code

#include <iostream>
#include <fstream>
#include <vector>
#include <iomanip>
using namespace std;

// Base class User
class User {
protected:
    string username, password;  // Username and password for the user
    float balance;              // Account balance
public:
    User() : balance(0.0) {}     // Default constructor initializing balance to 0.0
    virtual void menu() = 0;     // Pure virtual function for menu, implemented by derived classes
    string getUsername() { return username; }  // Getter for username

    // Login function to verify credentials
    bool login(string u, string p) {
        return (u == username && p == password);  // Returns true if username and password match
    }
};

// Derived class Customer
class Customer : public User {
    float fdAmount;    // Fixed deposit amount
    float loanAmount;  // Loan amount
public:
    // Constructor to initialize a customer with username, password, and balance
    Customer(string u, string p) {
        username = u;
        password = p;
        balance = 0.0;  // Initial balance is 0.0
        fdAmount = 0.0; // Initially, no fixed deposit
        loanAmount = 0.0; // Initially, no loan
    }

    // Overridden menu function for customer-specific operations
    void menu() override {
        int choice;
        do {
            // Displaying customer menu options
            cout << "\n[Customer] " << username << "'s Menu\n";
            cout << "1. Check Balance\n2. Deposit\n3. Withdraw\n4. Fixed Deposit\n5. Apply Loan\n6. Logout\nChoice: ";
            cin >> choice;  // Taking customer input for menu choice

            // Switch case for customer operations
            switch (choice) {
                case 1: 
                    cout << "Current Balance: Rs." << balance << endl; // Show balance
                    break;
                case 2: { 
                    float amt; 
                    cout << "Deposit Amount: Rs."; 
                    cin >> amt;   // Taking deposit amount as input
                    balance += amt;  // Add deposit to balance
                    cout << "Deposited Successfully.\n"; 
                    break;
                }
                case 3: { 
                    float amt; 
                    cout << "Withdraw Amount: Rs."; 
                    cin >> amt;   // Taking withdrawal amount as input
                    if (amt <= balance) { 
                        balance -= amt; 
                        cout << "Withdrawn.\n"; // Update balance after withdrawal
                    }
                    else cout << "Insufficient balance.\n";  // Insufficient balance error
                    break;
                }
                case 4: { 
                    float amt; 
                    cout << "FD Amount: Rs."; 
                    cin >> amt;  // Taking Fixed Deposit amount as input
                    if (amt <= balance) {
                        fdAmount += amt;  // Update fixed deposit amount
                        balance -= amt;  // Deduct from balance
                        cout << "FD of Rs." << amt << " created.\n";
                    } else cout << "Insufficient balance.\n";  // Insufficient balance error
                    break;
                }
                case 5: { 
                    float amt; 
                    cout << "Loan Amount: Rs."; 
                    cin >> amt;  // Taking loan amount as input
                    loanAmount += amt;  // Update loan amount
                    cout << "Loan Request Submitted.\n";  // Loan request confirmation
                    break;
                }
                case 6: 
                    cout << "Logging out...\n";  // Logout operation
                    break;
                default: 
                    cout << "Invalid!\n";  // Invalid choice error
            }
        } while (choice != 6);  // Loop continues until the user selects logout option (6)
    }
};

// Derived class Admin
class Admin : public User {
public:
    // Constructor initializing admin's default username and password
    Admin() {
        username = "admin";
        password = "admin123";
    }

    // Overridden menu function for admin-specific operations
    void menu() override {
        cout << "\n[Admin] Welcome, Admin!\n";
        cout << "(In full version: View all users, Approve loans, etc.)\n";  // Placeholder message
    }
};

// Bank system class to manage customers and admin operations
class BankSystem {
    vector<Customer> customers;  // List of customers
    Admin admin;  // Single admin instance

    // Function to save customer data to file
    void saveToFile() {
        ofstream fout("users.txt");  // Open file for writing
        for (auto &c : customers) {  // Iterate over customers
            fout << c.getUsername() << endl;  // Save each customer's username
        }
        fout.close();  // Close the file
    }

public:
    // Function to run the bank system
    void run() {
        int choice;
        do {
            // Displaying main menu
            cout << "\n--- Welcome to CLI Bank ---\n";
            cout << "1. Register\n2. Login as Customer\n3. Login as Admin\n4. Exit\nChoice: ";
            cin >> choice;

            if (choice == 1) {
                // Register new customer
                string u, p;
                cout << "Choose Username: "; cin >> u;
                cout << "Choose Password: "; cin >> p;
                customers.push_back(Customer(u, p));  // Add new customer to the list
                cout << "Registration Successful!\n";
                saveToFile();  // Save customer data to file
            } else if (choice == 2) {
                // Customer login
                string u, p;
                cout << "Username: "; cin >> u;
                cout << "Password: "; cin >> p;
                bool found = false;
                for (auto &c : customers) {
                    if (c.login(u, p)) {  // Check if login credentials match
                        c.menu();  // Show customer menu if login is successful
                        found = true;
                        break;
                    }
                }
                if (!found) cout << "Login Failed.\n";  // Login failure message
            } else if (choice == 3) {
                // Admin login
                string u, p;
                cout << "Admin Username: "; cin >> u;
                cout << "Admin Password: "; cin >> p;
                if (admin.login(u, p)) admin.menu();  // If admin login is successful, show admin menu
                else cout << "Invalid Admin Credentials.\n";  // Admin login failure message
            }
        } while (choice != 4);  // Loop continues until user selects Exit option (4)
        cout << "Thank you for using CLI Bank.\n";  // Exit message
    }
};

int main() {
    BankSystem bank;  // Create an instance of BankSystem
    bank.run();  // Run the bank system
    return 0;  // End of the program
}