django-shop-payer-backend 0.1.7
Payment backend for django SHOP and Payer.
License: MIT

Django SHOP Payer Backend
=========================

|Build Status| |Coverage Status| |Latest Version|

Django SHOP payment backend for `Payer <http://payer.se>`__. Uses
`python-payer-api <https://github.com/dessibelle/python-payer-api>`__
for interacting with the API.

Installation
------------

::

    pip install django-shop-payer-backend

Add to installed apps

.. code:: python

    INSTALLED_APPS = [
        ...
        'polymorphic',
        'shop'
        'shop.addressmodel',
        'django_shop_payer_backend',
        ...
    ]

Configure one ore more payment backends

.. code:: python

    SHOP_PAYMENT_BACKENDS = [
        'django_shop_payer_backend.backends.PayerCreditCardPaymentBackend',
        'django_shop_payer_backend.backends.PayerBankPaymentBackend',
        'django_shop_payer_backend.backends.PayerInvoicePaymentBackend',
        'django_shop_payer_backend.backends.PayerPhonePaymentBackend',
    ]

You could also use the ``GenericPayerBackend`` in order to let the user
choose payment method *after* being redirected to Payer, or define a
subclass of your own, listing a custom set of methods in the
``payment_methods`` property. This might be a good option if you are
using the Payer backend along with other backends such as Paypal etc.

Configuration
-------------

Add your keys to settings.py

.. code:: python

    SHOP_PAYER_BACKEND_AGENT_ID = "AGENT_ID"
    SHOP_PAYER_BACKEND_ID1 = "6866ef97a972ba3a2c6ff8bb2812981054770162"
    SHOP_PAYER_BACKEND_ID2 = "1388ac756f07b0dda2961436ba8596c7b7995e94"

The following settings are optional

.. code:: python

    # Used for white/blacklisting callback IPs
    SHOP_PAYER_BACKEND_IP_WHITELIST = ["192.168.0.1"]
    SHOP_PAYER_BACKEND_IP_BLACKLIST = ["10.0.1.1"] 
    # Used for suppliying an address model
    SHOP_PAYER_BACKEND_ADDRESS_HANDLER = 'project.app.path.to.address_model_callback'

    SHOP_PAYER_BACKEND_HIDE_DETAILS = False     # Hide order details during payment
    SHOP_PAYER_BACKEND_DEBUG_MODE = 'verbose'   # 'silent', 'brief'
    SHOP_PAYER_BACKEND_TEST_MODE = True

Considerations
--------------

Due to the fact that django SHOP by default does not store any relation
between the Order model and the AddressModel model there is no good way
for payment backends to determine the shipping/billing address for a
given order. For some backends this might not be an issue, but in this
case Payer expects to address data in the order details.

django-shop-payer-backend tries to tackle by determining the order
(billing) address using the following strategy:

1. Try to fetch AddressModel from current user (if
   ``user.is_authenticated()``).
2. Try to load an AddressModel using a callback supplied in the
   ``SHOP_PAYER_BACKEND_ADDRESS_HANDLER`` setting.
3. Try to extract address details from ``order.billing_address_text`` by
   reverse parsing the address template used by django SHOP.
4. Let you override/complete the data returned using the above methods
   using the ``populate_buyer_details_dict`` signal.

This has two implications:

1. For non-authenticated users it is simply not possible get an
   AddressModel object using the default setup. In this case a reverse
   parsing of the address template string django SHOP uses to store the
   textual address representation on the Order object. Due to the
   somewhat fragile nature of this parsing method, you should take
   extreme precautions when modifying the ``SHOP_ADDRESS_TEMPLATE``
   setting. For the parser to function it is recommended that you use
   some form identifying "key" to identify each keyword (as with
   "Name:"" etc. in the default pattern). Patterns such as
   ``%(name)s, %(address)s,[...]`` will likely fail as there is nothing
   differentiating the ``name`` and ``address`` keywords in the string
   format, and alas the regexp will not be able to identify the keywords
   correctly.
2. Fields supported by the Payer API that do not have an obvious
   counterpart on the AddressModel model (e.g. email, phone,
   organisation, etc.) will unsurprisingly not be included in the
   PayerBuyerDetails data using the default settings. To make sure they
   are included, use the methods described in the *Extensibility*
   section below.

The way to tackle both of the issues outlined above, is probably to add
a foreign key to AddressModel on Order and store the object used when
setting ``order.billing_address_text``. That way you could add a address
model callback handler (described below), which will let you return that
(or any other) object to the backend.

Extensibility
-------------

Let's say you have a custom address model based on
``shop.addressmodel.models.Address`` which adds the field ``company``.
Naturally you would want this data sent to Payer as well, in order to
have it appear on invoices etc. To accomplish that, add a receiver for
the ``populate_buyer_details_dict`` signal and update the buyer details
dict like so:

.. code:: python

    from django_shop_payer_backend.helper import populate_buyer_details_dict
    from django.dispatch import receiver

    @receiver(populate_buyer_details_dict)
    def add_additional_buyer_details(sender, **kwargs):

        buyer_details_dict = kwargs.get('buyer_details_dict', None)
        user = kwargs.get('user', None)
        address = kwargs.get('address', None)
        order = kwargs.get('order', None)

        buyer_details_dict.update({
            'organisation': address.company,
        })

There is a similar signal, ``populate_order_item_dict``, for order
items, allowing you to modify the data that before the PayerOrderItem
object is initialized. This can be useful for example if your Product
model has a field holding VAT percentages, in which case you could
inject that value using this method.

Another option for supplying an address to the backend is to implement
and address callback handler, and return an AddressModel object. This is
a good option if you are using a custom Order model that has foreign
keys to the AddressModel. In that case, you can implement a callback
something along the lines of the following:

.. code:: python

    def address_model_callback(*args, **kwargs):

        address = kwargs.get('address', None)
        order = kwargs.get('order', None)

        if address is None and order is not None:
            try:
                address = order.billing_address
            except Exception:
                pass

        return address

And add the following to ``settings.py``:

.. code:: python

    SHOP_PAYER_BACKEND_ADDRESS_HANDLER = 'project.app.path.to.address_model_callback'

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