console-crud-with-json.ts

import * as readline from 'readline';

// Interface for User data structure
interface User {
  id: number;
  name: string;
  email: string;
}

// Our simulated "JSON database" (in-memory array)
let users: User[] = [];

// Global variable to track the next ID for new users
let nextId = 1;

// Function to create a new user
function createUser() {
  const rl = readline.createInterface({ input: process.stdin, output: process.stdout });

  rl.question('Enter name: ', (name) => {
    rl.question('Enter email: ', (email) => {
      const newUser: User = { id: nextId++, name, email };
      users.push(newUser);
      console.log(`User created successfully!`);
      rl.close();
    });
  });
}

// Function to read all existing users
function readUsers() {
  if (!users.length) {
    console.log('No users found.');
    return;
  }

  console.log('List of Users:');
  users.forEach((user) => {
    console.log(`ID: ${user.id}, Name: ${user.name}, Email: ${user.email}`);
  });
}

// Function to update an existing user
function updateUser() {
  const rl = readline.createInterface({ input: process.stdin, output: process.stdout });

  rl.question('Enter the ID of the user to update: ', (id) => {
    const userId = parseInt(id);
    const existingUserIndex = users.findIndex((user) => user.id === userId);

    if (existingUserIndex === -1) {
      console.log('User not found.');
      rl.close();
      return;
    }

    rl.question('Enter new name (press Enter to keep existing): ', (newName) => {
      const newEmail = newName.trim() ? newName : users[existingUserIndex].name;

      rl.question('Enter new email (press Enter to keep existing): ', (newEmailInput) => {
        const newEmail = newEmailInput.trim() ? newEmailInput : users[existingUserIndex].email;

        users[existingUserIndex] = { id: userId, name: newEmail, email: newEmail };
        console.log('User updated successfully!');
        rl.close();
      });
    });
  });
}

// Function to delete a user
function deleteUser() {
  const rl = readline.createInterface({ input: process.stdin, output: process.stdout });

  rl.question('Enter the ID of the user to delete: ', (id) => {
    const userId = parseInt(id);
    const existingUserIndex = users.findIndex((user) => user.id === userId);

    if (existingUserIndex === -1) {
      console.log('User not found.');
      rl.close();
      return;
    }

    users.splice(existingUserIndex, 1);
    console.log('User deleted successfully!');
    rl.close();
  });
}

// Main function to display the menu and handle user input
function mainMenu() {
  console.log('\nUser CRUD');
  console.log('1. Create User');
  console.log('2. Read Users');
  console.log('3. Update User');
  console.log('4. Delete User');
  console.log('5. Exit');

  const rl = readline.createInterface({ input: process.stdin, output: process.stdout });
  rl.question('Enter your choice: ', (choice) => {
    const option = parseInt(choice);

    switch (option) {
      case 1:
        createUser();
        break;
      case 2:
        readUsers();
        break;
      case 3:
        updateUser();
        break;
      case 4:
        deleteUser();
        break;
      case 5:
        console.log('Exiting...');
        rl.close();
        process.exit(0); // Exit the program gracefully
      default:
        console.log('Invalid choice.');
    }

    rl.close(); // Close the readline interface after each option selection
  });
}

// Start the program by displaying the main menu
mainMenu();