GoFデザインパターン - ファサード編

#include <iostream>
#include <string>

class AuthService {
public:
    bool ValidateUser(const std::string& userId) const {
        return !userId.empty();
    }
};

class InventoryService {
public:
    bool HasStock(const std::string& sku, int qty) const {
        return !sku.empty() && qty > 0; // 学習用に簡略化
    }
};

class PaymentGateway {
public:
    bool Charge(const std::string& userId, int amount) const {
        return !userId.empty() && amount > 0;
    }
};

class ShippingService {
public:
    std::string ReserveShipment(const std::string& sku, int qty) const {
        if (sku.empty() || qty <= 0) return "";
        return "SHIP-20260529-001";
    }
};

class NotificationService {
public:
    void SendOrderCompleted(const std::string& userId, const std::string& shipmentId) const {
        std::cout << "Notify user=" << userId << " shipment=" << shipmentId << "\n";
    }
};

class OrderFacade {
public:
    bool PlaceOrder(const std::string& userId,
                    const std::string& sku,
                    int qty,
                    int amount) {
        if (!auth_.ValidateUser(userId)) {
            std::cout << "auth failed\n";
            return false;
        }
        if (!inventory_.HasStock(sku, qty)) {
            std::cout << "out of stock\n";
            return false;
        }
        if (!payment_.Charge(userId, amount)) {
            std::cout << "payment failed\n";
            return false;
        }

        const std::string shipmentId = shipping_.ReserveShipment(sku, qty);
        if (shipmentId.empty()) {
            std::cout << "shipping failed\n";
            return false;
        }

        notifier_.SendOrderCompleted(userId, shipmentId);
        return true;
    }

private:
    AuthService auth_;
    InventoryService inventory_;
    PaymentGateway payment_;
    ShippingService shipping_;
    NotificationService notifier_;
};

int main() {
    OrderFacade facade;

    const bool ok = facade.PlaceOrder(
        "user-001",  // userId
        "sku-coffee",// sku
        2,            // qty
        1800          // amount
    );

    std::cout << (ok ? "order success" : "order failed") << "\n";
    return 0;
}

// 実行例
// Notify user=user-001 shipment=SHIP-20260529-001
// order success