Plugin pre order product

<?php
defined('_JEXEC') or die;

class plgHikashopHika_preorder_stock_auto extends JPlugin
{
	
	function onAfterProductCreate(&$product) {
		
		$productClass	= hikashop_get('class.product');
		$db				= JFactory::getDbo();
		
		$categories		= self::getCategoriesIdWithChilds($this->params->get('cat', ''));
		if(array_intersect($categories, $product->categories)){
			if($product->product_quantity == 0){
				$query = $db->getQuery(true);
				$fields = array(
					$db->quoteName('product_quantity').' = '.$db->quote($this->params->get('qty', 0)),
					$db->quoteName('product_preorder').' = '.$db->quote($this->params->get('qty', 0))
				);
				$conditions = array(
					$db->quoteName('product_id').' = '.$db->quote($product->product_id)
				);
				$query->update($db->quoteName('#__hikashop_product'))->set($fields)->where($conditions);
				$db->setQuery($query);
				$result = $db->execute();
			}
			else{
				$query = $db->getQuery(true);
				$fields = array(
					$db->quoteName('product_preorder').' = '.$db->quote(0)
				);
				$conditions = array(
					$db->quoteName('product_id').' = '.$db->quote($product->product_id)
				);
				$query->update($db->quoteName('#__hikashop_product'))->set($fields)->where($conditions);
				$db->setQuery($query);
				$result = $db->execute();
			}
		}
		
	}
	
	function  onAfterProductUpdate(&$product){
		
		$productClass	= hikashop_get('class.product');
		$db				= JFactory::getDbo();
		
		$categories		= self::getCategoriesIdWithChilds($this->params->get('cat', ''));
		if(array_intersect($categories, $product->categories)){
			if($product->product_quantity == 0){
				$query = $db->getQuery(true);
				$fields = array(
					$db->quoteName('product_quantity').' = '.$db->quote($this->params->get('qty', 0)),
					$db->quoteName('product_preorder').' = '.$db->quote($this->params->get('qty', 0))
				);
				$conditions = array(
					$db->quoteName('product_id').' = '.$db->quote($product->product_id)
				);
				$query->update($db->quoteName('#__hikashop_product'))->set($fields)->where($conditions);
				$db->setQuery($query);
				$result = $db->execute();
			}
			else{
				$query = $db->getQuery(true);
				$fields = array(
					$db->quoteName('product_preorder').' = '.$db->quote(0)
				);
				$conditions = array(
					$db->quoteName('product_id').' = '.$db->quote($product->product_id)
				);
				$query->update($db->quoteName('#__hikashop_product'))->set($fields)->where($conditions);
				$db->setQuery($query);
				$result = $db->execute();
			}
		}
	
	}
	
	function  onAfterOrderUpdate(&$order,&$send_email) { 
	
		$db				= JFactory::getDBO();
		$config			=& hikashop_config();
		$confirmed		= $config->get('order_confirmed_status');
		$cancelled		= $config->get('order_cancelled_status');
		$orderClass		= hikashop_get('class.order');
		$productClass	= hikashop_get('class.product');
		$orderInDb		= $orderClass->loadFullOrder($order->order_id);

		if(!isset($order->order_status))
			return true;
		if(!empty($order->order_type) && $order->order_type != 'sale')
			return true;
		if($order->order_status != $confirmed) {
			return true;
		}
		if(isset($order->old->order_status) && $order->old->order_status == $confirmed) {
			return true;
		}

		if($order->order_status == $confirmed AND $order->old->order_status != $cancelled){
			
			$db->setQuery('SELECT * FROM #__hikashop_order_product WHERE order_id = '.$order->order_id);
			$products = $db->loadAssocList();

			foreach($products as $product){
				$product = json_decode(json_encode($product));
				
				$categories		= self::getCategoriesIdWithChilds($this->params->get('cat', ''));
				if(array_intersect($categories, $product->categories)){
					if($product->product_quantity == 0){
						$query = $db->getQuery(true);
						$fields = array(
							$db->quoteName('product_quantity').' = '.$db->quote($this->params->get('qty', 0)),
							$db->quoteName('product_preorder').' = '.$db->quote($this->params->get('qty', 0))
						);
						$conditions = array(
							$db->quoteName('product_id').' = '.$db->quote($product->product_id)
						);
						$query->update($db->quoteName('#__hikashop_product'))->set($fields)->where($conditions);
						$db->setQuery($query);
						$result = $db->execute();
					}
					else{
						$query = $db->getQuery(true);
						$fields = array(
							$db->quoteName('product_preorder').' = '.$db->quote(0)
						);
						$conditions = array(
							$db->quoteName('product_id').' = '.$db->quote($product->product_id)
						);
						$query->update($db->quoteName('#__hikashop_product'))->set($fields)->where($conditions);
						$db->setQuery($query);
						$result = $db->execute();
					}
				}
			}
			
		}
		
	}
		
	function getCategoriesId($root){
		
		$db = JFactory::getDBO();
		
		$query = 'SELECT category_id FROM #__hikashop_category WHERE category_published = 1 AND category_parent_id = '.$root.' ORDER BY category_left ASC';
		$db->setQuery($query);
		$items = $db->loadColumn();

		return $items;
			
	}
	
	function getCategoriesIdWithChilds($root = 1, $withRoot = true){
		
		$list	= self::getCategoriesId($root);
		$catids	= array();
		
		if($withRoot == true){
			$catids[] = $root;
		}
		if(!empty($list)){
			foreach($list as $item){
				if(!in_array($item, $catids)){
					$catids[] = $item;
				}
				if(count(self::getCategoriesId($item))){
					$catids = array_merge($catids, self::getCategoriesIdWithChilds($item));
				}
			}
		}

		return array_unique($catids);
			
	}
	
}