Splitting a God OrderService

#include <print>
#include <string>
#include <vector>

struct OrderItem {
    std::string name;
    int priceRupees;
    int quantity;
};

// Naive OrderService: one monolithic class handles validation, pricing, taxes,
// payments, database storage, and SMS notifications in a single placeOrder() method.
class NaiveOrderService {
    std::vector<std::string> savedOrders_;
public:
    bool placeOrder(const std::string& orderId,
                    const std::string& customerId,
                    const std::string& address,
                    double distanceKm,
                    const std::vector<OrderItem>& items,
                    const std::string& paymentMethod) {
        // 1. Validation logic
        if (items.empty()) {
            std::println("Error: Cart cannot be empty");
            return false;
        }
        if (address.empty()) {
            std::println("Error: Delivery address cannot be blank");
            return false;
        }
        for (const auto& item : items) {
            if (item.quantity <= 0 || item.priceRupees <= 0) {
                std::println("Error: Invalid item quantity or price");
                return false;
            }
        }

        // 2. Pricing & Tax calculation
        int subtotal = 0;
        for (const auto& item : items) {
            subtotal += item.priceRupees * item.quantity;
        }
        int gst = (subtotal * 5) / 100; // 5% GST
        int deliveryFee = (distanceKm <= 5.0) ? 30 : 50;
        int grandTotal = subtotal + gst + deliveryFee;

        // 3. Payment charging
        if (paymentMethod.empty()) {
            std::println("Error: Payment method missing");
            return false;
        }
        std::println("[PAYMENT] Charged Rs.{} via {}", grandTotal, paymentMethod);

        // 4. Persistence / Database saving
        std::string record = std::format("ORDER#{}|CUST#{}|AMT#{}", orderId, customerId, grandTotal);
        savedOrders_.push_back(record);
        std::println("[DB] Saved order record: {}", record);

        // 5. Receipt & SMS notification
        std::string sms = std::format("Order {} placed! Subtotal: Rs.{}, GST: Rs.{}, Delivery: Rs.{}. Total: Rs.{}. Delivering to: {}",
                                      orderId, subtotal, gst, deliveryFee, grandTotal, address);
        std::println("[SMS] Sent to customer {}: {}", customerId, sms);

        return true;
    }
};

int main() {
    NaiveOrderService service;
    std::vector<OrderItem> cart = {
        {"Paneer Butter Masala", 280, 1},
        {"Garlic Naan", 40, 2}
    };
    service.placeOrder("ORD-201", "CUST-42", "Flat 302, Green Glen Layout, Bengaluru", 4.2, cart, "UPI");
}