sync', array());
    unset($sync[$entity_type][$id]);
    title_entity_sync($entity_type, $entity, $entity_langcode);
  }
}

/**
 * Implements hook_field_attach_update().
 */
function title_field_attach_update($entity_type, $entity) {
  // Reset the field_attach_presave static cache so that subsequent saves work
  // correctly.
  $sync = &drupal_static('title_field_attach_presave', array());
  list($id, ,) = entity_extract_ids($entity_type, $entity);
  unset($sync[$entity_type][$id]);

  // Immediately after saving the entity we need to ensure that the legacy field
  // holds a value corresponding to the current active language, as it were
  // just loaded.
  title_entity_sync($entity_type, $entity);
}

/**
 * Implements hook_field_attach_load().
 *
 * Synchronization must be performed as early as possible to prevent other code
 * from accessing replaced fields before they get their actual value.
 *
 * @see title_entity_load()
 */
function title_field_attach_load($entity_type, $entities, $age, $options) {
  // Allow values to re-sync when field_attach_load_revision() is called.
  if ($age == FIELD_LOAD_REVISION) {
    title_entity_sync_static_reset($entity_type, array_keys($entities));
  }
  title_entity_load($entities, $entity_type);
}

/**
 * Implements hook_entity_load().
 *
 * Since the result of field_attach_load() is cached, synchronization must be
 * performed also here to ensure that there is always the correct value in the
 * replaced fields.
 */
function title_entity_load($entities, $type) {
  // Load entity translations otherwise field language will not be computed
  // correctly.
  if (module_exists('entity_translation')) {
    module_invoke('entity_translation', 'entity_load', $entities, $type);
  }
  foreach ($entities as &$entity) {
    // Synchronize values from the regular field unless we are intializing it.
    // When the node is not being edited, the language must be set to current
    // entity language if set, otherwise NULL.
    $language = NULL;
    if ((preg_match('/node\/\d+\/edit/', current_path()) == 0)
      && (preg_match('/node\/\d+$/', current_path()) == 0)) {
      if (!empty($entity->language)) {
        $language = $entity->language;
      }
    }
    title_entity_sync($type, $entity, $language, !empty($GLOBALS['title_field_replacement_init']));
  }
}

/**
 * Implements hook_entitycache_load().
 *
 * Entity cache might cache the entire $entity object, in which case
 * synchronization will not be performed on entity load.
 */
function title_entitycache_load($entities, $type) {
  title_entity_load($entities, $type);
}

/**
 * Implements hook_entitycache_reset().
 *
 * When the entity cache is reset the field sync has to be done again.
 */
function title_entitycache_reset($ids, $entity_type) {
  title_entity_sync_static_reset($entity_type, $ids);
}

/**
 * Implements hook_entity_prepare_view().
 *
 * On load synchronization is performed using the current display language. A
 * different language might be specified while viewing the entity in which case
 * synchronization must be performed again.
 */
function title_entity_prepare_view($entities, $type, $langcode) {
  foreach ($entities as &$entity) {
    title_entity_sync($type, $entity, $langcode);
  }
}

/**
 * Check whether field replacement is enabled for the given field.
 *
 * @param $entity_type
 *   The type of $entity.
 * @param $bundle
 *   The bundle the legacy field belongs to.
 * @param $legacy_field
 *   The name of the legacy field to be replaced.
 *
 * @return
 *   TRUE if field replacement is enabled for the given field, FALSE otherwise.
 */
function title_field_replacement_enabled($entity_type, $bundle, $legacy_field) {
  $info = title_field_replacement_info($entity_type, $legacy_field);
  if (!empty($info['field']['field_name'])) {
    $instance = field_info_instance($entity_type, $info['field']['field_name'], $bundle);
  }
  return !empty($instance);
}

/**
 * Toggle field replacement for the given field.
 *
 * @param $entity_type
 *   The name of the entity type.
 * @param $bundle
 *   The bundle the legacy field belongs to.
 * @param $legacy_field
 *   The name of the legacy field to be replaced.
 */
function title_field_replacement_toggle($entity_type, $bundle, $legacy_field) {
  $info = title_field_replacement_info($entity_type, $legacy_field);
  if (!$info) {
    return;
  }

  $field_name = $info['field']['field_name'];
  $instance = field_info_instance($entity_type, $field_name, $bundle);

  if (empty($instance)) {
    $options = variable_get('title_' . $entity_type, array());
    $field = field_info_field($field_name);
    if (empty($field)) {
      field_create_field($info['field']);
    }
    $info['instance']['entity_type'] = $entity_type;
    $info['instance']['bundle'] = $bundle;
    $info['instance']['settings']['hide_label']['page'] = isset($options['hide_label']['page']) ? $options['hide_label']['page'] : FALSE;
    $info['instance']['settings']['hide_label']['entity'] = isset($options['hide_label']['entity']) ? $options['hide_label']['entity'] : FALSE;
    field_create_instance($info['instance']);
    return TRUE;
  }

  field_delete_instance($instance);
  return FALSE;
}

/**
 * Set a batch process to initialize replacing field values.
 *
 * @param $entity_type
 *   The type of $entity.
 * @param $bundle
 *   The bundle the legacy field belongs to.
 * @param $legacy_field
 *   The name of the legacy field to be replaced.
 */
function title_field_replacement_batch_set($entity_type, $bundle, $legacy_field) {
  $batch = array(
    'title' => t('Replacing field values for %field', array('%field' => $legacy_field)),
    'operations' => array(
      array('title_field_replacement_batch', array($entity_type, $bundle, $legacy_field)),
    ),
  );
  batch_set($batch);
}

/**
 * Batch operation: initialize a batch of replacing field values.
 */
function title_field_replacement_batch($entity_type, $bundle, $legacy_field, &$context) {
  $info = entity_get_info($entity_type);
  $query = new EntityFieldQuery();
  $query->entityCondition('entity_type', $entity_type);

  // There is no general way to tell if an entity supports bundle conditions
  // (for instance taxonomy terms and comments do not), hence we may need to
  // loop over all the entities of the given type.
  if (!empty($info['efq bundle conditions'])) {
    $query->entityCondition('bundle', $bundle);
  }

  if (empty($context['sandbox'])) {
    $count_query = clone $query;
    $total = $count_query
      ->count()
      ->execute();

    $context['sandbox']['steps'] = 0;
    $context['sandbox']['progress'] = 0;
    $context['sandbox']['total'] = $total;
  }

  $step = variable_get('title_field_replacement_batch_size', 5);
  $start = $step * $context['sandbox']['steps']++;
  $results = $query
    ->entityCondition('entity_type', $entity_type)
    ->range($start, $step)
    ->execute();

  if (!empty($results[$entity_type])) {
    $ids = array_keys($results[$entity_type]);
    title_field_replacement_init($entity_type, $bundle, $legacy_field, $ids);
    $context['sandbox']['progress'] += count($ids);
  }

  if ($context['sandbox']['progress'] != $context['sandbox']['total']) {
    $context['finished'] = $context['sandbox']['progress'] / $context['sandbox']['total'];
  }
}

/**
 * Initialize a batch of replacing field values.
 *
 * @param $entity_type
 *   The type of $entity.
 * @param $bundle
 *   The bundle the legacy field belongs to.
 * @param $legacy_field
 *   The name of the legacy field to be replaced.
 * @param $ids
 *   An array of entity IDs.
 *
 * @return
 *   The number of entities processed.
 */
function title_field_replacement_init($entity_type, $bundle, $legacy_field, $ids) {
  $GLOBALS['title_field_replacement_init'] = TRUE;
  $entities = entity_load($entity_type, $ids);
  foreach ($entities as $id => $entity) {
    list(, , $entity_bundle) = entity_extract_ids($entity_type, $entity);
    if ($entity_bundle == $bundle) {
      field_attach_presave($entity_type, $entity);
      field_attach_update($entity_type, $entity);
    }
  }
  unset($GLOBALS['title_field_replacement_init']);
}

/**
 * Synchronize replaced fields with the regular field values.
 *
 * @param $entity_type
 *   The name of the entity type.
 * @param $entity
 *   The entity to work with.
 * @param $set
 *   Specifies the direction synchronization must be performed.
 */
function title_entity_sync($entity_type, &$entity, $langcode = NULL, $set = FALSE) {
  $sync = &drupal_static(__FUNCTION__, array());
  list($id, , $bundle) = entity_extract_ids($entity_type, $entity);

  if (!isset($langcode)) {
    $langcode = $set ? title_entity_language($entity_type, $entity) : title_active_language();
  }

  // We do not need to perform synchronization more than once.
  if (!$set && !empty($id) && !empty($sync[$entity_type][$id][$langcode][$set])) {
    return;
  }

  $sync[$entity_type][$id][$langcode][$set] = TRUE;
  $fr_info = title_field_replacement_info($entity_type);

  if ($fr_info) {
    foreach ($fr_info as $legacy_field => $info) {
      if (title_field_replacement_enabled($entity_type, $bundle, $legacy_field)) {
        $function = 'title_field_sync_' . ($set ? 'set' : 'get');
        $function($entity_type, $entity, $legacy_field, $info, $langcode);
      }
    }
  }
}

/**
 * Reset the list of entities whose fields have already been synchronized.
 *
 * @param $entity_type
 *   The name of the entity type.
 * @param $entity_ids
 *   Either an array of entity IDs to reset or NULL to reset all.
 */
function title_entity_sync_static_reset($entity_type, $entity_ids = NULL) {
  $sync = &drupal_static('title_entity_sync', array());
  if (is_array($entity_ids)) {
    foreach ($entity_ids as $id) {
      unset($sync[$entity_type][$id]);
    }
  }
  else {
    unset($sync[$entity_type]);
  }
}

/**
 * Synchronize a single legacy field with its regular field value.
 *
 * @param $entity_type
 *   The name of the entity type.
 * @param $entity
 *   The entity to work with.
 * @param $legacy_field
 *   The name of the legacy field to be replaced.
 * @param $info
 *   Field replacement information for the given entity.
 * @param $langcode
 *   The field language to use for the source value.
 */
function title_field_sync_get($entity_type, $entity, $legacy_field, $info, $langcode = NULL) {
  if (property_exists($entity, $legacy_field)) {
    // Save the legacy field value to LEGACY_FIELD_NAME_original.
    $entity->{$legacy_field . '_original'} = $entity->{$legacy_field};
    // Find out the actual language to use (field might be untranslatable).
    $langcode = field_language($entity_type, $entity, $info['field']['field_name'], $langcode);
    $values = $info['callbacks']['sync_get']($entity_type, $entity, $legacy_field, $info, $langcode);
    foreach ($values as $name => $value) {
      if ($value !== NULL) {
        $entity->{$name} = $value;
      }
    }
    // Save the actual language used to LEGACY_FIELD_NAME_language.
    $entity->{$legacy_field . '_language'} = $langcode;
    // Ensure we do not pollute field language static cache.
    $cache = &drupal_static('field_language');
    list($id, ,) = entity_extract_ids($entity_type, $entity);
    unset($cache[$entity_type][$id]);
  }
}

/**
 * Synchronize a single regular field from its legacy field value.
 *
 * @param $entity_type
 *   The name of the entity type.
 * @param $entity
 *   The entity to work with.
 * @param $legacy_field
 *   The name of the legacy field to be replaced.
 * @param $info
 *   Field replacement information for the given entity.
 * @param $langcode
 *   The field language to use for the target value.
 */
function title_field_sync_set($entity_type, $entity, $legacy_field, $info, $langcode) {
  if (property_exists($entity, $legacy_field)) {
    // Find out the actual language to use (field might be untranslatable).
    $field = field_info_field($info['field']['field_name']);
    $langcode = field_is_translatable($entity_type, $field) ? $langcode : LANGUAGE_NONE;
    $info['callbacks']['sync_set']($entity_type, $entity, $legacy_field, $info, $langcode);
  }
}

/**
 * Returns and optionally stores the active language.
 *
 * @param string $langcode
 *   (optional) The active language to be set. If none is provided the active
 *   language is just returned.
 *
 * @return string
 *   The active language code. Defaults to the current content language.
 */
function title_active_language($langcode = NULL) {
  static $drupal_static_fast;
  if (!isset($drupal_static_fast)) {
    $drupal_static_fast['active_language'] = &drupal_static(__FUNCTION__);
  }
  $active_langcode = &$drupal_static_fast['active_language'];
  if (isset($langcode)) {
    $active_langcode = $langcode;
  }
  if (empty($active_langcode)) {
    $active_langcode = $GLOBALS['language_content']->language;
  }
  return $active_langcode;
}

/**
 * Provide the original entity language.
 *
 * If a language property is defined for the current entity we synchronize the
 * field value using the entity language, otherwise we fall back to
 * LANGUAGE_NONE.
 *
 * @param $entity_type
 * @param $entity
 *
 * @return
 *   A language code
 */
function title_entity_language($entity_type, $entity) {
  if (module_exists('entity_translation') && entity_translation_enabled($entity_type)) {
    $handler = entity_translation_get_handler($entity_type, $entity, TRUE);
    $langcode = $handler->getLanguage();
  }
  else {
    $langcode = entity_language($entity_type, $entity);
  }
  return !empty($langcode) ? $langcode : LANGUAGE_NONE;
}

/**
 * Implements hook_field_attach_form().
 *
 * Hide legacy field widgets on the assumption that this is always called on
 * fieldable entity forms.
 */
function title_field_attach_form($entity_type, $entity, &$form, &$form_state, $langcode) {
  list(, , $bundle) = entity_extract_ids($entity_type, $entity);
  $fr_info = title_field_replacement_info($entity_type);

  if (!empty($fr_info)) {
    foreach ($fr_info as $legacy_field => $info) {
      if (isset($form[$legacy_field]) && title_field_replacement_enabled($entity_type, $bundle, $legacy_field)) {
        // Inherit the access from the title widget, so that other modules
        // restricting access to it keep working.
        $replaced = isset($form[$legacy_field]['#field_replacement']) ?
          $form[$legacy_field]['#field_replacement'] : FALSE;
        if (!$replaced && isset($form[$legacy_field]['#access'])) {
          $form[$info['field']['field_name']]['#access'] = $form[$legacy_field]['#access'];
        }

        // Add class from legacy field so behaviors can still be applied on
        // title widget.
        $form[$info['field']['field_name']]['#attributes']['class'] = array('form-item-' . $legacy_field);

        // Restrict access to the legacy field form element and mark it as
        // replaced.
        $form[$legacy_field]['#access'] = FALSE;
        $form[$legacy_field]['#field_replacement'] = TRUE;
      }
    }
  }
}

/**
 * Implements hook_field_attach_submit().
 *
 * Synchronize submitted field values into the corresponding legacy fields.
 */
function title_field_attach_submit($entity_type, $entity, $form, &$form_state) {
  $fr_info = title_field_replacement_info($entity_type);

  if (!empty($fr_info)) {
    // We copy (rather than reference) the values from $form_state because the
    // subsequent call to drupal_array_get_nested_value() is destructive and
    // will affect other hooks relying on data in $form_state. At the end, we
    // copy any modified value back into the $form_state array using
    // drupal_array_set_nested_value().
    $values = $form_state['values'];
    $values = drupal_array_get_nested_value($values, $form['#parents']);
    $langcode = entity_language($entity_type, $entity);

    foreach ($fr_info as $legacy_field => $info) {
      if (!empty($form[$legacy_field]['#field_replacement'])) {
        // Give a chance to operate on submitted values either.
        if (!empty($info['callbacks']['submit'])) {
          $info['callbacks']['submit']($entity_type, $entity, $legacy_field, $info, $langcode, $values);
        }

        drupal_static_reset('field_language');
        title_field_sync_get($entity_type, $entity, $legacy_field, $info, $langcode);
      }
    }

    drupal_array_set_nested_value($form_state['values'], $form['#parents'], $values);
  }
}

/**
 * Implements hook_menu().
 */
function title_menu() {
  $items = array();

  foreach (entity_get_info() as $entity_type => $entity_info) {
    if (!empty($entity_info['field replacement'])) {
      foreach ($entity_info['bundles'] as $bundle_name => $bundle_info) {
        // Blindly taken from field_ui_menu().
        if (isset($bundle_info['admin'])) {
          $path = $bundle_info['admin']['path'];

          if (isset($bundle_info['admin']['bundle argument'])) {
            $bundle_arg = $bundle_info['admin']['bundle argument'];
          }
          else {
            $bundle_arg = $bundle_name;
          }

          $access = array_intersect_key($bundle_info['admin'], drupal_map_assoc(array('access callback', 'access arguments')));
          $access += array(
            'access callback' => 'user_access',
            'access arguments' => array('administer site configuration'),
          );

          $path = "$path/fields/replace/%";
          $field_arg = substr_count($path, '/');
          $items[$path] = array(
            'load arguments' => array(),
            'title' => 'Replace fields',
            'page callback' => 'drupal_get_form',
            'page arguments' => array('title_field_replacement_form', $entity_type, $bundle_arg, $field_arg),
            'file' => 'title.admin.inc',
          ) + $access;
        }
      }
    }
  }

  $items['admin/config/content/title'] = array(
    'title' => 'Title settings',
    'description' => 'Settings for the Title module.',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('title_admin_settings_form'),
    'access arguments' => array('administer site configuration'),
    'file' => 'title.admin.inc',
  );

  return $items;
}

/**
 * Implements hook help.
 */
function title_help($path, $arg) {
  switch ($path) {
    case 'admin/config/content/title':
      return '<p>' . t('The settings below allow to configure the <em>default</em> settings to be used when creating new replacing fields. It is even possible to configure them so that the selected fields are created automatically when a new bundle is created.') . '</p>';
  }
}

/**
 * Implements hook_field_extra_fields_alter().
 */
function title_field_extra_fields_alter(&$info) {
  $entity_info = entity_get_info();
  foreach ($info as $entity_type => $bundles) {
    foreach ($bundles as $bundle_name => $bundle) {
      if (!empty($entity_info[$entity_type]['field replacement'])) {
        foreach ($entity_info[$entity_type]['field replacement'] as $field_name => $field_replacement_info) {
          if (title_field_replacement_enabled($entity_type, $bundle_name, $field_name)) {
            // Remove the replaced legacy field.
            unset($info[$entity_type][$bundle_name]['form'][$field_name], $info[$entity_type][$bundle_name]['display'][$field_name]);
          }
        }
      }
    }
  }
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function title_form_field_ui_field_overview_form_alter(&$form, &$form_state) {
  module_load_include('inc', 'title', 'title.admin');
  title_form_field_ui_overview($form, $form_state);
}

/**
 * Implements hook_tokens_alter().
 *
 * Make sure tokens are properly translated.
 */
function title_tokens_alter(array &$replacements, array $context) {
  $mapping = &drupal_static(__FUNCTION__);
  if (empty($mapping)) {
    foreach (entity_get_info() as $entity_type => $info) {
      if (!empty($info['token type'])) {
        $mapping[$info['token type']] = $entity_type;
      }
    }
  }

  if (isset($mapping[$context['type']])) {
    $entity_type = $mapping[$context['type']];
    $fr_info = title_field_replacement_info($entity_type);
    if ($fr_info && !empty($context['data'][$context['type']])) {
      $entity = $context['data'][$context['type']];
      list(, , $bundle) = entity_extract_ids($entity_type, $entity);
      $options = $context['options'];

      // Since Title tokens are mostly used in storage contexts we default to
      // the current working language, that is the entity language. Modules
      // using Title tokens in display contexts need to specify the current
      // display language.
      $langcode = isset($options['language']) ? $options['language']->language : entity_language($entity_type, $entity);

      if ($fr_info) {
        foreach ($fr_info as $legacy_field => $info) {
          if (isset($context['tokens'][$legacy_field])
            && title_field_replacement_enabled($entity_type, $bundle, $legacy_field)) {
            $langcode = field_language($entity_type, $entity, $info['field']['field_name'], $langcode);
            $item = $info['callbacks']['sync_get']($entity_type, $entity, $legacy_field, $info, $langcode);
            if (!empty($item)) {
              list($value, $format) = array_values($item);
              if (empty($format)) {
                $replacements[$context['tokens'][$legacy_field]] = check_plain($value);
              }
              else {
                $replacements[$context['tokens'][$legacy_field]] = check_markup($value, $format, $langcode);
              }
            }
          }
        }
      }
    }
  }
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function title_form_field_ui_field_edit_form_alter(&$form, $form_state) {
  $instance = $form['#instance'];
  $entity_type = $instance['entity_type'];

  if (title_field_replacement_is_label($entity_type, $instance['field_name'])) {
    $info = entity_get_info($entity_type);
    $form['instance']['settings']['hide_label'] = _title_hide_label_widget($instance['settings'], $info['label']);
  }
}

/**
 * Returns the hide label form widget.
 */
function _title_hide_label_widget($default, $entity_label) {
  return array(
    '#type' => 'checkboxes',
    '#title' => t('Label replacement'),
    '#description' => t('Check these options if you wish to hide the main page title or each label when displaying multiple items of type %entity_label.', array('%entity_label' => $entity_label)),
    '#default_value' => !empty($default['hide_label']) ? $default['hide_label'] : array(),
    '#options' => array(
      'page' => t('Hide page title'),
      'entity' => t('Hide label in %entity_label listings', array('%entity_label' => drupal_strtolower($entity_label))),
    ),
  );
}

/**
 * Checks whether the given field name is a replaced entity label.
 *
 * @param $entity_type
 *   The name of the entity type.
 * @param $field_name
 *   The replacing field name.
 *
 * @return
 *   TRUE id the give field is replacing the entity label, FALSE otherwise.
 */
function title_field_replacement_is_label($entity_type, $field_name) {
  $label = FALSE;
  $legacy_field = title_field_replacement_get_legacy_field($entity_type, $field_name);

  if ($legacy_field) {
    $info = entity_get_info($entity_type);
    $label = $legacy_field == $info['entity keys']['label'];
  }

  return $label;
}

/**
 * Returns the legacy field replaced by the given field name.
 *
 * @param $entity_type
 *   The name of the entity type.
 * @param $field_name
 *   The replacing field name.
 *
 * @return
 *   The replaced legacy field name or FALSE if none available.
 */
function title_field_replacement_get_legacy_field($entity_type, $field_name) {
  $result = FALSE;
  $fr_info = title_field_replacement_info($entity_type);

  if ($fr_info) {
    foreach ($fr_info as $legacy_field => $info) {
      if ($info['field']['field_name'] == $field_name) {
        $result = $legacy_field;
        break;
      }
    }
  }

  return $result;
}

/**
 * Returns the field instance replacing the given entity type's label.
 *
 * @param $entity_type
 *   The name of the entity type.
 * @param $bundle
 *   The name of the bundle the instance is attached to.
 *
 * @return
 *   The field instance replacing the label or FALSE if none available.
 */
function title_field_replacement_get_label_field($entity_type, $bundle) {
  $instance = FALSE;
  $info = entity_get_info($entity_type);

  if (!empty($info['field replacement'])) {
    $fr_info = $info['field replacement'];
    $legacy_field = $info['entity keys']['label'];
    if (!empty($fr_info[$legacy_field]['field'])) {
      $instance = field_info_instance($entity_type, $fr_info[$legacy_field]['field']['field_name'], $bundle);
    }
  }

  return $instance;
}

/**
 * Hides the label from the given variables.
 *
 * @param $entity_type
 *   The name of the entity type.
 * @param $entity
 *   The entity to work with.
 * @param $vaiables
 *   A reference to the variables array related to the template being processed.
 * @param $page
 *   (optional) The current render phase: page or entity. Defaults to entity.
 */
function title_field_replacement_hide_label($entity_type, $entity, &$variables, $page = FALSE) {
  list(, , $bundle) = entity_extract_ids($entity_type, $entity);
  $instance = title_field_replacement_get_label_field($entity_type, $bundle);
  $settings_key = $page ? 'page' : 'entity';

  if (!empty($instance['settings']['hide_label'][$settings_key])) {
    // If no key is passed default to the label one.
    if ($page) {
      $key = 'title';
    }
    else {
      $info = entity_get_info($entity_type);
      $key = $info['field replacement'][$info['entity keys']['label']]['preprocess_key'];
    }

    // We cannot simply unset the variable value since this may cause templates
    // to throw notices.
    $variables[$key] = FALSE;
  }
}

/**
 * Implements hook_views_api().
 */
function title_views_api() {
  return array(
    'api' => 3,
    'path' => drupal_get_path('module', 'title') . '/views',
  );
}

/**
 * Implements hook_field_attach_create_bundle().
 *
 * Automatically attach the replacement field to the new bundle.
 */
function title_field_attach_create_bundle($entity_type, $bundle) {
  $entity_info = entity_get_info($entity_type);
  if (empty($entity_info['field replacement'])) {
    return;
  }

  $options = variable_get('title_' . $entity_type, array());

  foreach (array_keys($entity_info['field replacement']) as $legacy_field) {
    if (empty($options['auto_attach'][$legacy_field])) {
      continue;
    }

    // Do not continue if the replacement field already exists.
    $field_name = $entity_info['field replacement'][$legacy_field]['field']['field_name'];
    if (field_info_instance($entity_type, $field_name, $bundle)) {
      continue;
    }

    title_field_replacement_toggle($entity_type, $bundle, $legacy_field);

    $instance = field_info_instance($entity_type, $field_name, $bundle);
    if ($instance) {
      $params = array(
        '@entity_label' => drupal_strtolower($entity_info['label']),
        '%field_name' => $instance['label'],
      );
      drupal_set_message(t('The @entity_label %field_name field was automatically replaced.', $params));
    }
  }
}

/**
 * Implements hook_field_info_alter().
 */
function title_field_info_alter(&$info) {
  $supported_types = array('taxonomy_term_reference' => TRUE);
  foreach ($info as $field_type => &$field_type_info) {
    if (isset($supported_types[$field_type])) {
      if (!isset($field_type_info['settings'])) {
        $field_type_info['settings'] = array();
      }
      $field_type_info['settings'] += array('options_list_callback' => 'title_taxonomy_allowed_values');
    }
  }
}

/**
 * Return taxonomy term values for taxonomy reference fields.
 */
function title_taxonomy_allowed_values($field) {
  // Since we call taxonomy_get_tree() with $load_entities = TRUE, there is a
  // chance that this will trigger theme functions. For this case, we need to
  // ensure that we are not in the process of theme registry rebuilding.
  $theme_registry_cache = drupal_static('theme_get_registry');
  /* @see theme_get_registry() */
  $theme_registry_is_rebuilding = is_array($theme_registry_cache) &&
    empty($theme_registry_cache);

  $bundle = !empty($field['settings']['allowed_values'][0]['vocabulary']) ?
    $field['settings']['allowed_values'][0]['vocabulary'] : NULL;
  if ($bundle && ($label = title_field_replacement_get_label_field('taxonomy_term', $bundle)) && !$theme_registry_is_rebuilding) {
    $options = array();
    foreach ($field['settings']['allowed_values'] as $tree) {
      $vocabulary = taxonomy_vocabulary_machine_name_load($tree['vocabulary']);
      if ($vocabulary && ($terms = taxonomy_get_tree($vocabulary->vid, $tree['parent'], NULL, TRUE))) {
        foreach ($terms as $term) {
          $options[$term->tid] = str_repeat('-', $term->depth) . entity_label('taxonomy_term', $term);
        }
      }
    }
    return $options;
  }
  return taxonomy_allowed_values($field);
}

/**
 * Implements hook_ctools_context_converter_alter().
 */
function title_ctools_context_converter_alter($context, $converter, &$value, &$converter_options) {
  // This is a temporary fix for https://www.drupal.org/node/2505311.
  // It fixes a language issue for the pane title containing entity
  // related keywords.
  if (isset($context->type[0]) && 0 === strpos($context->type[0], 'entity:') && empty($converter_options['language'])) {
    $plugin = ctools_get_context($context->plugin);
    if ($function = ctools_plugin_get_function($plugin, 'convert')) {
      // Provide "language" option for converter and perform the conversion
      // again.
      $converter_options['language'] = $GLOBALS[LANGUAGE_TYPE_CONTENT];
      $value = $function($context, $converter, $converter_options);
    }
  }
}