jsonld.module

<?php

/**
 * Generates a valid JSON-LD object from metadata from the current page
 *
 * @param $object Islandora Object
 *
 * @return array|bool|false|string
 */
function jsonld_create_script_tag($object) {
  if (!isset($object['MODS']) || !islandora_datastream_access(ISLANDORA_VIEW_OBJECTS, $object['MODS'])) {
    return FALSE;
  }

  /**
   *
   * Start mapping fields, ultimately we want something along the lines of
   * {
   * "@context": "http://schema.org",
   * "@type": "schema:Thesis",
   * "schema:identifier": {
   * "@type": "PropertyValue",
   * "propertyID": "DOI",
   * "value": "https://doi.org/10.6092/unibo/amsdottorato/2545"
   * },
   * "url": "http://example-repository.edu",
   * "schema:name": "Example Thesis Title",
   * "schema:inLanguage": "eng",
   * "schema:inSupportOf": "Doctor of Philosophy, Information and Computer Sciences",
   * "schema:author": {
   * "@type": "schema:Person",
   * "name": "Last, First",
   * "givenName": "First",
   * "familyName": "Last",
   * "@id": "https://orcid.org/0000-0001-7224-6462"
   * },
   * "schema:sourceOrganization": {
   * "@type": "schema:CollegeOrUniversity",
   * "schema:name": "College Name"
   * },
   * "schema:datePublished": "1991",
   * "schema:description": "Article abstract"
   * }
   */
  // Automatic creation using third party libraries such as easyRDF (included in D8 is not possible as RDF support is not available until CLAW(
  $cModel = $object->models[0];
  $jModel = getSchemaFromCModel($cModel);
  $jsonLd = [];
  if ($jModel) {
    $jsonLd['@context'] = 'http://schema.org';
    $jsonLd['@type'] = $jModel;

    // Generate image if this one object has any
    if (isset($object['TN'])) {
      $resource_url = url("islandora/object/{$object->id}/datastream/TN/view", ['absolute' => TRUE]);
      $jsonLd['image'] = $resource_url;
    }

    $mods = NULL;
    if ($object['MODS'] instanceof DOMNode) {
      $mods = simplexml_import_dom($object['MODS']);
    }
    else {
      try {
        //Load MODS data stream into  a simpleXML object for easy traversal
        $mods = simplexml_load_string($object['MODS']->content);
        // Generate Identifiers
        $jsonLd['@id'] = url("islandora/object/{$object->id}", ['absolute' => TRUE]);
        $jsond_xp_indentifiers = variable_get('islandora_scholar_xpaths_identifiers', '//mods:mods[1]/mods:identifier[@type]');
        $jsond_xp_indentifiers = $mods->xpath($jsond_xp_indentifiers);
        $jsonLd_xp_abstract = variable_get('islandora_scholar_xpaths_abstract', '//mods:mods[1]/mods:abstract');
        $jsonLd_xp_abstract = $mods->xpath($jsonLd_xp_abstract);
        $jsonLd['description'] = (!empty($jsonLd_xp_abstract)) ? (string) end($jsonLd_xp_abstract) : '';
        // Set identifier values
        foreach ($jsond_xp_indentifiers as $jsond_indentifier) {
          $attribute_name = $jsond_indentifier->attributes();
          $jsonLd['identifier'][] = [
            '@type' => 'PropertyValue',
            'propertyID' => strval($attribute_name['type']),
            'value' => strval($jsond_indentifier),
          ];
        }
        $jsonLd['url'] = $GLOBALS['base_root'] . request_uri();

        // Get topics
        $jsonLd_xp_topics = variable_get('islandora_scholar_xpaths_topics', '//mods:subject');
        $jsonLd_xp_topics = $mods->xpath($jsonLd_xp_topics);
        foreach ($jsonLd_xp_topics as $topic) {
          if (isset($topic->topic) && !empty(strval($topic->topic))) {
            $jsonLd['keywords'][] = strval($topic->topic);
          }
        }
        // Keywords or tags used to describe this content. Multiple entries in a keywords list are typically delimited by commas.
        if (!empty($jsonLd['keywords'])) {
          $jsonLd['keywords'] = implode(",", $jsonLd['keywords']);
        }

        // Set language
        // TODO get this from the object or a configration when available
        $jsonLd['inLanguage'] = "eng";
        // Set authors for this particular piece of work
        $jsonLd['sourceOrganization'] = [
          '@type' => 'CollegeOrUniversity',
          'name' => variable_get('site_name'),
        ];
        // Get title and subtitle
        $title_results = $mods->xpath(variable_get('islandora_scholar_xpaths_title', '//mods:mods[1]/mods:titleInfo/mods:title'));
        $title = (string) reset($title_results);
        $subtitle_results = $mods->xpath(variable_get('islandora_scholar_xpaths_title_sub_title', '//mods:mods[1]/mods:titleInfo/mods:subTitle'));
        $subtitle = (string) reset($subtitle_results);

        if (!empty($title)) {
          if (!empty($subtitle)) {
            $jsonLd['name'] = "{$title}: {$subtitle}";
          }
          else {
            $jsonLd['name'] = $title;
          }
          // Set headline
          $jsonLd['headline'] = $jsonLd['name'];
        }

        /**
         * Date in which this particular publication was published
         *
         * @see islandora_google_scholar:islandora_google_scholar_create_meta_tags
         **/
        $tags = islandora_google_scholar_create_meta_tags($object);
        if ($tags) {
          $jsonLd['datePublished'] = $tags['citation_publication_date'];

          foreach ($tags['citation_author'] as $author) {
            $author_parts = explode(', ', $author);
            $jsonLd['author'][] = [
              'name' => $author,
              'givenName' => (isset($author_parts[1]) ? $author_parts[1] : ''),
              'familyName' => (isset($author_parts[0]) ? $author_parts[0] : ''),
              '@type' => 'Person',
            ];
          }
        }

        return json_encode($jsonLd, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE | JSON_NUMERIC_CHECK);
      } catch (Exception $e) {
        watchdog('jsond', 'Got exception while parsing.  Message: !msg Errors: !error', [
          '!msg' => $e->getMessage(),
          '!error' => libxml_get_errors(),
        ]);
        return [];
      }
    }
  }
  return FALSE;
}

/**
 * Maps Islandora entities/models
 *
 * @param $model
 *
 * @return bool|mixed
 */
function getSchemaFromCModel($model) {
  $mapping = [
    'ir:thesisCModel' => 'Thesis',
    'ir:citationCModel' => 'ScholarlyArticle',
    'islandora:sp_basic_image' => 'ImageObject',
    'islandora:sp_large_image_cmodel' => 'ImageObject',
    'islandora:sp_pdf' => 'DigitalDocument',
    'islandora:sp-audioCModel' => 'AudioObject',
    'islandora:sp_videoCModel' => 'VideoObject',
    'islandora:bookCModel' => 'Book',
    'islandora:newspaperCModel' => 'Newspaper',
    'islandora:eventCModel' => 'Event',
    'islandora:placeCModel' => 'Place',
    'islandora:personCModel' => 'Person',
    'islandora:organizationCModel' => 'CollegeorUniversity',
    'islandora:sp_disk_image' => 'Dataset',
    'islandora:sp_web_archive' => 'WebPage',
  ];

  if (isset($mapping[$model])) {
    return $mapping[$model];
  }
  else {
    return FALSE;
  }
}

/**
 * Add JSON-LD scripts to pages
 *
 * @param $_script
 */
function jsonld_embed_scripts($_script) {
  // Get islandora mappings
  module_load_include('inc', 'islandora', 'includes/mimetype.utils');
  $mimetype = islandora_mime_mapping();
  // Generate script to hold the JSON data
  $script = [
    '#tag' => 'script',
    '#attributes' => [
      'type' => $mimetype['jsonld'],
    ],
    '#value' => $_script,
  ];
  drupal_add_html_head($script, 'script');
}

/**
 * Implements hook_CMODEL_islandora_view_object().
 */
function jsonld_islandora_view_object($object) {
  $tags = jsonld_create_script_tag($object);
  // Only display JSON-D metadata if the user has a valid data stream and the user has the right permissions
  if ($tags) {
    jsonld_embed_scripts($tags);
  }
}