UserService.java

import java.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class UserService {
    private static final String FILE_NAME = "users.txt";
    private Scanner scanner;
    
    public UserService() {
        scanner = new Scanner(System.in);
        createFileIfNotExists();
    }
    
    // Create file if not exists
    private void createFileIfNotExists() {
        File file = new File(FILE_NAME);
        try {
            if (file.createNewFile()) {
                System.out.println("Created new file: " + FILE_NAME);
            }
        } catch (IOException e) {
            System.err.println("Error creating file: " + e.getMessage());
        }
    }
    
    // Register new user (CREATE)
    public boolean registerUser() {
        System.out.println("\n=== USER REGISTRATION ===");
        
        String name = getValidatedInput("Enter Name (min 2 characters): ", 
                                       "^[a-zA-Z\\s]{2,}$", 
                                       "Invalid name! Use only letters and spaces, min 2 chars.");
        
        String email = getValidatedInput("Enter Email (valid format): ", 
                                        "^[A-Za-z0-9+_.-]+@(.+)$", 
                                        "Invalid email format!");
        
        // Check if email already exists
        if (isEmailExists(email)) {
            System.out.println("Error: Email already registered!");
            return false;
        }
        
        String password = getValidatedInput("Enter Password (min 6 chars): ", 
                                           "^.{6,}$", 
                                           "Password must be at least 6 characters!");
        
        String role = getValidatedInput("Enter Role (Admin/User/Guest): ", 
                                        "(?i)^(Admin|User|Guest)$", 
                                        "Invalid role! Choose: Admin, User, or Guest");
        
        User newUser = new User(name, email, password, role);
        
        if (saveUserToFile(newUser)) {
            System.out.println("✓ User registered successfully!");
            return true;
        } else {
            System.out.println("✗ Registration failed!");
            return false;
        }
    }
    
    // Save user to file
    private boolean saveUserToFile(User user) {
        try (FileWriter fw = new FileWriter(FILE_NAME, true);
             BufferedWriter bw = new BufferedWriter(fw)) {
            bw.write(user.toFileString());
            bw.newLine();
            return true;
        } catch (IOException e) {
            System.err.println("Error saving user: " + e.getMessage());
            return false;
        }
    }
    
    // Login user (READ for authentication)
    public User loginUser() {
        System.out.println("\n=== USER LOGIN ===");
        
        String email = getValidatedInput("Enter Email: ", 
                                        "^[A-Za-z0-9+_.-]+@(.+)$", 
                                        "Invalid email format!");
        
        String password = getValidatedInput("Enter Password: ", 
                                           "^.{1,}$", 
                                           "Password cannot be empty!");
        
        List<User> users = getAllUsers();
        
        for (User user : users) {
            if (user.getEmail().equals(email) && user.getPassword().equals(password)) {
                System.out.println("✓ Login successful! Welcome " + user.getName());
                return user;
            }
        }
        
        System.out.println("✗ Invalid email or password!");
        return null;
    }
    
    // Search user profile by email (READ)
    public User searchUserByEmail() {
        System.out.println("\n=== SEARCH USER ===");
        
        String email = getValidatedInput("Enter email to search: ", 
                                        "^[A-Za-z0-9+_.-]+@(.+)$", 
                                        "Invalid email format!");
        
        List<User> users = getAllUsers();
        
        for (User user : users) {
            if (user.getEmail().equals(email)) {
                System.out.println("\n✓ User Found:");
                displayUserInfo(user);
                return user;
            }
        }
        
        System.out.println("✗ User not found with email: " + email);
        return null;
    }
    
    // Update user profile (UPDATE)
    public boolean updateProfile(User currentUser) {
        if (currentUser == null) {
            System.out.println("Error: No user logged in!");
            return false;
        }
        
        System.out.println("\n=== UPDATE PROFILE ===");
        System.out.println("Current Information:");
        displayUserInfo(currentUser);
        
        System.out.println("\nWhat would you like to update?");
        System.out.println("1. Name");
        System.out.println("2. Password");
        System.out.println("3. Both");
        System.out.print("Enter choice (1-3): ");
        
        int choice = scanner.nextInt();
        scanner.nextLine(); // Consume newline
        
        String newName = currentUser.getName();
        String newPassword = currentUser.getPassword();
        
        switch (choice) {
            case 1:
                newName = getValidatedInput("Enter new Name (min 2 chars): ", 
                                           "^[a-zA-Z\\s]{2,}$", 
                                           "Invalid name!");
                break;
            case 2:
                newPassword = getValidatedInput("Enter new Password (min 6 chars): ", 
                                               "^.{6,}$", 
                                               "Password must be at least 6 characters!");
                break;
            case 3:
                newName = getValidatedInput("Enter new Name (min 2 chars): ", 
                                           "^[a-zA-Z\\s]{2,}$", 
                                           "Invalid name!");
                newPassword = getValidatedInput("Enter new Password (min 6 chars): ", 
                                               "^.{6,}$", 
                                               "Password must be at least 6 characters!");
                break;
            default:
                System.out.println("Invalid choice!");
                return false;
        }
        
        // Update user object
        currentUser.setName(newName);
        currentUser.setPassword(newPassword);
        
        // Update file with all users
        if (updateAllUsersInFile(currentUser)) {
            System.out.println("✓ Profile updated successfully!");
            return true;
        } else {
            System.out.println("✗ Failed to update profile!");
            return false;
        }
    }
    
    // Get all users from file
    private List<User> getAllUsers() {
        List<User> users = new ArrayList<>();
        
        try (FileReader fr = new FileReader(FILE_NAME);
             BufferedReader br = new BufferedReader(fr)) {
            
            String line;
            while ((line = br.readLine()) != null) {
                if (!line.trim().isEmpty()) {
                    User user = User.fromFileString(line);
                    if (user != null) {
                        users.add(user);
                    }
                }
            }
        } catch (IOException e) {
            System.err.println("Error reading file: " + e.getMessage());
        }
        
        return users;
    }
    
    // Update all users in file after modification
    private boolean updateAllUsersInFile(User updatedUser) {
        List<User> allUsers = getAllUsers();
        
        // Find and update the user
        for (int i = 0; i < allUsers.size(); i++) {
            if (allUsers.get(i).getEmail().equals(updatedUser.getEmail())) {
                allUsers.set(i, updatedUser);
                break;
            }
        }
        
        // Rewrite entire file
        try (FileWriter fw = new FileWriter(FILE_NAME);
             BufferedWriter bw = new BufferedWriter(fw)) {
            
            for (User user : allUsers) {
                bw.write(user.toFileString());
                bw.newLine();
            }
            return true;
            
        } catch (IOException e) {
            System.err.println("Error updating file: " + e.getMessage());
            return false;
        }
    }
    
    // Check if email already exists
    private boolean isEmailExists(String email) {
        List<User> users = getAllUsers();
        for (User user : users) {
            if (user.getEmail().equals(email)) {
                return true;
            }
        }
        return false;
    }
    
    // Display user information
    private void displayUserInfo(User user) {
        System.out.println("┌─────────────────────────┐");
        System.out.println("│ Name     : " + user.getName());
        System.out.println("│ Email    : " + user.getEmail());
        System.out.println("│ Role     : " + user.getRole());
        System.out.println("└─────────────────────────┘");
    }
    
    // Input validation method
    private String getValidatedInput(String prompt, String regex, String errorMessage) {
        String input;
        while (true) {
            System.out.print(prompt);
            input = scanner.nextLine().trim();
            
            if (input.matches(regex)) {
                return input;
            } else {
                System.out.println("✗ " + errorMessage);
            }
        }
    }
    
    // Display all users (for admin purposes)
    public void displayAllUsers() {
        List<User> users = getAllUsers();
        
        if (users.isEmpty()) {
            System.out.println("\nNo users found in the system.");
            return;
        }
        
        System.out.println("\n=== ALL REGISTERED USERS ===");
        System.out.println("Total users: " + users.size());
        System.out.println("┌────────────────────────────────────┐");
        
        for (int i = 0; i < users.size(); i++) {
            User user = users.get(i);
            System.out.println("│ " + (i + 1) + ". " + user.getName() + 
                             " | " + user.getEmail() + 
                             " | " + user.getRole());
        }
        System.out.println("└────────────────────────────────────┘");
    }
}