Billy

Billy - The Open Source Recurring Billing System, powered by Balanced

Install

$ git clone https://github.com/readevalprint/billy $ cd billy $ pip install -r ./requirements.txt

Proposal for Billy

Since Balanced is a dual-sided payments platform, Billy must support:

credit card charges
bank payments
bank deposits

These operations should be scheduled at an arbitrary frequency. Some customers might want a recurring payout schedule for 7 days and a recurring charge plan that's monthly.

Billy must be flexible enough to support scheduling changes, where appropriate business logic is executed.

This essentially boils down to a scheduling problem, that will have a large number of business rules on transition.

Given a timer, we subscribe to this timer with a scheduler, and that scheduler contains a task.

All tasks are wrapped with a scheduler, which control the tasks scheduling and exposes information such as when the time of next run is scheduled, as well as if a task is retryable. A scheduler may schedule other tasks.

All tasks are audited and generate events, which are called AuditEvents. These AuditEvents are essentially line-items for an AuditFeed. AuditFeeds are generated for a scheduler, or its frequency execution, and are more commonly known as invoices. Invoices are essentially the sum of all AuditEvents, or operations, that have happened for a particular task during its scheduled period of execution.

Here are some common tasks:

DebitTask - Invokes a method that does some calculation dynamically to charge an account for a computed price.
FixedDebitTask - What's commonly known as a plan, is a DebitTask with a FIXED price.
PayoutTask - Invokes a method that does some calculation dynamically to issue a bank payout to an account for a computed amount.
FixedPayoutTask - What's commonly known as payroll, is a PayoutTask with a FIXED price.

Glossary

frequency:

frequency = PERIOD_OF_TIME * f(x)

f(x) can be considered an identity function, which we will call the INTERVAL.

Through substitution:

frequency = PERIOD_OF_TIME * INTERVAL

Plans

import billy

# create the goat plan to bill every 3 months.

billy.Plan.create(
    amount=100,
    description='the goat - silver',
    trial_period=None,
    frequency=billy.Frequency.MONTHLY,
    interval=3
)

Plan Frequency

Frequency(object):
   YEARLY = 'yearly'
   MONTHLY = 'monthly'
   WEEKLY = 'weekly'

readevalprint/billy