Interview Task

index.js

async function checkout(userId, items) {
    const order = await db.orders.create({
        userId,
        status: "pending",
        createdAt: Date.now()
    });

    items.forEach(async item => {
        const inventory = await db.inventory.get(item.productId);

        if (inventory.stock < item.qty) {
            throw new Error("Out of stock");
        }

        await db.inventory.update(item.productId, {
            stock: inventory.stock - item.qty
        });
    });

    const paymentPromise = paymentGateway.charge(userId, calculateTotal(items));

    analytics.track("checkout_started", {
        userId,
        orderId: order.id
    });

    paymentPromise.then(result => {
        db.orders.update(order.id, {
            paymentId: result.id,
            status: "paid"
        });

        email.sendReceipt(userId, order.id);

        analytics.track("checkout_success", {
            orderId: order.id
        });
    });

    return order;
}