"""Versioned contribution shared by calculation, reconstruction and ledger."""

from decimal import Decimal


def carryover_contribution(kind: str, amount: Decimal, *, version: int = 2) -> Decimal:
    if version not in (1, 2):
        raise ValueError("Unsupported payroll balance rules version")
    increases = kind in {"adjustment_debit", "deduction"} or (
        kind == "payment" and version == 1
    )
    return amount if increases else -amount