class BanAdmin

class BanAdmin extends FormBase {
    
    /**
     * @var \Drupal\ban\BanIpManagerInterface
     */
    protected $ipManager;
    
    /**
     * Constructs a new BanAdmin object.
     *
     * @param \Drupal\ban\BanIpManagerInterface $ip_manager
     *   The ban IP manager.
     */
    public function __construct(BanIpManagerInterface $ip_manager) {
        $this->ipManager = $ip_manager;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('ban.ip_manager'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'ban_ip_form';
    }
    
    /**
     * {@inheritdoc}
     *
     * @param array $form
     *   A nested array form elements comprising the form.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The current state of the form.
     * @param string $default_ip
     *   (optional) IP address to be passed on to
     *   \Drupal::formBuilder()->getForm() for use as the default value of the IP
     *   address form field.
     */
    public function buildForm(array $form, FormStateInterface $form_state, $default_ip = '') {
        $rows = [];
        $header = [
            $this->t('banned IP addresses'),
            $this->t('Operations'),
        ];
        $result = $this->ipManager
            ->findAll();
        foreach ($result as $ip) {
            $row = [];
            $row[] = $ip->ip;
            $links = [];
            $links['delete'] = [
                'title' => $this->t('Delete'),
                'url' => Url::fromRoute('ban.delete', [
                    'ban_id' => $ip->iid,
                ]),
            ];
            $row[] = [
                'data' => [
                    '#type' => 'operations',
                    '#links' => $links,
                ],
            ];
            $rows[] = $row;
        }
        $form['ip'] = [
            '#title' => $this->t('IP address'),
            '#type' => 'textfield',
            '#size' => 48,
            '#maxlength' => 40,
            '#default_value' => $default_ip,
            '#description' => $this->t('Enter a valid IP address.'),
        ];
        $form['actions'] = [
            '#type' => 'actions',
        ];
        $form['actions']['submit'] = [
            '#type' => 'submit',
            '#value' => $this->t('Add'),
        ];
        $form['ban_ip_banning_table'] = [
            '#type' => 'table',
            '#header' => $header,
            '#rows' => $rows,
            '#empty' => $this->t('No blocked IP addresses available.'),
            '#weight' => 120,
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateForm(array &$form, FormStateInterface $form_state) {
        $ip = trim($form_state->getValue('ip'));
        if ($this->ipManager
            ->isBanned($ip)) {
            $form_state->setErrorByName('ip', $this->t('This IP address is already banned.'));
        }
        elseif ($ip == $this->getRequest()
            ->getClientIP()) {
            $form_state->setErrorByName('ip', $this->t('You may not ban your own IP address.'));
        }
        elseif (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_RES_RANGE) == FALSE) {
            $form_state->setErrorByName('ip', $this->t('Enter a valid IP address.'));
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        $ip = trim($form_state->getValue('ip'));
        $this->ipManager
            ->banIp($ip);
        $this->messenger()
            ->addStatus($this->t('The IP address %ip has been banned.', [
            '%ip' => $ip,
        ]));
        $form_state->setRedirect('ban.admin_page');
    }

}