From 7de7a08ac199483674fe66fdcdc3f5dec0e104f8 Mon Sep 17 00:00:00 2001
From: Seth Shaw <seth.shaw@unlv.edu>
Date: Thu, 19 Nov 2020 23:20:15 -0800
Subject: [PATCH] node_referenced_by_field condition plugin

---
 .../Condition/NodeReferencedByField.php       | 150 ++++++++++++++++++
 1 file changed, 150 insertions(+)
 create mode 100644 src/Plugin/Condition/NodeReferencedByField.php

diff --git a/src/Plugin/Condition/NodeReferencedByField.php b/src/Plugin/Condition/NodeReferencedByField.php
new file mode 100644
index 00000000..15de47c6
--- /dev/null
+++ b/src/Plugin/Condition/NodeReferencedByField.php
@@ -0,0 +1,150 @@
+<?php
+
+namespace Drupal\islandora\Plugin\Condition;
+
+use Drupal\Core\Condition\ConditionPluginBase;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Drupal\field\Entity\FieldStorageConfig;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Condition to detect if is a node is referenced by a configured field.
+ *
+ * @Condition(
+ *   id = "node_referenced_by_field",
+ *   label = @Translation("Node referenced by field"),
+ *   context = {
+ *     "node" = @ContextDefinition("entity:node", required = TRUE , label = @Translation("node"))
+ *   }
+ * )
+ */
+class NodeReferencedByField extends ConditionPluginBase implements ContainerFactoryPluginInterface {
+
+  /**
+   * Node storage.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
+   */
+  protected $entityTypeManager;
+
+  /**
+   * Constructor.
+   *
+   * @param array $configuration
+   *   The plugin configuration, i.e. an array with configuration values keyed
+   *   by configuration option name. The special key 'context' may be used to
+   *   initialize the defined contexts by setting it to an array of context
+   *   values keyed by context names.
+   * @param string $plugin_id
+   *   The plugin_id for the plugin instance.
+   * @param mixed $plugin_definition
+   *   The plugin implementation definition.
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
+   *   Entity type manager.
+   */
+  public function __construct(
+    array $configuration,
+    $plugin_id,
+    $plugin_definition,
+    EntityTypeManagerInterface $entity_type_manager
+  ) {
+    parent::__construct($configuration, $plugin_id, $plugin_definition);
+    $this->entityTypeManager = $entity_type_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultConfiguration() {
+    return parent::defaultConfiguration() + [
+      'reference_field' => 'field_member_of',
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $configuration,
+      $plugin_id,
+      $plugin_definition,
+      $container->get('entity_type.manager')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
+    $field_map = \Drupal::service('entity_field.manager')->getFieldMapByFieldType('entity_reference');
+    $node_fields = array_keys($field_map['node']);
+    $options = array_combine($node_fields, $node_fields);
+    $form['reference_field'] = [
+      '#type' => 'select',
+      '#title' => t('Field to check for reference to this node'),
+      '#options' => $options,
+      '#default_value' => $this->configuration['reference_field'],
+      '#required' => TRUE,
+      '#description' => t("Machine name of field that should be checked for references to this node."),
+    ];
+
+    return parent::buildConfigurationForm($form, $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
+    $this->configuration['reference_field'] = $form_state->getValue('reference_field');
+    parent::submitConfigurationForm($form, $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function evaluate() {
+    $node = $this->getContextValue('node');
+    if (!$node) {
+      return FALSE;
+    }
+    return $this->evaluateEntity($node);
+  }
+
+  /**
+   * Evaluates if an entity is referenced in the configured node field.
+   *
+   * @param \Drupal\Core\Entity\EntityInterface $entity
+   *   The entity to evaluate.
+   *
+   * @return bool
+   *   TRUE if entity is referenced..
+   */
+  protected function evaluateEntity(EntityInterface $entity) {
+    $reference_field = $this->configuration['reference_field'];
+    $config = FieldStorageConfig::loadByName('node', $reference_field);
+    if ($config) {
+      $id_count = \Drupal::entityQuery('node')
+        ->condition($reference_field, $entity->id())
+        ->count()
+        ->execute();
+      return ($id_count > 0);
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function summary() {
+    if (!empty($this->configuration['negate'])) {
+      return $this->t('The node is not referenced in the field @field.', ['@field' => $this->configuration['reference_field']]);
+    }
+    else {
+      return $this->t('The node is referenced in the field @field.', ['@field' => $this->configuration['reference_field']]);
+    }
+  }
+
+}