class RobotFormBase

class RobotFormBase extends EntityForm {
    
    /**
     * An entity query factory for the robot entity type.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $entityStorage;
    
    /**
     * Construct the RobotFormBase.
     *
     * For simple entity forms, there's no need for a constructor. Our robot form
     * base, however, requires an entity query factory to be injected into it
     * from the container. We later use this query factory to build an entity
     * query for the exists() method.
     *
     * @param \Drupal\Core\Entity\EntityStorageInterface $entity_storage
     *   An entity query factory for the robot entity type.
     */
    public function __construct(EntityStorageInterface $entity_storage) {
        $this->entityStorage = $entity_storage;
    }
    
    /**
     * Factory method for RobotFormBase.
     *
     * When Drupal builds this class it does not call the constructor directly.
     * Instead, it relies on this method to build the new object. Why? The class
     * constructor may take multiple arguments that are unknown to Drupal. The
     * create() method always takes one parameter -- the container. The purpose
     * of the create() method is twofold: It provides a standard way for Drupal
     * to construct the object, meanwhile it provides you a place to get needed
     * constructor parameters from the container.
     *
     * In this case, we ask the container for an entity query factory. We then
     * pass the factory to our class as a constructor parameter.
     */
    public static function create(ContainerInterface $container) {
        $form = new static($container->get('entity_type.manager')
            ->getStorage('robot'));
        $form->setMessenger($container->get('messenger'));
        return $form;
    }
    
    /**
     * Overrides Drupal\Core\Entity\EntityFormController::form().
     *
     * Builds the entity add/edit form.
     *
     * @param array $form
     *   An associative array containing the structure of the form.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   An associative array containing the current state of the form.
     *
     * @return array
     *   An associative array containing the robot add/edit form.
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        // Get anything we need from the base class.
        $form = parent::buildForm($form, $form_state);
        // Drupal provides the entity to us as a class variable. If this is an
        // existing entity, it will be populated with existing values as class
        // variables. If this is a new entity, it will be a new object with the
        // class of our entity. Drupal knows which class to call from the
        // annotation on our Robot class.
        $robot = $this->entity;
        // Build the form.
        $form['label'] = [
            '#type' => 'textfield',
            '#title' => $this->t('Label'),
            '#maxlength' => 255,
            '#default_value' => $robot->label(),
            '#required' => TRUE,
        ];
        $form['id'] = [
            '#type' => 'machine_name',
            '#title' => $this->t('Machine name'),
            '#default_value' => $robot->id(),
            '#machine_name' => [
                'exists' => [
                    $this,
                    'exists',
                ],
                'replace_pattern' => '([^a-z0-9_]+)|(^custom$)',
                'error' => 'The machine-readable name must be unique, and can only contain lowercase letters, numbers, and underscores. Additionally, it can not be the reserved word "custom".',
            ],
            '#disabled' => !$robot->isNew(),
        ];
        $form['floopy'] = [
            '#type' => 'checkbox',
            '#title' => $this->t('Floopy'),
            '#default_value' => $robot->floopy,
        ];
        // Return the form.
        return $form;
    }
    
    /**
     * Checks for an existing robot.
     *
     * @param string|int $entity_id
     *   The entity ID.
     * @param array $element
     *   The form element.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The form state.
     *
     * @return bool
     *   TRUE if this format already exists, FALSE otherwise.
     */
    public function exists($entity_id, array $element, FormStateInterface $form_state) {
        // Use the query factory to build a new robot entity query.
        $query = $this->entityStorage
            ->getQuery();
        // Query the entity ID to see if its in use.
        $result = $query->condition('id', $element['#field_prefix'] . $entity_id)
            ->accessCheck()
            ->execute();
        // We don't need to return the ID, only if it exists or not.
        return (bool) $result;
    }
    
    /**
     * Overrides Drupal\Core\Entity\EntityFormController::actions().
     *
     * To set the submit button text, we need to override actions().
     *
     * @param array $form
     *   An associative array containing the structure of the form.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   An associative array containing the current state of the form.
     *
     * @return array
     *   An array of supported actions for the current entity form.
     */
    protected function actions(array $form, FormStateInterface $form_state) {
        // Get the basic actins from the base class.
        $actions = parent::actions($form, $form_state);
        // Change the submit button text.
        $actions['submit']['#value'] = $this->t('Save');
        // Return the result.
        return $actions;
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateForm(array &$form, FormStateInterface $form_state) {
        parent::validateForm($form, $form_state);
        // Add code here to validate your config entity's form elements.
        // Nothing to do here.
    }
    
    /**
     * Overrides Drupal\Core\Entity\EntityFormController::save().
     *
     * Saves the entity. This is called after submit() has built the entity from
     * the form values. Do not override submit() as save() is the preferred
     * method for entity form controllers.
     *
     * @param array $form
     *   An associative array containing the structure of the form.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   An associative array containing the current state of the form.
     */
    public function save(array $form, FormStateInterface $form_state) {
        // EntityForm provides us with the entity we're working on.
        $robot = $this->getEntity();
        // Drupal already populated the form values in the entity object. Each
        // form field was saved as a public variable in the entity class. PHP
        // allows Drupal to do this even if the method is not defined ahead of
        // time.
        $status = $robot->save();
        // Grab the URL of the new entity. We'll use it in the message.
        $url = $robot->toUrl();
        // Create an edit link.
        $edit_link = Link::fromTextAndUrl($this->t('Edit'), $url)
            ->toString();
        if ($status == SAVED_UPDATED) {
            // If we edited an existing entity...
            $this->messenger()
                ->addMessage($this->t('Robot %label has been updated.', [
                '%label' => $robot->label(),
            ]));
            $this->logger('contact')
                ->notice('Robot %label has been updated.', [
                '%label' => $robot->label(),
                'link' => $edit_link,
            ]);
        }
        else {
            // If we created a new entity...
            $this->messenger()
                ->addMessage($this->t('Robot %label has been added.', [
                '%label' => $robot->label(),
            ]));
            $this->logger('contact')
                ->notice('Robot %label has been added.', [
                '%label' => $robot->label(),
                'link' => $edit_link,
            ]);
        }
        // Redirect the user back to the listing route after the save operation.
        $form_state->setRedirect('entity.robot.list');
    }

}