class TestFormApiFormBlock

class TestFormApiFormBlock extends BlockBase implements ContainerFactoryPluginInterface, FormInterface {
    
    /**
     * The form builder service.
     *
     * @var \Drupal\Core\Form\FormBuilderInterface
     */
    protected $formBuilder;
    
    /**
     * TestFormApiFormBlock 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\Form\FormBuilderInterface $form_builder
     *   The form builder service.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, FormBuilderInterface $form_builder) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->formBuilder = $form_builder;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($configuration, $plugin_id, $plugin_definition, $container->get('form_builder'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function build() {
        return $this->formBuilder
            ->getForm($this);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'layout_builder_form_block_test_search_form';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        $form['keywords'] = [
            '#title' => $this->t('Keywords'),
            '#type' => 'textfield',
            '#attributes' => [
                'placeholder' => $this->t('Keywords'),
            ],
            '#required' => TRUE,
            '#title_display' => 'invisible',
            '#weight' => 1,
        ];
        $form['actions'] = [
            '#type' => 'actions',
            'submit' => [
                '#name' => '',
                '#type' => 'submit',
                '#value' => $this->t('Search'),
            ],
            '#weight' => 2,
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateForm(array &$form, FormStateInterface $form_state) {
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
    }

}