class DateTimeDatelistWidget

class DateTimeDatelistWidget extends DateTimeWidgetBase {
  
  /**
   * {@inheritdoc}
   */
  public static function defaultSettings() {
    return [
      'increment' => '15',
      'date_order' => 'YMD',
      'time_type' => '24',
    ] + parent::defaultSettings();
  }
  
  /**
   * {@inheritdoc}
   */
  public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
    $element = parent::formElement($items, $delta, $element, $form, $form_state);
    // Wrap all of the select elements with a fieldset.
    $element['#theme_wrappers'][] = 'fieldset';
    $date_order = $this->getSetting('date_order');
    if ($this->getFieldSetting('datetime_type') == 'datetime') {
      $time_type = $this->getSetting('time_type');
      $increment = $this->getSetting('increment');
    }
    else {
      $time_type = '';
      $increment = '';
    }
    // Set up the date part order array.
    $date_part_order = match ($date_order) {  'YMD' => [
        'year',
        'month',
        'day',
      ],
      'MDY' => [
        'month',
        'day',
        'year',
      ],
      'DMY' => [
        'day',
        'month',
        'year',
      ],
    
    };
    $date_part_order = match ($time_type) {  '24' => array_merge($date_part_order, [
        'hour',
        'minute',
      ]),
      '12' => array_merge($date_part_order, [
        'hour',
        'minute',
        'ampm',
      ]),
      default => $date_part_order,
    
    };
    $element['value'] = [
      '#type' => 'datelist',
      '#date_increment' => $increment,
      '#date_part_order' => $date_part_order,
    ] + $element['value'];
    return $element;
  }
  
  /**
   * {@inheritdoc}
   */
  public function settingsForm(array $form, FormStateInterface $form_state) {
    $element = parent::settingsForm($form, $form_state);
    $element['date_order'] = [
      '#type' => 'select',
      '#title' => $this->t('Date part order'),
      '#default_value' => $this->getSetting('date_order'),
      '#options' => [
        'MDY' => $this->t('Month/Day/Year'),
        'DMY' => $this->t('Day/Month/Year'),
        'YMD' => $this->t('Year/Month/Day'),
      ],
    ];
    if ($this->getFieldSetting('datetime_type') == 'datetime') {
      $element['time_type'] = [
        '#type' => 'select',
        '#title' => $this->t('Time type'),
        '#default_value' => $this->getSetting('time_type'),
        '#options' => [
          '24' => $this->t('24 hour time'),
          '12' => $this->t('12 hour time'),
        ],
      ];
      $element['increment'] = [
        '#type' => 'select',
        '#title' => $this->t('Time increments'),
        '#default_value' => $this->getSetting('increment'),
        '#options' => [
          1 => $this->t('1 minute'),
          5 => $this->t('@count minutes', [
            '@count' => 5,
          ]),
          10 => $this->t('@count minutes', [
            '@count' => 10,
          ]),
          15 => $this->t('@count minutes', [
            '@count' => 15,
          ]),
          30 => $this->t('@count minutes', [
            '@count' => 30,
          ]),
        ],
      ];
    }
    else {
      $element['time_type'] = [
        '#type' => 'hidden',
        '#value' => 'none',
      ];
      $element['increment'] = [
        '#type' => 'hidden',
        '#value' => $this->getSetting('increment'),
      ];
    }
    return $element;
  }
  
  /**
   * {@inheritdoc}
   */
  public function settingsSummary() {
    $summary = [];
    $summary[] = $this->t('Date part order: @order', [
      '@order' => $this->getSetting('date_order'),
    ]);
    if ($this->getFieldSetting('datetime_type') == 'datetime') {
      $summary[] = $this->t('Time type: @time_type', [
        '@time_type' => $this->getSetting('time_type'),
      ]);
      $summary[] = $this->t('Time increments: @increment', [
        '@increment' => $this->getSetting('increment'),
      ]);
    }
    return $summary;
  }

}