ConfigTestForm.php

<?php

namespace Drupal\config_test;

use Drupal\Component\Render\FormattableMarkup;
use Drupal\Core\Entity\EntityForm;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Language\LanguageInterface;

/**
 * Form controller for the test config edit forms.
 *
 * @internal
 */
class ConfigTestForm extends EntityForm {

  /**
   * {@inheritdoc}
   */
  public function form(array $form, FormStateInterface $form_state) {
    $form = parent::form($form, $form_state);
    $entity = $this->entity;
    $form['label'] = [
      '#type' => 'textfield',
      '#title' => 'Label',
      '#default_value' => $entity
        ->label(),
      '#required' => TRUE,
    ];
    $form['id'] = [
      '#type' => 'machine_name',
      '#default_value' => $entity
        ->id(),
      '#required' => TRUE,
      '#machine_name' => [
        'exists' => [
          $this,
          'exists',
        ],
        'replace_pattern' => '[^a-z0-9_.]+',
      ],
    ];
    $form['weight'] = [
      '#type' => 'weight',
      '#title' => 'Weight',
      '#default_value' => $entity
        ->get('weight'),
    ];
    $form['style'] = [
      '#type' => 'select',
      '#title' => 'Image style',
      '#options' => [],
      '#default_value' => $entity
        ->get('style'),
      '#access' => FALSE,
    ];
    if ($this->moduleHandler
      ->moduleExists('image')) {
      $form['style']['#access'] = TRUE;
      $form['style']['#options'] = image_style_options();
    }

    // The main premise of entity forms is that we get to work with an entity
    // object at all times instead of checking submitted values from the form
    // state.
    $size = $entity
      ->get('size');
    $form['size_wrapper'] = [
      '#type' => 'container',
      '#attributes' => [
        'id' => 'size-wrapper',
      ],
    ];
    $form['size_wrapper']['size'] = [
      '#type' => 'select',
      '#title' => 'Size',
      '#options' => [
        'custom' => 'Custom',
      ],
      '#empty_option' => '- None -',
      '#default_value' => $size,
      '#ajax' => [
        'callback' => '::updateSize',
        'wrapper' => 'size-wrapper',
      ],
    ];
    $form['size_wrapper']['size_submit'] = [
      '#type' => 'submit',
      '#value' => t('Change size'),
      '#attributes' => [
        'class' => [
          'js-hide',
        ],
      ],
      '#submit' => [
        [
          static::class,
          'changeSize',
        ],
      ],
    ];
    $form['size_wrapper']['size_value'] = [
      '#type' => 'select',
      '#title' => 'Custom size value',
      '#options' => [
        'small' => 'Small',
        'medium' => 'Medium',
        'large' => 'Large',
      ],
      '#default_value' => $entity
        ->get('size_value'),
      '#access' => !empty($size),
    ];
    $form['langcode'] = [
      '#type' => 'language_select',
      '#title' => t('Language'),
      '#languages' => LanguageInterface::STATE_ALL,
      '#default_value' => $entity
        ->language()
        ->getId(),
    ];
    $form['actions'] = [
      '#type' => 'actions',
    ];
    $form['actions']['submit'] = [
      '#type' => 'submit',
      '#value' => 'Save',
    ];
    $form['actions']['delete'] = [
      '#type' => 'submit',
      '#value' => 'Delete',
    ];
    return $form;
  }

  /**
   * Ajax callback for the size selection element.
   */
  public static function updateSize(array $form, FormStateInterface $form_state) {
    return $form['size_wrapper'];
  }

  /**
   * Element submit handler for non-JS testing.
   */
  public static function changeSize(array $form, FormStateInterface $form_state) {
    $form_state
      ->setRebuild();
  }

  /**
   * {@inheritdoc}
   */
  public function save(array $form, FormStateInterface $form_state) {
    $entity = $this->entity;
    $status = $entity
      ->save();
    if ($status === SAVED_UPDATED) {
      $this
        ->messenger()
        ->addStatus(new FormattableMarkup('%label configuration has been updated.', [
        '%label' => $entity
          ->label(),
      ]));
    }
    else {
      $this
        ->messenger()
        ->addStatus(new FormattableMarkup('%label configuration has been created.', [
        '%label' => $entity
          ->label(),
      ]));
    }
    $form_state
      ->setRedirectUrl($this->entity
      ->toUrl('collection'));
    return $status;
  }

  /**
   * Determines if the entity already exists.
   *
   * @param string|int $entity_id
   *   The entity ID.
   * @param array $element
   *   The form element.
   * @param \Drupal\Core\Form\FormStateInterface $form_state
   *   The current state of the form.
   *
   * @return bool
   *   TRUE if the entity exists, FALSE otherwise.
   */
  public function exists($entity_id, array $element, FormStateInterface $form_state) {

    /** @var \Drupal\Core\Config\Entity\ConfigEntityInterface $entity */
    $entity = $form_state
      ->getFormObject()
      ->getEntity();

    /** @var \Drupal\Core\Config\Entity\ConfigEntityStorageInterface $storage */
    $storage = $this->entityTypeManager
      ->getStorage($entity
      ->getEntityTypeId());
    return (bool) $storage
      ->getQuery()
      ->condition($entity
      ->getEntityType()
      ->getKey('id'), $entity_id)
      ->execute();
  }

}