First working version

LICENSE

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+Copyright (c) 2011, Tangent Communications PLC and individual contributors.
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+    1. Redistributions of source code must retain the above copyright notice,
+       this list of conditions and the following disclaimer.
+
+    2. Redistributions in binary form must reproduce the above copyright
+       notice, this list of conditions and the following disclaimer in the
+       documentation and/or other materials provided with the distribution.
+
+    3. Neither the name of Tangent Communications PLC nor the names of its contributors 
+	   may be used to endorse or promote products derived from this software without
+       specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

MANIFEST.in

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+include *.rst
+include LICENSE

README.rst

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+=======
+Budgets
+=======
+
+.. warning::
+    This is a work in progress
+
+This package provides managed budgets for Oscar.  It uses double-ledger account
+to ensure all transaction have a source and destination.
+
+Features:
+
+* A user can have multiple budgets
+* A budget can be assigned to either a primary user or a group of other users
+* A budget can have a start and end date to allow its usage in a limited time
+  window
+
+TODO:
+
+* Make top-level models abstract for extensibility

budgets/__init__.py

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+VERSION = '0.1'

budgets/facade.py

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+from budgets import models
+
+
+def transfer(source, destination, amount):
+    models.Transaction.objects.create(
+        budget=source,
+        amount=-amount)
+    models.Transaction.objects.create(
+        budget=destination,
+        amount=amount)

budgets/models.py

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+from decimal import Decimal as D
+
+from django.db import models
+
+
+class Budget(models.Model):
+    name = models.CharField(max_length=128, unique=True, null=True)
+
+    # Some budgets are not linked to a specific user but are activated by
+    # entering a code at checkout.
+    code = models.CharField(max_length=128, unique=True, null=True)
+
+    # Budgets can have an date range when they can be used.
+    start_date = models.DateField(null=True)
+    end_date = models.DateField(null=True)
+
+    # Each budget can have multiple users who can use it for transactions.  In
+    # many cases, there will only be one user though and so we use a 'primary'
+    # user for this scenario.
+    primary_user = models.ForeignKey('auth.User', related_name="budgets",
+                                     null=True)
+    secondary_users = models.ManyToManyField('auth.User')
+
+    date_created = models.DateTimeField(auto_now_add=True)
+    date_last_transation = models.DateTimeField(null=True)
+
+
+class Transaction(models.Model):
+    # Every transfer of money should create two rows in this table.
+    # (a) the debit from the source budget
+    # (b) the credit to the destination budget
+    budget = models.ForeignKey(Budget)
+
+    # The sum of this field over the whole table should always be 0
+    # Credits should be positive while debits should be negative
+    amount = models.DecimalField(decimal_places=2, max_digits=12,
+                                       default=D('0.00'))
+
+    date_created = models.DateTimeField(auto_now_add=True)

makefile

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+install:
+	./setup.py develop
+	pip install -r requirements.txt

requirements.txt

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+South==0.7.3
+mock==0.7.2
+coverage==3.5.1
+django-nose==1.0
+nose==1.1.2
+django-extensions==0.8
+django-debug-toolbar==0.9.4

runtests.py

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+#!/usr/bin/env python
+import sys
+from coverage import coverage
+from optparse import OptionParser
+
+import logging
+logging.disable(logging.CRITICAL)
+
+from django.conf import settings
+
+if not settings.configured:
+    from oscar.defaults import *
+    extra_settings = {}
+    for key, value in locals().items():
+        if key.startswith('OSCAR'):
+            extra_settings[key] = value
+
+    from oscar import get_core_apps, OSCAR_MAIN_TEMPLATE_DIR
+
+    settings.configure(
+            DATABASES={
+                'default': {
+                    'ENGINE': 'django.db.backends.sqlite3',
+                    }
+                },
+            INSTALLED_APPS=[
+                'django.contrib.auth',
+                'django.contrib.admin',
+                'django.contrib.contenttypes',
+                'django.contrib.sessions',
+                'django.contrib.sites',
+                'django.contrib.flatpages',
+                'budgets',
+                'south',
+                ] + get_core_apps(),
+            MIDDLEWARE_CLASSES=(
+                'django.middleware.common.CommonMiddleware',
+                'django.contrib.sessions.middleware.SessionMiddleware',
+                'django.middleware.csrf.CsrfViewMiddleware',
+                'django.contrib.auth.middleware.AuthenticationMiddleware',
+                'django.contrib.messages.middleware.MessageMiddleware',
+                'django.middleware.transaction.TransactionMiddleware',
+                'oscar.apps.basket.middleware.BasketMiddleware',
+            ),
+            DEBUG=False,
+            SOUTH_TESTS_MIGRATE=False,
+            HAYSTACK_CONNECTIONS = {
+                'default': {
+                    'ENGINE': 'haystack.backends.simple_backend.SimpleEngine',
+                },
+            },
+            TEMPLATE_DIRS = (OSCAR_MAIN_TEMPLATE_DIR,),
+            SITE_ID=1,
+            NOSE_ARGS=['-s', '--with-spec'],
+            **extra_settings
+        )
+
+from django_nose import NoseTestSuiteRunner
+
+
+def run_tests(*test_args):
+    if 'south' in settings.INSTALLED_APPS:
+        from south.management.commands import patch_for_test_db_setup
+        patch_for_test_db_setup()
+
+    if not test_args:
+        test_args = ['tests']
+
+    # Run tests
+    test_runner = NoseTestSuiteRunner(verbosity=1)
+
+    c = coverage(source=['budgets'], omit=['*migrations*', '*tests*'])
+    c.start()
+    num_failures = test_runner.run_tests(test_args)
+    c.stop()
+
+    if num_failures > 0:
+        sys.exit(num_failures)
+    print "Generating HTML coverage report"
+    c.html_report()
+
+def generate_migration():
+    from south.management.commands.schemamigration import Command
+    com = Command()
+    com.handle(app='paypal', initial=True)
+
+
+if __name__ == '__main__':
+    parser = OptionParser()
+    (options, args) = parser.parse_args()
+    run_tests(*args)

setup.py

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+#!/usr/bin/env python
+from setuptools import setup, find_packages
+
+from budgets import VERSION
+
+setup(name='django-oscar-budgets',
+      version=VERSION,
+      author="David Winterbottom",
+      author_email="david.winterbottom@tangentlabs.co.uk",
+      description="Budgets module for django-oscar",
+      long_description=open('README.rst').read(),
+      license=open('LICENSE').read(),
+      packages=find_packages(exclude=['sandbox*', 'tests*']),
+      # See http://pypi.python.org/pypi?%3Aaction=list_classifiers
+      classifiers=['Environment :: Web Environment',
+                   'Framework :: Django',
+                   'Intended Audience :: Developers',
+                   'License :: OSI Approved :: BSD License',
+                   'Operating System :: Unix',
+                   'Programming Language :: Python'],
+      install_requires=['django-oscar>=0.2'])

tests/unit/model_tests.py

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+from decimal import Decimal as D
+
+from django.test import TestCase
+from django.contrib.auth.models import User
+from django.db.models import Sum
+
+from django_dynamic_fixture import G
+
+from budgets.models import Budget, Transaction
+from budgets import facade
+
+
+class TestATransferFromCompanyBudgetToCustomer(TestCase):
+
+    def setUp(self):
+        staff_member = G(User, is_staff=True)
+        source = Budget.objects.create(
+            name="Company")
+
+        customer = G(User, is_staff=False)
+        destination = Budget.objects.create(
+            primary_user=customer)
+
+        facade.transfer(source, destination, D('100.00'))
+
+        self.assertEqual(2, Transaction.objects.all().count())
+
+    def test_creates_two_transactions(self):
+        self.assertEqual(2, Transaction.objects.all().count())
+
+    def test_preserves_zero_sum_invariant(self):
+        aggregates = Transaction.objects.aggregate(sum=Sum('amount'))
+        self.assertEqual(D('0.00'), aggregates['sum'])