Add custom discount and show it on Cart and checkout in Magento 2

Question

I want to add a custom discount on the order total and want to show it on Cart and Checkout Page.

But, I want to apply that discount based on the Loyalty Points available for Customers. I have added a Loyalty Form on the checkout page.

When that form is submitted then and then I want to apply that discount. So How can I make a custom post API and achieve this in Magento 2.

Thanks.

Answer 1

Try with sales.xml in you module etc folder

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->    
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Sales:etc/sales.xsd">
     <section name="quote">
       <group name="totals">
         <item name="customer_discount" instance="Vendor\Module\Model\Total\Quote\Custom" sort_order="400"/>
       </group>
     </section>
</config>

Set the value of discount

<?php
namespace Vendor\Module\Model\Total\Quote;

class Custom extends \Magento\Quote\Model\Quote\Address\Total\AbstractTotal
    {
       /**
        * @var \Magento\Framework\Pricing\PriceCurrencyInterface
        */
       protected $priceCurrency;
       /**
        * Custom constructor.
        * @param \Magento\Framework\Pricing\PriceCurrencyInterface $priceCurrency
        */
       public function __construct(
           \Magento\Framework\Pricing\PriceCurrencyInterface $priceCurrency
       ){
           $this->priceCurrency = $priceCurrency;
       }

       public function collect(
           \Magento\Quote\Model\Quote $quote,
           \Magento\Quote\Api\Data\ShippingAssignmentInterface $shippingAssignment,
           \Magento\Quote\Model\Quote\Address\Total $total
       )
       {
           parent::collect($quote, $shippingAssignment, $total);
               $baseDiscount = 10;
               $discount =  $this->priceCurrency->convert($baseDiscount);
               $total->addTotalAmount('customdiscount', -$discount);
               $total->addBaseTotalAmount('customdiscount', -$baseDiscount);
               $total->setBaseGrandTotal($total->getBaseGrandTotal() - $baseDiscount);
               $quote->setCustomDiscount(-$discount);
           return $this;
       }
    }

Answer 2

If you want an advanced function my suggestion:

https://github.com/hodongnhut/magento2-payment-discount