interface FormWizardInterface

interface FormWizardInterface extends FormInterface {
    
    /**
     * Constant value for wizard load event.
     */
    const LOAD_VALUES = 'wizard.load';
    
    /**
     * Return an array of parameters required to construct this wizard.
     *
     * @return array
     */
    public static function getParameters();
    
    /**
     * Initialize wizard values.
     *
     * Return mixed.
     */
    public function initValues();
    
    /**
     * The shared temp store factory collection name.
     *
     * @return string
     */
    public function getTempstoreId();
    
    /**
     * The active SharedTempStore for this wizard.
     *
     * @return \Drupal\Core\TempStore\SharedTempStore
     */
    public function getTempstore();
    
    /**
     * The SharedTempStore key for our current wizard values.
     *
     * @return null|string
     */
    public function getMachineName();
    
    /**
     * Retrieve the current active step of the wizard.
     *
     * This will return the first step of the wizard if no step has been set.
     *
     * @param mixed $cached_values
     *   The values returned by $this->getTempstore()->get($this->getMachineName());.
     *
     * @return string
     */
    public function getStep($cached_values);
    
    /**
     * Retrieve a list of FormInterface classes by their step key in the wizard.
     *
     * @param mixed $cached_values
     *   The values returned by $this->getTempstore()->get($this->getMachineName());   *.
     *
     * @return array
     *   An associative array keyed on the step name with an array value with the
     *   following keys:
     *   - title (string): Human-readable title of the step.
     *   - form (string): Fully-qualified class name of the form for this step.
     *   - values (array): Optional array of cached values to override when on
     *     this step.
     *   - validate (array): Optional array of callables to be called when this
     *     step is validated.
     *   - submit (array): Optional array of callables to be called when this
     *     step is submitted.
     */
    public function getOperations($cached_values);
    
    /**
     * Retrieve the current Operation.
     *
     * @param mixed $cached_values
     *   The values returned by $this->getTempstore()->get($this->getMachineName());.
     *
     * @return string
     *   The class name to instantiate.
     */
    public function getOperation($cached_values);
    
    /**
     * The name of the route to which forward or backwards steps redirect.
     *
     * @return string
     */
    public function getRouteName();
    
    /**
     * The Route parameters for a 'next' step.
     *
     * If your route requires more than machine_name and step keys, override and
     * extend this method as needed.
     *
     * @param mixed $cached_values
     *   The values returned by $this->getTempstore()->get($this->getMachineName());.
     *
     * @return array
     *   An array keyed by:
     *     machine_name
     *     step
     */
    public function getNextParameters($cached_values);
    
    /**
     * The Route parameters for a 'previous' step.
     *
     * If your route requires more than machine_name and step keys, override and
     * extend this method as needed.
     *
     * @param mixed $cached_values
     *   The values returned by $this->getTempstore()->get($this->getMachineName());.
     *
     * @return array
     *   An array keyed by:
     *     machine_name
     *     step
     */
    public function getPreviousParameters($cached_values);
    
    /**
     * Form validation handler that populates the cached values from tempstore.
     *
     * Temporary values are only available for a single page load so form
     * submission will lose all the values. This was we reload and provide them
     * to the validate and submit process.
     *
     * @param array $form
     *   Drupal form array.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The initial form state before validation or submission of the steps.
     */
    public function populateCachedValues(array &$form, FormStateInterface $form_state);
    
    /**
     * Form submit handler to step backwards in the wizard.
     *
     * "Next" steps are handled by \Drupal\Core\Form\FormInterface::submitForm().
     *
     * @param array $form
     *   Drupal form array.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The current form state of the wizard. This will not contain values from
     *   the current step since the previous button does not actually submit
     *   those values.
     */
    public function previous(array &$form, FormStateInterface $form_state);
    
    /**
     * Form submit handler for finalizing the wizard values.
     *
     * If you need to generate an entity or save config or raw table data
     * subsequent to your form wizard, this is the responsible method.
     *
     * @param array $form
     *   Drupal form array.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The final form state of the wizard.
     */
    public function finish(array &$form, FormStateInterface $form_state);
    
    /**
     *
     */
    public function ajaxSubmit(array $form, FormStateInterface $form_state);
    
    /**
     *
     */
    public function ajaxPrevious(array $form, FormStateInterface $form_state);
    
    /**
     *
     */
    public function ajaxFinish(array $form, FormStateInterface $form_state);

}