Question

It’s quite simple to program just one product to get sold via my payment system (api.payson.se) but buying many products at the same time in various amounts posed trouble for me since it was not implemented and I didn’t have a good idea how to do it. Now I have a solution that I just put together which works but the modelling and control flow is kind of very quick and dirty and I wonder whether this is even acceptable or should need a rewrite. The system now behaves so that I can enter the shop (step 1) and enter the amounts for the products I want to buy

Then if I press Buy (“Köp”) my Python calculates the sum correctly and this works whatever combination of amounts and products I have saying which the total is and this page could also list the specification but that is not implemented yet:

The total sum is Swedish currency is correct and it has written an order to my datastore with status “unpaid” and containing which products are ordered and what amount for every product in the datastore:

The user can then either cancel the purchase or go on and actually pay through the payment system api.payson.se:

So all I need to do is listen to the response from Payson and update the status of the orders that get paid. But my solution does not look very clean and I wonder if I can go on with code like that, the data model is two stringlists, one with the amounts and one with which product (Item ID) since that was the easiest way I could solve it but it is then not directly accessible and only from the lists. Is there a better data model I can use?

The code that does the handling is slightly messy and could use a better data model and a better algorithm than just strings and lists:

class ShopHandler(NewBaseHandler):

    @user_required
    def get(self):
        user = \
            auth_models.User.get_by_id(long(self.auth.get_user_by_session()['user_id'
                ]))
        self.render_jinja('shop.htm', items=Item.recent(), user=user)
        return ''

    @user_required
    def post(self, command):
        user = \
            auth_models.User.get_by_id(long(self.auth.get_user_by_session()['user_id'
                ]))
        logging.info('in shophandler http post item id'+self.request.get('item'))

        items = [ self.request.get('items[1]'),self.request.get('items[2]'),self.request.get('items[3]'),self.request.get('items[4]'),self.request.get('items[5]'),self.request.get('items[6]'),self.request.get('items[7]'),self.request.get('items[8]')   ]   

        amounts = [ self.request.get('amounts[1]'),self.request.get('amounts[2]'),self.request.get('amounts[3]'),self.request.get('amounts[4]'),self.request.get('amounts[5]'),self.request.get('amounts[6]'),self.request.get('amounts[7]'),self.request.get('amounts[8]')  ]
        total = 0
        total = int(self.request.get('amounts[1]'))* long(Item.get_by_id(long(self.request.get('items[1]'))).price_fraction()) if self.request.get('amounts[1]') else total
        total = total + int(self.request.get('amounts[2]'))* long(Item.get_by_id(long(self.request.get('items[2]'))).price_fraction()) if self.request.get('amounts[2]') else total
        total = total + int(self.request.get('amounts[3]'))* long(Item.get_by_id(long(self.request.get('items[3]'))).price_fraction()) if self.request.get('amounts[3]') else total
        total = total + int(self.request.get('amounts[4]'))* long(Item.get_by_id(long(self.request.get('items[4]'))).price_fraction()) if self.request.get('amounts[4]') else total
        total = total + int(self.request.get('amounts[5]'))* long(Item.get_by_id(long(self.request.get('items[5]'))).price_fraction()) if self.request.get('amounts[5]') else total
        total = total + int(self.request.get('amounts[6]'))* long(Item.get_by_id(long(self.request.get('items[6]'))).price_fraction()) if self.request.get('amounts[6]') else total
        total = total + int(self.request.get('amounts[7]'))* long(Item.get_by_id(long(self.request.get('items[7]'))).price_fraction()) if self.request.get('amounts[7]') else total
        total = total + int(self.request.get('amounts[8]'))* long(Item.get_by_id(long(self.request.get('items[8]'))).price_fraction()) if self.request.get('amounts[8]') else total
        logging.info('total:'+str(total))
        trimmed = str(total)+',00'
        order = model.Order(status='UNPAID')
        order.items = items
        order.amounts = amounts
        order.put()
        logging.info('order was written')
        ExtraCost = 0
        GuaranteeOffered = 2
        OkUrl = 'http://' + self.request.host + r'/paysonreceive/'
        Key = '3110fb33-6122-4032-b25a-329b430de6b6'
        text = '[e-mail]' + ':' + str(trimmed) + ':' + str(ExtraCost) \
            + ':' + OkUrl + ':' + str(GuaranteeOffered) + Key
        m = hashlib.md5()

        BuyerEmail = user.email
        AgentID = 11366
        self.render_jinja('order.htm', order=order, user=user, total=total, Generated_MD5_Hash_Value = hashlib.md5(text).hexdigest(), BuyerEmail=user.email, Description='Bnano Webshop', trimmed=trimmed, OkUrl=OkUrl, BuyerFirstName=user.firstname, BuyerLastName=user.lastname)

My model for the order, where not all fields are used, is

class Order(db.Model):
  '''a transaction'''
  item = db.ReferenceProperty(Item)
  items = db.StringListProperty()
  amounts = db.StringListProperty()
  owner = db.UserProperty()
  purchaser = db.UserProperty()
  created = db.DateTimeProperty(auto_now_add=True)
  status = db.StringProperty( choices=( 'NEW', 'CREATED', 'ERROR', 'CANCELLED', 'RETURNED', 'COMPLETED', 'UNPAID', 'PAID' ) )
  status_detail = db.StringProperty()
  reference = db.StringProperty()
  secret = db.StringProperty() # to verify return_url
  debug_request = db.TextProperty()
  debug_response = db.TextProperty()
  paykey = db.StringProperty()
  shipping = db.TextProperty()

And the model for a product ie an item is

class Item(db.Model):
  '''an item for sale'''
  owner = db.UserProperty() #optional
  created = db.DateTimeProperty(auto_now_add=True)
  title = db.StringProperty(required=True)
  price = db.IntegerProperty() # cents / fractions, use price_decimal to get price in dollar / wholes
  image = db.BlobProperty()
  enabled = db.BooleanProperty(default=True)
  silver = db.IntegerProperty() #number of silver

  def price_dollars( self ):
    return self.price / 100.0

  def price_fraction( self ):
    return self.price / 100.0

  def price_silver( self ): #number of silvers an item "is worth"
    return self.silver / 1000.000

  def price_decimal( self ):
    return decimal.Decimal( str( self.price / 100.0 ) )

  def price_display( self ):
    return str(self.price_fraction()).replace('.',',')

  @staticmethod
  def recent():
    return Item.all().filter( "enabled =", True ).order('-created').fetch(10)

I think you now have an idea what’s going on and that this kind of works towards the user but the code is not looking good. Do you think I can leave the code like this and go on and keep this “solution” or must I do a rewrite to make it more proper? There are only 8 products in the store and with this solution it becomes difficult to add a new Item for sale since then I must reprogram the script which is not perfect.

Could you comment or answer, I’d be very glad to get some feedback about this quick and dirty solution to my use case.

Thank you

Update

I did a rewrite to allow for adding new products and the following seems better than the previous:

class ShopHandler(NewBaseHandler):

    @user_required
    def get(self):
        user = \
            auth_models.User.get_by_id(long(self.auth.get_user_by_session()['user_id'
                ]))
        self.render_jinja('shop.htm', items=Item.recent(), user=user)
        return ''

    @user_required
    def post(self, command):
        user = \
            auth_models.User.get_by_id(long(self.auth.get_user_by_session()['user_id'
                ]))
        logging.info('in shophandler http post')

        total = 0
        order = model.Order(status='UNPAID')

        for item in self.request.POST:
            amount = self.request.POST[item]
            logging.info('item:'+str(item))
            purchase = Item.get_by_id(long(item))
            order.items.append(purchase.key())
            order.amounts.append(int(amount))
            order.put()
            price = purchase.price_fraction()
            logging.info('amount:'+str(amount))
            logging.info('product price:'+str(price))
            total = total + price*int(amount)

        logging.info('total:'+str(total))
        order.total = str(total)
        order.put()
        trimmed = str(total).replace('.',',') + '0'
        ExtraCost = 0
        GuaranteeOffered = 2
        OkUrl = 'http://' + self.request.host + r'/paysonreceive/'
        Key = '6230fb54-7842-3456-b43a-349b340de3b8'
        text = '[e-mail]' + ':' + str(trimmed) + ':' \
            + str(ExtraCost) + ':' + OkUrl + ':' \
            + str(GuaranteeOffered) + Key
        m = hashlib.md5()
        BuyerEmail = user.email  # if user.email else user.auth_id[0]
        AgentID = 11366
        self.render_jinja(
            'order.htm',
            order=order,
            user=user,
            total=total,
            Generated_MD5_Hash_Value=hashlib.md5(text).hexdigest(),
            BuyerEmail=user.email,
            Description='Bnano Webshop',
            trimmed=trimmed,
            OkUrl=OkUrl,
            BuyerFirstName=user.firstname,
            BuyerLastName=user.lastname,
            )

Answer 1

Man, this is a really strange code. If you will want to add new items in you shop you must rewrite you shop’s script.
At the first unlink your items from interface, you must send POST request to controller with your items ids and quantity, i don know how work gae request object, but it must be like that:
from your order page make POST request with dict of items which really need {“item_id”:”qnt”}.
When in the controller you can fetch all objects like:

for item, qnt in request.POST:
    {do something with each item, for example where you can sum total}

and etc
Don’t link controllers with your interfaces directly. You must write more abstraction code, if you want make really flexible app.