/* A sample from main front-end factory in jQuery-in-drupal  */
var factory = {

  getViewArgument: function (data) {
    var currentView;
    if (drupalSettings.views && drupalSettings.views.ajaxViews) {
      $.each(drupalSettings.views.ajaxViews, function (view_id, params) {
        if (data.view_id === params.view_name && data.display_id ===
          params.view_display_id) {
          currentView = params;
        }
      });
    }
    return currentView;
  },

  setViewArgument: function (value, data) {
    if (drupalSettings.views && drupalSettings.views.ajaxViews) {
      $.each(drupalSettings.views.ajaxViews, function (view_id, params) {
        if (data.view_id === params.view_name && data.display_id ===
          params.view_display_id) {
          drupalSettings.views.ajaxViews[view_id].view_args = value;
        }
      });
    }
  },

  processQuery: function (path) {
    var queryString = window.location.search || '';
    if (queryString !== '') {
      queryString = queryString.slice(1).replace(/q=[^&]+&?|&?render=[^&]+/,
        '');
      if (queryString !== '') {
        queryString = (/\?/.test(path) ? '&' : '?') + queryString;
      }
    }
    return queryString;
  },

  isJson: function (input) {
    input = typeof input !== 'string' ? JSON.stringify(input) : input;

    try {
      input = JSON.parse(input);
    } catch (e) {
      console.log(e);
      return false;
    }

    if (typeof input === 'object' && input !== null) {
      return true;
    }
    return false;
  },

  getViewContentHighlight: function (params, highlightClass, hasArgument,
    hasQueryParam) {
    if (params.view && params.view.view_dom_id) {
      var view = $('.js-view-dom-id-' + params.view.view_dom_id);
      view.find('.text-highlight').each(function () {
        var highlightElement = $(this);
        var highlightText = $(this).text() ? $(this).text().toUpperCase() :
          null;
        var argumentValues;
        if (hasArgument) {
          argumentValues = hasArgument.indexOf(' ') > 0 ? hasArgument.toUpperCase()
            .split(' ') : [hasArgument.toUpperCase()];
        } else {
          if (hasQueryParam) {
            argumentValues = hasQueryParam.indexOf(' ') > 0 ?
              hasQueryParam.toUpperCase().split(' ') : [hasQueryParam.toUpperCase()];
          } else {
            argumentValues = ['all'];
          }
        }
        if (highlightElement.length && argumentValues) {
          $.each(argumentValues, function (i, argumentValue) {
            if (highlightText.indexOf(argumentValue) > -1) {
              highlightElement.addClass(highlightClass);
            }
          });
        }
      });
    }
  },

  processViewSubtitle: function (element, parentWrapper, widgetType = 'text',
    existing = {}, titleId = null) {
    if (!titleId) {
      titleId = element.data('title') ? 'diplo-ajax-filter-' + element.data(
        'title').toLowerCase().replace(' ', '_') : null;
    }

    if (titleId) {

      var titleValue;

      if (widgetType === 'select') {
        var option = element.val() ? element.find('option[value="' +
          element.val() + '"]') : null;
        if (option && option.length) {
          titleValue = option.text();
        }
      } else {
        titleValue = element.val();
      }

      if (titleValue && titleValue.length > 41) {
        titleValue = titleValue.replace(/^(.{41}[^\s]*).*/, "$1") + '...';
      }

      if (existing.length) {
        var currentValue = existing.find('.views-subtitle').text();
        if (currentValue !== element.val()) {
          existing.find('.views-subtitle').text(element.val());
        }
      } else {
        var titleHtml;
        if (element.hasClass('diplo-search-input')) {
          titleHtml = '<div id="' + titleId +
            '" class="animate bounceIn col-xs-12 pl-0 pr-0 mb-16">';
          titleHtml += '<div class="pl-0 col-xs-11">';
          titleHtml +=
            '<span class="views-subtitle pl-8 pr-8 bg-highlight-orange text-white border">' +
            titleValue;
          titleHtml += '</span></div></div>';
        } else {
          titleHtml = '<div id="' + titleId +
            '" class="animate bounceIn col-xs-12 pl-0 pr-0 mb-16">';
          titleHtml += '<div class="pl-0 col-xs-11">' + element.data(
            'title');
          titleHtml +=
            ': <span class="views-subtitle pl-8 pr-8 bg-highlight-blue border">' +
            titleValue + '</span></div></div>';
        }
        parentWrapper.append(titleHtml);
      }
    }
  }
};

// Highlight for filters and on search page
Drupal.AjaxCommands.prototype.diploHighlight = function (ajax, response) {
  var params = {
    view: {
      view_dom_id: response.view_dom_id,
    }
  };
  factory.getViewContentHighlight(params, 'orange', response.view_arg[0]);
};

// Append Views filters values to view/listing title
Drupal.AjaxCommands.prototype.diploSubtitles = function (ajax, response) {
  factory.processViewSubtitle($(this), $(response.append_block), 'search',
    response.existing, 'search-term-title-append');
};

<?php

namespace Drupal\diplo_formatters\EventSubscriber;
use Drupal\Core\Ajax\AjaxResponse;
use Drupal\views\Ajax\ViewAjaxResponse;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
use Symfony\Component\HttpKernel\KernelEvents;

/**
 * Custom EventSubscriber in Drupal/PHP.
 */
class AjaxResponseSubscriber implements EventSubscriberInterface {
  /**
   * Renders the ajax commands right before preparing the result.
   *
   * @param \Symfony\Component\HttpKernel\Event\FilterResponseEvent $event
   *   The response event, which contains the possible AjaxResponse object.
   */
  public function onResponse(FilterResponseEvent $event): void {

    $response = $event->getResponse();

    // Only alter views ajax responses.
    if ($response instanceof ViewAjaxResponse) {
      $commands = &$response->getCommands();
      $view = $response->getView();
      $filters = [];
      if (!empty($view->getExposedInput())) {
        $skip = ['content_identifier', 'single_filter'];
        foreach ($view->getExposedInput() as $key => $value) {
          if (!in_array($key, $skip) && !empty($value) && $value != 'All') {
            $filters[$key] = $value;
          }
        }
      }
      if ($view->display_handler->hasPath()) {
        $commands[] = [
          'command' => 'diploAjaxPager',
          'selector' => '.js-view-dom-id-' . $view->dom_id,
          'view_dom_id' => $view->dom_id,
          'view_arg' => $view->args,
          'view_filters' => $filters,
          'view_pager' => $view->pager->current_page,
          'view_path' => '/' . $view->display_handler->getPath(),
        ];
      }
      $commands[] = [
        'command' => 'diploHighlight',
        'selector' => '.js-view-dom-id-' . $view->dom_id,
        'view_dom_id' =>  $view->dom_id,
        'view_arg' => $view->args
      ];
    }
    else if ($response instanceof AjaxResponse) {
      $commands = &$response->getCommands();
      $commands[] = [
        'command' => 'diploAjax',
      ];
    }
  }

  /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents(): array {
    return [KernelEvents::RESPONSE => [['onResponse']]];
  }

}

namespace Drupal\diplo_mailchimp\Form;

use Drupal\Core\Form\FormBase;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Ajax\AjaxResponse;
use Drupal\Core\Ajax\InvokeCommand;

use Drupal\filter\Render\FilteredMarkup;
use Drupal\Component\Utility\NestedArray;
use Drupal\Component\Utility\Html;

use Drupal\diplo_mailchimp\DiploMailChimpTrait;

/**
 * Class DiploMailchimpForm
 */
class DiploMailchimpForm extends FormBase {

  use DiploMailChimpTrait;

  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    static $count = 0;
    $count++;
    return 'diplo_mailchimp_form_' . $count;
  }

  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state, array $config = []) {
  
  
    $config_storage = \Drupal::config('diplo_mailchimp.settings')->getRawData(); 
    $config = array_merge($config_storage, $config);

    // Set config variables
    $form_state->set('subscribe_config', $config);

    // Get the form values
    $values = $form_state->getValues();

    $form_class = isset($config['form_class']) && !empty($config['form_class']) ? $config['form_class'] : '';

    $form['#theme'] = 'diplo_mailchimp_form';

    $form_container = Html::getId('mailchimp-subscriptions-' . $config['block_id']);

    $form['#prefix'] = '<div id="' . $form_container . '" class="' . $form_class . '">';
    $form['#suffix'] = '</div>'; 
    
    // Force this, may be essential for multiple forms on the same page
    $form['#id'] = $this->getFormId();

    // Kudos to MDJ
    $form_state->setRequestMethod('POST');
    $form_state->setCached(TRUE);
    // $form['#attached']['library'][] = 'diplo_mailchimp/geturlparam';

    // We do use a little JS for a special event, like a delayed 'keyup'
    // @see js/diplo_mailchimp.js
    $form['#attached']['library'][] = 'diplo_mailchimp/main';

    $form['#attributes']['class'][] = 'diplo-mailchimp-form';
   
    $audiences = isset($config['audiences']) ? $config['audiences'] : NULL;
    
    $form['audiences'] = [
      '#type' => 'value',
      '#value' => $audiences,
    ];

    if (isset($config['form_title']) && !empty($config['form_title'])) {
     $form['form_title'] = [
       '#type' => 'markup',
       '#markup' => $config['form_title'],
       '#weight' => -5, 
     ];
   }

    if (isset($config['description']) && isset($config['description']['value']) && !empty($config['description']['value'])) {
      $form['description'] = [
        '#prefix' => '<div class="mailchimp-subscription description">',
        '#suffix' => '</div>',
        '#type' => 'markup',
        '#markup' => FilteredMarkup::create($config['description']['value']),
        '#weight' => -4, 
      ];
    }
 
    // Use static method to "hardcode" from time to time mandatory fields
    // Those are the ones that are set so in MC - actually none of the fields should be set there so, then we do validation on our end, possibly front-end too
    $mandatory_fields = static::mandatoryFields();

    $member_fields = [];
    $member_info = NULL;
    if (!empty($values['fields']['EMAIL']) && $audiences) {
      $member_info = static::getMemberInfo($audiences, $values['fields']['EMAIL'], TRUE);
      $form_state->set('member_info', (array)$member_info);
      $member_fields = is_object($member_info) && isset($member_info->merge_fields) ? (array) $member_info->merge_fields : [];
    }

    $fields_container = Html::getId($config['block_id'] . '-fetch-container');

    $form['fields'] = [
      '#type' => 'container',
      '#tree' => TRUE,
      '#prefix' => '<div id="' . $fields_container .'">',
      '#suffix' => '</div>',
    ];

    if (isset($config['fields']) && !empty($config['fields'])) {

      foreach ($config['fields'] as $field_id => $field_type) {
        
        if (isset($field_type['type'])) { // Precaution, due many possible scenarios
          
          $form['fields'][$field_id] = [
            '#type' => $field_type['type'],
            '#title' => $field_type['label'],
            '#title_display' => 'invisible',
            '#default_value' => isset($values[$field_id]) ? $values[$field_id] : NULL,
            '#required' => FALSE, //TRUE,
            '#attributes' => [
              'class' => []
            ],
          ];

          switch ($field_type['type']) {

            // Dropdown/select widget
            case 'select':
              $form['fields'][$field_id]['#options'] = $field_type['options'];
              $form['fields'][$field_id]['#multiple'] = FALSE;
              $form['fields'][$field_id]['#empty_option'] = $field_type['label'];
            break;
          
            // Checkboxes and radios
            case 'checkboxes':
            case 'radios':
              $form['fields'][$field_id]['#options'] = $field_type['options'];
            break;  
 
            // Textfield, email and the others for now
            default: 
              $form['fields'][$field_id]['#size'] = 60;
              $form['fields'][$field_id]['#maxlength'] = 128;
              $form['fields'][$field_id]['#attributes']['placeholder'] = $field_type['label'];
            break;

          }

          // Set required fields
          if ($field_id == 'EMAIL' || in_array($field_id, $mandatory_fields)) {
            $form['fields'][$field_id]['#required'] = TRUE;
          }

          // Set value callback for all the other fields than email which triggers retrieving those from remote MC
          if ($field_id != 'EMAIL') {
            //$form['fields'][$field_id]['#value_callback'] = [$this, 'valuesCallback'];
            
          }
        } 
      }
    }
    else {
      $form['fields']['EMAIL'] = [
        '#title' => $this->t('Email address'),
        '#title_display' => 'invisible',
        '#type' => 'email',
        '#required' => TRUE,
        '#default_value' => isset($values['EMAIL']) ? $values['EMAIL'] : NULL,
        //'#attached' => [],
        //'#prefix' => '<div id="' . $fields_container .'">',
        //'#suffix' => '</div>',
        '#attributes' => [
          'placeholder' => $this->t('Email address'),
          'class' => []
        ],
        '#weight' => -1,
      ];
    }
 
    // Add ajax callback on email field, retrieves fields' data from remote MC
    $form['fields']['EMAIL']['#ajax'] = [
      'disable-refocus' => TRUE, // Essential for multiple forms on the same page
      'event' => 'finishedinput',
      'callback' => [$this, 'fetchMember'],
      'effect' => 'fade',
      'wrapper' => $fields_container,
      'progress' => [
        'type' => 'throbber',
        'message' => t('Fetching your data from MailChimp...'),
      ],
    ];

    // If we do NOT have some of mandatory fields displayed on the form - example dig.watch newsletter
    // Then set either existing values (previously retrieved from MC or 'None' in case of brand new member
    foreach ($mandatory_fields as $mid) {
      if (!isset($config['fields'][$mid])) {
        
        $field_value = !empty($member_fields) && isset($member_fields[$mid]) ? $member_fields[$mid] : 'None';
        
        $form['fields'][$mid] = [
          '#type' => 'value',
          '#value' => $field_value
        ];
      }
    } 

    // Prepare and render groups
    if (isset($config['groups']) && !empty($config['groups'])) {
      
      if ($config['hide_groups']) { // If we opted for not showing them set them as value elements on the form
        $form['groups'] = [
          '#type' => 'value',
          '#value' => $config['groups']
        ];
      }
      else {
        $list_id = isset($config['audiences']) && !empty($config['audiences']) ? $config['audiences'] : NULL;
        $group_options = [];
        $member_groups = [];
        if ($list_id) {
          $groups = static::getGroups($list_id);
          if (!empty($groups)) {

            // Get all the groups this existing member belongs to 
            $member_groups_all = static::getMemberGroups($member_info);
            
            foreach ($groups as $delta => $group) {
              if (in_array($group->id, array_keys($config['groups']))) {

                // Match possible existing member groups with those attached to the current form 
                if (!empty($member_groups_all) && in_array($group->id, array_keys($member_groups_all))) {
                  $member_groups[$group->id] = $group->name;
                }
                // Define groups #options
                $group_options[$group->id] = $group->name;      
              }
            }
          }
        }

        $form_state->set('member_groups', $member_groups); 
        
        $groups_default_value = isset($values['groups']) && !empty($values['groups']) ? $values['groups'] : [];
        
        // Seems like we do want chekboxes to be default checked for user
        // Even though for existing member only the ones that this member was previously subscribed will remain checked (via ajax call on email input) 
        if (empty($groups_default_value)) {
          // $groups_default_value = array_keys($group_options);          
        }
        
        $form['groups'] = [
          '#type' => 'checkboxes',
          '#title' => t('Subscription type'),
          '#title_display' => 'invisible',
          '#required' => TRUE,
          '#default_value' => $groups_default_value,
          // '#validated' => TRUE,
          '#options' => $group_options,
          '#attributes' => [
            'class' => []
          ] 
        ];
      }

    }

    if (isset($config['privacy']) && $config['privacy']) {
      
      if (isset($config['privacy_note']) && isset($config['privacy_note']['value']) && !empty($config['privacy_note']['value'])) {
        $accept_label = FilteredMarkup::create($config['privacy_note']['value']);
      }
      else {
        $accept_label = $this->t('Subscribe and Agree - by submitting this form, you are agreeing to our privacy policy');
      }

      $form['subscribe_op'] =[
        '#type' => 'radios',
        '#title' => $this->t('Please select your preference'),
        '#title_display' => 'invisible',
        '#default_value' => isset($values['subscribe_op']) ? $values['subscribe_op'] : NULL,
        '#required' => TRUE,
        '#options' => [
          'accept' => $accept_label
        ],
      ];

      // Unsubscribe
      if (isset($config['unsubscribe']) && $config['unsubscribe']) {
        $unsubscribe_label = isset($config['unsubscribe_label']) && isset($config['unsubscribe_label']['value']) && !empty($config['unsubscribe_label']['value']) ? $config['unsubscribe_label']['value'] : $this->t('Unsubscribe - tick if you are already subscribed and you wish to stop receiving our emails.');
        $form['subscribe_op']['#options'] = ['unsubscribe' => $unsubscribe_label] + $form['subscribe_op']['#options'];
      }
    }
  
    // Buttons
    $form['actions'] = [
      '#type' => 'container', 
      '#attributes' => [
        'class' => [
          'container-inline'
        ]
      ]
    ];

    $btn_value = isset($config['subscribe_button']) && !empty($config['subscribe_button']) ? $this->t('@subscribe_button', ['@subscribe_button' => $config['subscribe_button']]) : $this->t('Subscribe');

    $form['actions']['submit'] = [
      '#type' => 'submit',
      '#value' => $btn_value,
      '#ajax' => [
        'callback' => [get_class($this), 'submitAjax'],
        'wrapper' => $form_container,
        'progress' => [
          'type' => 'throbber',
          'message' => t('Verifying entry...'),
        ],
      ],
      '#attributes' => [
      ],
    ];

    if (isset($config['cancel']) && $config['cancel']) {
      $form['actions']['cancel'] = [
        '#type' => 'button',
        '#value' => $this->t('Cancel'),
        '#attributes' => [
          'id' => 'cancel-subscription',
        ],
      ];
    }

    return $form;
  
  }  
 
  
  /**
   * {@inheritdoc}
   * Values callback, for all the other fields but email which triggers request to MC for field values
   */
  
  /*
  public function valuesCallback(&$element, $input, FormStateInterface $form_state) {
    
    if ($input != '' && $input !== FALSE) {
      return $input;
    }

    $values = $form_state->getValues();
    $trigger = $form_state->getTriggeringElement();
    $email = $form_state->getValue(['fields', 'EMAIL']);
    $audiences =  $form_state->getValue('audiences');
    
    if ($audiences && $email) {
      $member_fields = [];
      $member_info = static::getMemberInfo($audiences, $email);
      $form_state->set('member_info', (array)$member_info);
     
      $name = end($element['#parents']);
      $member_fields = isset($member_info->merge_fields) ? (array) $member_info->merge_fields : [];
      $default_value = !empty($member_fields) && isset($member_fields[$name]) && $member_fields[$name] != 'None' ? $member_fields[$name] : NULL;
      if ($default_value) {
        return $default_value;
      }
      else {
        return isset($element['#default_value']) ? $element['#default_value'] : NULL;
      } 
    }
    else {
      return isset($element['#default_value']) ? $element['#default_value'] : NULL;
    }
  }
  */

  /**
   * {@inheritdoc}
   * Mandatory parent method
   * Checks on member subscription, based on email, via MailChimp API and fires appropriate action, based on action option selection subscribe/unsubscribe 
  */
  public function submitForm(array &$form, FormStateInterface $form_state) {

    // If basic Drupal form validation failed we do not want any further processing
    if (!empty($form_state->getErrors())) { 
      return;
    }

    $config = $form_state->get('subscribe_config');
    $values = $form_state->getValues();
  
    $audiences = isset($values['audiences']) && !empty($values['audiences']) ? $values['audiences'] : NULL;

    if (isset($values['fields']) && isset($values['fields']['EMAIL'])) {
      $email = !empty($values['fields']['EMAIL']) ? $values['fields']['EMAIL'] : NULL;
    }
    $groups_opt = isset($values['groups']) && !empty($values['groups']) ? $values['groups'] : [];
  
    if ($audiences && $email && !empty($groups_opt)) {
      
      // Fetch this list object
      $list = static::getList($audiences);
      
      // Get all the infor of this member (if existing one)
      $member_info = static::getMemberInfo($list->id, $email, TRUE); 
  
      // Fetch groups to which this user is already subcribed
      $member_groups_subscriptions = static::matchSubscriptions($form['groups'], $member_info, $values);

      if (is_object($list)) {
        $op = isset($values['subscribe_op']) && !empty($values['subscribe_op']) ? $values['subscribe_op'] : 'accept';
        if ($op == 'accept') { 
          // A main subscribe callback now
          $this->subscribe($form, $form_state, $list, $values, $email, $audiences, $member_info, $member_groups_subscriptions, $config);
        }
        else if ($op == 'unsubscribe') {
          foreach ($groups_opt as $group_id => $group) {
            if ($group && $group != '0') {
              // A main un-subscribe callback
              $this->unsubscribe($form, $form_state, $list, $email, $audiences, $config, $member_groups_subscriptions, $group_id, $group);
            }
          }     
        }
      }
    }
  }
  
  /**
   * Custom method for a various requests to remote MC API
   */
  protected function subscribe(array &$form, FormStateInterface $form_state, $list, $values, $email, $audiences, $member_info, $member_groups_subscriptions, &$config) {
    
    $merge_vars = NULL;
    
    $double_optin =isset($config['double_optin']) && $config['double_optin'] ? TRUE : FALSE; // Seems like we need to turn integers into bool here
    
    $zoom_id =isset($config['zoom_id']) && !empty($config['zoom_id']) ? $config['zoom_id'] : NULL;
    $zoom_type = isset($config['zoom_type']) && !empty($config['zoom_type']) ? $config['zoom_type'] : NULL;
    
    $debug = isset($config['debug']) && $config['debug'] ? TRUE : FALSE;
 
    $op = isset($values['subscribe_op']) && !empty($values['subscribe_op']) ? $values['subscribe_op'] : 'accept';
   
    if (is_object($member_info) && isset($member_info->status) && $member_info->status == 'subscribed') { // Anyhow we do not want double optin for existing member?
      $double_optin = FALSE;
    }

    $groups = [
      'already_subscribed' => [
        'ids' => [],
        'labels' => [],
        'op' => $op,
      ],
      'subscribe' => [
        'ids' => [],
        'labels' => [],
        'op' => $op,
      ],
    ];
    
    foreach ($values['groups'] as $group_id => $group) {
      
      if ($group && $group != '0') {
        $groups['subscribe']['ids'][] = $group_id;
        $groups['subscribe']['labels'][] = isset($form['groups'][$group_id]) ? $form['groups'][$group_id]['#title'] : $list->name . ': ' . $group_id;
      }
      else {

        // This group was un-checked by user in UI yet the user was previously subscribed to it so unsubscribe right away 
        if (isset($member_groups_subscriptions[$group_id]) && !empty($member_groups_subscriptions[$group_id])) {

          // Unsubscribe member from this group 
          if (!$debug) {
            $this->unsubscribe($form, $form_state, $list, $email, $audiences, $config, $member_groups_subscriptions, $group_id, $group);
          }
        }
      }
    }
    
    // Subscribe user now into the groups that is not member yet    
    if (!empty($groups['subscribe']['ids'])) {

      $labels = !empty($groups['subscribe']['labels']) ? implode(', ' , $groups['subscribe']['labels']) : $list->name;
      $messages = $this->validationStrings($config, $list, ['label' => $labels]);

      $merge_vars = [];

      if (isset($values['fields'])) {
        $merge_vars = $values['fields'];
      }

      // First check on Zoom opt
      if ($zoom_id && $zoom_type && !empty($merge_vars)) {
      
        $zoom_body = [
          'email' => $email,
          'first_name' => $merge_vars['FNAME'], // Note that these are not hardcode, since we secure all the mandatory fields have value in $this->buildForm()
          'last_name' => $merge_vars['LNAME'],
        ];
        
        /**
         * Add zoom registrant
         * @var \Drupal\diplo_mailchimp\DiploMailChimpTrait 
         */
        static::zoomAddRegistrant($zoom_id, $zoom_type, $zoom_body, [], $debug); 
       
      }

      // Finally a "subscribe" to groups (or even first time member) request to remote API 
      $result = !$debug ? static::subscribeMember($list->id, $email, $merge_vars, $groups['subscribe']['ids'], $double_optin) : NULL;
          
      if ($result) { 

        if (isset($values['tags']) && !empty($values['tags'])) {
          $tags = $values['tags'];
          static::addTags($list, $email, $tags); 
        }
        // This is our case for now, the above is assumption of possible tag on the form as a field
        else {
          // Do this explicitely for entity/i.e. our diplo mailchimp form
          // This is because apart from a form attached via field there can be another form on the same page
          $route = \Drupal::service('current_route_match');
          $is_node = $route->getParameters()->has('node') ? $route->getParameter('node') : NULL; 
          if (is_object($is_node)) { // && strpos($config['block_id'], 'entity') !== FALSE) {
            $tag = substr($is_node->getTitle(), 0, 99); 
            $tags = [$tag];
            static::addTags($list, $email, $tags); 
          }
        }
        
        // Send success message to user
        if (!empty($messages['success'])) {
          \Drupal::service('messenger')->addStatus($messages['success']);
        }

        // Now log this for admin
        $log = $this->t('A new subscriber @email on @labels MailChimp groups', ['@email' => $email, '@labels' => $labels]);
        \Drupal::service('logger.factory')->get('Diplo Mailchimp')->notice($log);
      }
      // Something went wrong, "blame" MC
      else {
        if (!$debug) {
          \Drupal::service('messenger')->addError($this->t('Remote service MailChimp returned an error, please try again later. If you are authenticated user check logs.'));
        }
        else {
          \Drupal::service('messenger')->addWarning('Working in the debug mode, no (un) subscriptions calls are sent to remote API. turn off Debug mode via checkbox on configuration.');  
        }
      }
    }
  }
  
   /**
   * Custom method for a Unsubscribe member to remote MC API
   * This actually "updates" on membership in MC grooups, this is in line with our basic logic set on MC that groups are distinction, not audiences / lists
   */
  protected function unsubscribe(array &$form, FormStateInterface $form_state, $list, $email, $audiences, $config, $member_groups_subscriptions, $group_id, $group) {

    if ($debug) {
      \Drupal::service('messenger')->addWarning('Working in the debug mode, no (un) subscriptions calls are sent to remote API. turn off Debug mode via checkbox on configuration.');
      return;
    }

    // Set drupal message to user about this event
    $label = isset($form['groups'][$group_id]) ? $form['groups'][$group_id]['#title'] : $group_id;
    $messages = $this->validationStrings($config, $list, ['label' => $label]);
          
    // This group was un-checked by user in UI yet the user was previously subscribed to it so unsubscribe right away 
    if (!isset($member_groups_subscriptions[$group_id]) || empty($member_groups_subscriptions[$group_id])) { 
      \Drupal::service('messenger')->addWarning($messages['unsubscribed_warning']);
    }
    else {
    
      // Get MC API
      $api = static::getApi('api_lists');
    
      // This is the "MC way" to do it
      $parameters = [
        'interests' => []
      ];
      $parameters['interests'][$group_id] = FALSE;
   
      if (is_object($api) && $unsubscribed = $api->updateMember($audiences, $email, $parameters)) { 

        \Drupal::service('messenger')->addStatus($messages['unsubscribed_message']);
      
        // Log the same for admin
        $log = $this->t('An existing subscriber @email un-subscribed from @labels MailChimp groups', ['@email' => $email, '@labels' => $label]);
        \Drupal::service('logger.factory')->get('Diplo Mailchimp')->notice($log);
      
      } 
      // Something went wrong, "blame" MC
      else {
        \Drupal::service('messenger')->addError($this->t('Remote service MailChimp returned an error, please try again later. If you are authenticated user check logs.'));
      }
    }
 
    // DO NOT uncomment - this is example call to unsubscribe member from the list itself, we do not use it
    // $unsubscribed = static::unsubscribeMember($list_id, $email);

  }

  /**
   * Ajax callback - fetch member data from remote MC
   */
  public function fetchMember(array &$form, FormStateInterface $form_state) {
    
    /*
    // This chunk of code goes when valuesCallback() is active and set on form elements 
    $trigger = $form_state->getTriggeringElement();
    $parents = array_slice($trigger['#array_parents'], 0, -1);
    $element = NestedArray::getValue($form, $parents);
    return $element;
    */

    $config = $form_state->get('subscribe_config'); 
    $values = $form_state->getValues();
    $trigger = $form_state->getTriggeringElement();
    $email = $form_state->getValue(['fields', 'EMAIL']);
    $audiences =  $form_state->getValue('audiences');
    $response = new AjaxResponse();
    
    if ($audiences && $email) {
      $member_fields = [];

      $member_info = static::getMemberInfo($audiences, $email);
      $form_state->set('member_info', (array)$member_info);

      $member_fields = isset($member_info->merge_fields) ? (array) $member_info->merge_fields : [];
      $member_groups = $form_state->get('member_groups') ? $form_state->get('member_groups') : [];

      $data = [
        'parent' => Html::getId('mailchimp-subscriptions-' . $config['block_id']),
        'groups' => empty($member_groups) ? $member_groups : array_keys($member_groups),
        'fields' => $member_fields 
      ];
      $response->addCommand(new InvokeCommand(NULL, 'fetchMemberCallback', [$data]));
    }

    return $response;

  }

  /**
   * Ajax callback for form submit event
   */
  public static function submitAjax(array $form, FormStateInterface $form_state) {
    return $form;
  }

  /**
   * Custom method - prepare and process messages strings
   */
  protected function validationStrings(array &$config, object $list, array $group_info = []) {
  
    $label = isset($group_info['label']) && !empty($group_info['label']) ? $group_info['label'] : $list->name; 

    // Unsubscribe user action success
    if (isset($config['unsubscribe_message']) && isset($config['unsubscribe_message']['value'])) {
      if (!empty($config['unsubscribe_message']['value']) ){
        $unsubscribed_text = str_replace('@label', $label, $config['unsubscribe_message']['value']);
        $unsubscribed_message = FilteredMarkup::create($unsubscribed_text);
      }
      else {
        $unsubscribed_message = FilteredMarkup::create($this->t('You have successfully un-subscribed from <em>@label</em>. No further notifications will come.', ['@label' => $label]));
      }
    }
    else {
      $unsubscribed_message = FilteredMarkup::create($this->t('You have successfully un-subscribed from <em>@label</em>. No further notifications will come.', ['@label' => $label]));
    } 

    // Unsubscribe warning (already subscribed)
    if (isset($config['unsubscribed_message']) && isset($config['unsubscribed_message']['value'])) {
      if (!empty($config['unsubscribed_message']['value'])) {
        $unsubscribed_warning_text = str_replace('@label', $label, $config['unsubscribed_message']['value']);
        $unsubscribed_warning =  FilteredMarkup::create($unsubscribed_warning_text);
      }
      else {
        $unsubscribed_warning = FilteredMarkup::create($this->t('You were previously un-subscribed to <em>@label</em> and no further action is needed.', ['@label' => $label]));
      } 
    }
    else {
      $unsubscribed_warning = FilteredMarkup::create($this->t('You were previously un-subscribed to <em>@label</em> and no further action is needed.', ['@label' => $label]));
    }

    // Subscribed success message
    if (isset($config['subscribe_message']) && isset($config['subscribe_message']['value']) && !empty($config['subscribe_message']['value'])) {
      $subscribed_text = str_replace('@label', $label, $config['subscribe_message']['value']);
      $success = FilteredMarkup::create($subscribed_text); 
    }
    else {
      $success = FilteredMarkup::create($this->t('Thank you! Yo have successfully subscribed to @label', ['@label' => $label]));
    }

    // Subscribe warning - user is previously subscribed
    if (isset($config['subscribed_message']) && isset($config['subscribed_message']['value']) && !empty($config['subscribed_message']['value'])) {
      $subscribed_warning_text = str_replace('@label', $label, $config['subscribed_message']['value']);
      $subscribed_warning = FilteredMarkup::create($subscribed_warning_text);
    }
    else {
      $subscribed_warning = FilteredMarkup::create($this->t('You were previously subscribed to <em>@label</em>.', ['@label' => $label]));
    }

    return [
      'unsubscribed_message' => $unsubscribed_message,
      'unsubscribed_warning' => $unsubscribed_warning,
      'subscribed_warning' => $subscribed_warning,
      'success' => $success,
    ]; 
  
  }
}

namespace Drupal\diplo_mailchimp\Element;

use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Render\Element\FormElement;
use Drupal\Core\Url;
use Drupal\Core\Link;
use Drupal\Core\Datetime\DrupalDateTime;

use Drupal\Component\Utility\NestedArray;

use Drupal\diplo_mailchimp\DiploMailChimpTrait;

/**
 * Provides a form element for extending MailChimp related custom data.
 *
 * Usage example:
 * @code
 * $form['mailchimp_data'] = [
 *   '#type' => 'diplo_mailchimp_related_data',
 *   '#title' => t('Related data'),
 *   '#default_value' => [
 *     'audiences' => $audiences,
 *     'groups' => [
 *        "$gid" => $gid
 *      ],
        'fields' => [
          $field_id => $field_name
        ],
 *      'description' => $description 
 *   ],
 * ];
 * @endcode
 *
 * @see \Drupal\Core\Render\Element\Checkboxes
 * @see \Drupal\Core\Render\Element\Radios
 * @see \Drupal\Core\Render\Element\Select
 *
 * @FormElement("diplo_mailchimp_related_data")
 */

class DiploMailchimpRelatedData extends FormElement {

  use DiploMailChimpTrait;
  
  /**
   * {@inheritdoc}
   */
  public function getInfo() {
   
    $class = get_class($this);

    $element = [
      '#input' => TRUE,
      '#process' => [
        [$class, 'process'],
      ],
    ];
    return $element;
  }

  /**
   * Process this custom composite element
   */
  public static function process(&$element, FormStateInterface $form_state, &$complete_form) {

    // When invoking this element we may have a chance to place some custom data/variables that were sent "from invoker"
    $context = $form_state->get('mailchimp_context');
   
    // Pick current form_state values
    $values = $form_state->getValues();

    if (!empty($context) && isset($context['name'])) {
      // This is a call from field formatter, very specific array 
      if (isset($values['fields']) && isset($values['fields'][$context['name']]) && isset($values['fields'][$context['name']]['settings_edit_form']) && isset($values['fields'][$context['name']]['settings_edit_form']['settings'])) {
        if (isset($values['fields'][$context['name']]['settings_edit_form']['settings']['related_data']) && isset($values['fields'][$context['name']]['settings_edit_form']['settings']['related_data']['audiences'])) {
          $values = $values['fields'][$context['name']]['settings_edit_form']['settings']['related_data'];
        }
      }
      else {
        if (isset($values['default_value_input'])) {
           if (isset($values['default_value_input'][$context['name']]) && !empty($values['default_value_input'][$context['name']]) && isset($values['default_value_input'][$context['name']][0]['related_data'])) {
            $values = $values['default_value_input'][$context['name']][0]['related_data']; 
          }
        }
        else { 
          if (isset($values[$context['name']]) && !empty($values[$context['name']]) && isset($values[$context['name']][0]['related_data'])) {
            $values = $values[$context['name']][0]['related_data'];  
          }
        }
      } 
    }

    $audiences = NULL;

    // MailChimpa API key was entered, store it in mailchimp config
    // Note, this way all the calls on diplo related data element run out of the box 
    $config = \Drupal::service('config.factory')->getEditable('diplo_mailchimp.settings');
    $config_data = $config->getRawData();

    $api_key = $config_data['api_key'];
    if (!$api_key) {
      $api_key = isset($values['api_key']) && !empty($values['api_key']) ? $values['api_key'] : NULL;
    }

    if ($api_key) {

      // We want this exclusively for entity/node attached fields and NOT for Drupal blocks (those should be disabled or deleted in drupal when we do not want to show a form anymore
      if (is_array($context) && isset($context['name']) && strpos($context['name'], 'field_') !== FALSE) {

        $element['hide_form'] = [ 
          '#type' => 'checkbox',
          '#title' => t('Do not show subscription form'),
          '#description' => t('Check this to exclude / do not show a form at all. <strong>Important:</strong> This shows only on node/content form because it is more than recommended that in case of a "block" you just delete or disable such block in Drupal, on the block config. '), 
          '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['hide_form']) ? $element['#default_value']['hide_form'] : NULL,
          '#attributes' => [
            'id' => 'hide-form-wrapper',
          ]
        ];

        $date_field_value = NULL;
        $date_object = NULL;
        if (isset($values['date_field']) && !empty($values['date_field'])) {
          $date_field_value = is_array($values['date_field']) ? implode(' ', array_values($values['date_field'])) : $values['date_field'];
        }
        else {
          if (isset($element['#default_value']) && isset($element['#default_value']['date_field'])) {
            $date_field_value = is_array($element['#default_value']['date_field']) ? implode(' ', array_values($element['#default_value']['date_field'])) : $element['#default_value']['date_field'];
          }
        }       
      
        $element['date_field'] = [
          '#title' => t('Expiration date'),
          '#description' => t('Select a date/time from which a form will not be shown anymore.'),
          '#type' => 'datetime',
          '#validated' => TRUE,
          // '#date_date_element' => 
          '#default_value' => is_array($element['#default_value']['date_field']) ? implode(' ', array_values($element['#default_value']['date_field'])) : $element['#default_value']['date_field'],
          '#states' => [
            'invisible' => [
              ':input[id="hide-form-wrapper"]' => ['checked' => TRUE],
            ],
          ],
        ];

        $element['form_title'] = [
          '#type' => 'textfield',
          '#title' => t('Subscription form title'),
          '#description' => t('Choose a specific title for this form.'), 
          '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['form_title']) ? $element['#default_value']['form_title'] : NULL,
        ];
      }

     $list_options = static::listsWidget();
      
      $element['audiences'] = [
        '#type' => 'radios',
        '#title' => t('MailChimp Audience'),
        //'#required' => TRUE,
        '#description' => t('Select your Audience, it will retrieve available groups and render here. See how to find Audience ID < a href="https://mailchimp.com/help/find-audience-id/" target="blank_">here</a>'),
        '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['audiences']) ? $element['#default_value']['audiences'] : NULL,
        '#options' => $list_options,
        '#validated' => TRUE,
        '#ajax' => [
          //'method' => 'after',
          'event' => 'change',
          'callback' => __CLASS__ . '::fetch',
          'effect' => 'fade',
          'wrapper' => 'diplo-mailchimp-fetch-container',
          'progress' => [
            'type' => 'throbber',
            'message' => t('Requesting groups from MailChimp...'),
          ],
        ],
      ];
    
      $element['fetch_group'] = [
        '#type' => 'container',
        '#prefix' => '<div id="diplo-mailchimp-fetch-container">',
        '#suffix' => '</div>',
      ];

      $element['fetch_group']['groups'] = [
        '#title' => t('MailChimp Interest Groups IDs'),
        '#type' => 'checkboxes',
        '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['groups']) && is_array($element['#default_value']['groups']) ? array_keys($element['#default_value']['groups']) : [],
        //'#value_callback' => '\Drupal\diplo_mailchimp\Element\DiploMailchimpRelatedData::groupsValueCallback',
        '#validated' => TRUE,
        '#options' => [], 
        '#prefix' => '<div id="diplo-mailchimp-groups-container">',
        '#suffix' => '</div>',
      ];
   
      $element['fetch_group']['hide_groups'] =[
        '#type' => 'checkbox',
        '#title' => t('Do not show Groups in UI'),
        '#description' => t('Checkboxes to select group will not be shown on the subscription form. Default values (group id for subscribing) will be taken from config above.'), 
        '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['hide_groups']) ? $element['#default_value']['hide_groups'] : NULL,
      ];

      $element['fetch_group']['fields'] = [
        '#type' => 'checkboxes',
        '#title' => t('Available MailChimp fields'),
        '#description' => t('The fields are automatically retrieved from remote MC API, in order as those are set there.'),
        '#validated' => TRUE, // Essential
        '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['fields']) ? $element['#default_value']['fields'] : [],
        '#options' => [],
      ];

      if (isset($values['audiences']) && !empty($values['audiences'])) { // This is ajax on Main configuration
        $audiences = $values['audiences'];
      }
      else if (isset($values['related_data']) && isset($values['related_data']['audiences'])) {
        $audiences = !empty($values['related_data']['audiences']) ? $values['related_data']['audiences'] : NULL;
      }
      // This is the case when ajax change, called from a Block (create new)
      else if (isset($values['settings']) && isset($values['settings']['related_data']) && isset($values['settings']['related_data']['audiences'])) {
        $audiences = !empty($values['settings']['related_data']['audiences']) ? $values['settings']['related_data']['audiences'] : NULL;
      }
      // Default value, editing either existing main configuration form or block
      else {
        if (isset($element['#default_value']) && isset($element['#default_value']['audiences'])) {
          $audiences = !empty($element['#default_value']['audiences']) ? $element['#default_value']['audiences'] : NULL;
        }
      }
    }
    
    $merge_vars = NULL;
    $groups_options = [];
 
    if ($audiences) {
      $groups_options = static::groupsWidget($audiences);

      if (!empty($groups_options)) {
        $element['fetch_group']['groups']['#options'] = $groups_options;
      }

      $merge_vars = static::mergeVars([$audiences]);

      $fields = static::getFields([$audiences], TRUE);
      if (!empty($fields)) {
        $fields_options = [];
        foreach ($fields as $field_id => $field) {
          $fields_options[$field_id] = $field['name'];
        }
        $element['fetch_group']['fields']['#options'] = $fields_options;
        $element['fetch_group']['fields']['#after_build'][] = [__CLASS__ , 'processCheckboxes'];
      }
    }
     
    $element['subscribe_button'] = [
      '#type' => 'textfield',
      '#title' => t('Subscribe button text'),
      '#description' => t('Text for a subscribe button, can be anything of meaningful length.'), 
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['subscribe_button']) ? $element['#default_value']['subscribe_button'] : NULL,
    ];

    $element['double_optin'] = [ 
      '#type' => 'checkbox',
      '#title' => t('Double optin'),
      '#description' => t('Check this to have MailChimp sends confirmation email to a brand new subscriber. Un-check is useful developing as you can with any placeholder email see change in MC right away.'), 
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['double_optin']) ? $element['#default_value']['double_optin'] : NULL,
      '#attributes' => [
        'id' => 'unsubscribe_option',
      ]
    ];

    // Zoom
    if (\Drupal::service('module_handler')->moduleExists('zoomapi')) { // Make zoom feature optional (only if zoomapi module installed)
      $zoomapi = \Drupal::config('zoomapi.settings');
      if ($zoomapi->get('api_key') && $zoomapi->get('api_secret')) { // Double check that credentials were previously stored
        
        $element['zoom'] = [
          '#type' => 'fieldset',
          '#title' => t('Zoom'),
          '#prefix' => '<div id="diplo-mailchimp-fetch-zoom-container">',
          '#suffix' => '</div>',
        ];
       
        $element['zoom']['zoom_id'] = [
          '#type' => 'textfield',
          '#title' => t('Zoom ID'),
          '#description' => t('Provide zoom meeting or webinar ID here. Can be something like this "94479752531" Note: <strong>make sure you do not leave any spaces</strong> between characters/numbers'), 
          '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['zoom_id']) ? $element['#default_value']['zoom_id'] : NULL,
          '#attributes' => [
            'id' => 'zoom-id-value',
          ]
        ];

        $element['zoom']['zoom_type'] = [
          '#type' => 'select',
          '#title' => t('Zoom type'),
          '#description' => t('Select which type of zoom event you are referring to'), 
          '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['zoom_type']) ? $element['#default_value']['zoom_type'] : NULL,
          '#options' => [
            //'' => t('- Select type -'),
            'meetings' => t('Meeting'),
            'webinars' => t('Webinar'), 
          ],
          '#empty_option' => t('- Select type -'),
          '#ajax' => [
            'event' => 'change',
            'callback' => __CLASS__ . '::fetchZoom',
            'effect' => 'fade',
            'wrapper' => 'diplo-mailchimp-fetch-zoom-container',
            'progress' => [
              'type' => 'throbber',
              'message' => t('Please stand by, validating Zoom event...'),
            ],
          ],
          '#states' => [
            'invisible' => [
              ':input[id="zoom-id-value"]' => ['value' => ''],
            ],
          ],

        ];
      }
    } 
 
    $element['description'] = [
      '#base_type' => 'textarea',
      '#type' => 'text_format',
      '#title' => t('Description'),
      '#description' => t('A short information about subscription.'),
      '#format' => isset($element['#default_value']) && isset($element['#default_value']['description']) && isset($element['#default_value']['description']['format']) ? $element['#default_value']['description']['format'] : 'basic_html',
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['description']) && isset($element['#default_value']['description']['value']) ? $element['#default_value']['description']['value'] : NULL,
    ];

    $element['subscribe_message'] = [
      '#base_type' => 'textfield',
      '#type' => 'text_format',
      '#title' => t('Override subscribe message'),
      '#description' => t('A text/message to display for successful subscription.'),
      '#maxlength' => '1024',
      '#format' => isset($element['#default_value']) && isset($element['#default_value']['subscribe_message']) && isset($element['#default_value']['subscribe_message']['format']) ? $element['#default_value']['subscribe_message']['format'] : 'basic_html',
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['subscribe_message']) && isset($element['#default_value']['subscribe_message']['value']) ? $element['#default_value']['subscribe_message']['value'] : NULL,
    ];

    $element['subscribed_message'] = [
      '#base_type' => 'textfield',
      '#type' => 'text_format',
      '#title' => t('Override already subscribed warning'),
      '#description' => t('If user was previously subscribed to the same list this is information returned.'),
      '#maxlength' => '1024',
      '#format' => isset($element['#default_value']) && isset($element['#default_value']['subscribed_message']) && isset($element['#default_value']['subscribed_message']['format']) ? $element['#default_value']['subscribed_message']['format'] : 'basic_html',
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['subscribed_message']) && isset($element['#default_value']['subscribed_message']['value']) ? $element['#default_value']['subscribed_message']['value'] : NULL,
    ];

    $element['form_class'] =[
      '#type' => 'textfield',
      '#title' => t('Additional CSS class(es)'),
      '#description' => t('This goes on the first parent of a "form" element. Just separate classes with space as in html.'), 
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['form_class']) ? $element['#default_value']['form_class'] : NULL,
    ];

    $element['unsubscribe'] = [ 
      '#type' => 'checkbox',
      '#title' => t('Show unsubscribe option'),
      '#description' => t('An additional radio for user to be able to unsubscribe from the mailing list.'), 
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['unsubscribe']) ? $element['#default_value']['unsubscribe'] : NULL,
    ];

    $element['unsubscribe_wrapper'] = [ 
      '#type' => 'fieldset',
      '#states' => [ // @see https://www.drupal.org/docs/8/api/form-api/conditional-form-fields
        'invisible' => [
          ':input[name="field_mailchimp_subscriptions[0][related_data][unsubscribe]"]' => ['checked' => FALSE],
        ],
      ],
    ];
    
    $element['unsubscribe_wrapper']['unsubscribe_label'] = [
      '#base_type' => 'textfield',
      '#type' => 'text_format',
      '#title' => t('Override Unsubscribe note'),
      '#description' => t('Override default unsubscribe note for unsubscribe checkbox'),
      '#maxlength' => '1024',
      '#format' => isset($element['#default_value']) && isset($element['#default_value']['unsubscribe_label']) && isset($element['#default_value']['unsubscribe_label']['format']) ? $element['#default_value']['unsubscribe_label']['format'] : 'basic_html',
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['unsubscribe_label']) && isset($element['#default_value']['unsubscribe_label']['value']) ? $element['#default_value']['unsubscribe_label']['value'] : NULL,
    ];

    $element['unsubscribe_wrapper']['unsubscribe_message'] = [
      '#base_type' => 'textfield',
      '#type' => 'text_format',
      '#title' => t('Override unsubscribe message'),
      '#description' => t('A text/message to display upon cancelling subscription (unsubscribed)'),
      '#maxlength' => '1024',
      '#format' => isset($element['#default_value']) && isset($element['#default_value']['unsubscribe_message']) && isset($element['#default_value']['unsubscribe_message']['format']) ? $element['#default_value']['unsubscribe_message']['format'] : 'basic_html',
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['unsubscribe_message']) && isset($element['#default_value']['unsubscribe_message']['value']) ? $element['#default_value']['unsubscribe_message']['value'] : NULL,
    ]; 
    
    $element['unsubscribe_wrapper']['unsubscribed_message'] = [
      '#base_type' => 'textfield',
      '#type' => 'text_format',
      '#title' => t('Override already unsubscribed message'),
      '#description' => t('A text/message to display to user who tries to unsubscribe yet already, previously, being unsubscribed.'),
      '#maxlength' => '1024',
      '#format' => isset($element['#default_value']) && isset($element['#default_value']['unsubscribed_message']) && isset($element['#default_value']['unsubscribed_message']['format']) ? $element['#default_value']['unsubscribed_message']['format'] : 'basic_html',
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['unsubscribed_message']) && isset($element['#default_value']['unsubscribed_message']['value']) ? $element['#default_value']['unsubscribed_message']['value'] : NULL,
    ]; 

    $element['privacy'] =[
      '#type' => 'checkbox',
      '#title' => t('Show Privacy policy note'),
      '#description' => t('Show checkbox for user to confirm reading privacy policy.'), 
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['privacy']) ? $element['#default_value']['privacy'] : NULL,
      '#attributes' => [
        'id' => 'privacy_option',
      ]
    ];
     
    $element['privacy_wrapper'] = [ 
      '#type' => 'fieldset',
      '#states' => [ // @see https://www.drupal.org/docs/8/api/form-api/conditional-form-fields
        'invisible' => [
          ':input[id="privacy_option"]' => ['checked' => FALSE],
        ],
      ],
    ];

    $element['privacy_wrapper']['privacy_note'] = [
      '#base_type' => 'textfield',
      '#type' => 'text_format',
      '#title' => t('Privacy policy note'),
      '#description' => t('Set default Privacy policy note for accepting checkbox'),
      '#format' => isset($element['#default_value']) && isset($element['#default_value']['privacy_note']) && isset($element['#default_value']['privacy_note']['format']) ? $element['#default_value']['privacy_note']['format'] : 'basic_html',
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['privacy_note']) && isset($element['#default_value']['privacy_note']['value']) ? $element['#default_value']['privacy_note']['value'] : NULL,
      '#maxlength' => '1024',
      '#states' => [ // @see https://www.drupal.org/docs/8/api/form-api/conditional-form-fields
        'invisible' => [
          ':input[id="privacy_option"]' => ['checked' => FALSE],
        ],
      ],
    ];

    $element['cancel'] = [ 
      '#type' => 'checkbox',
      '#title' => t('Show cancel button'),
      '#description' => t('This does not make any sense for now, therefore disabled.'), 
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['cancel']) ? $element['#default_value']['cancel'] : NULL,
      '#disabled' => TRUE,
      '#attributes' => [
        'id' => 'cancel_button',
      ]
    ];

    $element['developer_data'] = [ 
      '#type' => 'details',
      '#title' => t('Developer data'),
      '#description' => t('Just some additional useful data returned from MailChimp.'), 
    ];

    $element['developer_data']['debug'] = [ 
      '#type' => 'checkbox',
      '#title' => t('Debug'),
      //'#disabled' => TRUE,
      '#description' => t('Check this if you want to prevent new subscriptions during testing or similar. <strong>Not ready yet.</strong>'), 
      '#default_value' => isset($element['#default_value']) && isset($element['#default_value']['debug']) ? $element['#default_value']['debug'] : NULL,
    ];

    $element['developer_data']['list_id'] = [
      '#type' => 'textfield',
      '#title' => $audiences ? $audiences : NULL,
      '#description' => t('Selected MailChimp Audience ID'), 
      '#default_value' => $audiences,
      '#disabled' => TRUE
    ];

    
    if (!empty($groups_options)) {
      $element['developer_data']['groups_ids'] = [
        '#type' => 'details',
        '#title' => t('MailChimp Groups IDs'),
        '#description' => t('Selected MailChimp Groups IDs'), 
      ];

      foreach ($groups_options as $group_key => $group_value) {
        $element['developer_data']['groups_ids'][$group_key] = [
          '#type' => 'textfield',
          '#title' => $group_value,
          '#default_value' => $group_key,
          '#disabled' => TRUE
        ];
      }
    }

    // Developer data part, just printing some MC API keys/values/variables
    if (is_array($merge_vars) && !empty($merge_vars)) {
      
      $vars = static::prepareVars($merge_vars);
      
      $element['developer_data']['merge_vars'] = [
        '#type' => 'details',
        '#title' => t('MailChimp fields list'),
        '#description' => t('Merge vars data retrieved from MailChimp'), 
      ];
      foreach ($vars as $tag_id => $var) {
        $element['developer_data']['merge_vars'][$tag_id] = [
          '#type' => 'textfield',
          '#size' => 20,
          '#title' =>  $var->name . ' ID',
          '#default_value' => $tag_id,
          '#disabled' => TRUE
        ];
      }
    }
 
    return $element;
  }

  /**
   *  A custom after_build method for our checkboxes
   */
  public static function processCheckboxes($element, FormStateInterface $form_state) {
    if (isset($element['EMAIL']) && !empty($element['EMAIL'])) {
      $element['EMAIL']['#attributes']['disabled'] = 'disabled'; //TRUE;
      $element['EMAIL']['#checked'] = TRUE; 
      $element['EMAIL']['#return_value'] = 1; //'EMAIL';
      $element['EMAIL']['#value'] = 1; //'EMAIL';
    }
    return $element;
  }

  /**
   *  Ajax callback, return refreshed group element
   */
  public static function fetch(array &$form, FormStateInterface $form_state) {
    $trigger = $form_state->getTriggeringElement();
    $parents = array_slice($trigger['#array_parents'], 0, -2);
    $parents[] = 'fetch_group';
    $element = NestedArray::getValue($form, $parents);
    return $element; 
  }

  /**
   *  Ajax callback, validate zoom event
   */
  public static function fetchZoom(array &$form, FormStateInterface $form_state) {

    $values = $form_state->getvalues();
    $trigger = $form_state->getTriggeringElement();
    $parents = array_slice($trigger['#array_parents'], 0, -2);
    $parents[] = 'zoom';

    $field_name = $trigger['#parents'][0];
    $element = NestedArray::getValue($form, $parents);

    if (empty($values[$field_name])) {
      return $element;
    }

    // This is a configuration on a Block plugin
    if ($trigger['#parents'][0] == 'settings' && isset($values[$field_name]['related_data']) && isset($values[$field_name]['related_data']['zoom'])) {
      $zoom_type = isset($values[$field_name]['related_data']['zoom']['zoom_type']) && !empty($values[$field_name]['related_data']['zoom']['zoom_type']) ? $values[$field_name]['related_data']['zoom']['zoom_type'] : NULL;
      $zoom_id = isset($values[$field_name]['related_data']['zoom']['zoom_id']) && !empty($values[$field_name]['related_data']['zoom']['zoom_id']) ? $values[$field_name]['related_data']['zoom']['zoom_id'] : NULL;  
      // Validate zoom event (for exitance or expiration or any other errors)
      if ($zoom_type && $zoom_id) {
        static::validateZoom($zoom_type, $zoom_id);
      }
    }  
    else {

      // Yet this is a field widget (i.e. node edit form)
      if (isset($values[$field_name][0]['related_data']) && isset($values[$field_name][0]['related_data']['zoom'])) {
        $zoom_type = isset($values[$field_name][0]['related_data']['zoom']['zoom_type']) && !empty($values[$field_name][0]['related_data']['zoom']['zoom_type']) ? $values[$field_name][0]['related_data']['zoom']['zoom_type'] : NULL;
        $zoom_id = isset($values[$field_name][0]['related_data']['zoom']['zoom_id']) && !empty($values[$field_name][0]['related_data']['zoom']['zoom_id']) ? $values[$field_name][0]['related_data']['zoom']['zoom_id'] : NULL;
  
        // Validate zoom event (for existance or expiration or any other errors)
        if ($zoom_type && $zoom_id) {
          static::validateZoom($zoom_type, $zoom_id);
        }
      }
    }
 
    return $element; 
  }

  /**
   *  Custom method, // Validate zoom event (for existance or expiration or any other errors)
   */
  public static function validateZoom($zoom_type, $zoom_id) {
   
    $response = static::zoomCheckEvent($zoom_id, $zoom_type);
    if (isset($response['success']) && !empty($response['success'])) {
      \Drupal::messenger()->addStatus(t('Valid event <em>@topic</em>', [
        '@topic' => $response['success']['topic']
      ]));
    }
    else if (isset($response['error']) && !empty($response['error'])) {
      \Drupal::messenger()->addError($response['error']);
    }
  }
 
}