islandora/includes/utilities.inc

<?php

/**
 * @file
 * Utility functions.
 *
 * @todo this file should be broken out into other files.
 */

/**
 * Convert bytes to human readable format.
 *
 * XXX: Shouldn't Drupal's format_size() be preferred?
 *
 * @param int $bytes
 *   Size in bytes to convert.
 * @param int $precision
 *   The amount of decimal precision to show.
 *
 * @return string
 *   Human readable size.
 */
function islandora_convert_bytes_to_human_readable($bytes, $precision = 2) {
  $kilobyte = 1024;
  $megabyte = $kilobyte * 1024;
  $gigabyte = $megabyte * 1024;
  $terabyte = $gigabyte * 1024;

  if (($bytes >= 0) && ($bytes < $kilobyte)) {
    return $bytes . ' B';
  }
  elseif (($bytes >= $kilobyte) && ($bytes < $megabyte)) {
    return round($bytes / $kilobyte, $precision) . ' KiB';
  }
  elseif (($bytes >= $megabyte) && ($bytes < $gigabyte)) {
    return round($bytes / $megabyte, $precision) . ' MiB';
  }
  elseif (($bytes >= $gigabyte) && ($bytes < $terabyte)) {
    return round($bytes / $gigabyte, $precision) . ' GiB';
  }
  elseif ($bytes >= $terabyte) {
    return round($bytes / $terabyte, $precision) . ' TiB';
  }
  else {
    return $bytes . ' B';
  }
}

/**
 * Add a file as managed if is not already.
 *
 * @param string $file_uri
 *   The given file URI location.
 *
 * @return object
 *   The file, as returned from file_save().
 */
function islandora_temp_file_entry($file_uri, $mime = NULL) {
  $query = new EntityFieldQuery();
  $result = $query
    ->entityCondition('entity_type', 'file')
    ->propertyCondition('uri', $file_uri)
    ->execute();
  if (isset($result['file'])) {
    $fid = current($result['file'])->fid;
    $file = file_load($fid);
  }
  else {
    $file = new stdClass();
    $file->uri = $file_uri;
    $file->filename = drupal_basename($file_uri);
    if (isset($mime)) {
      $file->filemime = $mime;
    }
    else {
      $file->filemime = file_get_mimetype($file_uri);
    }
  }
  $file->status = 0;
  return file_save($file);
}

/**
 * Creates a label for control group symbols.
 */
function islandora_control_group_to_human_readable($control_group) {
  switch ($control_group) {
    case 'M':
      return '<strong>M</strong>anaged';

    case 'X':
      return 'Inline <strong>X</strong>ML';

    case 'R':
      return '<strong>R</strong>edirect';

    case 'E':
      return '<strong>E</strong>xternally Referenced';

    default:
      return $control_group;
  }
}

/**
 * Checks if the given pid is valid.
 *
 * @param string $pid
 *   The object id to check.
 *
 * @return bool
 *   TRUE if valid, FALSE otherwise.
 */
function islandora_is_valid_pid($pid) {
  return drupal_strlen(trim($pid)) <= 64 && preg_match('/^([A-Za-z0-9]|-|\.)+:(([A-Za-z0-9])|-|\.|~|_|(%[0-9A-F]{2}))+$/', trim($pid));
}

/**
 * Checks if the given namespace is valid.
 *
 * @param string $namespace
 *   The namespace to check without the ":" character.
 *
 * @return bool
 *   TRUE if valid, FALSE otherwise.
 */
function islandora_is_valid_namespace($namespace) {
  return drupal_strlen(trim($namespace)) <= 64 && preg_match('/^([A-Za-z0-9]|-|\.)+$/', trim($namespace));
}

/**
 * Checks if the given datastream id is valid.
 *
 * @param string $dsid
 *   The datastream id to check.
 *
 * @return bool
 *   TRUE if valid, FALSE otherwise.
 */
function islandora_is_valid_dsid($dsid) {
  return drupal_strlen(trim($dsid)) <= 64 && preg_match('/^[a-zA-Z0-9\_\-\.]+$/', trim($dsid));
}

/**
 * Helper function to describe a Fedora repository.
 *
 * Can be used to check if Fedora is available.
 *
 * @param string $url
 *   A url to a Fedora repository, if NULL the default is used.
 *
 * @return array
 *   Returns an array describing the repository. Returns FALSE if Fedora is down
 *   or if the url is incorrect.
 */
function islandora_describe_repository($url = NULL) {
  $url = isset($url) ? $url : variable_get('islandora_base_url', 'http://localhost:8080/fedora');
  $connection = islandora_get_tuque_connection();
  if ($connection) {
    try {
      $info = $connection->api->a->describeRepository();
      return $info;
    }
    catch (RepositoryException $e) {
      return FALSE;
    }
  }
  return FALSE;
}

/**
 * Build and invoke a list of hooks by combining the given hook and refinements.
 *
 * The given hook will be called as MODULE_HOOK, and for each hook refinement
 * as MODULE_REFINEMENT_HOOK. Any additional arguments passed to this function
 * will be passed as arguments to module_invoke_all().
 *
 * @param string $hook
 *   A hook to call.
 * @param array $refinements
 *   An array of strings, that will be escaped and concatinated with the given
 *   hook. This will most likely be PIDs/DSIDs/Labels etc. We often refine our
 *   hooks using an objects model.
 * @param array $args
 *   Any arguments to pass onto module_invoke_all().
 *
 * @return array
 *   The merged results from all the hooks.
 *
 * @see islandora_build_hook_list()
 */
function islandora_invoke_hook_list($hook, array $refinements, array $args) {
  $return = array();
  foreach (islandora_build_hook_list($hook, $refinements) as $refined_hook) {
    array_unshift($args, $refined_hook);
    $result = call_user_func_array('module_invoke_all', $args);
    $return = array_merge_recursive($return, $result);
    array_shift($args);
  }
  if (module_exists('rules')) {
    $event_info = rules_get_event_info($hook);
    if (isset($event_info['module'])) {
      $parameters = $event_info['variables'];
      $rule_args = array_slice($args, 0, count($parameters));
      array_unshift($rule_args, $hook);
      $result = call_user_func_array('rules_invoke_event', $rule_args);
    }
  }
  return $return;
}

/**
 * Build a list of all the hooks to call.
 *
 * Concatenates each hook $refinement (escaped) to the hook name, for calling
 * with module_invoke_all().
 *
 * Any non-valid PHP function characters in the given refinements are
 * converted to "_" characters.
 *
 * @param string $hook
 *   The base hook to concatenate.
 * @param array $refinements
 *   An array of strings, that will be escaped and concatinated with the given
 *   hook. This will most likely be PIDs/DSIDs/Labels etc. We often refine our
 *   hooks using an objects model.
 *
 * @return array
 *   An array with each refinement escaped and concatenated with the base hook
 *   name, in addition to the base hook name.
 */
function islandora_build_hook_list($hook, array $refinements = array()) {
  $refinements = array_unique($refinements);
  $hooks = array($hook);
  foreach ($refinements as $refinement) {
    $refinement = preg_replace('/[^a-zA-Z0-9_]/', '_', $refinement);
    $hooks[] = "{$refinement}_{$hook}";
  }
  return $hooks;
}

/**
 * Escape a Fedora PID to be valid inside of a PHP function name.
 *
 * Originally intended to allow inclusion of a PID in a module_invoke_all()
 * call.
 */
function islandora_escape_pid_for_function($pid) {
  // Apparently, case doesn't matter for function calls in PHP, so let's not
  // really worry about changing the case.
  return str_replace(
  // Any PID characters which are not valid in the name of a PHP function.
      array(
        ':',
        '-',
      ),
      '_',
      $pid
  );
}

/**
 * Gets the namespace of the given id.
 *
 * @param string $id
 *   Either a PID or namespace to check for accessibility. Any string like those
 *   below are fine.
 *
 * @code
 *   'islandora',
 *   'islandora:',
 *   'islandora:1234',
 * @endcode
 *
 * @return string
 *   The namespace portion of the given string.
 */
function islandora_get_namespace($id) {
  $matches = array();
  preg_match('/^([^:]*)/', $id, $matches);
  return $matches[0];
}

/**
 * Checks the given namespace/PID is/has an  accessible namespace.
 *
 * Accessible is defined by the "islandora_pids_allowed" variable.
 *
 * @param string $id
 *   Either a PID or namespace to check for accessibility. Any string like those
 *   below are fine.
 *
 * @code
 *   'islandora',
 *   'islandora:',
 *   'islandora:1234',
 * @endcode
 *
 * @return bool
 *   TRUE if accessible, FALSE otherwise.
 */
function islandora_namespace_accessible($id) {
  if (variable_get('islandora_namespace_restriction_enforced', FALSE)) {
    $namespace = islandora_get_namespace($id);
    $allowed_namespaces = islandora_get_allowed_namespaces();
    return in_array($namespace, $allowed_namespaces);
  }
  return TRUE;
}

/**
 * Gets any objects that the given object has a parent relationship with.
 *
 * Parent relationships are defined as (isMemberOf, isMemberOfCollection).
 *
 * This function gets its info from the RELS-EXT directly rather than through an
 * risearch.
 *
 * @param AbstractObject $object
 *   The object whose parents will be returned.
 *
 * @return array
 *   An array of FedoraObject's that the given object has a
 *   (isMemberOf, isMemberOfCollection) relationship with.
 */
function islandora_get_parents_from_rels_ext(AbstractObject $object) {
  try {
    $collections = array_merge(
      $object->relationships->get(FEDORA_RELS_EXT_URI, 'isMemberOfCollection'),
      $object->relationships->get(FEDORA_RELS_EXT_URI, 'isMemberOf'));
  }
  catch (RepositoryException $e) {
    // @todo some logging would be nice, not sure what this throws.
    return array();
  }
  $map = function ($o) {
    return islandora_object_load($o['object']['value']);
  };
  $collections = array_map($map, $collections);
  return array_filter($collections);
}

/**
 * Gets the datastreams requirments that are missing.
 *
 * @param AbstractObject $object
 *   The object which models will be used to determine what datastreams it
 *   should have.
 *
 * @return array
 *   The DS-COMPOSITE-MODEL defined datastreams that are required for the given
 *   object, but not already present.
 */
function islandora_get_missing_datastreams_requirements(AbstractObject $object) {
  module_load_include('inc', 'islandora', 'includes/utilities');
  $datastreams = islandora_get_datastreams_requirements($object);
  foreach ($datastreams as $dsid => $requirements) {
    if (isset($object[$dsid])) {
      unset($datastreams[$dsid]);
    }
  }
  return $datastreams;
}

/**
 * Gets the required datastreams for the given object.
 *
 * Checks the object's content model's for which datastream are expected to be
 * used with this object, as defined by the DS-COMPOSITE-MODEL datastreams.
 *
 * For duplicate datastreams in the models, the first model defines the
 * datastreams attributes regardless of what other models define.
 * This should be undefined behavior according to the documentation.
 *
 * @link https://wiki.duraspace.org/display/FEDORA34/Fedora+Digital+Object+Model#FedoraDigitalObjectModel-ContentModelObjectCMODEL @endlink
 *
 * @see islandora_get_required_datastreams_from_content_model()
 *
 * @param AbstractObject $object
 *   The object which models will be used to determine what datastreams it
 *   should have.
 *
 * @return array
 *   The DS-COMPOSITE-MODEL defined datastreams that are required for the given
 *   object.
 */
function islandora_get_datastreams_requirements(AbstractObject $object) {
  return islandora_get_datastreams_requirements_from_models($object->models);
}

/**
 * Get the list of which datastreams are valid in the given set of models.
 *
 * @param array $models
 *   An array of content models PIDs from which to parse the DS-COMPOSITE-MODEL
 *   stream.
 *
 * @return array
 *   An associative array of associative arrays, merged from calls to
 *   islandora_get_datastreams_requirements_from_content_model().
 */
function islandora_get_datastreams_requirements_from_models(array $models) {
  $dsids = array();
  foreach ($models as $model_pid) {
    $model = islandora_object_load($model_pid);
    if (isset($model) && $model) {
      $dsids += islandora_get_datastreams_requirements_from_content_model($model);
    }
  }
  // The AUDIT Datastream can not really be added, so it can't really be
  // missing.
  unset($dsids['AUDIT']);
  return $dsids;
}

/**
 * Checks the given content model for which datastreams are required.
 *
 * As defined by it's DS-COMPOSITE-MODEL datastream.
 *
 * @todo Add support for fetching the schema information.
 *
 * @param AbstractObject $object
 *   The content model whose DS-COMPOSITE-MODEL datastream will be used to
 *   determine what datastreams are required.
 *
 * @return array
 *   An associative array mapping datastream IDs to associative arrays
 *   containing the values parsed from the DS-COMPOSITE-MODEL on the given
 *   object--of the form:
 *   - DSID: A datastream ID being described.
 *     - "id": A string containing ID of the datastream.
 *     - "mime": A array containing MIME-types the stream may have.
 *     - "optional": A boolean indicating if the given stream is optional.
 */
function islandora_get_datastreams_requirements_from_content_model(AbstractObject $object) {
  if (empty($object[ISLANDORA_DS_COMP_STREAM]) || !islandora_datastream_access(ISLANDORA_VIEW_OBJECTS, $object[ISLANDORA_DS_COMP_STREAM])) {
    return array();
  }
  $xml = new SimpleXMLElement($object[ISLANDORA_DS_COMP_STREAM]->content);
  foreach ($xml->dsTypeModel as $ds) {
    $dsid = (string) $ds['ID'];
    $optional = strtolower((string) $ds['optional']);
    $mime = array();
    foreach ($ds->form as $form) {
      $mime[] = (string) $form['MIME'];
    }
    $dsids[$dsid] = array(
      'id' => $dsid,
      'mime' => $mime,
      'optional' => ($optional == 'true') ? TRUE : FALSE,
    );
  }
  return $dsids;
}

/**
 * Prepare an ingestable object.
 *
 * @param string $name_source
 *   Either a pid or namespace in which the PID for the new object will be
 *   created.
 * @param string $label
 *   An optional label to apply to the object.
 * @param array $datastreams
 *   A array of datastreams to add, where each datastream definition is an
 *   associative array containing:
 *   - dsid: The datastream ID.
 *   - label: An optional label for the datastream.
 *   - mimetype: A MIMEtype for the datastream; defaults to text/xml.
 *   - control_group: One of X, M, R and E; defaults to M.
 *   - datastream_file: A web-accessible path, for which we try to get an
 *     absolute path using url().
 * @param array $content_models
 *   An array of content model PIDs to which the new object should subscribe.
 * @param array $relationships
 *   An array of relationships, where each relationship is an associative array
 *   containing:
 *   - relationship: The predicate for the relationship, from the Fedora
 *     RELS-EXT namespace.
 *   - pid: The object for the relationship, to which we are creating the
 *     relationhsip.
 *
 * @return NewFedoraObject
 *   An ingestable NewFedoraObject.
 */
function islandora_prepare_new_object($name_source = NULL,
                                      $label = NULL,
                                      array $datastreams = array(),
                                      array $content_models = array(),
                                      array $relationships = array()) {
  global $user;
  $tuque = islandora_get_tuque_connection();
  $object = isset($name_source) ? $tuque->repository->constructObject($name_source) : new IslandoraNewFedoraObject(NULL, $tuque->repository);
  $object->owner = isset($user->name) ? $user->name : $object->owner;
  $object->label = isset($label) ? $label : $object->label;
  foreach ($content_models as $content_model) {
    $object->relationships->add(FEDORA_MODEL_URI, 'hasModel', $content_model);
  }
  foreach ($relationships as $relationship) {
    $object->relationships->add(FEDORA_RELS_EXT_URI, $relationship['relationship'], $relationship['pid']);
  }
  foreach ($datastreams as $ds) {
    $dsid = $ds['dsid'];
    $label = isset($ds['label']) ? $ds['label'] : '';
    $mimetype = isset($ds['mimetype']) ? $ds['mimetype'] : 'text/xml';
    // Default 'Managed'.
    $control_group = 'M';
    $groups = array('X', 'M', 'R', 'E');
    if (isset($ds['control_group']) && in_array($ds['control_group'], $groups)) {
      $control_group = $ds['control_group'];
    }

    $as_file = FALSE;
    if (file_valid_uri($ds['datastream_file'])) {
      // A local file with as a Drupal file/stream wrapper URI.
      $datastream_file = $ds['datastream_file'];
      $as_file = TRUE;
    }
    elseif (is_readable($ds['datastream_file'])) {
      // A local file as a filesystem path.
      $datastream_file = drupal_realpath($ds['datastream_file']);
      $as_file = TRUE;
    }
    else {
      $scheme = parse_url($ds['datastream_file'], PHP_URL_SCHEME);
      if (in_array($scheme, stream_get_wrappers())) {
        // A URI which gets handled by one of the PHP-native stream wrappers.
        $datastream_file = $ds['datastream_file'];
        $as_file = TRUE;
      }
      else {
        // Schema does not match available php stream wrapper. Attempt to
        // set datastream_file by url for the given scheme. Https (SSL) can
        // cause this to fail, and trigger an output log in watchdog.
        $datastream_file = url($ds['datastream_file'], array('absolute' => TRUE));
        watchdog(
          'islandora',
          'Attempting to ingest %file in islandora_prepare_new_object(), but it does not appear to be readable. We will pass the path through url(), and pass along as such.',
          array('%file' => $datastream_file),
          WATCHDOG_WARNING
        );
      }
    }

    $datastream = $object->constructDatastream($dsid, $control_group);
    $datastream->label = $label;
    $datastream->mimetype = $mimetype;
    switch ($control_group) {
      case 'M':
        if ($as_file) {
          $datastream->setContentFromFile($datastream_file);
        }
        else {
          $datastream->setContentFromUrl($datastream_file);
        }
        break;

      case 'X':
        $datastream->setContentFromString(file_get_contents($datastream_file));
        break;
    }

    $object->ingestDatastream($datastream);
  }

  return $object;
}

/**
 * Displays the repository is inaccessible message.
 *
 * Use anywhere we want to ensure a consitent error message when the repository
 * is not accessible.
 */
function islandora_display_repository_inaccessible_message() {
  $text = t('Islandora configuration');
  $link = l($text, 'admin/islandora/configure', array('attributes' => array('title' => $text)));
  $message = t('Could not connect to the repository. Please check the settings on the !link page.',
  array('!link' => $link));
  drupal_set_message(filter_xss($message), 'error', FALSE);

}

/**
 * Create a message stating if the given executable is available.
 *
 * If the both the version and required version are given then only if the
 * version is equal to or greater than the required version the executable
 * will be considered correct.
 *
 * @param string $path
 *   The absolute path to an executable to check for availability.
 * @param string $version
 *   The version of exectuable.
 * @param string $required_version
 *   The required version of exectuable.
 *
 * @return string
 *   A message in html detailing if the given executable is accessible.
 */
function islandora_executable_available_message($path, $version = NULL, $required_version = NULL) {
  $available = is_executable($path);
  if ($available) {
    $image = theme_image(array('path' => 'misc/watchdog-ok.png', 'attributes' => array()));
    $message = t('Executable found at @path', array('@path' => $path));
    if ($version) {
      $message .= t('<br/>Version: @version', array('@version' => $version));
    }
    if ($required_version) {
      $message .= t('<br/>Required Version: @version', array('@version' => $required_version));
      if (version_compare($version, $required_version) < 0) {
        $image = theme_image(array('path' => 'misc/watchdog-error.png', 'attributes' => array()));
      }
    }
  }
  else {
    $image = theme_image(array('path' => 'misc/watchdog-error.png', 'attributes' => array()));
    $message = t('Unable to locate executable at @path', array('@path' => $path));
  }
  return $image . $message;
}

/**
 * Create a message stating if the given directory exists.
 *
 * @param string $path
 *   The absolute path to an executable to check for availability.
 *
 * @return string
 *   A message in HTML detailing if the given directory is exists.
 */
function islandora_directory_exists_message($path) {
  $available = is_dir($path);
  if ($available) {
    $image = theme_image(array('path' => 'misc/watchdog-ok.png', 'attributes' => array()));
    $message = t('Directory found at @path', array('@path' => $path));
  }
  else {
    $image = theme_image(array('path' => 'misc/watchdog-error.png', 'attributes' => array()));
    $message = t('Unable to locate directory at @path', array('@path' => $path));
  }
  return $image . $message;
}

/**
 * Gets the default value for the given system_settings_form() element.
 *
 * Checks the $form_state for the default value if not it checks
 * variable_get(). Assumes #tree is FALSE. This is only really required
 * for elements that utilize AJAX, as their value can change before the
 * submit actually takes place.
 *
 * @param string $name
 *   The name of the system settings form element.
 * @param mixed $default_value
 *   The default value for the system settings form element.
 * @param array $form_state
 *   The Drupal form state.
 *
 * @return mixed
 *   The default value for use in a the system_settings_form().
 */
function islandora_system_settings_form_default_value($name, $default_value, array &$form_state) {
  return isset($form_state['values'][$name]) ? $form_state['values'][$name] : variable_get($name, $default_value);
}

/**
 * Gets the list of allowed namespaces as defined by 'islandora_pids_allowed'.
 *
 * @return array
 *   The list of namespaces striped of trailing ":" characters.
 */
function islandora_get_allowed_namespaces() {
  $matches = array();
  $allowed_namespaces = variable_get('islandora_pids_allowed', 'default: demo: changeme: islandora:');
  preg_match_all('/([A-Za-z0-9-\.]+):/', $allowed_namespaces, $matches);
  $accessible_namespaces = $matches[1];
  // Ensure that the "islandora" namespace is explicitly allowed
  // no matter what happens.
  if (!in_array('islandora', $accessible_namespaces)) {
    $accessible_namespaces[] = 'islandora';
  }
  return $accessible_namespaces;
}

/**
 * Gets a list of all existing content models.
 *
 * If 'islandora_namespace_restriction_enforced' is set to true only return
 * content models in the allowed namespace.
 *
 * @param bool $ignore_system_namespace
 *   Ignore content models in the 'fedora-system' namespace.
 *
 * @return array
 *   An associative array of all existing content models.
 *   - pid: The PID of the content model object.
 *     - pid: The PID of the content model object.
 *     - label: The label of the content model object.
 */
function islandora_get_content_models($ignore_system_namespace = TRUE) {
  module_load_include('inc', 'islandora', 'includes/utilities');
  $tuque = islandora_get_tuque_connection();
  $query = "PREFIX fm: <" . FEDORA_MODEL_URI . ">
            PREFIX fr: <" . FEDORA_RELS_EXT_URI . ">
            SELECT ?object ?label
            FROM <#ri>
            WHERE {
              {?object fm:hasModel <info:fedora/fedora-system:ContentModel-3.0>;
                       fm:state fm:Active
              }
            UNION{
                ?object fr:isMemberOfCollection <info:fedora/islandora:ContentModelsCollection>;
                fm:state fm:Active
              }
            OPTIONAL{
                 ?object fm:label ?label
            }
           }";
  $content_models = array();
  $results = $tuque->repository->ri->sparqlQuery($query, 'unlimited');
  foreach ($results as $result) {
    $content_model = $result['object']['value'];
    $label = $result['label']['value'];
    $namespace = islandora_get_namespace($content_model);
    $ignore = $ignore_system_namespace && $namespace == 'fedora-system';
    $ignore |= !islandora_namespace_accessible($namespace);
    if (!$ignore) {
      $content_models[$content_model] = array('pid' => $content_model, 'label' => $label);
    }
  }
  return $content_models;
}

/**
 * Returns Drupal tableselect element allowing selection of Content Models.
 *
 * @param string $drupal_variable
 *   The name of the Drupal variable holding selected content models
 *   Content models held in this variable will appear at the top of
 *   the displayed list.
 * @param array $default_values_array
 *   Default values to display if $drupal_variable is unset.
 *
 * @return array
 *   Drupal form element allowing content model selection
 */
function islandora_content_model_select_table_form_element($drupal_variable, array $default_values_array = array('')) {
  $defaults = array();
  $rows = array();
  $content_models = array();
  $options = islandora_get_content_models(TRUE);
  foreach ($options as $option) {
    $content_models[$option['pid']] = $option['label'];
  }

  $selected = array_values(variable_get($drupal_variable, $default_values_array));
  $comparator = function ($a, $b) use ($selected) {
    $a_val = $b_val = 0;
    if (in_array($a, $selected)) {
      $a_val = 1;
    }
    if (in_array($b, $selected)) {
      $b_val = 1;
    }
    return $b_val - $a_val;
  };
  uksort($content_models, $comparator);
  foreach ($content_models as $pid => $label) {
    $rows[$pid] = array(
      'pid' => $pid,
      'title' => $label,
    );
    $defaults[$pid] = in_array($pid, $selected);
  }
  $header = array(
    'pid' => array('data' => t('PID')),
    'title' => array('data' => t('Content Model')),
  );
  // Build and return table element.
  $element = array(
    '#type' => 'tableselect',
    '#header' => $header,
    '#options' => $rows,
    '#default_value' => $defaults,
    '#empty' => t("There are no content models in this Fedora Repository."),
  );

  return $element;
}

/**
 * Convience function for generating a E_USER_DEPRECATED message.
 *
 * To utilitize this function pass the results to trigger_error() like so:
 *
 * @code
 *   $message = islandora_deprecated('7.x-1.1', t('Use more cowbell.'))
 *   trigger_error(filter_xss($message), E_USER_DEPRECATED)
 * @endcode
 *
 * @param string $release
 *   The release the calling function was depreciated in.
 * @param string $solution
 *   A message describing an alternative solution to the deprecated function.
 *   It's assumed to be already passed though the t() function.
 *
 * @return string
 *   The deprecated message.
 */
function islandora_deprecated($release, $solution = NULL) {
  $bt = debug_backtrace();
  assert($bt[0]['function'] == __FUNCTION__);
  $function = $bt[1]['function'];
  $message = t('@function() has been deprecated. As of @release, please update your code before the next release.', array(
    '@function' => $function,
    '@release' => $release,
  ));
  if (isset($solution)) {
    $message .= "<br/>\n" . $solution;
  }
  return $message;
}

/**
 * Transform recursively-merged array of strings to renderable arrays.
 *
 * Renderable arrays are passed-through as-is.
 *
 * Previously, functions/hooks like islandora_view_object would return an
 * associative array with string values containing markup. These values were
 * then imploded into one large piece of markup. Here, we transform this older
 * structure which was generated into a renderable array, because renderable
 * arrays are awesome!
 *
 * @param array $markup_array
 *   An associative array of which the values are either a string or an array
 *   of strings, which we transform to renderable markup elements (by
 *   reference).
 */
function islandora_as_renderable_array(array &$markup_array) {
  foreach ($markup_array as &$value) {
    if (!is_array($value)) {
      // Not a renderable array, just a string. Let's convert it to a
      // renderable '#markup' element.
      $value = array('#markup' => $value);
    }
    elseif (!isset($value['#type']) && !isset($value['#markup'])) {
      // A simple array--possibly the result of a recursive merge? Let's
      // look at each, to possibly convert them to a renderable '#markup'
      // elements.
      foreach ($value as &$inner) {
        if (!is_array($inner)) {
          // If it is an array at this level, we can assume that it is a
          // renderable array. If it is not an array, convert to a renderable
          // '#markup' element.
          $inner = array('#markup' => $inner);
        }
      }
      unset($inner);
    }
  }
  unset($value);
}

/**
 * Sanitizes an input string to be valid XML.
 *
 * @param string $input
 *   An input string.
 * @param string $replacement
 *   What we are replacing invalid characters with, defaults to ''.
 *
 * @return string
 *   The sanitized string.
 */
function islandora_sanitize_input_for_valid_xml($input, $replacement = '') {
  $input = preg_replace('/[^\x9\xA\xD\x20-\x{D7FF}\x{E000}-\x{FFFD}\x{10000}-\x{10FFFF}]/u', $replacement, $input);
  return $input;
}

/**
 * Page callback for session status messages to be sent to drupal_set_message().
 *
 * @return array
 *   Render array containing markup.
 */
function islandora_event_status() {
  $results = FALSE;
  if (isset($_SESSION['islandora_event_messages'])) {
    foreach ($_SESSION['islandora_event_messages'] as $message) {
      drupal_set_message($message['message'], $message['severity']);
      $results = TRUE;
    }
    unset($_SESSION['islandora_event_messages']);
  }
  $text = ($results) ? t('The status messages above will be deleted after viewing this page.') : t('No messages to display.');
  return array('#markup' => $text);
}

/**
 * Scales the given image.
 *
 * @param object $file
 *   The image file to scale.
 * @param int $width
 *   The width to scale the derived image to.
 * @param int $height
 *   The height to scale the derived image to.
 *
 * @return bool
 *   TRUE if successful, FALSE otherwise.
 */
function islandora_scale_thumbnail($file, $width, $height) {
  $real_path = drupal_realpath($file->uri);
  $image = image_load($real_path);
  try {
    if (!empty($image)) {
      $scale = image_scale($image, $width, $height, TRUE);
      if ($scale) {
        return image_save($image);
      }
    }
  }
  catch (exception $e) {
    drupal_set_message(t(
        "Islandora failed to scale image with message: '@message'",
        array("@message" => $e->getMessage())));
    watchdog(
      'islandora',
      'Islandora failed to scale image.<br/> With stack: @trace',
      array('@trace' => $e->getTraceAsString()),
      WATCHDOG_ERROR
    );
  }
  return FALSE;
}

/**
 * Determines if the server operating system is Windows.
 *
 * @return bool
 *   TRUE if Windows, FALSE otherwise.
 */
function islandora_deployed_on_windows() {
  // Determine if PHP is currently running on Windows.
  if (strpos(strtolower(php_uname('s')), 'windows') !== FALSE) {
    return TRUE;
  }
  return FALSE;
}

/**
 * Build the edit registry for a given datastream.
 *
 * @param AbstractDatastream $datastream
 *   The datastream being edited.
 *
 * @return array
 *   The built edit registry array.
 */
function islandora_build_datastream_edit_registry(AbstractDatastream $datastream) {
  $edit_registry = module_invoke_all(ISLANDORA_EDIT_DATASTREAM_REGISTRY_HOOK, $datastream->parent, $datastream);
  $context = array(
    'object' => $datastream->parent,
    'datastream' => $datastream,
    'original_edit_registry' => $edit_registry,
  );
  drupal_alter(ISLANDORA_EDIT_DATASTREAM_REGISTRY_HOOK, $edit_registry, $context);
  return $edit_registry;
}