modmore SimpleCart - Adjust cart quantities based on stock

scCartQuantities.snippet.php

<?php
/**
 * Created by PhpStorm.
 * User: Mat
 * Date: 6/19/2017
 * Time: 3:33 AM
 */
$sc = $modx->getService('simplecart','SimpleCart',$modx->getOption('simplecart.core_path',null,$modx->getOption('core_path').'components/simplecart/').'model/simplecart/',$scriptProperties);

if (!($sc instanceof SimpleCart)) return '';
$controller = $sc->loadController('Cart', 'ContentsController');
$controller->initialize();
$controller->loadProducts();
foreach ($controller->getProducts() as $product) {
    $productid = $product->id;
    $resource = $modx->getObject('modResource',$productid);
    $meta = (($resource instanceof scProductResource) ? $resource->getProductMeta() : $sc->getDeprecatedProductMeta($resource));
    if(
        $product->totals['quantity'] > $meta['product_stock'] && $meta['product_stock'] !== null
    ){
        foreach($controller->storageData['products'] as $key=>$value){
            if($value['productid'] == $productid){
                $controller->storageData['products'][$key]['quantity'] = $meta['product_stock'];
                if($meta['product_stock'] <= 0){
                    unset($controller->storageData['products'][$key]);
                }
                $controller->setStorageData();
                $url = $modx->makeUrl($modx->resource->get('id'), '', array('quantity'=>'adjusted'), 'https');
                $modx->sendRedirect($url);
            }
        }
    }
}
if(isset($_GET['quantity']) && $_GET['quantity'] == 'adjusted'){
    echo '<div class="btn success">Product quantities have been adjusted based on current availability.</div>';
}

It's better to use return in snippets, instead of echo due to the way the parser handles things ;) Other than that, looks very useful!