refund_calculation 0.1

Turns a chronological sequence of balance-adjustment events into a timeline of periods during which particular balances were held.

For example, this sequence of events …

• A: $10

• B: $10

• C: ($18)

• D: ($2)

… is turned into this timeline:

A             B             C             D
|             |             |             |
|_____________|_____________|             |
|                           |             |
|           $10             |             |
|___________________________|             |
              |             |             |
              |     $8      |             |
              |_____________|_____________|
              |                           |
              |            $2             |
              |___________________________|

This lets you determine, for each balance reduction event, the events from which the balance was added. In this example, we can see that:

• The $18 reduction in event C came from $10 of event A and $8 of B.

• The $2 reduction in event D came entirely from event B.

Code for this example:

from refund_calculation import *

history_from_event_sequence([
    Event(time='A', delta='10'),
    Event(time='B', delta='10'),
    Event(time='C', delta='-18'),
    Event(time='D', delta='-2'),
])

# Result:
History(
    closed=(
        Closed(amount=Decimal('10'), start='A', end='C'),
        Closed(amount=Decimal('8'),  start='B', end='C'),
        Closed(amount=Decimal('2'),  start='B', end='D'),
    ),
    open=(),
    debt=Decimal('0'),
)