Package: django-oscar-accounts-wt
A ‘managed account’ is an allocation of money that can be debited and credited.
This package provides managed account functionality for use with the e-commerce
frameworkOscar.  It can also be used standalone without Oscar.Accounts can be used to implement a variety of interesting components,
including:GiftcardsWeb accountsLoyalty schemesBasically anything that involves tracking the movement of funds within a closed
system.This package usesdouble-entry bookkeepingwhere every transaction is
recorded twice (once for the source and once for the destination).  This
ensures the books always balance and there is full audit trail of all
transactional activity.If your project manages money, you should be using a library like this.  Your
finance people will thank you.FeaturesAn account has a credit limit which defaults to zero.  Accounts can be set up
with no credit limit so that they are a ‘source’ of money within the system.
At least one account must be set up without a credit limit in order for money
to move around the system.Accounts can have:
- No users assigned
- A single “primary” user - this is the most common case
- A set of users assignedA user can have multiple accountsAn account can have a start and end date to allow its usage in a limited time
windowAn account can be restricted so that it can only be used to pay for a range of
products.Accounts can be categorisedScreenshotsInstallationInstall using pip:pipinstalldjango-oscar-accountsand addoscar_accountstoINSTALLED_APPS.  Runnningmanage.py migrate oscar_accountswill create the appropriate database tables. To create initial
some core accounts and account-types usemanage.py oscar_accounts_init.
The names of these accounts can be controlled using settings (see below).If running with Oscar, add an additional path to yourTEMPLATE_DIRS:fromaccountsimportTEMPLATE_DIRasACCOUNTS_TEMPLATE_DIRTEMPLATE_DIRS=(...ACCOUNTS_TEMPLATE_DIR)This allows the templates to be customised by overriding blocks instead of
replacing the entire template.In order to make the accounts accessible via the Oscar dashboard you need to
append it to yourOSCAR_DASHBOARD_NAVIGATIONfromoscar.defaultsimport*OSCAR_DASHBOARD_NAVIGATION.append({'label':'Accounts','icon':'icon-globe','children':[{'label':'Accounts','url_name':'accounts-list',},{'label':'Transfers','url_name':'transfers-list',},{'label':'Deferred income report','url_name':'report-deferred-income',},{'label':'Profit/loss report','url_name':'report-profit-loss',},]})Furthermore you need to add the url-pattern to yoururls.pyfromoscar_accounts.dashboard.appimportapplicationasaccounts_app# ...urlpatterns=[...url(r'^dashboard/accounts/',include(accounts_app.urls)),]You should also set-up a cronjob that calls:./manage.py close_expired_accountsto close any expired accounts and transfer their funds to the ‘expired’
account.APICreate account instances using the manager:fromdecimalimportDecimalimportdatetimefromdjango.contrib.auth.modelsimportUserfromoscar_accountsimportmodelsanonymous_account=models.Account.objects.create()barry=User.objects.get(username="barry")user_account=models.Account.objects.create(primary_user=barry)no_credit_limit_account=models.Account.objects.create(credit_limit=None)credit_limit_account=models.Account.objects.create(credit_limit=Decimal('1000.00'))today=datetime.date.today()next_week=today+datetime.timedelta(days=7)date_limited_account=models.Account.objects.create(start_date=today,end_date=next_week)Transfer funds using the facade:fromoscar_accountsimportfacadestaff_member=User.objects.get(username="staff")trans=facade.transfer(source=no_credit_limit_account,destination=user_account,amount=Decimal('10.00'),user=staff_member)Reverse transfers:facade.reverse(trans,user=staff_member,description="Just an example")If the proposed transfer is invalid, an exception will be raised.  All
exceptions are subclasses ofoscar_accounts.exceptions.AccountException.
Your client code should look for exceptions of this type and handle them
appropriately.Client code should only use theoscar_accounts.models.Budgetclass and the
two functions fromoscar_accounts.facade- nothing else should be required.Error handlingNote that the transfer operation is wrapped in its own database transaction to
ensure that only complete transfers are written out.  When using Django’s
transaction middleware, you need to be careful.  If you have an unhandled
exception,  then account transfers will still be committed even though nothing
else will be.  To handle this, you need to make sure that, if an exception
occurs during your post-payment code, then you roll-back any transfers.Here’s a toy example:fromoscar_accountsimportfacadedefsubmit(self,order_total):# Take payment firsttransfer=facade.transfer(self.get_user_account(),self.get_merchant_account(),order_total)# Create order modelstry:self.place_order()exceptException,e:# Something went wrong placing the order.  Roll-back the previous# transferfacade.reverse(transfer)In this situation, you’ll end up with two transfers being created but no order.
While this isn’t ideal, it’s the best way of handling exceptions that occur
during order placement.Multi-transfer paymentsProjects will often allow users to have multiple accounts and pay for an order
using more than one.  This will involve several transfers and needs some
careful handling in your application code.It normally makes sense to write your own wrapper around the accounts API to
encapsulate your business logic and error handling.  Here’s an example:fromdecimalimportDecimalasDfromoscar_accountsimportmodels,exceptions,facadedefredeem(order_number,user,amount):# Get user's non-empty accounts ordered with the first to expire firstaccounts=models.Account.active.filter(user=user,balance__gt=0).order_by('end_date')# Build up a list of potential transfers that cover the requested amounttransfers=[]amount_to_allocate=amountforaccountinaccounts:to_transfer=min(account.balance,amount_to_allocate)transfers.append((account,to_transfer))amount_to_allocate-=to_transferifamount_to_allocate==D('0.00'):breakifamount_to_allocate>D('0.00'):raiseexceptions.InsufficientFunds()# Execute transfers to some 'Sales' accountdestination=models.Account.objects.get(name="Sales")completed_transfers=[]try:foraccount,amountintransfers:transfer=facade.transfer(account,destination,amount,user=user,description="Order%s"%order_number)completed_transfers.append(transfer)exceptexceptions.AccountException,transfer_exc:# Something went wrong with one of the transfers (possibly a race condition).# We try and roll back all completed ones to get us back to a clean state.try:fortransferincompleted_transfers:facade.reverse(transfer)exceptException,reverse_exc:# Uh oh: No man's land.  We could be left with a partial# redemption. This will require an admin to intervene.  Make# sure your logger mails admins on error.logger.error("Order%s, transfers failed (%s) and reverse failed (%s)",order_number,transfer_exc,reverse_exc)logger.exception(reverse_exc)# Raise an exception so that your client code can inform the user appropriately.raiseRedemptionFailed()else:# All transfers completed okreturncompleted_transfersAs you can see, there is some careful handling of the scenario where not all
transfers can be executed.If you using Oscar then ensure that you create anOrderSourceinstance for
every transfer (rather than aggregating them all into one).  This will provide
better audit information.  Here’s some example code:try:transfers=api.redeem(order_number,user,total_incl_tax)exceptException:# Inform user of failed paymentelse:fortransferintransfers:source_type,__=SourceType.objects.get_or_create(name="Accounts")source=Source(source_type=source_type,amount_allocated=transfer.amount,amount_debited=transfer.amount,reference=transfer.reference)self.add_payment_source(source)Core accounts and account typesA post-syncdb signal will create the common structure for account types and
accounts.  Some names can be controlled with settings, as indicated in
parentheses.AssetsSalesRedemptions (ACCOUNTS_REDEMPTIONS_NAME) - where money is
transferred to when an account is used to pay for something.Lapsed (ACCOUNTS_LAPSED_NAME) - where money is transferred to
when an account expires.  This is done by the
‘close_expired_accounts’ management command.  The name of this
account can be set using theACCOUNTS_LAPSED_NAME.Cash“Bank” (ACCOUNTS_BANK_NAME) - the source account for creating new
accounts that are paid for by the customer (eg a giftcard).  This
account will not have a credit limit and will normally have a
negative balance as money is only transferred out.Unpaid- This contains accounts that are used as sources for other
accounts but aren’t paid for by the customer.  For instance, you might
allow admins to create new accounts in the dashboard.  An account of this
type will be the source account for the initial transfer.LiabilitiesDeferred income- This contains customer accounts/giftcards.  You may
want to create additional account types within this type to categorise
accounts.Example transactionsConsider the following accounts and account types:AssetsSalesRedemptionsLapsedCashBankUnpaidMerchant fundedLiabilitiesDeferred incomeNote that all accounts start with a balance of 0 and the sum of all balances
will always be zero.A customer purchases a £50 giftcardA new account is created of type ‘Deferred income’ with an end date - £50 is
transferred from the Bank to this new accountA customer pays for a £30 order using their £50 giftcard£30 is transferred from the giftcard account to the redemptions accountThe customer’s giftcard expires with £20 still on it£20 is transferred from the giftcard account to the lapsed accountThe customer phones up to complain and a staff member creates a new giftcard
for £20A new account is created of type ‘Deferred income’ - £20 is transferred from
the “Merchant funded” account to this new accountSettingsThere are settings to control the naming and initial unpaid and deferred income
account types:ACCOUNTS_MIN_INITIAL_VALUEThe minimum value that can be used to create an
account (or for a top-up)ACCOUNTS_MAX_INITIAL_VALUEThe maximum value that can be transferred to an
account.ContributingFork repo, set-up virtualenv and run:make installRun tests with:./runtests.py