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from datetime import datetime
from decimal import Decimal
from typing import Generator
from finance.model import Flow
def integrate(flow: Flow, start: datetime, end: datetime) -> Decimal:
"""Integrate the flow between two dates to an amount of money"""
payments: int = 0
if flow.since is not None:
if start < flow.since:
start = flow.since
if flow.until is not None:
if end > flow.until:
end = flow.until
for candidate in monthly_candidates(start):
if start <= candidate <= end:
payments += 1
if candidate > end:
break
return flow.amount * Decimal(payments)
def monthly_candidates(start: datetime) -> Generator[datetime, None, None]:
current = datetime(start.year, start.month, 1)
while True:
yield current
if current.month == 12:
current = datetime(current.year + 1, 1, 1)
else:
current = datetime(current.year, current.month + 1, 1)
def simulate(
start: datetime, end: datetime, flows: tuple[Flow, ...]
) -> list[tuple[datetime, Decimal]]:
dates: list[datetime] = []
values: list[Decimal] = []
for candidate in monthly_candidates(start):
if start <= candidate <= end:
dates.append(candidate)
if candidate > end:
break
for date in dates:
value = Decimal(0.0)
for flow in flows:
value += integrate(flow, start, date)
values.append(value)
return [(date, values[index]) for index, date in enumerate(dates)]
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