<?php
/**
 * @file
 * UUID Features module allows to export data stored in the db by features.
 */

define('UUID_FEATURES_DEFAULT_FALLBACK_ID', 1);

// Ensure our on-behalf implementations are detected.
uuid_features_include();

/**
 * Load include files for on-behalf implementations of other modules.
 *
 * This modules provides on-behalf-of integrations for other modules. The
 * required files can be included with this function.
 *
 * Similar to:
 *
 * @see features_include()
 */
function uuid_features_include() {
  static $loaded = FALSE;

  if (!$loaded) {
    $inc_path = drupal_get_path('module', 'uuid_features') . '/includes/modules';
    foreach (module_list() as $module) {
      $file = "$inc_path/$module.inc";
      if (file_exists($file)) {
        include_once DRUPAL_ROOT . '/' . $file;
      }
    }
    $loaded = TRUE;
  }
}

/**
 * Implements hook_menu().
 */
function uuid_features_menu() {
  $items['admin/structure/features/uuid_features'] = array(
    'access arguments' => array('administer site configuration'),
    'page callback' => 'drupal_get_form',
    'page arguments' => array('uuid_features_settings'),
    'title' => 'UUID Export Settings',
    'type' => MENU_LOCAL_TASK,
    'description' => 'Configure the settings for UUID Features Integration.',
    'weight' => 20,
  );
  return $items;
}

/**
 * Implements hook_entity_info_alter().
 */
function uuid_features_entity_info_alter(&$entity_info) {
  // Provide a list of entities that provide bundles
  // to be exported by uuid_features.
  $entity_types = array(
    'bean',
    'node',
    'taxonomy_term',
    'fieldable_panels_pane',
    'commerce_product',
    'field_collection_item',
    'paragraphs_item',
    'user',
  );
  if (module_exists('file_entity')) {
    $entity_types[] = 'file';
  }
  foreach ($entity_types as $type) {
    // Only add flag on existing entity types.
    if (isset($entity_info[$type])) {
      $entity_info[$type]['uuid features'] = TRUE;
    }
  }
}

/**
 * Implements hook_features_api().
 */
function uuid_features_features_api() {
  $components = array();

  $components['uuid_node'] = array(
    'name' => t('Content'),
    'feature_source' => TRUE,
    'default_hook' => 'uuid_features_default_content',
    'default_file' => FEATURES_DEFAULTS_INCLUDED,
    'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_node.features.inc',
  );

  $components['uuid_user'] = array(
    'name' => t('Users'),
    'feature_source' => TRUE,
    'default_hook' => 'uuid_features_default_users',
    'default_file' => FEATURES_DEFAULTS_INCLUDED,
    'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_user.features.inc',
  );

  if (module_exists('taxonomy')) {
    $components['uuid_term'] = array(
      'name' => t('Taxonomy Term'),
      'feature_source' => TRUE,
      'default_hook' => 'uuid_features_default_terms',
      'default_file' => FEATURES_DEFAULTS_INCLUDED,
      'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_term.features.inc',
    );
  }

  if (module_exists('book')) {
    $components['uuid_book'] = array(
      'name' => t('Book'),
      'default_hook' => 'uuid_features_default_book',
      'default_file' => FEATURES_DEFAULTS_INCLUDED,
      'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_book.features.inc',
    );
  }

  if (function_exists('uuid_file_insert')) {
    $components['uuid_file'] = array(
      'name' => t('File'),
      'default_hook' => 'uuid_features_default_files',
      'default_file' => FEATURES_DEFAULTS_INCLUDED,
      'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_file.features.inc',
    );
  }

  if (module_exists('file_entity')) {
    $components['uuid_file_entity'] = array(
      'name' => t('File Entity'),
      'default_hook' => 'uuid_features_default_file_entities',
      'default_file' => FEATURES_DEFAULTS_INCLUDED,
      'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_file_entity.features.inc',
    );
  }

  if (module_exists('bean')) {
    $components['uuid_bean'] = array(
      'name' => t('Bean'),
      'feature_source' => TRUE,
      'default_hook' => 'uuid_features_default_beans',
      'default_file' => FEATURES_DEFAULTS_INCLUDED,
      'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_bean.features.inc',
    );
  }

  if (module_exists('field_collection')) {
    $components['uuid_field_collection'] = array(
      'name' => t('Field collection'),
      'feature_source' => TRUE,
      'default_hook' => 'uuid_features_default_field_collections',
      'default_file' => FEATURES_DEFAULTS_INCLUDED,
      'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_field_collection.features.inc',
    );
  }

  if (module_exists('nodequeue')) {
    $components['uuid_nodequeue_item'] = array(
      'name' => t('Nodequeue item'),
      'feature_source' => TRUE,
      'default_hook' => 'uuid_features_default_nodequeue_items',
      'default_file' => FEATURES_DEFAULTS_INCLUDED,
      'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_nodequeue_item.features.inc',
    );
  }

  if (module_exists('current_search')) {
    $components['uuid_current_search_configuration'] = array(
      'name' => t('Current search block configuration'),
      'feature_source' => TRUE,
      'default_hook' => 'uuid_features_default_current_search_configurations',
      'default_file' => FEATURES_DEFAULTS_INCLUDED,
      'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_current_search_configuration.features.inc',
    );
  }

  if (module_exists('fieldable_panels_panes')) {
    $components['uuid_fpp'] = array(
      'name' => t('Fieldable Panels Panes Content'),
      'feature_source' => TRUE,
      'default_hook' => 'uuid_features_default_fpps',
      'default_file' => FEATURES_DEFAULTS_INCLUDED,
      'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_fpp.features.inc',
    );
  }

  if (module_exists('panelizer')) {
    // Only enable panelizer support if the current version of the module uses
    // a schema we are compatible with. Ie. Panelizer 7.x-3.x or later.
    $panelizer_schema_info = drupal_get_schema('panelizer_entity');
    if (!empty($panelizer_schema_info['fields']['view_mode'])) {
      $components['uuid_panelizer'] = array(
        'name' => t('Panelizer Entity Displays'),
        'feature_source' => TRUE,
        'default_hook' => 'uuid_features_default_panelizer',
        'default_file' => FEATURES_DEFAULTS_INCLUDED,
        'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_panelizer.features.inc',
      );
    }
  }

  if (module_exists('commerce_uuid')) {
    if (module_exists('commerce_product')) {
      $components['uuid_commerce_product'] = array(
        'name' => t('Commerce Product'),
        'feature_source' => TRUE,
        'default_hook' => 'uuid_features_default_commerce_product',
        'default_file' => FEATURES_DEFAULTS_INCLUDED,
        'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_commerce_product.features.inc',
      );
    }
  }

  if (module_exists('paragraphs')) {
    $components['uuid_paragraphs'] = array(
      'name' => t('Paragraphs'),
      'feature_source' => TRUE,
      'default_hook' => 'uuid_features_default_paragraphs',
      'default_file' => FEATURES_DEFAULTS_INCLUDED,
      'file' => drupal_get_path('module', 'uuid_features') . '/includes/uuid_paragraphs.features.inc',
    );
  }

  return $components;
}

/**
 * Implements hook_features_pipe_COMPONENT_alter().
 *
 * When exporting a vocabulary, include its terms.
 */
function uuid_features_features_pipe_taxonomy_alter(&$pipe, $data, $export) {
  if (variable_get('uuid_features_vocabulary_terms', FALSE) == TRUE) {
    if (!is_array($data)) {
      $data = array($data);
    }
    if (empty($pipe['uuid_term'])) {
      $pipe['uuid_term'] = array();
    }
    foreach ($data as $machine_name) {
      if ($vocab = taxonomy_vocabulary_machine_name_load($machine_name)) {
        $export['features']['uuid_term'] = array();
        foreach (taxonomy_get_tree($vocab->vid) as $term) {
          uuid_term_features_get_dependencies($export, $term->uuid, $export['module_name']);
        }
        if (!empty($export['features']['uuid_term'])) {
          $pipe['uuid_term'] = array_merge($pipe['uuid_term'], $export['features']['uuid_term']);
        }
      }
    }
  }
}

/**
 * Implements hook_features_pipe_COMPONENT_alter().
 *
 * When exporting a Panel, include any attached Fieldable Panels Panes.
 */
function uuid_features_features_pipe_uuid_fpp_alter(&$pipe, $data, $export) {
  $fpp_uuids = array();
  foreach ($export['features'] as $component => $feature) {
    if ($component == 'page_manager_pages') {
      $page_name = key($feature);
      $handlers = db_select('page_manager_handlers', 'pmh')
        ->fields('pmh', array('did'))
        ->condition('subtask', $page_name)
        ->execute()
        ->fetchAll();
      foreach ($handlers as $handler) {
        $display_id = $handler->did;
        $panes = db_select('panels_pane', 'pp')
          ->fields('pp', array('subtype'))
          ->condition('type', 'fieldable_panels_pane')
          ->condition('did', $display_id)
          ->execute()
          ->fetchAll();
        foreach ($panes as $pane) {
          $fpp_uuids[] = str_replace('uuid:', '', $pane->subtype);
        }
      }
    }
    elseif ($component == 'panels_mini') {
      $panel_name = key($feature);
      $display_id = db_select('panels_mini', 'pm')
        ->fields('pm', array('did'))
        ->condition('name', $panel_name)
        ->execute()
        ->fetchField();
      if (empty($display_id)) {
        continue;
      }

      $panes = db_select('panels_pane', 'pp')
        ->fields('pp', array('subtype'))
        ->condition('type', 'fieldable_panels_pane')
        ->condition('did', $display_id)
        ->execute()
        ->fetchAll();
      foreach ($panes as $pane) {
        $fpp_uuids[] = str_replace('uuid:', '', $pane->subtype);
      }
    }
  }
  $pipe['uuid_fpp'] = $fpp_uuids;
}

/**
 * Menu callback to configure module settings.
 */
function uuid_features_settings($form, &$form_state) {

  $form['settings']['uuid_features_vocabulary_terms'] = array(
    '#type' => 'checkbox',
    '#title' => t('Auto detect uuid terms'),
    '#description' => t('When exporting a vocabulary, include its terms.'),
    '#default_value' => variable_get('uuid_features_vocabulary_terms', FALSE),
  );

  $entity_info = entity_get_info();

  foreach ($entity_info as $type => $info) {
    if (!isset($info['uuid features']) || !$info['uuid features']) {
      unset($entity_info[$type]);
    }
  }
  foreach ($entity_info as $type => $info) {
    $options = array();
    $entities = array();
    $files = array();
    foreach ($info['bundles'] as $key => $value) {
      $options[$key] = $value['label'];
      $entities[$key] = variable_get("uuid_features_entity_${type}_${key}", FALSE);
      $files[$key] = variable_get("uuid_features_file_${type}_${key}", FALSE);
    }
    $form['entity']["uuid_features_entity_${type}"] = array(
      '#type' => 'checkboxes',
      '#title' => t('Exportable @label bundles', array('@label' => $info['label'])),
      '#default_value' => $entities,
      '#options' => $options,
    );
    $form['file']["uuid_features_file_${type}"] = array(
      '#type' => 'checkboxes',
      '#title' => t('Files exported for @label bundles', array('@label' => $info['label'])),
      '#default_value' => $files,
      '#options' => $options,
    );
  }

  $form['file']['uuid_features_file_mode'] = array(
    '#type' => 'radios',
    '#title' => t('File export mode'),
    '#default_value' => variable_get('uuid_features_file_mode', 'inline'),
    '#options' => array(
      'inline' => t('Inline Base64'),
      'local' => t('Local file export'),
      'packaged' => t('Package files with generated module.'),
      'remote' => t('Remote file export, URL'),
    ),
    '#description' => t('Should file exports be inline inside the export code, a local path to the file, or a URL? Inline Base64 is the easiest option to use but can sometimes exceed PHP post limits, local and remote modes are more useful for power users.  <em>NOTE: Remote mode only works with a public files directory.</em>'),
  );

  $form['file']['uuid_features_file_assets_path'] = array(
    '#type' => 'textfield',
    '#title' => t('Local file field assets path'),
    '#size' => 60,
    '#maxlength' => 255,
    '#default_value' => variable_get('uuid_features_file_assets_path', ''),
    '#description' => t(
      'Optionally, copy files to this path when the node is exported.
      The primary advantage of this is to divert exported files into a
      safe location so they can be committed to source control (eg: SVN,
      CVS, Git).  <em>Tip: For install profile developers, setting this
      path to <code>profiles/my_profile/uuid_features_assets</code> may be
      useful.</em>'
    ),
    '#required' => FALSE,
    '#states' => array(
      'visible' => array(
        ':input[name=uuid_features_file_mode]' => array('value' => 'local'),
      ),
    ),
  );

  $form['file']['uuid_features_packaged_file_assets_path'] = array(
    '#type' => 'textfield',
    '#title' => t('Packaged file field assets path'),
    '#size' => 60,
    '#maxlength' => 255,
    '#default_value' => variable_get('uuid_features_packaged_files_assets_path', 'assets'),
    '#description' => t(
      "Copy files to this path, relative to the feature's export path,
      when the entity is exported. The primary advantage of this is to
      avoid the memory overhead of base64 encoding exported files."
    ),
    '#required' => TRUE,
    '#states' => array(
      'visible' => array(
        ':input[name=uuid_features_file_mode]' => array('value' => 'packaged'),
      ),
    ),
  );

  $form['file']['uuid_features_file_supported_fields'] = array(
    '#type' => 'textfield',
    '#title' => t('Supported file field types'),
    '#default_value' => variable_get('uuid_features_file_supported_fields', 'file, image'),
    '#maxlength' => 512,
    '#description' => t('Comma seperated list of file field types to detect for export/import.'),
  );

  $form['settings']['uuid_features_vocabulary_terms'] = array(
    '#type' => 'checkbox',
    '#title' => t('Auto detect uuid terms'),
    '#description' => t('When exporting a vocabulary, include its terms.'),
    '#default_value' => variable_get('uuid_features_vocabulary_terms', FALSE),
  );

  $form['#submit'][] = 'uuid_features_settings_submit';

  return system_settings_form($form);
}

/**
 * Submit function for uuid_features_settings().
 */
function uuid_features_settings_submit($form, &$form_state) {
  foreach ($form_state['values'] as $key => $value) {
    if (preg_match('/^uuid_features_(entity|file)_/', $key) && is_array($value)) {
      foreach ($value as $type => $state) {
        variable_set("${key}_${type}", $state);
      }
      unset($form_state['values'][$key]);
    }
  }
}

/**
 * Handle exporting file fields.
 */
function uuid_features_file_field_export(&$export, $entity_type) {
  list($entity_id, $revision_id, $export_bundle) = entity_extract_ids($entity_type, $export);

  $fields = field_info_instances($entity_type, $export_bundle);
  $supported_fields = array_map('trim', explode(',', variable_get('uuid_features_file_supported_fields', 'file, image')));
  // Check what entity types are enabled for uuid features file export.
  $bundles = array();
  $entity_info = entity_get_info($entity_type);
  foreach ($entity_info['bundles'] as $key => $value) {
    if (variable_get("uuid_features_file_${entity_type}_${key}", FALSE)) {
      $bundles[$key] = $key;
    }
  }
  if (!in_array($export_bundle, $bundles)) {
    foreach ($fields as $field_instance) {
      $field = &$export->{$field_instance['field_name']};
      $info = field_info_field($field_instance['field_name']);
      // If this field should implement file import/export system but
      // filefield exports are not enabled for this entity, just set the field
      // to an empty array.
      if (in_array($info['type'], $supported_fields)) {
        $field = array();
      }
    }
  }
  else {
    $export_mode = variable_get('uuid_features_file_mode', 'inline');

    switch ($export_mode) {
      case 'local':
        $export_var = 'uuid_features_file_path';
        break;

      case 'packaged':
        $export_var = 'uuid_features_packaged_file_path';
        $file_list = array();
        break;

      case 'remote':
        $export_var = 'uuid_features_file_url';
        break;

      default:
      case 'inline':
        $export_var = 'uuid_features_file_data';
        break;
    }
    // Get all fields from this entity.
    foreach ($fields as $field_instance) {
      // Load field infos to check the type.
      if (empty($field_instance['field_name'])) {
        continue;
      }
      $field = &$export->{$field_instance['field_name']};
      $info = field_info_field($field_instance['field_name']);
      // Check if this field should implement file import/export system.
      if (in_array($info['type'], $supported_fields)) {
        // We need to loop into each language because i18n translation can build
        // fields with different language than the node one.
        foreach ($field as $language => $files) {
          if (is_array($files)) {
            foreach ($files as $i => $file) {
              try {
                $export_data = uuid_features_file_export($file, $export_mode);
              }
              catch (Exception $e) {
                // There was an error exporting the file - skip it.
                drupal_set_message($e->getMessage(), 'warning', FALSE);
                continue;
              }

              // Build the field again, and remove fid to be sure that imported
              // node will rebuild the file again, or keep an existing one with
              // a different fid.
              unset(
                $field[$language][$i]['fid'],
                $field[$language][$i]['timestamp']
              );
              $field[$language][$i][$export_var] = $export_data;
              if ($export_mode == 'packaged') {
                $file_list[$export_data] = array(
                  'file_path' => $file['uri'],
                );
              }
            }
          }
        }
      }
    }
    if ($export_mode == 'packaged') {
      return $file_list;
    }
  }
}

/**
 * Exports the file and returns a handle to store in the features export.
 *
 * @param object $file
 *   The file object to handle.
 * @param string $export_mode
 *   The export mode - currently supported:
 *   - remote
 *   - local
 *   - inline
 *   - packaged
 *
 * @throws Exception
 *
 * @return string
 *   Returns the handle to store in the features export or FALSE on failure.
 */
function uuid_features_file_export($file, $export_mode) {
  // Convert file to array to stay into the default
  // uuid_features_file format.
  $file = (object) $file;

  // Check the file.
  if (!isset($file->uri) || !is_file($file->uri)) {
    $path = (isset($file->uri)) ? $file->uri : 'unknown';
    throw new Exception(t("File field found on, but file '!path' doesn't exist on disk?", array('!path' => $path)));
  }

  if ($export_mode == 'local') {
    $orig_assets_path = $assets_path = variable_get('uuid_features_file_assets_path', '');

    // If files are supposed to be copied to the assets path.
    if ($assets_path) {
      // Ensure the assets path is created.
      if ((!is_dir($assets_path) && mkdir($assets_path, 0777, TRUE) == FALSE)
        || !is_writable($assets_path)
      ) {
        // Try creating a public path if the local path isn't writeable.
        // This is a kludgy solution to allow writing file assets to places
        // such as the profiles/myprofile directory, which isn't supposed to
        // be writeable.
        $new_assets_path = 'public://' . $assets_path;
        if (!is_dir($new_assets_path) && mkdir($new_assets_path, 0777, TRUE) == FALSE) {
          // Don't continue if the assets path is not ready.
          throw new Exception(t("Could not create assets path! '!path'", array('!path' => $assets_path)), 'error');
        }
        $assets_path = $new_assets_path;
      }

      // The writable path may be different from the path that gets
      // saved during the feature export to handle the
      // public path/local path dilemma mentioned above.
      $writeable_export_data = $assets_path . '/' . basename($file->uri);
      $export_data = $orig_assets_path . '/' . basename($file->uri);
      if (!copy($file->uri, $writeable_export_data)) {
        drupal_set_message(t("Export file error, could not copy '%filepath' to '%exportpath'.", array('%filepath' => $file->uri, '%exportpath' => $writeable_export_data)), 'error');
        return FALSE;
      }
    }
    else {
      $export_data = $file->uri;
    }
  }
  // Remote export mode.
  elseif ($export_mode == 'remote') {
    $export_data = file_create_url($file->uri);
  }
  elseif ($export_mode == 'packaged') {
    $assets_path = variable_get('uuid_features_packaged_file_assets_path', 'assets');
    $export_data = $assets_path . '/' . drupal_basename($file->uri);
  }
  // Default is 'inline' export mode.
  else {
    $export_data = base64_encode(file_get_contents($file->uri));
  }
  return $export_data;
}

/**
 * Handle importing file fields.
 */
function uuid_features_file_field_import(&$import, $entity_type, $module = NULL) {
  list($entity_id, $revision_id, $import_bundle) = entity_extract_ids($entity_type, $import);

  // Get all fields from this bundle.
  $fields = field_info_instances($entity_type, $import_bundle);

  foreach ($fields as $field_instance) {
    if (isset($import->{$field_instance['field_name']})) {
      // Load field info to check the type.
      $field = &$import->{$field_instance['field_name']};
      $info = field_info_field($field_instance['field_name']);
      $supported_fields = array_map('trim', explode(',', variable_get('uuid_features_file_supported_fields', 'file, image')));
      // Check if this field should implement file import/export system.
      if (in_array($info['type'], $supported_fields)) {
        // We need to loop into each language because i18n translation can build
        // fields with different language than the term one.
        foreach ($field as $language => $files) {
          if (is_array($files)) {
            foreach ($files as $i => $file) {
              // Convert file to array to stay into the default
              // uuid_features_file format.
              $file_object = (object) $file;
              $result = _uuid_features_file_field_import_file($file_object, $module);
              // The file was saved successfully, update the file field
              // (by reference).
              if ($result == TRUE && isset($file_object->fid)) {
                // Mash up the file object and the file field data to ensure
                // all data are present. The handling might strip properties
                // required by the field that stores the file.
                $field[$language][$i] = ((array) $file_object) + $file;
              }
              else {
                $field[$language][$i] = array();
              }
            }
          }
        }
      }
    }
  }
}

/**
 * Detects remote and local file exports and imports accordingly.
 *
 * @param object &$file
 *   The file, passed by reference.
 * @param string $module
 *   The module name.
 *
 * @return bool
 *   TRUE on success. On success the $file object will have a valid
 *   $file->fid attribute.
 */
function _uuid_features_file_field_import_file(&$file, $module = NULL) {
  // This is here for historical reasons to support older exports.  It can be
  // removed in the next major version.
  if (isset($file->uri)) {
    $file->uri = strtr($file->uri, array('#FILES_DIRECTORY_PATH#' => 'public:/'));
  }

  // The file is referenced but not defined because it's already
  // contained in a file_entity include.
  if (!isset($file->uri) && module_exists('file_entity')) {
    return FALSE;
  }
  // The file is already in the right location AND either the
  // uuid_features_file_path is not set or the uuid_features_file_path and
  // filepath contain the same file.
  elseif (isset($file->uri) && isset($file->uri) && is_file($file->uri) &&
    (
      (!isset($file->uuid_features_file_path) || !is_file($file->uuid_features_file_path)) ||
      (
        is_file($file->uuid_features_file_path) &&
        filesize($file->uri) == filesize($file->uuid_features_file_path) &&
        strtoupper(dechex(crc32(file_get_contents($file->uri)))) ==
          strtoupper(dechex(crc32(file_get_contents($file->uuid_features_file_path))))
      )
    )
  ) {
    // Keep existing file if it exists already at this uri (see also #1023254)
    // Issue #1058750.
    $query = db_select('file_managed', 'f')
        ->fields('f', array('fid'))
        ->condition('uri', $file->uri)
        ->execute()
        ->fetchCol();

    if (!empty($query)) {
      watchdog('uuid_features', 'kept existing managed file at uri "%uri"', array('%uri' => $file->uri), WATCHDOG_NOTICE);
      // Load file from db and use it as source.
      $db_file = file_load(array_shift($query));
      // Remove empty fid. Earlier code exported the fid with a NULL value.
      // @TODO Remove in next major version.
      if (empty($file->fid)) {
        unset($file->fid);
      }
      $file = (object) ((array) $file + (array) $db_file);
    }

    $file = file_save($file);
  }
  elseif (isset($file->uuid_features_file_data)) {
    $directory = drupal_dirname($file->uri);
    if (file_prepare_directory($directory, FILE_CREATE_DIRECTORY)) {
      if (file_put_contents($file->uri, base64_decode($file->uuid_features_file_data))) {
        $file = file_save($file);
      }
    }
  }
  // The file is in a local location and available in DB as managed file, but
  // missed in the destination, move it to the destination without file save.
  elseif (isset($file->uuid_features_file_path) && is_file($file->uuid_features_file_path)
    && !is_file($file->uri) && file_load_multiple(array(), array('uri' => $file->uri))) {
    $directory = drupal_dirname($file->uri);
    if (file_prepare_directory($directory, FILE_CREATE_DIRECTORY)) {
      $uuid_features_file_path = $file->uuid_features_file_path;
      file_unmanaged_copy($uuid_features_file_path, $file->uri, FILE_EXISTS_REPLACE);
    }
  }
  // The file is in a local location, move it to the destination then finish the
  // save.
  elseif (isset($file->uuid_features_file_path) && is_file($file->uuid_features_file_path)) {
    $directory = drupal_dirname($file->uri);
    if (file_prepare_directory($directory, FILE_CREATE_DIRECTORY)) {
      // The $file->uuid_features_file_path is passed to reference, and modified
      // by file_unmanaged_copy().  Making a copy to avoid tainting the
      // original.
      $uuid_features_file_path = $file->uuid_features_file_path;
      file_unmanaged_copy($uuid_features_file_path, $directory, FILE_EXISTS_REPLACE);

      // At this point the $file->uuid_features_file_path will contain the
      // destination of the copied file $file->uri = $uuid_features_file_path;
      $file = file_save($file);
    }
  }
  // The file is packaged in the feature, so move it to the destination then
  // finish the save.
  elseif (isset($file->uuid_features_packaged_file_path)) {
    $module_path = drupal_get_path('module', $module);
    $packaged_file_path = $module_path . '/' . $file->uuid_features_packaged_file_path;
    $directory = drupal_dirname($file->uri);
    if (file_prepare_directory($directory, FILE_CREATE_DIRECTORY)) {
      file_unmanaged_copy($packaged_file_path, $directory, FILE_EXISTS_REPLACE);
      $file = file_save($file);
    }
  }
  // The file is in a remote location, attempt to download it.
  elseif (isset($file->uuid_features_file_url)) {
    // Need time to do the download.
    ini_set('max_execution_time', 900);

    $temp_path = file_directory_temp() . '/' . md5(mt_rand()) . '.txt';
    if (($source = fopen($file->uuid_features_file_url, 'r')) == FALSE) {
      drupal_set_message(t("Could not open '@file' for reading.", array('@file' => $file->uuid_features_file_url)));
      return FALSE;
    }
    elseif (($dest = fopen($temp_path, 'w')) == FALSE) {
      drupal_set_message(t("Could not open '@file' for writing.", array('@file' => $file->uri)));
      return FALSE;
    }
    else {
      // PHP5 specific, downloads the file and does buffering automatically.
      $bytes_read = @stream_copy_to_stream($source, $dest);

      // Flush all buffers and wipe the file statistics cache.
      @fflush($source);
      @fflush($dest);
      clearstatcache();

      if ($bytes_read != filesize($temp_path)) {
        drupal_set_message(t("Remote export '!url' could not be fully downloaded, '@file' to temporary location '!temp'.", array(
          '!url' => $file->uuid_features_file_url,
          '@file' => $file->uri,
          '!temp' => $temp_path,
        )));
        return FALSE;
      }
      // File was downloaded successfully!.
      else {
        if (!@copy($temp_path, $file->uri)) {
          unlink($temp_path);
          drupal_set_message(t("Could not move temporary file '@temp' to '@file'.", array(
            '@temp' => $temp_path,
            '@file' => $file->uri,
          )));
          return FALSE;
        }

        unlink($temp_path);
        $file->filesize = filesize($file->uri);
        $file->filemime = file_get_mimetype($file->uri);
      }
    }

    fclose($source);
    fclose($dest);

    $file = file_save($file);
  }
  // Unknown error.
  else {
    drupal_set_message(t("Unknown error occurred attempting to import file: @filepath", array('@filepath' => $file->uri)), 'error');
    return FALSE;
  }

  return TRUE;
}

/**
 * Helper function to get a filtered list of fields of the same type.
 *
 * @param object $export
 *   The entity object to export e.g. a node.
 * @param string $entity_type
 *   The entity type.
 * @param string $field_type
 *   The field type to look for e.g. 'field_collection',
 *   'taxonomy_term_reference'.
 *
 * @return array
 *   A filtered list of fields of the same type.
 */
function uuid_features_get_field_items_iterator(&$export, $entity_type, $field_type) {
  list($entity_id, $revision_id, $export_bundle) = entity_extract_ids($entity_type, $export);
  $fields = field_info_instances($entity_type, $export_bundle);
  if (!isset($export_bundle)) {
    $fields = reset($fields);
  }
  $return = array();
  foreach ($fields as $field_instance) {
    $info = field_info_field($field_instance['field_name']);
    if (isset($export->{$info['field_name']})) {
      $field = &$export->{$info['field_name']};
      if ($info['type'] == $field_type) {
        foreach ($field as $language => &$field_items) {
          $return[$field_instance['field_name']] = array(
            $language => &$field_items,
          );
        }
      }
    }
  }
  return $return;
}

/**
 * Walks through a list of fields and sets UUID property using entity ids.
 *
 * @param array $fields
 *   Filtered array of fields of the same type.
 * @param string $entity_type
 *   The entity type.
 */
function uuid_features_set_uuid_references(&$fields, $entity_type) {
  foreach ($fields as $field_name => &$field_languages) {
    foreach ($field_languages as &$field_values) {
      foreach ($field_values as &$field_value) {
        $field_info = field_info_field($field_name);
        $columns = array_keys($field_info['columns']);
        $id_column = $columns[0];
        $entities = entity_get_uuid_by_id($entity_type, array($field_value[$id_column]));
        $field_reference_uuid = reset($entities);
        if ($field_reference_uuid) {
          $field_value['uuid'] = $field_reference_uuid;
          foreach ($columns as $column) {
            $field_value[$column] = $field_reference_uuid;
          }
        }
      }
    }
  }
}

/**
 * Walks through list of fields and updates entity references using the UUID.
 *
 * @param array $fields
 *   Filtered array of fields of the same type.
 * @param string $entity_type
 *   The entity type.
 * @param array $map
 *   Mapping from entity to reference fields properties.
 *   Example:
 *     Taxonomy term:
 *     array(
 *       'tid' => 'tid',
 *     )
 *
 *     Field collection:
 *     array(
 *       'item_id' => 'value',
 *       'revision_id' => 'revision_id',
 *     )
 */
function uuid_features_fetch_uuid_references(&$fields, $entity_type, $map) {
  foreach ($fields as $field_name => &$field_languages) {
    foreach ($field_languages as &$field_values) {
      if (is_array($field_values)) {
        foreach ($field_values as &$field_value) {
          $uuid = 'not found';
          if (isset($field_value['uuid'])) {
            $uuid = $field_value['uuid'];
          }
          else {
            // Try our best to load a reference even if the explicit uuid key is
            // missing. It's likely that the uuid was stored in the first map
            // key. This is for backward compatibility.
            $target_key = reset($map);
            if (isset($field_value[$target_key]) && uuid_is_valid($field_value[$target_key])) {
              $uuid = $field_value[$target_key];
            }
          }

          if ($uuid != 'not found') {
            $entities = entity_uuid_load($entity_type, array($uuid), array(), TRUE);
            $referenced_entity = reset($entities);

            foreach ($map as $source => $destination) {
              if ($referenced_entity) {
                $field_value[$destination] = $referenced_entity->{$source};
              }
              else {
                // Fallback.
                $field_value[$destination] = UUID_FEATURES_DEFAULT_FALLBACK_ID;
              }
            }
          }
        }
      }
    }
  }
}

// As it's quite likely someone else will build this as well, create it
// conditionally.
if (!function_exists('entity_load_single_by_uuid')) {
  /**
   * Loads a single local entity by it's uuid.
   *
   * @param string $entity_type
   *   The entity type.
   * @param string $uuid
   *   The uuid of the entity.
   *
   * @return object|FALSE
   *   The entity or FALSE on failure.
   */
  function entity_load_single_by_uuid($entity_type, $uuid) {
    $entity_id = current(entity_get_id_by_uuid($entity_type, array($uuid)));
    return ($entity_id) ? entity_load_single($entity_type, $entity_id) : FALSE;
  }
}