Appointments+ Update Inventory

app_mp_inventory.php

<?php
/*
Plugin Name: Appointments+ Update Inventory
Plugin URI: https://premium.wpmudev.org/
Description: Requires Appointments+ and MarketPress. After new appointment it should update product incventory.
Author: Panos Lyrakis @ WPMUDEV
Author URI: https://premium.wpmudev.org/
License: GPLv2 or later
*/

if( ! class_exists( 'WPMUDEV_App_MP_Inventory' ) ){

	class WPMUDEV_App_MP_Inventory{
		private static $_instance = null;

		public static function get_instance() {
			if ( is_null( self::$_instance ) ) {
				self::$_instance = new WPMUDEV_App_MP_Inventory();
			}
			return self::$_instance;
		}

		private function __construct(){

			add_action( 'mp_order/new_order', array( $this, 'maybe_update_inventory' ), 10 );

		}

		public function maybe_update_inventory( $order ){

			$payment_method = mp_get_post_value( 'payment_method', '' );

			$cart_info = is_object( $order ) && is_callable( array( $order, 'get_cart' ) )
				? $order->get_cart()->get_items()
				: ( isset( $order->mp_cart_info ) ? $order->mp_cart_info : array() )
			;
	
			if( !is_object( $cart_info ) || epmty( $cart_info ) ){
				global $mp_cart;
				$cart_info = $mp_cart->get_items();
			}

			$variation_type = MP_Product::get_variations_post_type();
	
			if ( is_array( $cart_info ) && count( $cart_info ) ) {
				
				foreach ( $cart_info as $cart_id => $count ) {
					$variation = get_post( $cart_id );
					if ( ! empty( $variation->post_type ) && $variation_type === $variation->post_type && $this->_is_app_mp_page( $variation->post_parent ) ) {
						$product_id = $variation->post_parent;
						$item = new MP_Product( $product_id );

						if ( $item->get_meta( 'inventory_tracking' ) ) {

							$stock = $item->get_stock();

							// Update inventory
							$new_stock = ( $stock - $item->qty );

							$item->update_meta( 'inventory', $new_stock );
							$item->update_meta( 'inv_inventory', $new_stock );

							// Send low-stock notification if needed
							if ( $new_stock <= mp_get_setting( 'inventory_threshhold' ) ) {
								$item->low_stock_notification();
							}

							if ( mp_get_setting( 'inventory_remove' ) && $new_stock <= 0 ) {
								// Flag product as out of stock - @version 2.9.5.8
								wp_update_post( array(
									'ID'          => $item->ID,
									'post_status' => 'draft'
								) );
							}
						}
						
					}
				}
			}
			
		}

		private function _is_app_mp_page ( $product ) {

			$product = get_post($product);
			$result = is_object( $product ) && strpos( $product->post_content, '[app_' ) !== false
				? true
				: false
			;
			// Maybe required for templates
			return apply_filters( 'app_is_mp_page', $result, $product );

		}

	}

	add_action( 'plugins_loaded', function(){
        $GLOBALS['WPMUDEV_App_MP_Inventory'] = WPMUDEV_App_MP_Inventory::get_instance();
    }, 10 );

}