Fixes #5446 Improve Description Metatag defaults.

composer.json

@@ -135,6 +135,7 @@
         "npm-asset/bootstrap-datepicker": "1.10.1",
         "npm-asset/easepick--bundle": "1.2.1",
         "npm-asset/slick-carousel": "1.6.0",
+        "php-science/textrank": "1.2.3",
         "renanbr/bibtex-parser": "2.2.0",
         "seboettg/citeproc-php": "2.7.1"
     },

modules/custom/az_core/az_core.module

@@ -18,6 +18,8 @@ use Drupal\node\NodeInterface;
 use Drupal\pathauto\PathautoPatternInterface;
 use Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException;
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+use PhpScience\TextRank\TextRankFacade;
+use PhpScience\TextRank\Tool\StopWords\English;
 
 /**
  * Implements hook_help().
@@ -207,6 +209,10 @@ function az_core_token_info() {
           'name' => t("AZ Canonical Summary Link Title"),
           'description' => t("Returns the link title value of field_az_link if present on the node or nothing if not."),
         ],
+        'az-automatic-summary' => [
+          'name' => t("AZ Automatic Summary"),
+          'description' => t("Returns the node summary field if not empty, or a generated summary."),
+        ],
       ],
     ],
   ];
@@ -232,13 +238,60 @@ function az_core_tokens($type, $tokens, array $data, array $options, BubbleableM
         case 'az-canonical-summary-link-title':
           $replacements[$original] = az_core_canonical_summary_link_title($data);
           break;
+
+        case 'az-automatic-summary':
+          $replacements[$original] = az_core_automatic_summary($data);
+          break;
       }
     }
   }
 
   return $replacements;
 }
 
+/**
+ * Token replacement callback for automatic summary.
+ *
+ * Computes an automatic summary via TextRank.
+ *
+ * @param array $data
+ *   Node data from hook_tokens().
+ *
+ * @return string
+ *   The node's generated summary.
+ */
+function az_core_automatic_summary(array $data) {
+  $summary = '';
+  /** @var \Drupal\node\NodeInterface $node */
+  $node = $data['node'] ?? NULL;
+
+  if ($node) {
+    // @todo check for actual summary fields and use those in preference to automatic summary.
+    // Build and render the node.
+    $builder = \Drupal::entityTypeManager()->getViewBuilder('node');
+    $build = $builder->view($node, 'full');
+    $output = \Drupal::service('renderer')->renderRoot($build);
+    $text = strip_tags($output->__toString());
+    $text = html_entity_decode($text);
+    // @todo make end of tag text considered to be the end of a sentence.
+    // Fetch programmatic summary.
+    $rank = new TextRankFacade();
+    // @todo langcode handling
+    $stops = new English();
+    $rank->setStopWords($stops);
+    $result = $rank->summarizeTextBasic($text);
+
+    // Get most important sentence.
+    // @todo refuse to consider a sentence with low score. (e.g. no clear summary)
+    $best = array_shift($result);
+    if (!empty($best)) {
+      $summary = $best;
+    }
+  }
+
+  return $summary;
+}
+
 /**
  * Token replacement callback providing the canonical link title.
  *

modules/custom/az_seo/config/quickstart/metatag.metatag_defaults.node.yml

@@ -5,8 +5,8 @@ id: node
 label: Content
 tags:
   canonical_url: '[node:field_az_link:uri]'
-  description: '[node:field_az_summary]'
-  og_description: '[node:field_az_summary]'
+  description: '[node:az-automatic-summary]'
+  og_description: '[node:az-automatic-summary]'
   og_image: '[node:field_az_media_image:entity:field_media_az_image]'
   og_title: '[node:title]'
   og_url: '[node:az-canonical-absolute-url]'