OrderEngine.h

#ifndef ORDER_ENGINE_H
#define ORDER_ENGINE_H

#include <iostream>
#include <string>
#include <vector>
#include <mutex>
#include <fstream> 

struct Product {
    int product_id;
    std::string name;
    int stock_count;
    double price;
};

struct Order {
    int order_id;
    int user_id;
    int product_id;
    std::string status;
};

class ConcurrentOrderProcessor {
private:
    std::vector<Product> inventory;
    std::vector<Order> order_history;
    std::mutex inventory_mutex; 
    int next_order_id = 1;

public:
    void add_product(int id, std::string name, int stock, double price) {
        inventory.push_back({id, name, stock, price});
    }

    bool process_checkout(int user_id, int product_id) {
        std::lock_guard<std::mutex> lock(inventory_mutex);
        std::ofstream log_file("orders_log.txt", std::ios::app);

        for (size_t i = 0; i < inventory.size(); ++i) {
            if (inventory[i].product_id == product_id) {
                
                if (inventory[i].stock_count > 0) {
                    inventory[i].stock_count--;
                    order_history.push_back({next_order_id++, user_id, product_id, "SUCCESS"});
                    
                    std::cout << "[SUCCESS] Order #" << (next_order_id - 1) 
                              << ": User " << user_id << " bought " << inventory[i].name << std::endl;
                    if (log_file.is_open()) {
                        log_file << "ORDER_ID: " << (next_order_id - 1) 
                                 << " | USER_ID: " << user_id 
                                 << " | STATUS: SUCCESS | ITEM: " << inventory[i].name << "\n";
                    }
                    return true;
                } else {
                    order_history.push_back({next_order_id++, user_id, product_id, "FAILED_OUT_OF_STOCK"});
                    
                    std::cout << "[REJECTED] User " << user_id << ": Item Sold Out!" << std::endl;
                    
                    if (log_file.is_open()) {
                        log_file << "ORDER_ID: " << (next_order_id - 1) 
                                 << " | USER_ID: " << user_id 
                                 << " | STATUS: FAILED_OUT_OF_STOCK\n";
                    }
                    return false;
                }
            }
        }
        return false;
    }
};

#endif