islandora_context.module

<?php

/**
 * @file
 * Defines all the hooks this module implements.
 */

/**
 * Implements hook_theme().
 */
function islandora_context_theme() {
  $items = array();
  $items['islandora_context_reaction_inserted_message'] = array(
    'variables' => array('message_text' => NULL),
    'path' => drupal_get_path('module', 'islandora_context') . '/theme',
    'template' => 'islandora-context-reaction-inserted-message',
    'file' => 'islandora_context_theme.inc',
  );
  return $items;
}

/**
 * Implements hook_ctools_plugin_api().
 */
function islandora_context_ctools_plugin_api($module, $api) {
  if ($module == 'context' && $api == 'plugins') {
    return array('version' => 3);
  }
}

/**
 * Implements hook_context_plugins().
 */
function islandora_context_context_plugins() {
  $plugins = array();
  $plugins['islandora_context_condition_is_islandora_object'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_condition_is_islandora_object.inc',
      'class' => 'IslandoraContextConditionIsIslandoraObject',
      'parent' => 'context_condition',
    ),
  );
  $plugins['islandora_context_condition_ds_mimetype'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_condition_ds_mimetype.inc',
      'class' => 'IslandoraContextConditionDsMimetype',
      'parent' => 'context_condition',
    ),
  );
  $plugins['islandora_context_condition_namespace'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_condition_namespace.inc',
      'class' => 'IslandoraContextConditionNamespace',
      'parent' => 'context_condition',
    ),
  );
  $plugins['islandora_context_condition_collection_member'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_condition_collection_member.inc',
      'class' => 'IslandoraContextConditionCollectionMember',
      'parent' => 'context_condition',
    ),
  );
  $plugins['islandora_context_condition_collection_is_empty'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_condition_collection_is_empty.inc',
      'class' => 'IslandoraContextConditionCollectionIsEmpty',
      'parent' => 'context_condition',
    ),
  );
  $plugins['islandora_context_condition_content_models'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_condition_cmodels.inc',
      'class' => 'IslandoraContextConditionContentModels',
      'parent' => 'context_condition',
    ),
  );
  $plugins['islandora_context_condition_keyword_in_datastream'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_condition_keyword_in_datastream.inc',
      'class' => 'IslandoraContextConditionKeywordInDatastream',
      'parent' => 'context_condition',
    ),
  );
  $plugins['islandora_context_condition_relationship'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_condition_relationship.inc',
      'class' => 'IslandoraContextConditionRelationship',
      'parent' => 'context_condition',
    ),
  );
  $plugins['islandora_context_condition_rdf_requested'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_condition_rdf_requested.inc',
      'class' => 'IslandoraContextConditionRdfRequested',
      'parent' => 'context_condition',
    ),
  );

  $plugins['islandora_context_reaction_insert_text'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_reaction_insert_text.inc',
      'class' => 'IslandoraContextReactionInsertText',
      'parent' => 'context_reaction',
    ),
  );
  if (module_exists('islandora_solr_metadata')) {
    $plugins['islandora_context_reaction_display_solr_metadata'] = array(
      'handler' => array(
        'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
        'file' => 'islandora_context_reaction_display_solr_metadata.inc',
        'class' => 'IslandoraContextReactionDisplaySolrMetadata',
        'parent' => 'context_reaction',
      ),
    );
    $plugins['islandora_context_reaction_display_solr_metadata_description'] = array(
      'handler' => array(
        'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
        'file' => 'islandora_context_reaction_display_solr_metadata_description.inc',
        'class' => 'IslandoraContextReactionDisplaySolrMetadataDescription',
        'parent' => 'context_reaction',
      ),
    );
  }
  $plugins['islandora_context_reaction_return_rdf'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_reaction_return_rdf.inc',
      'class' => 'IslandoraContextReactionReturnRdf',
      'parent' => 'context_reaction',
    ),
  );
  $plugins['islandora_context_reaction_hide_metadata_details'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_reaction_hide_metadata_details.inc',
      'class' => 'IslandoraContextReactionHideMetadataDetails',
      'parent' => 'context_reaction',
    ),
  );
  $plugins['islandora_context_reaction_hide_metadata_description'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_reaction_hide_metadata_description.inc',
      'class' => 'IslandoraContextReactionHideMetadataDescription',
      'parent' => 'context_reaction',
    ),
  );
  $plugins['islandora_context_reaction_hide_in_collections'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_reaction_hide_in_collections.inc',
      'class' => 'IslandoraContextReactionHideInCollections',
      'parent' => 'context_reaction',
    ),
  );
  $plugins['islandora_context_reaction_restrict_by_ip'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_reaction_restrict_by_ip.inc',
      'class' => 'IslandoraContextReactionRestrictByIp',
      'parent' => 'context_reaction',
    ),
  );
  $plugins['islandora_context_reaction_display_parent_metadata'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_reaction_display_parent_metadata.inc',
      'class' => 'IslandoraContextReactionDisplayParentMetadata',
      'parent' => 'context_reaction',
    ),
  );
  $plugins['islandora_context_reaction_use_viewer'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_reaction_use_viewer.inc',
      'class' => 'IslandoraContextReactionUseViewer',
      'parent' => 'context_reaction',
    ),
  $plugins['islandora_context_reaction_filter_derivatives'] = array(
    'handler' => array(
      'path' => drupal_get_path('module', 'islandora_context') . '/plugins',
      'file' => 'islandora_context_reaction_filter_derivatives.inc',
      'class' => 'IslandoraContextReactionFilterDerivatives',
      'parent' => 'context_reaction',
    ),
  ));
  return $plugins;
}

/**
 * Implements hook_context_registry().
 */
function islandora_context_context_registry() {
  return array(
    'conditions' => array(
      'islandora_context_condition_is_islandora_object' => array(
        'title' => t('Is Islandora Object'),
        'description' => t("Choose this condition if you want the context to apply to all Islandora objects."),
        'plugin' => 'islandora_context_condition_is_islandora_object',
      ),
      'islandora_context_condition_ds_mimetype' => array(
        'title' => t('Islandora Datastream has Mime Type'),
        'description' => t("Choose this condition if you want to detect a datastream's Mime Type."),
        'plugin' => 'islandora_context_condition_ds_mimetype',
      ),
      'islandora_context_condition_namespace' => array(
        'title' => t('Islandora PID Namespace'),
        'description' => t("Choose this condition if you want to detect an object's PID namespace."),
        'plugin' => 'islandora_context_condition_namespace',
      ),
      'islandora_context_condition_collection_member' => array(
        'title' => t('Islandora Collection Membership'),
        'description' => t("Choose this condition if you want to detect an object's membership in a collection."),
        'plugin' => 'islandora_context_condition_collection_member',
      ),
      'islandora_context_condition_collection_is_empty' => array(
        'title' => t('Islandora Collection Is Empty'),
        'description' => t("Choose this condition if you want to detect whether a collection object is empty (has no members)."),
        'plugin' => 'islandora_context_condition_collection_is_empty',
      ),
      'islandora_context_condition_content_models' => array(
        'title' => t('Islandora Content Models'),
        'description' => t("Choose this condition if you want to detect an object's content models."),
        'plugin' => 'islandora_context_condition_content_models',
      ),
      'islandora_context_condition_keyword_in_datastream' => array(
        'title' => t('Islandora Keyword in Datastream'),
        'description' => t("Choose this condition if you want to detect keywords in an XML or text datastream."),
        'plugin' => 'islandora_context_condition_keyword_in_datastream',
      ),
      'islandora_context_condition_relationship' => array(
        'title' => t('Islandora Relationship'),
        'description' => t("Choose this condition if you want to detect a particluar relationship defined in the object's RELS-EXT."),
        'plugin' => 'islandora_context_condition_relationship',
      ),
      'islandora_context_condition_rdf_requested' => array(
        'title' => t('RDF has been requested'),
        'description' => t("Choose this condition if you want to detect if a request has been made for RDF XML."),
        'plugin' => 'islandora_context_condition_rdf_requested',
      ),
    ),
    'reactions' => array(
      'islandora_context_reaction_insert_text' => array(
        'title' => t("Insert text into Islandora object's display"),
        'description' => t("Insert text into an object's display."),
        'plugin' => 'islandora_context_reaction_insert_text',
      ),
      'islandora_context_reaction_display_solr_metadata' => array(
        'title' => t("Use an Islandora Solr Metadata configuration"),
        'description' => t("Display a Solr Metadata configuration."),
        'plugin' => 'islandora_context_reaction_display_solr_metadata',
      ),
      'islandora_context_reaction_display_solr_metadata_description' => array(
        'title' => t("Use the corresponding Islandora Solr Metadata description"),
        'description' => t("Display a description element corresponding to the selected Solr Metadata configuration."),
        'plugin' => 'islandora_context_reaction_display_solr_metadata_description',
      ),
      'islandora_context_reaction_return_rdf' => array(
        'title' => t("Return RDF for an Islandora object"),
        'description' => t("Returns RDF representation of an Islandora object."),
        'plugin' => 'islandora_context_reaction_return_rdf',
      ),
      'islandora_context_reaction_hide_metadata_details' => array(
        'title' => t("Hide an object's metadata \"Details\" div"),
        'description' => t("Hides the metadata \"Details\" div of an Islandora object."),
        'plugin' => 'islandora_context_reaction_hide_metadata_details',
      ),
      'islandora_context_reaction_hide_metadata_description' => array(
        'title' => t("Hide an object's metadata \"Description\" markup"),
        'description' => t("Hides the metadata \"Description\" markup of an Islandora object."),
        'plugin' => 'islandora_context_reaction_hide_metadata_description',
      ),
      'islandora_context_reaction_hide_in_collections' => array(
        'title' => t("Hide an object's \"In collections\" markup"),
        'description' => t("Hides the metadata \"In collections\" markup of an Islandora object."),
        'plugin' => 'islandora_context_reaction_hide_in_collections',
      ),
      'islandora_context_reaction_restrict_by_ip' => array(
        'title' => t("User's IP address"),
        'description' => t("Restrict access to an Islandora object based on the user's IP address."),
        'plugin' => 'islandora_context_reaction_restrict_by_ip',
      ),
      'islandora_context_reaction_display_parent_metadata' => array(
        'title' => t("Display the metadata of an object's compound parent"),
        'description' => t("If an object is a child in a compound, display its parent's metadata."),
        'plugin' => 'islandora_context_reaction_display_parent_metadata',
      ),
      'islandora_context_reaction_use_viewer' => array(
        'title' => t("Use an Islandora viewer"),
        'description' => t("Use an Islandora viewer."),
        'plugin' => 'islandora_context_reaction_use_viewer',
      ),
      'islandora_context_reaction_filter_derivatives' => array(
        'title' => t("Filter generation of Islandora derivatives"),
        'description' => t("Determine which Islandora derivatives are generated."),
        'plugin' => 'islandora_context_reaction_filter_derivatives',
      ),
    ),
  );
}

/**
 * Implements hook_islandora_view_object().
 */
function islandora_context_islandora_view_object(AbstractObject $object) {
  // Check for conditions that we want to set when an object is viewed.
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_is_islandora_object')) {
    $plugin->execute($object);
  }
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_ds_mimetype')) {
    $plugin->execute($object);
  }
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_collection_member')) {
    $plugin->execute($object);
  }
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_collection_is_empty')) {
    $plugin->execute($object);
  }
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_content_models')) {
    $plugin->execute($object);
  }
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_keyword_in_datastream')) {
    $plugin->execute($object);
  }
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_relationship')) {
    $plugin->execute($object);
  }
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_rdf_requested')) {
    $plugin->execute($object);
  }
  // We call this plugin here since redirection, in this case to a proxy URL, has to happen
  // in this hook. Access to the object is handled in hook_islandora_object_access().
  if ($plugin = context_get_plugin('reaction', 'islandora_context_reaction_restrict_by_ip')) {
    $redirect = $plugin->execute($object);
    if (is_array($redirect)) {
      global $base_url;
      $redirect_target = $redirect[0] . $base_url . '/islandora/object/' . $object->id;
      drupal_goto($redirect_target);
    }
  }

  return array();
}

/**
 * Implements hook_islandora_view_object_alter().
 */
function islandora_context_islandora_view_object_alter(&$object, &$rendered) {
  // Check for reactions that alter the output of an object's display output.
  if ($plugin = context_get_plugin('reaction', 'islandora_context_reaction_return_rdf')) {
    $plugin->execute($object);
  }
  if ($plugin = context_get_plugin('reaction', 'islandora_context_reaction_display_parent_metadata')) {
    drupal_add_js('misc/form.js');
    drupal_add_js('misc/collapse.js');
    if ($markup = $plugin->execute($object)) {
      if (isset($rendered[NULL]['#markup'])) {
        $rendered[NULL]['#markup'] = $rendered[NULL]['#markup'] . $markup;
      }
      else {
        // To accommodate Binary Solution Pack content model objects.
        $rendered[NULL][] = $markup;
      }
    }
  }
  if ($plugin = context_get_plugin('reaction', 'islandora_context_reaction_insert_text')) {
    if ($markup = $plugin->execute()) {
      if (isset($rendered[NULL])) {
        $rendered[NULL]['#markup'] = $rendered[NULL]['#markup'] . $markup['#markup'];
      }
    }
  }
  if ($plugin = context_get_plugin('reaction', 'islandora_context_reaction_hide_metadata_details')) {
    $plugin->execute($object);
  }
  if ($plugin = context_get_plugin('reaction', 'islandora_context_reaction_hide_metadata_description')) {
    $plugin->execute($object);
  }
  if ($plugin = context_get_plugin('reaction', 'islandora_context_reaction_hide_in_collections')) {
    $plugin->execute($object);
  }
}

/**
 * Implements hook_islandora_object_access().
 */
function islandora_context_islandora_object_access($op, $object, $user) {
  // This condition needs to be set as early as possible in the object
  // access lifecycle.
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_namespace')) {
    $plugin->execute($object->id);
  }

  // Deine ISLANDORA_REST_DATASTREAM_GET_PERM if it is not already defined.
  if (!defined('ISLANDORA_REST_OBJECT_GET_PERM')) {
    define('ISLANDORA_REST_OBJECT_GET_PERM', ISLANDORA_VIEW_OBJECTS);
  }

  if ($op == ISLANDORA_VIEW_OBJECTS || $op == ISLANDORA_REST_OBJECT_GET_PERM) {
    if ($plugin = context_get_plugin('reaction', 'islandora_context_reaction_restrict_by_ip')) {
      $current_path = current_path();
      $ip_is_allowed = $plugin->execute();

      // Handle REST API requests.
      if (preg_match('#islandora/rest/v1/object#', $current_path)) {
        // Provide access to TN datastreams to everyone.
        if (preg_match('#/datastream/TN#', $current_path)) {
          return TRUE;
        }
        else {
          if ($ip_is_allowed === FALSE || is_array($ip_is_allowed)) {
            return FALSE;
          }
        }
      }

      // Handle non-REST requests, which need to delegate redirecting to a proxy
      // hook_islandora_view_object().
      if (is_array($ip_is_allowed)) {
        // First member will be the redirect URL, and second, if present,
        // will be a boolean indicating whether to append the object's URL
        // to the redirect URL. If this is the case, retun NULL so
        // hook_islandora_view_object() can redirect the user to the proxy URL.
        if (count($ip_is_allowed) == 1) {
          if (is_array($ip_is_allowed)) {
            return NULL;
          }
          else {
            return FALSE;
          }
        }
        else {
          // Make an exception to the redirect for thumbnails, since
          // they should be viewable by everyone.
          if (!preg_match('#datastream/TN/view#', $current_path)) {
            return NULL;
          }
        }
        return NULL;
      }
      elseif ($ip_is_allowed) {
        return TRUE;
      }
      elseif (is_null($ip_is_allowed)) {
        return NULL;
      }
      else {
        return FALSE;
      }
    }
  }
}

/**
 * Implements hook_islandora_datastream_access().
 */
function islandora_context_islandora_datastream_access($op, $datastream, $user) {
  // Thumbnails should be viewable by everyone, including REST clients.
  // Counterintuitively, ISLANDORA_REST_DATASTREAM_GET_PERM is the correct
  // permission here and in the next check for requests via the islandora_rest
  // API; TNs remain viewable, other datastreams are correctly restricted.
  // First, we need to handle the case where ISLANDORA_REST_DATASTREAM_GET_PERM
  // is not defined because the REST module is not enabled.
  if (!defined('ISLANDORA_REST_DATASTREAM_GET_PERM')) {
    define('ISLANDORA_REST_DATASTREAM_GET_PERM', ISLANDORA_VIEW_OBJECTS);
  }

  if (($op == ISLANDORA_VIEW_OBJECTS || $op == ISLANDORA_REST_DATASTREAM_GET_PERM) && ($datastream->id == 'TN')) {
    return TRUE;
  }

  // This condition needs to be set as early as possible in the datastream
  // access lifecycle.
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_namespace')) {
    $parent_object = $datastream->parent;
    $plugin->execute($parent_object->id);
  }

  // Assumption here is that if a user is not allowed to view an object, they
  // are not allowed to view any of the object's datastreams other than TN.
  if ($op == ISLANDORA_VIEW_OBJECTS || $op == ISLANDORA_REST_DATASTREAM_GET_PERM) {
    if ($plugin = context_get_plugin('reaction', 'islandora_context_reaction_restrict_by_ip')) {
      $current_path = current_path();
      $ip_is_allowed = $plugin->execute();

      // Handle REST API requests.
      if (preg_match('#islandora/rest/v1/object/#', $current_path)) {
        if ($ip_is_allowed === FALSE || is_array($ip_is_allowed)) {
          return FALSE;
        }
      }

      // Handle non-REST requests.
      if ($ip_is_allowed) {
        return TRUE;
      }
      elseif (is_null($ip_is_allowed)) {
        return NULL;
      }
      else {
        return FALSE;
      }

    }
  }
}

/**
 * Implements hook_islandora_metadata_display_info().
 */
function islandora_context_islandora_metadata_display_info() {
  return array(
    'islandora_context' => array(
      'label' => t('Islandora Solr Metadata managed by the Islandora Context module'),
      'description' => t('Context-sensitive metadata display driven by the Islandora Solr Search module'),
      'metadata callback' => 'islandora_context_solr_metadata_display_callback',
      'description callback' => 'islandora_context_solr_metadata_description_callback',
      'configuration' => 'admin/islandora/search/islandora_solr/metadata',
    ),
  );
}

/**
 * Metadata display callback for rendering metadata from Solr.
 *
 * @param AbstractObject $object
 *   An AbstractObject representing an object within Fedora.
 * @param bool $print
 *   Whether this is for printing purposes.
 *
 * @return string
 *   Markup representing the metadata display pulled from Solr.
 */
function islandora_context_solr_metadata_display_callback(AbstractObject $object, $print = FALSE) {
  if ($plugin = context_get_plugin('reaction', 'islandora_context_reaction_display_solr_metadata')) {
    if ($markup = $plugin->execute($object)) {
      return $markup;
    }
    else {
      return islandora_solr_metadata_display_callback($object, $print);
    }
  }
}

/**
 * Metadata display callback for rendering metadata from Solr.
 *
 * @param AbstractObject $object
 *   An AbstractObject representing an object within Fedora.
 *
 * @return string
 *   Markup representing the metadata display pulled from Solr.
 */
function islandora_context_solr_metadata_description_callback(AbstractObject $object) {
  if ($plugin = context_get_plugin('reaction', 'islandora_context_reaction_display_solr_metadata_description')) {
    if ($markup = $plugin->execute($object)) {
      return $markup;
    }
    else {
      return islandora_solr_metadata_description_callback($object);
    }
  }
}

/**
 * Implements hook_islandora_derivative_alter().
 *
 * This hook is only fired during derivative generation, so we need to use
 * it as the integration point for Context conditions and the reaction.
 * Integrating the reaction and conditions in the same hook is not typical.
 */
function islandora_context_islandora_derivative_alter(&$derivatives, AbstractObject $object) {
  // Define conditions that can trigger the reacion.
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_is_islandora_object')) {
    $plugin->execute($object);
  }
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_collection_member')) {
    $plugin->execute($object);
  }
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_content_models')) {
    $plugin->execute($object);
  }
  if ($plugin = context_get_plugin('condition', 'islandora_context_condition_namespace')) {
    $plugin->execute($object->id);
  }

  // Implement the reaction.
  if ($plugin = context_get_plugin('reaction', 'islandora_context_reaction_filter_derivatives')) {
    $filter_settings = $plugin->execute();
    if (!isset($filter_settings['action'])) {
      $filter_settings['action'] = NULL;
    }
    if ($filter_settings['action'] == 'include') {
      foreach ($derivatives as $key => $derivative) {
        if (!in_array($derivative['destination_dsid'], $filter_settings['dsids'])) {
          unset($derivatives[$key]);
        }
      }
    }
    if ($filter_settings['action'] == 'exclude') {
      foreach ($derivatives as $key => $derivative) {
        if (in_array($derivative['destination_dsid'], $filter_settings['dsids'])) {
          unset($derivatives[$key]);
        }
      }
    }
  }
}

/**
 * Implements hook_form_alter().
 */
function islandora_context_form_islandora_solr_metadata_config_form_alter(&$form, &$form_state, $form_id) {
  $note = t("If you want to use a content model with a Display configuration triggered by Islandora Context, you need to create an 'Islandora Content Models' Context condition. The content model defined here is ignored.");
  $form['islandora_solr_metadata_cmodels']['table_wrapper']['cmodel_options']['#description'] = $note;
}

/**
 * Preprocessor for theme('islandora_basic_image').
 *
 * Other content models to come....
 */
function islandora_context_preprocess_islandora_basic_image(&$vars) {
  $islandora_object = $vars['islandora_object'];
  if ($plugin = context_get_plugin('reaction', 'islandora_context_reaction_use_viewer')) {
    if ($viewer = $plugin->execute($islandora_object)) {
      $vars['islandora_content'] = $viewer;
    }
  }
}