Review the provided Java code snippet for the LegacyOrderProcessor module, which is a critical part of a legacy system with no existing tests. Identify at least 5 distinct code smells. For each identified smell, you must:

1. Clearly name and describe the code smell.
2. Explain its negative implications on the system (e.g., maintainability, testability, extensibility, understandability, refactoring difficulty, debugging complexity).
3. Reference specific lines or sections of the provided code that exemplify the smell.

1public class LegacyOrderProcessor {
2    // Magic Numbers / Constants
3    private static final double MIN_ORDER_VALUE_FOR_DISCOUNT = 100.0;
4    private static final double VIP_DISCOUNT_PERCENTAGE = 0.15; // 15%
5    private static final double BULK_DISCOUNT_THRESHOLD = 5;
6    private static final double BULK_DISCOUNT_PERCENTAGE = 0.10; // 10%
7    private static final int MAX_ITEM_QUANTITY = 100;
8
9    // Simulating a static/global utility, a tightly coupled dependency
10    public static class SystemLogger {
11        public static void log(String message) {
12            System.out.println("SYSTEM_LOG: " + message);
13        }
14    }
15
16    /**
17     * Processes a customer order, handling validation, pricing, discounts, and status updates.
18     * This method is a critical part of a legacy monolith and has grown organically over time.
19     *
20     * @param order The order to process.
21     * @param customer The customer placing the order.
22     * @return The final calculated price of the order, or -1.0 if processing fails.
23     */
24    public double processOrder(Order order, Customer customer) {
25        if (order == null || customer == null) {
26            SystemLogger.log("Error: Invalid input (order or customer is null) for order processing.");
27            return -1.0; // Indicate immediate failure
28        }
29
30        // --- SECTION 1: Pre-processing and Validation ---
31        for (OrderItem item : order.getItems()) {
32            if (item.getQuantity() <= 0 || item.getQuantity() > MAX_ITEM_QUANTITY) { // Magic Number
33                SystemLogger.log("Validation Error: Item quantity out of allowed range for Product ID: " + item.getProductId());
34                order.setStatus("REJECTED_INVALID_QUANTITY");
35                return -1.0;
36            }
37            // Tight coupling to static InventoryService
38            if (!InventoryService.checkStock(item.getProductId(), item.getQuantity())) {
39                SystemLogger.log("Validation Error: Insufficient stock for Product ID: " + item.getProductId() + ", Requested: " + item.getQuantity());
40                order.setStatus("REJECTED_INSUFFICIENT_STOCK");
41                return -1.0;
42            }
43        }
44
45        // --- SECTION 2: Base Price Calculation ---
46        double totalBasePrice = 0;
47        for (OrderItem item : order.getItems()) {
48            // Tight coupling to static ProductCatalog
49            totalBasePrice += item.getQuantity() * ProductCatalog.getPrice(item.getProductId());
50        }
51        order.setCalculatedPrice(totalBasePrice); // Mutating input object directly
52
53        // --- SECTION 3: Discount Application Logic ---
54        double finalPrice = totalBasePrice;
55        if (totalBasePrice >= MIN_ORDER_VALUE_FOR_DISCOUNT) { // Magic Number
56            // Excessive Conditional Logic (Smell: Feature Envy, Long Method)
57            if ("VIP".equalsIgnoreCase(customer.getCustomerType())) {
58                finalPrice -= totalBasePrice * VIP_DISCOUNT_PERCENTAGE; // Magic Number
59                SystemLogger.log("Discount Applied: VIP discount for customer " + customer.getCustomerId());
60            } else if (order.getItems().size() >= BULK_DISCOUNT_THRESHOLD) { // Magic Number
61                finalPrice -= totalBasePrice * BULK_DISCOUNT_PERCENTAGE; // Magic Number
62                SystemLogger.log("Discount Applied: Bulk discount for order " + order.getOrderId());
63            }
64        }
65
66        // --- SECTION 4: Payment Processing & Status Update ---
67        // Tight coupling to static PaymentGateway
68        boolean paymentSuccess = PaymentGateway.processPayment(order.getOrderId(), finalPrice);
69        if (paymentSuccess) {
70            order.setStatus("COMPLETED");
71            SystemLogger.log("Order " + order.getOrderId() + " processed successfully. Final price: " + finalPrice);
72            // More hidden responsibilities (e.g., updating inventory, sending notifications)
73            InventoryService.updateStock(order); // Tight coupling
74            NotificationService.sendConfirmation(customer, order); // Tight coupling
75        } else {
76            order.setStatus("PAYMENT_FAILED");
77            SystemLogger.log("Processing Failed: Payment failed for order " + order.getOrderId());
78            finalPrice = -1.0; // Indicate failure
79        }
80
81        return finalPrice;
82    }
83
84    // --- Minimal Helper Classes for Context (Simplified) ---
85    public static class Order {
86        private String orderId;
87        private java.util.List<OrderItem> items;
88        private String status;
89        private double calculatedPrice;
90
91        public Order(String orderId, java.util.List<OrderItem> items) {
92            this.orderId = orderId;
93            this.items = items;
94            this.status = "NEW";
95        }
96        public String getOrderId() { return orderId; }
97        public java.util.List<OrderItem> getItems() { return items; }
98        public String getStatus() { return status; }
99        public void setStatus(String status) { this.status = status; }
100        public double getCalculatedPrice() { return calculatedPrice; }
101        public void setCalculatedPrice(double calculatedPrice) { this.calculatedPrice = calculatedPrice; }
102    }
103
104    public static class OrderItem {
105        private String productId;
106        private int quantity;
107
108        public OrderItem(String productId, int quantity) {
109            this.productId = productId;
110            this.quantity = quantity;
111        }
112        public String getProductId() { return productId; }
113        public int getQuantity() { return quantity; }
114    }
115
116    public static class Customer {
117        private String customerId;
118        private String customerType; // e.g., "REGULAR", "VIP"
119
120        public Customer(String customerId, String customerType) {
121            this.customerId = customerId;
122            this.customerType = customerType;
123        }
124        public String getCustomerId() { return customerId; }
125        public String getCustomerType() { return customerType; }
126    }
127
128    // --- Mock External Dependencies ---
129    public static class InventoryService {
130        public static boolean checkStock(String productId, int quantity) { return true; } // Mock success
131        public static void updateStock(Order order) { /* Mock implementation */ }
132    }
133
134    public static class ProductCatalog {
135        public static double getPrice(String productId) { return 10.0; } // Mock price
136    }
137
138    public static class PaymentGateway {
139        public static boolean processPayment(String orderId, double amount) { return true; } // Mock success
140    }
141
142    public static class NotificationService {
143        public static void sendConfirmation(Customer customer, Order order) { /* Mock implementation */ }
144    }
145}

Based on your analysis of the LegacyOrderProcessor and considering the critical nature of the module with no existing tests, propose a comprehensive, step-by-step refactoring strategy. Your strategy must explicitly address the following:

• Risk Mitigation: How will you safely refactor a critical module without existing unit tests? Discuss specific techniques (e.g., characterization tests, micro-commits, IDE refactoring tools).
• Incremental Nature: Outline a logical sequence of refactoring steps, emphasizing an incremental approach rather than a 'big bang' rewrite.
• Prioritization: How would you prioritize the refactoring steps based on impact, safety, and enabling further changes?
• Design Pattern Application: Propose the application of at least two relevant Gang of Four (GoF) design patterns to improve the module's design, maintainability, and testability. For each chosen pattern:
  • Explain why it is suitable for this specific context.
  • Describe how it addresses one or more of the code smells you identified in Part 1.

Using the refactoring strategy and design patterns you proposed, write pseudo-code (or high-level Java-like code) for a significantly refactored, more modular, and highly testable version of the LegacyOrderProcessor.processOrder logic.

Your pseudo-code should clearly demonstrate:

1. The application of your proposed refactoring steps and design patterns.
2. How the new structure inherently supports unit testing and mockability.

Finally, provide a brief conceptual example (not full code, but highlighting key aspects) of how a unit test for one of your refactored components would look, emphasizing its simplicity and isolation compared to attempting to test the original monolithic code.