SRP_together.ts

class OrderManager {
    public createOrder(orderData): Order {
        this.validate(orderData);
        const order = new Order(orderData);
        order.setTotalPrice(this.calculateTotal(orderData));
        this.pay(orderData)
        await this.save(orderData);
        return order;
    }

    private calculateTotal(orderData): number {
        let totalPrice = orderData.items.reduce( (totalPrice, orderItem) => totalPrice + (orderItem.price *  orderItem.quantity));
        totalPrice = totalPrice + totalPrice * 0.05;    // add service commission
        return totalPrice;
    }

    private validate(orderData) {
        if (!orderData.items.length) {
            throw new ValidationError("Cannot create an order: cart is empty");
        }
        orderData.items.forEach((orderItem) => {
            if (orderItem.productId === undefined || orderItem.quantity === undefined || orderItem.price === undefined) {
                throw new ValidationError("Cannot create an order: product ID is missing");
            }
        })
    }

    private pay(orderData) {
        const paymentGateway = new MyPaymentGateway(process.env.STRIPE_KEY);
        paymentGateway.pay(orderData.totalPrice, orderData.paymentInfo);
    }

    private async save(orderData): Order {
        await orderRepository.save(orderData);
        return order;
    }
}