Draft: Series per Entity per Entity Reference

Issue #1478012

modules/serialper/src/Plugin/Field/FieldType/SerialPerEntityReferenceItem.php

+<?php
+
+namespace Drupal\serialper\Plugin\Field\FieldType;
+
+use Drupal\serial\Plugin\Field\FieldType\SerialItem;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\TypedData\DataDefinition;
+use Drupal\Core\TypedData\TranslatableInterface;
+
+/**
+ * Plugin implementation of the 'serialper' field type.
+ *
+ * @todo should not be translatable, by default
+ *
+ * @FieldType(
+ *   id = "serialper",
+ *   label = @Translation("Serial per Entity Reference"),
+ *   description = @Translation("Auto increment per referenced entity serial field type."),
+ *   category = "number",
+ *   default_widget = "serial_default_widget",
+ *   default_formatter = "serial_default_formatter"
+ * )
+ */
+class SerialPerEntityReferenceItem extends SerialItem {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function defaultStorageSettings() {
+    return [
+      'reference_field' => '',
+    ] + parent::defaultStorageSettings();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function storageSettingsForm(array &$form, FormStateInterface $form_state, $has_data) {
+    $element = [];
+
+    $options = [];
+    $fields = $this->getEntity()->getFields() ?? [];
+    foreach ($fields as $field_name => $field_info) {
+      /** @var Drupal\Core\Field\EntityReferenceFieldItemList $field_info */
+      // Cannot use ->get('field_type') as it only works on non-base fields.
+      $field_definition = $field_info->getDataDefinition();
+      $field_type = $field_definition->getType() ?? '';
+      if ($field_type === 'entity_reference') {
+        if (method_exists($field_definition, 'label')) {
+          // If there was no label, it's probably a whack entity reference field
+          // that we cannot use anyway, i don't understand why content type,
+          // revision_uid, uid, and menu_link base fields claim the entity
+          // reference mantel and then drop the ball on something so basic.
+          $options[$field_name] = $field_definition->label();
+        }
+      }
+    }
+
+    $element['reference_field'] = [
+      '#type' => 'select',
+      '#title' => $this->t('Reference field'),
+      '#description' => $this->t('The field that contains the entity reference which will determine when this field starts a new series.'),
+      '#default_value' => $this->getSetting('reference_field'),
+      '#options' => $options,
+      '#required' => TRUE,
+      '#disabled' => $has_data,
+    ];
+
+    return $element + parent::storageSettingsForm($form, $form_state, $has_data);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function preSave() {
+    /** @var \Drupal\serial\SerialStorageInterface $serialStorage */
+    $serialStorage = \Drupal::getContainer()->get('serial.sql_storage');
+    $storageName = $serialStorage->createStorageNameFromField($this->getFieldDefinition(), $this->getEntity());
+    // Create table if it does not exist already.
+    if (!\Drupal::database()->schema()->tableExists($storageName)) {
+      $serialStorage->createStorageFromName($storageName);
+    }
+    parent::preSave();
+  }
+
+}