So I realized that in using the WP REST API to create orders, the discount_total parameter shows the discount amount (which is probably calculated by subtracting the line_items['total'] value from the total cost of the items the customer purchased).

I am not entirely sure if this is true though as it’s just a temporary solution I came up with to understand how WOOCOMMERCE does the discount calculation.

So in my code snippet below, I mocked an order request via the WP API with an externally calculated discount amount after which I passed the new $totalPrice value to the API so that it’ll reflect the discount on the Admin Dashboard. The code WORKED and the discount was reflected on the dashboard

   //code snippet
   $order_data = [
        'payment_method' => 'bacs',
        'payment_method_title' => 'Checkout',
        'customer_id' => intval($customer_id),
        'transaction_id' => (string)$transaction_id,
        'set_paid' => true,
        'status' => 'completed',
        'billing' => $billing_data,
        'shipping' => $shipping_data,
        'meta_data' => array(
            array(
                'key' => 'created by',
                'value' => 'api request
            )
        ),
        'line_items' => array(
            array(
                'product_id' => intval($product_id),
                'quantity' => intval($quantityToBuy),
                'total' => (string)$totalPrice,
            )
        ),
        'shipping_lines' => array(
            array(
                'method_id' => 'free_shipping',
                'method_title' => 'Free Shipping',
                'total' => '0.00'
            )
        ),
    ];

However when I repeated the same process for orders that included COUPONS, only the coupon discount was reflected.

   $order_data = [
        'payment_method' => 'bacs',
        'payment_method_title' => 'Checkout',
        'customer_id' => intval($customer_id),
        'transaction_id' => (string)$transaction_id,
        'set_paid' => true,
        'status' => 'completed',
        'billing' => $billing_data,
        'shipping' => $shipping_data,
        'meta_data' => array(
            array(
                'key' => 'created by',
                'value' => 'api request'
            )
        ),
        'line_items' => array(
            array(
                'product_id' => intval($product_id),
                'quantity' => intval($quantityToBuy),
                'total' => (string)$totalPrice,
            )
        ),
        'shipping_lines' => array(
            array(
                'method_id' => 'free_shipping',
                'method_title' => 'Free Shipping',
                'total' => '0.00'
            )
        ),
        'coupon_lines' => array(
            array(
                'code' => (string)$coupon_code
            )
        )
    ];

So in cases where a customer uses a coupon in addition to some other discount, the total amount to be paid by the user would be different (lesser) than the amount reflected on the dashboard.

How do I resolve this issue, I am open to any suggestions.

Thank you