"""The POST /api/transactions request shape this suite assumes.

Neither spec pins down the request field names for creating a transaction --
only the response envelope (phase-0-base-project-spec.md §6.1) is specified.
Since the test suite is the contract, this module fixes the shape Agent B's
implementation must accept. See tests/README.md, "Request contract
assumptions", for the rationale.
"""


def tx_payload(
    account_id,
    kind="deposit",
    amount_minor=1000,
    currency="EUR",
    merchant_name="Test Merchant",
    category_id=None,
):
    payload = {
        "account_id": account_id,
        "kind": kind,
        "amount_minor": amount_minor,
        "currency": currency,
        "merchant_name": merchant_name,
    }
    if category_id is not None:
        payload["category_id"] = category_id
    return payload