This project differ from the original django-prepaid. On this project, each Unit consumed generate a new row on the database, like a historical of consumption.
Django-prepaid is a low-level Django application to support prepaid
service functionality. User can purchase a pack of units (it is up
to project to define meaning of units, but think prepaid phone service
and calling minutes to see the desired meaning). Every pack has an
expiry date, defaulting to `settings.PREPAID_DEFAULT_EXPIRY_PERIOD'
days, if set. Units are available until the expiry date, and user can
have multiple unit packs with different number of units and expiry
dates at the same time. Units can be consumed; they are substracted
from valid (not expired) packs' quantities, starting from pack that
has nearest expiry date.
This application is designed to be purely back-end, i.e. defines no views or URLs, uses no templates.
1 Installation 2 Settings 3 Model 3.1 Managers 3.2 Methods 3.3 Class methods 4 License
1 Installation
Copy or symlink `prepaid/' subdirectory to Python path (`setup.py'
script for automated installation will be supplied later on). Module
contents are available in the `prepaid' module.
In order to use application, add `prepaid' to INSTALLED_APPS in
Django project `settings.py' file,
2 Settings
~~~~~~~~~~
`PREPAID_DEFAULT_EXPIRY_PERIOD' defines default value for
`UnitPack.expires' field; is set, default for `UnitPack.expires' is
today + `PREPAID_DEFAULT_EXPIRY_PERIOD' days. If not set, `expires'
field has no default.
3 Model
~~~~~~~
The `prepaid.models.UnitPack' class is only model defined by the
application. It has following fields:
- `user' is ForeignKey to `auth.User' model. It specifies user who
owns the pack's units;
- `quantity' is IntegerField containing current amount of units
contained in pack. It is decreased when units are consumed;
- `expires' is `DateField' containing pack's expiry date. If
`PREPAID_DEFAULT_EXPIRY_PERIOD' setting is set, default value is
today + `PREPAID_DEFAULT_EXPIRY_PERIOD' days; otherwise, there is
no default value and expiry date has to be explicitly specified.
- `timestamp' is a DateTimeField containing timestamp of pack's
creation. It should be used for bookkeeping purposes only.
- `initial_quantity' is the initial value of `quantity' field. It
should be used for bookkeeping purposes only.
3.1 Managers
============
Default manager, `objects', adds filter to make only valid (see
`is_valid()' method below) instances visible. Additional manager,
`all_objects', is provided, that provides access to all instances,
including invalid ones.
3.2 Methods
===========
`is_valid()' method returns True if pack is valid, i.e. `quantity'
is greater than 0, and `expires' date is in the future.
3.3 Class methods
=================
Three class methods are provided for convenience:
- `UnitPack.get_user_packs(user)' returns QuerySet of all valid
`UserPack' instances belonging to `user';
- `UnitPack.get_user_credits(user)' returns sum of `quantity'
instance of `UnitPack.get_user_packs(user)', i.e. sum of all
units available to `user';
- `UnitPack.consume(user, amount=1)' consumes `amount' units from
`user''s credit. If `amount' is greater than
`UnitPack.get_user_credits(user)', `ValueError' is raised.
Otherwise, `amount' is subsctracted from `quantity' fields of
user's valid UnitPacks, starting from pack with nearest expiry
date.
4 License
~~~~~~~~~
This project is licensed on terms of GPL (GPL-LICENSE.txt) licenses