Metadata-Version: 1.1
Name: django-account-balances
Version: 0.4
Summary: Track account credits in Django
Home-page: UNKNOWN
Author: Jason Carver
Author-email: jason@membright.com
License: Copyright (c) 2011, Tangent Communications PLC and individual contributors.
All rights reserved.

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Description: Accounts credit tracking for Django
        ===========================
        
        Accounts can be used to implement a variety of interesting components, including:
        
        * Giftcards
        * Web accounts
        * Loyalty schemes
        
        Basically anything that involves tracking the movement of funds within a closed
        system.
        
        This package uses [double-entry bookkeeping](http://en.wikipedia.org/wiki/Double-entry_bookkeeping_system)
        where 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.
        
        Features
        --------
        
        * An 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 assigned
        
        * A user can have multiple accounts
        
        * An account can have a start and end date to allow its usage in a limited time
          window
        
        * Accounts can be categorised
        
        Installation
        ------------
        
        TODO: make available on pypi for pip installation.
        
        You should set-up a cronjob that calls:
        
            ./manage.py close_expired_accounts
        
        to close any expired accounts and transfer their funds to the 'expired'
        account.
        
        API
        ---
        
        Create account instances using the manager:
        
        ``` python
        
        from decimal import Decimal
        import datetime
        
        from django.contrib.auth.models import User
        
        from accounts import models
        
        anonymous_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:
        
        ``` python
        
        from accounts import facade
        
        staff_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:
        
        ``` python
        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 of `accounts.exceptions.AccountException`.  Your
        client code should look for exceptions of this type and handle them
        appropriately.
         
        Client code should only use the `accounts.models.Budget` class and the
        two functions from `accounts.facade` - nothing else should be required.
        
        Error handling
        --------------
        
        Note 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:
        
        ``` python
        from accounts import facade
        
        def submit(self, order_total):
        	# Take payment first
        	transfer = facade.transfer(self.get_user_account(),
        							   self.get_merchant_account(),
        							   order_total)
        	# Create order models
        	try:
        		self.place_order()
        	except Exception, e:
        		# Something went wrong placing the order.  Roll-back the previous
        		# transfer
        		facade.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 payments
        -----------------------
        
        Projects 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:
        
        ``` python
        from decimal import Decimal as D
        from accounts import models, exceptions, facade
        
        
        def redeem(order_number, user, amount):
            # Get user's non-empty accounts ordered with the first to expire first
            accounts = models.Account.active.filter(
                user=user, balance__gt=0).order_by('end_date')
        
            # Build up a list of potential transfers that cover the requested amount
            transfers = []
            amount_to_allocate = amount
            for account in accounts:
                to_transfer = min(account.balance, amount_to_allocate)
                transfers.append((account, to_transfer))
                amount_to_allocate -= to_transfer
                if amount_to_allocate == D('0.00'):
                    break
            if amount_to_allocate > D('0.00'):
                raise exceptions.InsufficientFunds()
        
            # Execute transfers to some 'Sales' account
            destination = models.Account.objects.get(name="Sales")
            completed_transfers = []
            try:
                for account, amount in transfers:
                    transfer = facade.transfer(
                        account, destination, amount, user=user,
                        description="Order %s" % order_number)
                    completed_transfers.append(transfer)
            except exceptions.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:
                    for transfer in completed_transfers:
                        facade.reverse(transfer)
                except Exception, 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.
                raise RedemptionFailed()
            else:
                # All transfers completed ok
                return completed_transfers
        ```
        
        As you can see, there is some careful handling of the scenario where not all transfers can be 
        executed.
        
        ``` python
        
            try:
                transfers = api.redeem(order_number, user, total_incl_tax)
            except Exception:
                # Inform user of failed payment
            else:
                for transfer in transfers:
                    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 types
        -------------------------------
        
        A post-syncdb signal will create the common structure for account types and
        accounts.  Some names can be controlled with settings, as indicated in parentheses. 
        
        - **Assets**
        
            - **Sales**
                - Redemptions (`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 the `ACCOUNTS_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.
        
        - **Liabilities**
        
            - **Deferred income** - This contains customer accounts/giftcards.  You may want to create
            additional account types within this type to categorise accounts.
        
        Example transactions
        --------------------
        
        Consider the following accounts and account types:
        
        - **Assets**
            - **Sales** 
                - Redemptions 
                - Lapsed
            - **Cash**
                - Bank 
            - **Unpaid**
                - Merchant funded 
        - **Liabilities**
            - **Deferred income**
        
        Note that all accounts start with a balance of 0 and the sum of all balances will always be zero.
        
        *A customer purchases a £50 giftcard*
        
        - A new account is created of type 'Deferred income' with an end date
        - £50 is transferred from the Bank to this new account
        
        *A customer pays for a £30 order using their £50 giftcard*
        
        - £30 is transferred from the giftcard account to the redemptions account
        
        *The customer's giftcard expires with £20 still on it*
        
        - £20 is transferred from the giftcard account to the lapsed account
        
        *The customer phones up to complain and a staff member creates a new giftcard for £20*
        
        - A new account is created of type 'Deferred income' 
        - £20 is transferred from the "Merchant funded" account to this new account
        
        Settings
        --------
        
        There are settings to control the naming and initial unpaid and deferred income account
        types:
        
        * `ACCOUNTS_MIN_INITIAL_VALUE` The minimum value that can be used to create an
          account (or for a top-up)
        
        * `ACCOUNTS_MAX_INITIAL_VALUE` The maximum value that can be transferred to an
          account.
        
        Contributing
        ------------
        
        Fork repo, set-up virtualenv and run:
        
            make install
        
        Run tests with:
            
            ./runtests.py
        
        History
        -------
        
        This project used to depend on the e-commerce framework [Oscar](https://github.com/tangentlabs/django-oscar) in a number of places.  You may be interested in the upstream repos if you want Oscar integration. This repo was forked off for people who want account balances without Oscar integration.
        
Platform: UNKNOWN
Classifier: Development Status :: 4 - Beta
Classifier: Environment :: Web Environment
Classifier: Framework :: Django
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: BSD License
Classifier: Operating System :: Unix
Classifier: Programming Language :: Python
