minimum_maximum_order.module

<?php

/**
 * @file
 * Contains minimum_maximum_order.module.
 */

use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\Form\FormStateInterface;

/**
 * Implements hook_help().
 */
function minimum_maximum_order_help($route_name, RouteMatchInterface $route_match) {
  switch ($route_name) {
    // Main module help for the minimum_maximum_order module.
    case 'help.page.minimum_maximum_order':
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('Validate Order Based On Minimum and Maximum Total') . '</p>';
      return $output;

    default:
  }
}

function minimum_maximum_order_form_alter(array &$form, FormStateInterface $form_state, $form_id) {
  if (strpos($form_id,"views_form_commerce_cart_form_default_") !== false) {
    $minimum = $config = \Drupal::config('minimum_maximum_order.adminsettings')->get('minimum_order');
    $order_id = $form['output'][0]['#view']->footer['commerce_order_total']->view->args[0];
    $orders = \Drupal::entityTypeManager()
                ->getStorage('commerce_order')
                ->loadByProperties(['order_id' => $order_id]);
    $order = reset($orders);
    $total_price = $order->getTotalprice()->getNumber();
    if ($total_price < $minimum) {
      // make checkout button as disabled
      $form['actions']['checkout']['#attributes']['disabled'] = true;
      $form['#prefix'] = '<div class="alert alert-danger" role="alert">$35 Minimum not met</div>';

    }
  }
}