E-commerce

import java.util.*;

// Enum to represent the status of an order
public enum OrderStatus {
    PENDING,
    SHIPPED,
    DELIVERED,
    CANCELLED
}

// Interface for Product
public interface Product {
    String getId();
    String getName();
    double getPrice();
    String getDescription();
    int getStockQuantity();
    void setStockQuantity(int quantity);
}

// Interface for User
public interface User {
    String getId();
    String getName();
    String getEmail();
    String getPassword();
    void setPassword(String password);
}

// Interface for Order
public interface Order {
    String getOrderId();
    User getUser();
    void addProduct(Product product, int quantity);
    void removeProduct(Product product);
    double getTotalPrice();
    OrderStatus getStatus();  
    void setStatus(OrderStatus status);
    void cancelOrder();  // New method for cancelling the order
}

// Interface for PaymentProcessor
public interface PaymentProcessor {
    boolean processPayment(Order order, User user);
    boolean processRefund(Order order, User user);
}

// Interface for Reviewable
public interface Reviewable {
    void addReview(User user, int rating, String comment);
    List<Review> getReviews();
}

// Implementation of Product
public class ProductImpl implements Product, Reviewable {
    private String id;
    private String name;
    private double price;
    private String description;
    private int stockQuantity;
    private List<Review> reviews;

    public ProductImpl(String id, String name, double price, String description, int stockQuantity) {
        this.id = id;
        this.name = name;
        this.price = price;
        this.description = description;
        this.stockQuantity = stockQuantity;
        this.reviews = new ArrayList<>();
    }

    @Override
    public String getId() {
        return id;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public double getPrice() {
        return price;
    }

    @Override
    public String getDescription() {
        return description;
    }

    @Override
    public int getStockQuantity() {
        return stockQuantity;
    }

    @Override
    public void setStockQuantity(int quantity) {
        this.stockQuantity = quantity;
    }

    @Override
    public void addReview(User user, int rating, String comment) {
        reviews.add(new Review(user, rating, comment));
    }

    @Override
    public List<Review> getReviews() {
        return reviews;
    }
}

// Implementation of User
public class UserImpl implements User {
    private String id;
    private String name;
    private String email;
    private String password;

    public UserImpl(String id, String name, String email, String password) {
        this.id = id;
        this.name = name;
        this.email = email;
        this.password = password;
    }

    @Override
    public String getId() {
        return id;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public String getEmail() {
        return email;
    }

    @Override
    public String getPassword() {
        return password;
    }

    @Override
    public void setPassword(String password) {
        this.password = password;
    }
}

// Implementation of Order
public class OrderImpl implements Order {
    private String orderId;
    private User user;
    private Map<Product, Integer> products;
    private OrderStatus status;

    public OrderImpl(String orderId, User user) {
        this.orderId = orderId;
        this.user = user;
        this.products = new HashMap<>();
        this.status = OrderStatus.PENDING;
    }

    @Override
    public String getOrderId() {
        return orderId;
    }

    @Override
    public User getUser() {
        return user;
    }

    @Override
    public void addProduct(Product product, int quantity) {
        products.put(product, quantity);
    }

    @Override
    public void removeProduct(Product product) {
        products.remove(product);
    }

    @Override
    public double getTotalPrice() {
        return products.entrySet().stream()
                       .mapToDouble(entry -> entry.getKey().getPrice() * entry.getValue())
                       .sum();
    }

    @Override
    public OrderStatus getStatus() {
        return status;
    }

    @Override
    public void setStatus(OrderStatus status) {
        this.status = status;
    }

    @Override
    public void cancelOrder() {
        if (status == OrderStatus.SHIPPED || status == OrderStatus.DELIVERED) {
            System.out.println("Cannot cancel the order as it has already been " + status.name().toLowerCase());
        } else {
            this.status = OrderStatus.CANCELLED;
            System.out.println("Order " + orderId + " has been cancelled.");
        }
    }
}

// Implementation of PaymentProcessor
public class CreditCardPaymentProcessor implements PaymentProcessor {

    @Override
    public boolean processPayment(Order order, User user) {
        System.out.println("Processing credit card payment for order " + order.getOrderId());
        return true;  // Simplified payment logic
    }

    @Override
    public boolean processRefund(Order order, User user) {
        System.out.println("Processing credit card refund for order " + order.getOrderId());
        return true;  // Simplified refund logic
    }
}

// Class to represent a Review
public class Review {
    private User user;
    private int rating;
    private String comment;

    public Review(User user, int rating, String comment) {
        this.user = user;
        this.rating = rating;
        this.comment = comment;
    }

    public User getUser() {
        return user;
    }

    public int getRating() {
        return rating;
    }

    public String getComment() {
        return comment;
    }
}

// Main Application to demonstrate the e-commerce system
public class ECommerceApp {

    public static void main(String[] args) {
        // Create a user
        User user = new UserImpl(UUID.randomUUID().toString(), "Alice", "alice@example.com", "password123");

        // Create a product
        Product product = new ProductImpl(UUID.randomUUID().toString(), "Laptop", 1200.00, "High-end gaming laptop", 10);

        // Create an order
        Order order = new OrderImpl(UUID.randomUUID().toString(), user);
        order.addProduct(product, 1);

        // Process the payment
        PaymentProcessor paymentProcessor = new CreditCardPaymentProcessor();
        paymentProcessor.processPayment(order, user);

        // Change the order status to pending
        order.setStatus(OrderStatus.PENDING);

        // Attempt to cancel the order while it's still pending
        order.cancelOrder();

        // Process order if not cancelled
        if (order.getStatus() != OrderStatus.CANCELLED) {
            // Change the order status to shipped
            order.setStatus(OrderStatus.SHIPPED);

            // Attempt to cancel the order after it's shipped
            order.cancelOrder();
        }

        // User reviews the product if the order was not cancelled
        if (order.getStatus() == OrderStatus.DELIVERED) {
            product.addReview(user, 5, "Excellent product!");
        }

        // Output the review
        System.out.println("Reviews for " + product.getName() + ":");
        for (Review review : product.getReviews()) {
            System.out.println(review.getUser().getName() + ": " + review.getRating() + " stars - " + review.getComment());
        }
    }
}