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;
    }

}