product-based-order-limit.php

<?php
/**
if a slot has already reached the max quanity allowed 
for the product and user has this product in his cart then the slot will be removed
*/
class pisol_quanity_limit_for_product{
	
	private $product_id = 637; // this is the product for order restriction
	private $limit = 2; // this is the slot limit of product quantity, 
	
	function __construct(){
		
		add_filter('pisol_disable_order_limit_check', function(){ return true; });
		add_filter('pisol_dtt_time_slot_filter', array($this,'timeFilter'),100, 2);
	}
	
	function timeFilter($slots, $date){
		
		foreach($slots as $key => $slot){
			$orders = $this->getOrdersInSlot($slot['id'], $date);
			if(!empty($orders)){
				$product_quantity = $this->productQuantityInOrders($orders);
				if($product_quantity >= $this->limit){
					unset($slots[$key]);
				}
			}
		}
		return $slots;
	}
	
	function getOrdersInSlot( $slot, $date){
		$args = array(
            'limit' => -1,
            'status' => array('pending', 'processing', 'on-hold', 'completed'),
            'meta_query' => array(
				'relation'=>'AND',
                array(
                    'key' => 'pi_system_delivery_date',
                    'compare' => '==',
                    'value'   => $date,
				),
				array(
					'key' => 'pi_delivery_time',
					'compare' => 'LIKE',
					'value'   => $slot,
				)
            )
        );
        
        $orders = wc_get_orders($args);

		return $orders;
	}

	function productQuantityInOrders($orders){
		$total_qty = 0;
		foreach($orders as $order){
			
			$order_items = $order->get_items();
        	foreach( $order_items as $item ) {
				$product_id = $item['product_id'];
				$quantity = $item['quantity'];
				if($product_id == $this->product_id){
					$total_qty = $total_qty + $quantity;
				}
			}
		}
		return $total_qty;
	}
}
new pisol_quanity_limit_for_product();