📱 Electronics Shop

4.1 Layout Model

Root is BorderPane:

• top: header nav component (fixed)
• center: ScrollPane containing VBox pageFlow
• pageFlow children always in order: (1) active page node, (2) footer node

4.2 Route Loop Model (replaces console while-loop)

1. User action creates NavIntent.
2. Router evaluates user state and permissions.
3. Router returns RouteDecision.
4. Renderer swaps page content.
5. Optional lifecycle hooks run (onBeforeLeave, onAfterEnter).

4.3 Access Guards

• Guest routes: only when not logged in.
• Customer routes: require logged-in non-admin user.
• Admin routes: require admin user.
• Invalid request: redirected with user-visible reason.

6.1 New Product Model Fields

private String imageName;   // shown in UI
private String imagePath;   // relative path persisted in CSV

6.2 CSV Schema Change

Old header:

id,name,price,category,description,stockQuantity,isDiscounted,discountPercentage

New header:

id,name,price,category,description,stockQuantity,isDiscounted,discountPercentage,imageName,imagePath

6.3 File Storage Policy

• Store image files under data/images/.
• Persist only relative path, never machine-specific absolute path.
• Remove file on delete/replace as best effort.
• Allowed extensions: png, jpg, jpeg, webp.

MainFx — com.university.shopping

JavaFX entry application. Builds dependency graph and root shell.

Fields:
  AuthService authService
  ShopService shopService
  AdminService adminService
  AppState appState
  Router router
  UiRenderer renderer

Methods:
  void start(Stage stage)         // initialize app, create scene, render initial route
  static void main(String[] args) // launch JavaFX app

AppState — app

Single source of UI state.

Fields:
  User currentUser
  Route currentRoute
  Integer selectedProductId
  String flashMessage
  boolean loading

Key method:
  String consumeFlashMessage()  // returns flash message and clears it

NavIntent — app

Immutable navigation input to router. Factory methods:

static NavIntent appStart()
static NavIntent open(Route route)
static NavIntent openProduct(int productId)
static NavIntent loginSuccess()
static NavIntent registerSuccess()
static NavIntent checkoutSuccess()
static NavIntent logout()

Router — app

State-aware and role-aware route decision engine.

RouteDecision dispatch(NavIntent intent)
RouteDecision evaluateCurrentState()
boolean canAccess(Route route)

ScreenContext — view.contracts

Shared dependency container for all screens and pages.

AppState appState
Router router
UiRenderer renderer
AuthService authService
ShopService shopService
AdminService adminService
ProductImageService productImageService

UiRenderer — view.renderer

Route-to-screen resolution and center content swap.

void render(Route route, ScreenContext context)
void setNotification(String message, boolean error)
ScreenComponent resolveScreen(Route route)

AppShell — view.layout

Owns stable regions and enforces header/footer layout behavior.

Fields:
  BorderPane root
  HeaderNavComponent header
  ScrollPane scrollRoot
  VBox pageFlow
  FooterComponent footer

Methods:
  Parent buildRoot(ScreenContext context)
  void setPageContent(Node pageNode)  // keeps order: [pageNode, footer]
  BorderPane getRoot()

ProductImageService — service.media

Validates, copies, and removes product image files.

String storeProductImage(ProductImageUpdateRequest request)
  // validate extension + copy file -> returns stored relative path

boolean removeProductImage(String relativePath)
  // delete file -> returns delete status

boolean isSupportedImage(String fileName)
  // checks extension validity (png, jpg, jpeg, webp)

2.1 Startup Flow

1. Main.main creates repositories.
2. Repository static init delegates to CsvBootstrapInitializer.initializeIfNeeded().
3. Initializer ensures directory/files/headers.
4. Initializer safely resets in-memory arrays/counts.
5. Initializer loads users/products/orders/order_items CSV files.
6. Initializer recalculates next IDs from loaded data.
7. Application continues with normal service/UI startup.

2.2 Runtime Read Flow

Services call repositories, repositories read from MockDatabase arrays, and no per-request disk reads are done.

2.3 Runtime Write Flow (Triggered Persistence)

1. Service requests a mutation in repository.
2. Repository mutates in-memory array/count.
3. Repository immediately calls CSV store writeAll(...).
4. Store writes temp file and atomically replaces real file.
5. On failure, repository returns failure and logs error.

2.4 Report Export Flow

AdminService.exportSystemReport("csv") delegates to CsvReportService.exportReport(), which returns SUCCESS:<path> or ERROR:<message>.

4.5 Required Multi-Catch + Finally Block

BufferedReader reader = null;
try {
    reader = new BufferedReader(new FileReader(path));
    // parse rows
} catch (NumberFormatException e) {
    // row numeric issues
} catch (DateTimeParseException e) {
    // date issues
} catch (IOException e) {
    // file IO issues
} finally {
    if (reader != null) {
        try {
            reader.close();
        } catch (IOException closeError) {
            // log close error
        }
    }
}

Persistence Helpers

• CsvPaths.java: centralize paths for data files and error log.
• CsvEscaper.java: CSV escaping and robust line splitting.
• CsvErrorLogger.java: append structured non-fatal logs to errors.log.

Model Adjustments

• User.java: add overload/factory for persisted ID restore with optional auto-register control.
• Product.java: add overload/factory for explicit persisted ID.
• Order.java: add overload/factory for explicit persisted ID.
• MockDatabase.java: add deterministic reset and next-ID recalculation helper(s).

CSV Stores

• UserCsvStore: ensureFileWithHeader, loadAll, writeAll.
• ProductCsvStore: ensureFileWithHeader, loadAll, writeAll.
• OrderCsvStore: ensureFileWithHeader, loadAllWithoutItems, writeAll.
• OrderItemCsvStore: grouped loading by orderId and full write support.

Bootstrap + Repository Wiring

• CsvBootstrapInitializer.java: one-time idempotent CSV bootstrap with file ensuring, loading, and counter finalization.
• UserRepository.java: call bootstrap; persist on save, update, delete.
• ProductRepository.java: call bootstrap; persist on save, update, delete, updateStock.
• OrderRepository.java: persist both orders.csv and order_items.csv on save/update path.
• CartRepository.java: keep in-memory for this step (cart CSV is non-goal now).

Service and Main Wiring

• CsvReportService.java: robust file write with defensive try/catch/finally and logging.
• Main.java: preferred explicit bootstrap call for transparency/testability.

MenuActions (interface)

Methods: void showMenu(), void handleOption(int option)

// Example polymorphic usage
MenuActions active = authService.isAdmin() ? adminScreen : customerScreen;
active.showMenu();
int choice = getIntInput();
active.handleOption(choice);

DiscountPolicy (interface)

DiscountPolicy policy = new SeasonalDiscountPolicy(5.0);
double finalPrice = policy.apply(product);

Modified Existing Classes

Scenario 1: Menu polymorphism

login as admin   -> menu shows "Product Management", "User Management"
login as customer -> menu shows "Add Product to Cart", "Checkout"

Scenario 2: Pricing strategy

StandardDiscountPolicy:  base 1000, discount 10% -> charged: 900
SeasonalDiscountPolicy(5): same product         -> charged: 850

Scenario 3: Report destination

format = "console" -> report printed in terminal
format = "csv"    -> SUCCESS:reports/system.csv
format = "xml"    -> ERROR:Unsupported format

User.java

private int userId;
private String username;
private String password;
private boolean isAdmin;
private String createdDate;

// Getters for all fields
// Setters: setUsername, setPassword, setIsAdmin (NO setUserId)

Product.java

private int productId;
private String name;
private double price;
private String category;
private String description;
private int stockQuantity;
private boolean isDiscounted;
private double discountPercentage;

public double getFinalPrice()  // price * (1 - discountPct/100) if discounted

Order.java / OrderItem.java / Cart.java

Order holds OrderItem[]. OrderItem is fully immutable (no setters). Cart manages a 50-slot OrderItem[] with addItem, removeItem, clear, getTotalPrice.

MockDatabase.java STATIC ONLY

public static User[] users = new User[100];
public static int userCount = 0;
public static Product[] products = new Product[200];
public static int productCount = 0;
public static Order[] orders = new Order[500];
public static int orderCount = 0;
// ... nextUserId, nextProductId, nextOrderId

private MockDatabase() {}  // No instantiation

UserRepository — key methods

User findByUsername(String username)
User findById(int userId)
boolean save(User user)
boolean update(User user)
boolean delete(int userId)
User[] getAllUsers()
int getNextUserId()

ProductRepository — key methods

Product findById(int productId)
Product[] findAll()
boolean save(Product product)
boolean update(Product product)
boolean delete(int productId)
boolean updateStock(int productId, int quantityChange)  // critical
Product[] searchByName(String keyword)
int getNextProductId()

Seeded with 15 products (phones, laptops, accessories, tablets).

AuthService

String login(String username, String password)
  // returns: "SUCCESS" | "WRONG_PASSWORD" | "USER_NOT_FOUND"
String register(String username, String password)
  // returns: "SUCCESS" | "USERNAME_EXISTS" | "INVALID_PASSWORD"
void logout()
User getCurrentUser()
boolean isLoggedIn()
boolean isAdmin()
private boolean validatePassword(String password)
  // 6+ chars, must have letter AND digit

ShopService — Checkout Algorithm

1. Check isLoggedIn() or return "NOT_LOGGED_IN"
2. Get cart; check itemCount > 0 or return "EMPTY_CART"
3. VALIDATION: for each item, check stock >= quantity
   -> any fail: return "STOCK_ERROR:<productName>"
4. DEDUCTION: productRepository.updateStock(id, -qty) for each
5. CREATE ORDER: generate id, timestamp, calculate total, save
6. CLEAR CART: cartRepository.clear(userId)
7. Return "SUCCESS"

AdminService

Every method checks authService.isAdmin() first, returns "NOT_ADMIN" if false.

Product methods: addNewProduct, addStockToExistingProduct, removeStock, deleteProduct, updateProductPrice, updateProductName, setProductDiscount.

User methods: addUser, updateUser, deleteUser (prevents self-deletion), getAllUsers.

ConsoleUI.java

Only public method: start() — main application loop. All UI methods are private.

public void start()   // while(true) loop -> mainMenu()
private void mainMenu()
private void showProductList()  // paginated, Z/M navigation
private void showBasket()
private void handleCheckout()
private void adminMenu()
private void adminProductMenu()
private void adminUserMenu()
// ... etc