class Number

class Number extends FormElement {
    
    /**
     * {@inheritdoc}
     */
    public function getInfo() {
        $class = get_class($this);
        return [
            '#input' => TRUE,
            '#step' => 1,
            '#process' => [
                [
                    $class,
                    'processAjaxForm',
                ],
            ],
            '#element_validate' => [
                [
                    $class,
                    'validateNumber',
                ],
            ],
            '#pre_render' => [
                [
                    $class,
                    'preRenderNumber',
                ],
            ],
            '#theme' => 'input__number',
            '#theme_wrappers' => [
                'form_element',
            ],
        ];
    }
    
    /**
     * Form element validation handler for #type 'number'.
     *
     * Note that #required is validated by _form_validate() already.
     */
    public static function validateNumber(&$element, FormStateInterface $form_state, &$complete_form) {
        $value = $element['#value'];
        if ($value === '') {
            return;
        }
        $name = empty($element['#title']) ? $element['#parents'][0] : $element['#title'];
        // Ensure the input is numeric.
        if (!is_numeric($value)) {
            $form_state->setError($element, t('%name must be a number.', [
                '%name' => $name,
            ]));
            return;
        }
        // Ensure that the input is greater than the #min property, if set.
        if (isset($element['#min']) && $value < $element['#min']) {
            $form_state->setError($element, t('%name must be higher than or equal to %min.', [
                '%name' => $name,
                '%min' => $element['#min'],
            ]));
        }
        // Ensure that the input is less than the #max property, if set.
        if (isset($element['#max']) && $value > $element['#max']) {
            $form_state->setError($element, t('%name must be lower than or equal to %max.', [
                '%name' => $name,
                '%max' => $element['#max'],
            ]));
        }
        if (isset($element['#step']) && strtolower($element['#step']) != 'any') {
            // Check that the input is an allowed multiple of #step (offset by #min if
            // #min is set).
            $offset = isset($element['#min']) ? $element['#min'] : 0.0;
            if (!NumberUtility::validStep($value, $element['#step'], $offset)) {
                $form_state->setError($element, t('%name is not a valid number.', [
                    '%name' => $name,
                ]));
            }
        }
    }
    
    /**
     * Prepares a #type 'number' render element for input.html.twig.
     *
     * @param array $element
     *   An associative array containing the properties of the element.
     *   Properties used: #title, #value, #description, #min, #max, #placeholder,
     *   #required, #attributes, #step, #size.
     *
     * @return array
     *   The $element with prepared variables ready for input.html.twig.
     */
    public static function preRenderNumber($element) {
        $element['#attributes']['type'] = 'number';
        Element::setAttributes($element, [
            'id',
            'name',
            'value',
            'step',
            'min',
            'max',
            'placeholder',
            'size',
        ]);
        static::setAttributes($element, [
            'form-number',
        ]);
        return $element;
    }

}