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def place_order(order_data):
    item = db.query("SELECT * FROM items"
        " WHERE id = %s", order_data["item"])

    # mark as sold
    db.execute("UPDATE items SET status='sold'"
        " WHERE id = %s", order_data["item"])

    # make invoice
    inv_id = str(random.randint(1000, 9999))
    db.execute(
        "INSERT INTO invoices VALUES (%s,%s,%s)",
        inv_id, order_data["user"], item["price"]
    )

    # email it
    requests.post(MAIL_URL, json={
        "to": order_data["email"],
        "body": "invoice: " + inv_id
    })

    # send to delivery
    requests.post(DELIVERY_URL, json={
        "order": order_data["item"],
        "addr": order_data["address"]
    })

    return "ok"

@dataclass
class OrderRequest:
    item_id:   UUID
    user_id:   UUID
    address:   str


@dataclass
class OrderResult:
    order_id:   UUID
    invoice_id: UUID
    status:     OrderStatus


async def place_order(
    req: OrderRequest,
    db: Database,
    mailer: MailService,
    fulfilment: FulfilmentService,
) -> OrderResult:

    async with db.transaction():
        item = await db.items.get_or_raise(req.item_id)
        item.mark_sold()
        await db.items.save(item)

        invoice = Invoice.create(item, req.user_id)
        await db.invoices.save(invoice)

        order = Order.create(req, invoice)
        await db.orders.save(order)

    await mailer.send_invoice(invoice, req.user_id)
    await fulfilment.dispatch(order)

    logger.info("order.placed", order_id=order.id)
    return OrderResult(order.id, invoice.id,
                       OrderStatus.CONFIRMED)