trait FileTestFormTrait

trait FileTestFormTrait {
    
    /**
     * Adds common form elements to the form.
     *
     * @param array $form
     *   An associative array containing the structure of the form.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The current state of the form.
     *
     * @return array
     *   The form structure.
     */
    public function baseForm(array $form, FormStateInterface $form_state) : array {
        $form['file_test_replace'] = [
            '#type' => 'select',
            '#title' => t('Replace existing image'),
            '#options' => [
                FileExists::Rename->name => new TranslatableMarkup('Appends number until name is unique'),
                FileExists::Replace->name => new TranslatableMarkup('Replace the existing file'),
                FileExists::Error->name => new TranslatableMarkup('Fail with an error'),
            ],
            '#default_value' => FileExists::Rename->name,
        ];
        $form['file_subdir'] = [
            '#type' => 'textfield',
            '#title' => t('Subdirectory for test file'),
            '#default_value' => '',
        ];
        $form['extensions'] = [
            '#type' => 'textfield',
            '#title' => t('Allowed extensions.'),
            '#default_value' => '',
        ];
        $form['allow_all_extensions'] = [
            '#title' => t('Allow all extensions?'),
            '#type' => 'radios',
            '#options' => [
                'false' => 'No',
                'empty_array' => 'Empty array',
                'empty_string' => 'Empty string',
            ],
            '#default_value' => 'false',
        ];
        $form['is_image_file'] = [
            '#type' => 'checkbox',
            '#title' => t('Is this an image file?'),
            '#default_value' => TRUE,
        ];
        $form['submit'] = [
            '#type' => 'submit',
            '#value' => t('Submit'),
        ];
        return $form;
    }

}