Stash a complex AJAX form

NyplIpCheckerAdminForm.php

<?php

namespace Drupal\nypl_ip_checker\Form;

/**
 * @file
 * Contains \Drupal\contact_info\Form\NyplIpCheckerAdminForm.
 */

use Drupal\Core\Config\ConfigFactoryInterface;
use Drupal\Core\Form\ConfigFormBase;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Render\Element;

/**
 * Class AdminForm.
 */
class NyplIpCheckerAdminForm extends ConfigFormBase {

  /**
   * Constructs a new NyplIpCheckerAdminForm.
   *
   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
   *   The factory for configuration objects.
   */
  public function __construct(ConfigFactoryInterface $config_factory) {
    parent::__construct($config_factory);
  }

  /**
   * {@inheritdoc}
   */
  protected function getEditableConfigNames(): array {
    return [
      'nypl_ip_checker.nypl_ip_checker_admin_form',
    ];
  }

  /**
   * {@inheritdoc}
   */
  public function getFormId(): string {
    return 'nypl_ip_checker_admin_form';
  }

  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state): array {
    // Get the config this form saves to, for default_values.
    $config = $this->config('nypl_ip_checker.settings');

    // Determine if an AJAX callback is rebuilding the form.
    $addElement = $form_state->get('addElement');
    $removeElement = $form_state->get('removeElement');

    // Make that form a tree.
    $form['#tree'] = TRUE;
    $form_state->setCached(FALSE);

    // Form description.
    $form['description'] = [
      '#type' => 'item',
      '#markup' => $this->t('This form stores the RegEx patterns associated with various NYPL locations.'),
    ];

    // Fieldset with one or more fields holding onsite RegEx patterns.
    $form['onsite'] = [
      '#type' => 'fieldset',
      '#title' => $this->t('On-site patterns'),
      '#description' => $this->t('Broad RegEx patterns indicating whether an IP is within or outside NYPL property.'),
    ];
    // Fill in onsite pattern field if there is no existing value.
    $form['onsite']['pattern'][0] = [
      '#type' => 'textfield',
      '#title' => $this->t('RegEx pattern'),
      '#default_value' => '',
    ];

    // Fill in saved config values, if present.
    $onsite_patterns = $config->get('onsite.pattern');
    if (isset($onsite_patterns) && count($onsite_patterns)) {
      $form['onsite']['pattern'] = [];
      foreach ($onsite_patterns as $i => $val) {
        $form['onsite']['pattern'][$i] = [
          '#type' => 'textfield',
          '#title' => $this->t('RegEx pattern'),
          '#default_value' => $val,
        ];
      }
    }

    // Check if the AJAX triggered an add.
    if (isset($addElement) && $addElement === ['onsite', 'pattern']) {
      $form['onsite']['pattern'][] = [
        '#type' => 'textfield',
        '#title' => $this->t('RegEx pattern'),
        '#default_value' => '',
      ];
    }
    // Check if the AJAX triggered a remove.
    if (isset($removeElement) && $removeElement === ['onsite', 'pattern']) {
      array_pop($form['onsite']['pattern']);
    }
    $form['onsite'] = $this->appendAddRemoveActions($form['onsite']);

    // Fieldset of fieldsets holding match patterns for specific locations.
    $form['mappings'] = [
      '#type' => 'fieldset',
      '#title' => $this->t('Location patterns'),
    ];
    // Create one blank fieldset if no saved values present.
    $blankMapping = [
      '#type' => 'fieldset',
      '#title' => $this->t('Location'),
      'pattern' => [
        0 => [
          '#type' => 'textfield',
          '#title' => $this->t('RegEx pattern'),
          '#default_value' => '',
        ],
      ],
    ];
    // Include a zeroth element in order to make AJAX play nice.
    $form['mappings']['location'][0] = [
      '#type' => 'item',
      '#markup' => $this->t('Each location has a require node reference, plus one or more patterns.'),
    ];
    $form['mappings']['location'][] = [
      '#type' => 'item',
      '#markup' => $this->t('Neither zero nor 1 are good.'),
    ];
    $form['mappings']['location'][] = $blankMapping;
    $form['mappings']['location'][] = $blankMapping;

    // Fill in saved config values, if present.
    $mappings = $config->get('mappings');
    if (isset($mappings) && count($mappings)) {
      $form['mappings']['location'] = [];
      foreach ($mappings as $i => $val) {
        $form['mappings']['location'][$i] = [
          '#type' => 'fieldset',
          '#title' => $this->t('Location'),
          'pattern' => [
            0 => [
              '#type' => 'textfield',
              '#title' => $this->t('RegEx pattern'),
              '#default_value' => $val[0]['pattern'],
            ],
          ],
        ];
      }
    }

    // Check if the AJAX triggered an add for a whole mapping.
    if (isset($addElement) && count($addElement) === 2
      && $addElement === ['mappings', 'location']
    ) {
      $form['mappings']['location'][] = $blankMapping;
    }
    // Check if the AJAX triggered a remove for a whole mapping.
    if (isset($removeElement) && count($addElement) === 2
      && $removeElement === ['mappings', 'location']
    ) {
      array_pop($form['mappings']['location']);
    }
    //$form['mappings'] = $this->appendAddRemoveActions($form['mappings']);

    // Check if the AJAX triggered add/remove on patterns within a location.
    if (isset($addElement) && count($addElement) === 4
      && in_array('mappings', $addElement)
      && in_array('location', $addElement)
    ) {
      $form['mappings']['location'][$addElement[2] - 1]['pattern'][] = [
        '#type' => 'textfield',
        '#title' => $this->t('RegEx pattern'),
        '#default_value' => '',
      ];
    }
    if (isset($removeElement) && count($removeElement) === 4
      && in_array('mappings', $removeElement)
      && in_array('location', $removeElement)
    ) {
      array_pop($form['mappings']['location'][$addElement[2] - 1]['pattern']);
    }

    // Add in actions for all the mappings/locations after the parent.
    foreach ($form['mappings']['location'] as $i => $set) {
      if ($i >= 1) {
        $form['mappings']['location'][$i] = $this->appendAddRemoveActions($form['mappings']['location'][$i]);
      }
    }

    return parent::buildForm($form, $form_state);
  }

  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    $values = $form_state->getValues();
    $config = $this->configFactory->getEditable('nypl_ip_checker.settings');

    $config->set('onsite.pattern', $values['onsite']['pattern']);

    $config->save();
    parent::submitForm($form, $form_state);
  }

  /**
   * Add the add/remove buttons to elements that take such AJAX toggles.
   *
   * @param array $element
   *   A form element with its constituent parts.
   *
   * @return array
   *   The element with the buttons appended.
   */
  public function appendAddRemoveActions(array $element): array {
    $element['actions'] = [
      '#type' => 'actions',
      'add' => [
        '#type' => 'submit',
        '#value' => $this->t('Add'),
        '#submit' => ['::addCallback'],
        '#ajax' => [
          'callback' => '::addRemoveAjaxCallback',
          'wrapper' => 'nypl-ip-checker-admin-form',
        ],
      ],
      'remove' => [
        '#type' => 'submit',
        '#value' => $this->t('Remove'),
        '#submit' => ['::removeCallback'],
        '#ajax' => [
          'callback' => '::addRemoveAjaxCallback',
          'wrapper' => 'nypl-ip-checker-admin-form',
        ],
      ],
    ];

    return $element;
  }

  /**
   * Callback for both ajax-enabled buttons.
   *
   * Selects and returns the fieldset with the names in it.
   */
  public function addRemoveAjaxCallback(array &$form, FormStateInterface $form_state) {
    return $form;
  }

  /**
   * AJAX callback for adding an element within the form.
   *
   * @param array $form
   *   The form.
   * @param \Drupal\Core\Form\FormStateInterface $form_state
   *   The form's state, as defined in Drupal core.
   */
  public function addCallback(array &$form, FormStateInterface $form_state) {
    // Get the array keys of the triggering element within $form.
    $trigger = $form_state->getTriggeringElement()['#parents'];

    // Add/remove actions add two levels, which we remove here.
    $parent = array_splice($trigger, 0, -2);

    // Use the helper method to get the parent element in the form.
    $parentElement = $this->addressFormFromArray($form, $parent);

    // Get the non-hashtagged array elements of the parent.
    $elements = Element::children($parentElement);

    // Assuming the actions are last, get the element key for the field to add.
    $addElement = $elements[count($elements) - 2];

    // Append the add element to the overall form keys.
    $parent[] = $addElement;

    // Pass the information needed to add a row via $form_state.
    $form_state->set('addElement', $parent);
    $form_state->setRebuild();
  }

  /**
   * Submit handler for the "remove one" button.
   *
   * Decrements the max counter and causes a form rebuild.
   */
  public function removeCallback(array &$form, FormStateInterface $form_state) {
    // Get the array keys of the triggering element within $form.
    $trigger = $form_state->getTriggeringElement()['#parents'];

    // Add/remove actions add two levels, which we remove here.
    $parent = array_splice($trigger, 0, -2);

    // Use the helper method to get the parent element in the form.
    $parentElement = $this->addressFormFromArray($form, $parent);

    // Get the non-hashtagged array elements of the parent.
    $elements = Element::children($parentElement);

    // Assuming the actions are last, get the element key for the field to add.
    $addElement = $elements[count($elements) - 2];

    // Append the add element to the overall form keys.
    $parent[] = $addElement;

    // Pass the information needed to add a row via $form_state.
    $form_state->set('removeElement', $parent);
    $form_state->setRebuild();
  }

  /**
   * Helper to get a form element from an array of keys.
   *
   * @param array $form
   *   The form.
   * @param array $addresses
   *   Array keys for an element in the form of count($addresses) depth.
   *
   * @return array
   *   The $form element referenced from the addresses.
   */
  public function addressFormFromArray(array $form, array $addresses): array {
    $addressed = $form;

    foreach ($addresses as $i => $key) {
      $addressed = $addressed[$key];
    }

    return $addressed;
  }

}