Support discounts in basket

[judgej]

Moved from Ticket #26

The earlier SagePay spec (2013-03-25) this package was coded from, did not document the discount records in the basket. This is now documented in the later version (2013-09-30). The API remains at version 3.00

The current workaround in the meantime is to extend the BasketAbstract and code your own discounts.

[dignat]

hello,
What you mean with code your own discounts

[judgej]

The details of how discounts are supported by Sage Pay can be found here:

#26 (comment)

Instead of using the Basket as it is currently defined, you would write your own extending the BasketAbstract. That custom basket would add in methods like addDiscount($fixed, $description). That would store the discount details in the basket. Then override toXml() to output those discounts in the XML that Sage Pay receives.

That way the discounts are sent to Sage Pay, and when the customer goes to the Sage Pay site to make a payment, they see the "Discounts" line on their order, separate to the order lines. Also you will see it in your control panel (I think).

I've not implemented this yet, and have never needed it. If anyone else needs it and can do a pull request with an implementation, then I would be happy to include it. Otherwise just define your own Basket:

<?php namespace My\Project\Namespace;
class Basket extends Academe\SagePay\Model\BasketAbstract
{
    // Add support for discounts here...
}

[judgej]

There are half a dozen other pieces of data that can go into a basket too, that has not been implemented - carRentail, cruise, tourOperator, airline, dinerCustomer. They are all pretty niche.

[judgej]

Did that answer your question? Are you looking to support discounts on a project, or were you just curious about what it meant?

[dignat]

Hello,
Thank you , your answer did answer my question, and yes I am looking to support discounts in our team project. I did try to include discounts in basket with the SagePay BasketXML itself, as according to the documentation (protocol 3.0 )the discounts are part of the basket root in Basket XML and can be added to the basket, but unfortunately I was not able to see the discounts in basket (only items in SagePay account in section additional information). I had a long email exchange witth SagePay support, but they only could confirm that the XML I am sending is correct, and the can not find any reason discounts to not appear in basket.

[judgej]

I'm trying to add this feature, and this is being added to the end of the basket, just before the closing </basket> tag:

<discounts>
<discount><fixed>1.20</fixed><description>Discount One!</description></discount>
<discount><fixed>10.00</fixed><description>Another Discount!</description></discount>
</discounts>

Sage Pay is giving me:

3021: The Basket format is invalid.

So you have got further than me. I'm guessing it is a typo, but I just can't see it.

[judgej]

The example on the Sage Pay site does not have the fixed amounts formatted in the currency format, which is a bit strange:

http://www.sagepay.co.uk/support/basket-xml

<discounts> 
    <discount>
        <fixed>5</fixed>
        <description>Save 5 pounds</description>
    </discount> 
    <discount>
        <fixed>1</fixed>
        <description>Spend 5 pounds and save 1 pound</description>
    </discount> 
</discounts>

[judgej]

I'll push the changes to master so you can have a play with it if you wish. Use it like this:

$basket->addDiscount(1.00, 'A discount because you are a lovely customer');

That breaks it for me, but you may have better luck.

[judgej]

It does say in the specs that:

The value sent will be subtracted from the overall total.

What that means is unclear to me. Does that mean when I am asking for £10 to be paid, and add a discount of £2, then Sage Pay only really asks the customer for £8? If so, I don't like that. I'm also assuming the contents of the basket must add up correctly to the amount being asked for (before or after discount has been added, I don't know).

[judgej]

Ah, covered:

No validation is performed on the totals of the basket, it is your responsibility to ensure that the amounts are correct and that the total of the basket matches the transaction
amount sent in the Registration.

The "your responsibility" bit is a given regardless of whether it is validated. But not being validated means Sage Pay just treat it as metadata for display purposes only. With the old-style basket, all the amounts were validated and had to sum up to the totals exactly.

[judgej]

Doh:

The XML tags should follow the order stated in the table.

Why is this even a thing? I'd love to hear the reasoning.

Order changed and basket now validates. It does not appear on the front end, as you state. This is the new responsive front end, so it may just be teething troubles. Do you see the discounts in the control panel (MySagePay)?

[judgej]

Actually, they do appear. You need to enter CC details (on SP Server) then expand the "Your Shopping Basket" block on the next page (why it's not expanded already for desktop, is probably another teething thing) and the discount will appear in the list of lines, between the items and the delivery charge.

What concerns me here, is that despite what the documentation states, the totals from the basket are all added up (and subtracted in the case of the discounts) and this gives the amount the customer will be asked for. So make sure your basket is 100% correct, and contains absolutely everything that needs to go into it (in 2000 characters or less) otherwise you may not be asking for the full amount. I might put a function in the basket to add up the total amount locally, so you can double-check at your application end. A Currency package will be useful here, so we can deal with the basket lines as integers and avoid rounding errors when adding stuff up. The new Sage Pay Integration API - replacing V3.00 at some distant time - already does this, with all amounts handled as integers (pennies, cents etc.)

I'll push the fix now.