Get all the text fields type and alter value after save

Question

I'm trying to alter the value of entity text fields upon node save, even the custom-made fields

so far I've managed to do that with the title and default body field but not with a custom field, I'm trying to target any field that might be a text field, here's my code:

function MODULENAME_entity_presave(Drupal\Core\Entity\EntityInterface $entity) {
  $replacement_pattern = array("/a/", "/b/"); 
  $replacement = array("c", "d");

  /* Check whether it's a node */
  if ($entity instanceof \Drupal\node\NodeInterface) {
    // Node title
    $nodeTitle = $entity->getTitle();
    $entity->setTitle(preg_replace($replacement_pattern, $replacement , $nodeTitle));

    // Body main
    if(!empty($entity->body->value)) {
      $entity->body->value = preg_replace($replacement_pattern, $replacement , $entity->body->value);
    }

    // Body Summary
    if(!empty($entity->body->summary)) {
      $entity->body->summary = preg_replace($replacement_pattern, $replacement , $entity->body->summary);
    }
  }
}

Answer 1

Another approach by checking field name. I think this will get you the "custom" field part, but not the "all" fields part:

MYMODULE.module:

use Drupal\Core\Entity\EntityInterface;

function MYMODULE_node_presave(EntityInterface $entity) {
  if ($entity->hasField('field_name')) {
    $entity->get('field_name')->value = preg_replace(
      $toReplace,
      $newText,
      $entity->get('field_name')->value
    );
  }
}

But this only checks for fields of that name. I am also looking for a way to alter the value of a ckeditor/text field by testing field type instead of field name.

I would have hoped setting the field name value to something like text_long would have worked. This is a base field hook suggestion, but I am not having any luck at this time.

To add to the use case, it would be nice to alter ckeditor/text fields whether attached directly to the node, or via a Paragraph type.

The answer in the comment link above is helpful, but I have not succeeded in implementation.