class RestExampleClientSettings

class RestExampleClientSettings extends ConfigFormBase {
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'rest_example_client_settings';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        $form['intro'] = [
            '#markup' => t('Set here the remote server options.'),
        ];
        $form['server_url'] = [
            '#type' => 'textfield',
            '#title' => $this->t('Remote server URL'),
            '#description' => $this->t('Format like this: http://www.example.com or http://www.example.com/test-site (no trailing slash)'),
            '#default_value' => $this->config('rest_example.settings')
                ->get('server_url'),
            '#required' => TRUE,
        ];
        $form['server_username'] = [
            '#type' => 'textfield',
            '#title' => $this->t('Remote server username'),
            '#default_value' => $this->config('rest_example.settings')
                ->get('server_username'),
            '#description' => $this->t('A user on the remote system that has the proper rights to use the REST service'),
            '#required' => TRUE,
        ];
        $form['server_password'] = [
            '#type' => 'textfield',
            '#title' => $this->t('Remote server password'),
            '#default_value' => $this->config('rest_example.settings')
                ->get('server_password'),
            '#description' => $this->t('Remote users password'),
            '#required' => TRUE,
        ];
        return parent::buildForm($form, $form_state);
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        $form_values = $form_state->getValues();
        $this->config('rest_example.settings')
            ->set('server_url', $form_values['server_url'])
            ->set('server_username', $form_values['server_username'])
            ->set('server_password', $form_values['server_password'])
            ->save();
        parent::submitForm($form, $form_state);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getEditableConfigNames() {
        return [
            'rest_example.settings',
        ];
    }

}