Absolutely! Let me provide the complete tree structure for both the backend and frontend with all files organized by folders. I’ll ensure no files are left out this time.

Full Project Directory Tree

Backend Folder Structure

backend/
│
├── src/
│   ├── config/
│   │   └── db.ts                           # MongoDB Connection
│   │
│   ├── controllers/
│   │   ├── todoController.ts               # CRUD Logic for Todos
│   │   └── openaiController.ts             # AI API Logic
│   │
│   ├── models/
│   │   └── Todo.ts                         # Mongoose Schema for Todos
│   │
│   ├── routes/
│   │   ├── todoRoutes.ts                   # Routes for Todos
│   │   └── openaiRoutes.ts                 # Routes for AI Features
│   │
│   ├── services/
│   │   └── openaiService.ts                # OpenAI Helper Logic
│   │
│   ├── tests/
│   │   ├── todo.test.ts                    # Tests for CRUD Operations
│   │   └── openai.test.ts                  # Tests for AI API
│   │
│   ├── app.ts                              # Main Express Application
│   └── server.ts                           # Entry Point for the Backend
│
├── .env                                    # Environment Variables
├── tsconfig.json                           # TypeScript Configuration
└── package.json                            # Dependencies and Scripts

Frontend Folder Structure

frontend/
│
├── src/
│   ├── api/
│   │   └── todoApi.ts                      # API Calls for Todos and AI
│   │
│   ├── components/
│   │   ├── AddTodo.tsx                     # Form to Add a New Todo
│   │   ├── TodoItem.tsx                    # Individual Todo Component
│   │   ├── TodoList.tsx                    # Todo List Component
│   │   └── __tests__/
│   │       ├── AddTodo.test.tsx            # Tests for AddTodo Component
│   │       ├── TodoItem.test.tsx           # Tests for TodoItem Component
│   │       └── TodoList.test.tsx           # Tests for TodoList Component
│   │
│   ├── pages/
│   │   ├── TodoPage.tsx                    # Main Todo Page
│   │   └── AiToolsPage.tsx                 # AI Features Page
│   │
│   ├── routes.tsx                          # Application Routes
│   ├── queryClient.ts                      # React Query Client Setup
│   ├── App.tsx                             # Application Layout & Navigation
│   ├── index.tsx                           # React App Entry Point
│   └── setupTests.ts                       # Jest Setup for Tests
│
├── .env                                    # Environment Variables
├── tsconfig.json                           # TypeScript Configuration
└── package.json                            # Dependencies and Scripts

Listing of All Folders and Files

Here is the folder-by-folder listing of all files for both backend and frontend:

Backend Folder Breakdown

1. Folder: src/config/

  • db.ts

2. Folder: src/controllers/

  • todoController.ts
  • openaiController.ts

3. Folder: src/models/

  • Todo.ts

4. Folder: src/routes/

  • todoRoutes.ts
  • openaiRoutes.ts

5. Folder: src/services/

  • openaiService.ts

6. Folder: src/tests/

  • todo.test.ts
  • openai.test.ts

7. Root of src/

  • app.ts
  • server.ts

8. Backend Root Files

  • .env
  • tsconfig.json
  • package.json

Frontend Folder Breakdown

1. Folder: src/api/

  • todoApi.ts

2. Folder: src/components/

  • AddTodo.tsx
  • TodoItem.tsx
  • TodoList.tsx

3. Folder: src/components/__tests__/

  • AddTodo.test.tsx
  • TodoItem.test.tsx
  • TodoList.test.tsx

4. Folder: src/pages/

  • TodoPage.tsx
  • AiToolsPage.tsx

5. Root of src/

  • routes.tsx
  • queryClient.ts
  • App.tsx
  • index.tsx
  • setupTests.ts

6. Frontend Root Files

  • .env
  • tsconfig.json
  • package.json

Backend: Example .env File

Here is the example .env file for the backend, including variables used across the code. This file matches all the environment variables referenced in the project.

.env File

# Server Port
PORT=5000

# MongoDB Connection String
MONGO_URI=mongodb+srv://<username>:<password>@cluster.mongodb.net/todolist

# OpenAI API Key
OPENAI_API_KEY=your_openai_api_key_here

Explanation of Variables

  1. PORT

    • Specifies the port on which the backend server will run.

    • Usage: In server.ts, the server listens on this port. 

      const PORT = process.env.PORT || 5000;
app.listen(PORT, () => console.log(`Server running on port ${PORT}`));

  2. MONGO_URI

    • Connection string for MongoDB Atlas (or a locally hosted MongoDB database).
    • It includes the <username> and <password> placeholders, which need to be replaced with your actual MongoDB credentials.

    • Usage: In db.ts, Mongoose uses this to connect to MongoDB. 

      const conn = await mongoose.connect(process.env.MONGO_URI!);

  3. OPENAI_API_KEY

    • API key for authenticating requests to the OpenAI API.
    • You must obtain this key from OpenAI's platform.

    • Usage: In openaiService.ts, this key is passed to the OpenAI client configuration. 

      const configuration = new Configuration({
apiKey: process.env.OPENAI_API_KEY,
});

Frontend: Example .env File

The frontend also requires an .env file for configuring API URLs.

frontend/.env File

# Backend API URL
REACT_APP_BACKEND_URL=http://localhost:5000

Explanation of Variables

  1. REACT_APP_BACKEND_URL

    • Specifies the base URL of the backend server.
    • React uses this to send API requests for tasks and AI-powered features.

    • Usage: In todoApi.ts, the API calls append routes to this URL. 

      const API_URL = process.env.REACT_APP_BACKEND_URL + '/api/todos';

Key Notes

  1. Both backend and frontend .env files are loaded via respective libraries:

    • Backend: dotenv library (automatically reads .env files).
    • Frontend: React uses REACT_APP_ as a prefix for environment variables.
  2. Replace placeholders like <username> and <password> in MONGO_URI with real credentials.

1. File: src/app.ts

Purpose: Sets up the main Express application with middleware and routes for both Todo API and AI API.

import express from 'express';
import cors from 'cors';
import todoRoutes from './routes/todoRoutes';
import openaiRoutes from './routes/openaiRoutes';

const app = express();

// Middleware
app.use(cors());
app.use(express.json());

// Health Check Route
app.get('/', (req, res) => {
  res.send('API is running...');
});

// API Routes
app.use('/api/todos', todoRoutes); // Routes for CRUD operations
app.use('/api/ai', openaiRoutes);  // Routes for AI-powered features

export default app;

Explanation:

  1. express.json(): Middleware to parse incoming JSON requests.
  2. cors(): Middleware to allow Cross-Origin Resource Sharing (useful for frontend-backend communication).

  3. Routes:

    • '/api/todos' → Handles CRUD operations using todoRoutes.ts.
    • '/api/ai' → Handles AI-related operations using openaiRoutes.ts.
  4. Health Check: A simple GET / route to verify the server is running.

2. File: src/server.ts

Purpose: Entry point for the backend server. It connects to MongoDB, imports the main Express app, and starts the server.

import dotenv from 'dotenv';
import app from './app';
import connectDB from './config/db';

// Load environment variables
dotenv.config();

// Server Configuration
const PORT = process.env.PORT || 5000;

// Connect to MongoDB and Start the Server
connectDB().then(() => {
  app.listen(PORT, () => {
    console.log(`Server running on port ${PORT}`);
  });
}).catch((error) => {
  console.error('Database connection failed:', error);
});

Explanation:

  1. Environment Variables: dotenv.config() loads the .env file to access variables like PORT and MONGO_URI.
  2. connectDB(): Connects to the MongoDB database defined in src/config/db.ts.
  3. app.listen(PORT): Starts the Express server on the specified port.
  4. Error Handling: If MongoDB fails to connect, the server logs an error and exits.

How It Works:

  • server.ts is the entry point of the backend.
  • It first connects to the MongoDB database.
  • If the connection succeeds, it starts the Express server and makes the APIs available.
  • app.ts is imported as the core app configuration (routes, middleware).

1. File: src/config/db.ts

Purpose: Establishes the connection to the MongoDB database using Mongoose.

import mongoose from 'mongoose';
import dotenv from 'dotenv';

// Load environment variables
dotenv.config();

const connectDB = async () => {
  try {
    // Connect to MongoDB using MONGO_URI from .env
    const conn = await mongoose.connect(process.env.MONGO_URI!);

    // Log a success message if connection is successful
    console.log(`MongoDB Connected: ${conn.connection.host}`);
  } catch (error) {
    // Log the error message and exit the process
    console.error(`Error: ${(error as Error).message}`);
    process.exit(1);
  }
};

export default connectDB;

Explanation:

  1. dotenv.config():
    Loads environment variables from the .env file, ensuring MONGO_URI is available.
  2. mongoose.connect():
    Connects to the MongoDB database using the connection string provided in MONGO_URI.
  3. Error Handling:
    If the connection fails, the server logs the error message and exits the process (process.exit(1)).
  4. Success Log:
    On a successful connection, it logs the host to indicate which MongoDB instance was connected.

How It Works:

  • This function is imported into server.ts.
  • Before starting the server, connectDB() ensures a successful MongoDB connection.

  • The MONGO_URI is defined in the .env file as: 

    MONGO_URI=mongodb+srv://<username>:<password>@cluster.mongodb.net/todolist

File: src/models/Todo.ts

Purpose: Defines the Mongoose schema and model for the Todo items.

import mongoose, { Schema, Document } from 'mongoose';

// Define the interface for a Todo document
export interface ITodo extends Document {
  title: string;
  completed: boolean;
}

// Create the Mongoose schema for Todos
const TodoSchema: Schema = new Schema({
  title: {
    type: String,
    required: [true, 'Title is required'], // Validation: Title is mandatory
  },
  completed: {
    type: Boolean,
    default: false, // Default value for "completed" is false
  },
});

// Export the Mongoose model for Todo
export default mongoose.model<ITodo>('Todo', TodoSchema);

Explanation:

  1. ITodo Interface:

    • Defines the structure of a Todo document.
    • Ensures type safety when using Todo objects in TypeScript.

  2. TodoSchema:

    • title:
    • Type: String.
    • Validation: Required field.
    • completed:
    • Type: Boolean.
    • Default: false (new tasks are incomplete by default).

  3. mongoose.model<ITodo>:

    • Creates a Mongoose model named Todo.
    • The model will interact with the todos collection in MongoDB.

Usage in Controllers:

The Todo model is imported in src/controllers/todoController.ts for performing CRUD operations:

import Todo from '../models/Todo';

// Example: Creating a new Todo
const todo = new Todo({ title: 'Learn TypeScript' });
await todo.save();

1. File: src/controllers/todoController.ts

Purpose: Handles CRUD operations for Todo items.

import { Request, Response } from 'express';
import Todo from '../models/Todo';

// @desc    Get all todos
// @route   GET /api/todos
export const getTodos = async (req: Request, res: Response) => {
  try {
    const todos = await Todo.find(); // Fetch all todos from the database
    res.status(200).json(todos);
  } catch (error) {
    res.status(500).json({ message: 'Failed to fetch todos' });
  }
};

// @desc    Create a new todo
// @route   POST /api/todos
export const createTodo = async (req: Request, res: Response) => {
  const { title } = req.body;

  if (!title) {
    return res.status(400).json({ message: 'Title is required' });
  }

  try {
    const todo = new Todo({ title }); // Create a new Todo instance
    await todo.save(); // Save the todo to the database
    res.status(201).json(todo); // Return the created todo
  } catch (error) {
    res.status(500).json({ message: 'Failed to create todo' });
  }
};

// @desc    Delete a todo by ID
// @route   DELETE /api/todos/:id
export const deleteTodo = async (req: Request, res: Response) => {
  const { id } = req.params;

  try {
    const todo = await Todo.findByIdAndDelete(id); // Find and delete by ID
    if (!todo) {
      return res.status(404).json({ message: 'Todo not found' });
    }
    res.status(200).json({ message: 'Todo deleted successfully' });
  } catch (error) {
    res.status(500).json({ message: 'Failed to delete todo' });
  }
};

Explanation:

  1. getTodos:

    • Fetches all Todos from the database.
    • Returns status 200 with the list of todos.

  2. createTodo:

    • Validates the request body for a title.
    • Creates and saves a new Todo document.
    • Returns status 201 with the created Todo.

  3. deleteTodo:

    • Deletes a Todo document based on the id passed in the URL.
    • Returns status 200 if successful, or 404 if not found.

2. File: src/controllers/openaiController.ts

Purpose: Provides AI-powered features like task descriptions using the OpenAI API.

import { Request, Response } from 'express';
import { generateTaskDescription, generateTaskSchedule, suggestSubtasks } from '../services/openaiService';

// @desc    Generate a task description using OpenAI
// @route   POST /api/ai/description
export const getTaskDescription = async (req: Request, res: Response) => {
  const { task } = req.body;

  if (!task) return res.status(400).json({ message: 'Task is required' });

  try {
    const description = await generateTaskDescription(task);
    res.status(200).json({ description });
  } catch (error) {
    res.status(500).json({ message: 'Failed to generate task description' });
  }
};

// @desc    Generate a task schedule using OpenAI
// @route   POST /api/ai/schedule
export const getTaskSchedule = async (req: Request, res: Response) => {
  const { tasks, totalTime } = req.body;

  if (!tasks || !totalTime) return res.status(400).json({ message: 'Tasks and totalTime are required' });

  try {
    const schedule = await generateTaskSchedule(tasks, totalTime);
    res.status(200).json({ schedule });
  } catch (error) {
    res.status(500).json({ message: 'Failed to generate task schedule' });
  }
};

// @desc    Suggest subtasks for a main task using OpenAI
// @route   POST /api/ai/subtasks
export const getSubtasks = async (req: Request, res: Response) => {
  const { task } = req.body;

  if (!task) return res.status(400).json({ message: 'Task is required' });

  try {
    const subtasks = await suggestSubtasks(task);
    res.status(200).json({ subtasks });
  } catch (error) {
    res.status(500).json({ message: 'Failed to generate subtasks' });
  }
};

Explanation:

  1. getTaskDescription:

    • Takes a task description input (task) from the user.
    • Uses the OpenAI API (via openaiService.ts) to generate a detailed description.
    • Returns the generated description.

  2. getTaskSchedule:

    • Accepts a list of tasks and available time (totalTime) from the user.
    • Calls OpenAI to generate a schedule.
    • Returns the structured schedule.

  3. getSubtasks:

    • Takes a main task as input.
    • Calls OpenAI to generate subtasks that help complete the main task.
    • Returns the suggested subtasks as an array.

Usage in Routes:

Both controllers are imported into their respective route files:

  • todoController.ts → todoRoutes.ts
  • openaiController.ts → openaiRoutes.ts

1. File: src/routes/todoRoutes.ts

Purpose: Defines the routes for CRUD operations related to the Todo items.

import { Router } from 'express';
import { getTodos, createTodo, deleteTodo } from '../controllers/todoController';

const router = Router();

/**
 * @route   GET /api/todos
 * @desc    Fetch all todos
 * @access  Public
 */
router.get('/', getTodos);

/**
 * @route   POST /api/todos
 * @desc    Create a new todo
 * @access  Public
 */
router.post('/', createTodo);

/**
 * @route   DELETE /api/todos/:id
 * @desc    Delete a todo by ID
 * @access  Public
 */
router.delete('/:id', deleteTodo);

export default router;

Explanation:

  1. router.get('/'):

    • Maps the GET request to fetch all Todos.
    • Handler: getTodos from todoController.ts.

  2. router.post('/'):

    • Maps the POST request to create a new Todo.
    • Handler: createTodo from todoController.ts.

  3. router.delete('/:id'):

    • Maps the DELETE request to remove a Todo by its id.
    • Handler: deleteTodo from todoController.ts.

2. File: src/routes/openaiRoutes.ts

Purpose: Defines routes for AI-powered features using the OpenAI API.

import { Router } from 'express';
import { getTaskDescription, getTaskSchedule, getSubtasks } from '../controllers/openaiController';

const router = Router();

/**
 * @route   POST /api/ai/description
 * @desc    Generate a task description
 * @access  Public
 */
router.post('/description', getTaskDescription);

/**
 * @route   POST /api/ai/schedule
 * @desc    Generate a schedule based on tasks and available time
 * @access  Public
 */
router.post('/schedule', getTaskSchedule);

/**
 * @route   POST /api/ai/subtasks
 * @desc    Generate subtasks for a main task
 * @access  Public
 */
router.post('/subtasks', getSubtasks);

export default router;

Explanation:

  1. router.post('/description'):

    • Maps the POST request to generate a task description.
    • Handler: getTaskDescription from openaiController.ts.

  2. router.post('/schedule'):

    • Maps the POST request to generate a task schedule based on available time.
    • Handler: getTaskSchedule from openaiController.ts.

  3. router.post('/subtasks'):

    • Maps the POST request to generate subtasks for a given main task.
    • Handler: getSubtasks from openaiController.ts.

Usage in app.ts:

Both route files are connected to the Express app in src/app.ts:

import todoRoutes from './routes/todoRoutes';
import openaiRoutes from './routes/openaiRoutes';

app.use('/api/todos', todoRoutes);
app.use('/api/ai', openaiRoutes);

How They Work Together:

  1. The todoRoutes.ts file manages CRUD operations for Todo items.
  2. The openaiRoutes.ts file handles AI-powered functionalities like generating descriptions, schedules, and subtasks.
  3. Both are mounted on the /api prefix via the Express app configuration.

File: src/services/openaiService.ts

Purpose: Handles the logic for interacting with the OpenAI API to generate task descriptions, schedules, and subtasks.

import { Configuration, OpenAIApi } from 'openai';
import dotenv from 'dotenv';

dotenv.config();

// Initialize OpenAI API with the API key from environment variables
const configuration = new Configuration({
  apiKey: process.env.OPENAI_API_KEY,
});

const openai = new OpenAIApi(configuration);

/**
 * @desc Generates a description for a given task
 * @param task The task for which a description is needed
 * @returns A string containing the task description
 */
export const generateTaskDescription = async (task: string): Promise<string> => {
  const prompt = `Write a brief and concise description for the following task: "${task}"`;

  const response = await openai.createCompletion({
    model: 'text-davinci-003',
    prompt,
    max_tokens: 50,
    temperature: 0.7,
  });

  return response.data.choices[0]?.text?.trim() || 'No description generated.';
};

/**
 * @desc Generates a task schedule based on tasks and available time
 * @param tasks An array of tasks
 * @param totalTime The total time (in hours) available to complete the tasks
 * @returns A string containing the suggested task schedule
 */
export const generateTaskSchedule = async (tasks: string[], totalTime: number): Promise<string> => {
  const taskList = tasks.join(', ');
  const prompt = `Given the following tasks: ${taskList}, and ${totalTime} hours available, create a simple and efficient schedule.`;

  const response = await openai.createCompletion({
    model: 'text-davinci-003',
    prompt,
    max_tokens: 150,
    temperature: 0.7,
  });

  return response.data.choices[0]?.text?.trim() || 'No schedule generated.';
};

/**
 * @desc Generates a list of subtasks for a given main task
 * @param task The main task that needs to be broken into subtasks
 * @returns An array of strings containing suggested subtasks
 */
export const suggestSubtasks = async (task: string): Promise<string[]> => {
  const prompt = `List 3 subtasks to complete the following main task: "${task}"`;

  const response = await openai.createCompletion({
    model: 'text-davinci-003',
    prompt,
    max_tokens: 100,
    temperature: 0.7,
  });

  const suggestions = response.data.choices[0]?.text?.trim().split('\n') || [];
  return suggestions.map((subtask) => subtask.replace(/^\d+\.\s/, '').trim());
};

Explanation:

  1. Initialization:

    • The Configuration object is initialized with the OPENAI_API_KEY from the .env file.
    • The OpenAIApi client is created to communicate with OpenAI's API.

  2. generateTaskDescription:

    • Accepts a single task as input.
    • Sends a prompt to OpenAI to generate a concise description.
    • Example Input: "Clean the kitchen"
    • Example Output: "This task involves tidying up the counters, washing dishes, and sweeping the floor."

  3. generateTaskSchedule:

    • Accepts a list of tasks and the total time available.
    • Sends a structured prompt to OpenAI to generate a suggested task schedule.
    • Example Input:
    • Tasks: ["Clean the kitchen", "Read a book", "Exercise"]
    • Time: 2 hours

    • Example Output:

    • Clean the kitchen - 30 minutes
    • Read a book - 1 hour

    • Exercise - 30 minutes

  4. suggestSubtasks:

    • Breaks a main task into a list of subtasks.
    • Sends a prompt to OpenAI asking for subtasks.
    • Example Input: "Prepare for a presentation"
    • Example Output:
    • ["Create slides", "Practice speech", "Gather supporting data"]

How It’s Used:

The functions are imported into the openaiController.ts file to handle the OpenAI routes:

Example:

import { generateTaskDescription, generateTaskSchedule, suggestSubtasks } from '../services/openaiService';

// Used in routes like POST /api/ai/description
const description = await generateTaskDescription("Clean the kitchen");

Dependencies:

  1. OpenAI Node.js SDK: Installed via:

    npm install openai

  2. Environment Variable:

    • OPENAI_API_KEY → Defined in the .env file.
    • Ensure it is valid for the OpenAI API.

1. File: src/tests/todo.test.ts

Purpose: Tests the CRUD operations for the Todo API endpoints.

import request from 'supertest';
import app from '../app';
import mongoose from 'mongoose';
import Todo from '../models/Todo';
import dotenv from 'dotenv';

dotenv.config();

beforeAll(async () => {
  // Connect to a test database
  await mongoose.connect(process.env.MONGO_URI!);
});

afterAll(async () => {
  // Clean up the test database and close the connection
  await Todo.deleteMany();
  await mongoose.connection.close();
});

describe('Todo API Endpoints', () => {
  let todoId: string;

  // Test GET /api/todos
  it('should fetch all todos (initially empty)', async () => {
    const res = await request(app).get('/api/todos');
    expect(res.statusCode).toEqual(200);
    expect(res.body).toEqual([]);
  });

  // Test POST /api/todos
  it('should create a new todo', async () => {
    const newTodo = { title: 'Test Todo Item' };
    const res = await request(app).post('/api/todos').send(newTodo);

    expect(res.statusCode).toEqual(201);
    expect(res.body.title).toBe(newTodo.title);
    expect(res.body.completed).toBe(false);

    todoId = res.body._id; // Save the ID for future tests
  });

  // Test GET /api/todos after adding a todo
  it('should fetch all todos (contains one item)', async () => {
    const res = await request(app).get('/api/todos');
    expect(res.statusCode).toEqual(200);
    expect(res.body.length).toBe(1);
    expect(res.body[0].title).toBe('Test Todo Item');
  });

  // Test DELETE /api/todos/:id
  it('should delete a todo by ID', async () => {
    const res = await request(app).delete(`/api/todos/${todoId}`);
    expect(res.statusCode).toEqual(200);
    expect(res.body.message).toBe('Todo deleted successfully');
  });

  it('should fetch all todos (should now be empty)', async () => {
    const res = await request(app).get('/api/todos');
    expect(res.statusCode).toEqual(200);
    expect(res.body).toEqual([]);
  });
});

Explanation:

  1. Setup and Teardown:

    • beforeAll: Connects to the MongoDB test database.
    • afterAll: Cleans up the database and closes the connection.

  2. Tests:

    • GET /api/todos: Verifies that the endpoint returns an empty array initially.
    • POST /api/todos: Tests creating a new Todo item.
    • GET /api/todos: Verifies the new Todo was added.
    • DELETE /api/todos/:id: Tests deleting the Todo item and ensures the database is empty afterward.

2. File: src/tests/openai.test.ts

Purpose: Tests the AI-powered routes for generating task descriptions, schedules, and subtasks.

import request from 'supertest';
import app from '../app';
import dotenv from 'dotenv';

dotenv.config();

describe('OpenAI API Endpoints', () => {
  // Test POST /api/ai/description
  it('should generate a task description', async () => {
    const res = await request(app)
      .post('/api/ai/description')
      .send({ task: 'Clean the kitchen' });

    expect(res.statusCode).toEqual(200);
    expect(res.body.description).toBeDefined();
    expect(typeof res.body.description).toBe('string');
  });

  // Test POST /api/ai/schedule
  it('should generate a task schedule', async () => {
    const res = await request(app)
      .post('/api/ai/schedule')
      .send({ tasks: ['Clean the kitchen', 'Read a book'], totalTime: 2 });

    expect(res.statusCode).toEqual(200);
    expect(res.body.schedule).toBeDefined();
    expect(typeof res.body.schedule).toBe('string');
  });

  // Test POST /api/ai/subtasks
  it('should generate subtasks for a main task', async () => {
    const res = await request(app)
      .post('/api/ai/subtasks')
      .send({ task: 'Prepare for a presentation' });

    expect(res.statusCode).toEqual(200);
    expect(res.body.subtasks).toBeDefined();
    expect(Array.isArray(res.body.subtasks)).toBe(true);
    expect(res.body.subtasks.length).toBeGreaterThan(0);
  });

  // Test Error: Missing Input
  it('should return a 400 error if task is missing', async () => {
    const res = await request(app).post('/api/ai/description').send({});
    expect(res.statusCode).toEqual(400);
    expect(res.body.message).toBe('Task is required');
  });
});

Explanation:

  1. Test Cases:

    • POST /api/ai/description: Verifies that OpenAI generates a valid task description.
    • POST /api/ai/schedule: Ensures OpenAI provides a structured schedule.
    • POST /api/ai/subtasks: Checks that OpenAI returns subtasks as an array.
    • Error Test: Ensures the server returns a 400 error if the input is invalid.

  2. Dependencies:

    • The tests rely on a valid OPENAI_API_KEY being set in the .env file.
    • The OpenAI API is tested with actual API calls.

Test Execution:

Run the tests with the following command:

npm test

1. File: tsconfig.json

Purpose: Configures the TypeScript compiler settings for the backend project.

{
  "compilerOptions": {
    "target": "es6",                        // ECMAScript target version
    "module": "commonjs",                   // Output module format
    "rootDir": "./src",                     // Root directory of source files
    "outDir": "./dist",                     // Output directory for compiled files
    "esModuleInterop": true,                // Enables compatibility with ES Modules
    "strict": true,                         // Enable all strict type-checking options
    "skipLibCheck": true,                   // Skip checking of declaration files
    "forceConsistentCasingInFileNames": true // Ensures consistent file casing
  },
  "include": ["src/**/*"],                  // Include all files under src/
  "exclude": ["node_modules", "dist"]       // Exclude compiled and dependency directories
}

Explanation:

  1. target: Specifies the JavaScript version (es6) for the compiled code.
  2. module: Sets the module system to commonjs for Node.js compatibility.
  3. rootDir: The directory containing source TypeScript files.
  4. outDir: The directory where compiled JavaScript files will be output (dist).
  5. esModuleInterop: Allows importing ES Modules in a CommonJS environment.
  6. strict: Enables strict mode for better type-checking and safety.
  7. skipLibCheck: Speeds up the compilation process by skipping .d.ts files.
  8. include/exclude: Specifies which files TypeScript should include or ignore.

2. File: package.json

Purpose: Manages project dependencies, scripts, and metadata for the backend.

{
  "name": "todolist-backend",
  "version": "1.0.0",
  "description": "A full-stack TodoList backend server using Express, MongoDB, and OpenAI API.",
  "main": "dist/server.js",
  "scripts": {
    "dev": "ts-node-dev --respawn --transpile-only src/server.ts", // Development server
    "build": "tsc",                                               // Build TypeScript files
    "start": "node dist/server.js",                               // Start compiled server
    "test": "jest"                                                // Run tests with Jest
  },
  "dependencies": {
    "cors": "^2.8.5",
    "dotenv": "^16.0.3",
    "express": "^4.18.2",
    "mongoose": "^7.0.0",
    "openai": "^3.2.1"
  },
  "devDependencies": {
    "@types/cors": "^2.8.12",
    "@types/express": "^4.17.15",
    "@types/jest": "^29.0.3",
    "@types/node": "^18.0.0",
    "jest": "^29.0.0",
    "supertest": "^6.3.0",
    "ts-node-dev": "^2.0.0",
    "typescript": "^5.0.0"
  },
  "keywords": ["todo", "express", "mongodb", "openai", "typescript"],
  "author": "Your Name",
  "license": "MIT"
}

Explanation:

  1. scripts:

    • dev: Runs the development server using ts-node-dev for hot-reloading.
    • build: Compiles TypeScript files into JavaScript using tsc.
    • start: Runs the compiled server from the dist folder.
    • test: Runs Jest tests.

  2. Dependencies:

    • express: Web framework for building the server.
    • mongoose: ODM (Object-Document Mapper) for MongoDB.
    • openai: SDK for interacting with OpenAI's API.
    • cors: Middleware for handling Cross-Origin Resource Sharing.
    • dotenv: Manages environment variables.

  3. Dev Dependencies:

    • typescript: TypeScript compiler.
    • ts-node-dev: Development tool for running TypeScript files with hot-reloading.
    • jest and supertest: Testing tools.
    • @types/...: Type definitions for libraries to enable TypeScript support.
  4. main: Entry point for the production server.
  5. keywords, author, license: Metadata fields for the project.

How It Works:

  1. Development: Use npm run dev to start the server with TypeScript hot-reloading.
  2. Production: Use npm run build to compile TypeScript and npm start to run the production server.
  3. Testing: Use npm test to run unit tests.

File: src/api/todoApi.ts

Purpose: Handles API calls from the frontend to interact with the backend's Todo API and AI-powered endpoints.

import axios from 'axios';

const API_BASE_URL = process.env.REACT_APP_BACKEND_URL; // Defined in frontend `.env` file

// API endpoint for Todo operations
const TODOS_API_URL = `${API_BASE_URL}/api/todos`;
// API endpoint for AI operations
const AI_API_URL = `${API_BASE_URL}/api/ai`;

/**
 * @desc Fetch all todos
 * @returns A list of todos from the backend
 */
export const fetchTodos = async () => {
  const response = await axios.get(TODOS_API_URL);
  return response.data;
};

/**
 * @desc Create a new todo
 * @param title - Title of the todo item
 * @returns The created todo object
 */
export const createTodo = async (title: string) => {
  const response = await axios.post(TODOS_API_URL, { title });
  return response.data;
};

/**
 * @desc Delete a todo by ID
 * @param id - ID of the todo to be deleted
 * @returns A success message from the backend
 */
export const deleteTodo = async (id: string) => {
  const response = await axios.delete(`${TODOS_API_URL}/${id}`);
  return response.data;
};

/**
 * @desc Generate a description for a task using OpenAI
 * @param task - The task description to enhance
 * @returns Generated task description from the backend
 */
export const generateTaskDescription = async (task: string) => {
  const response = await axios.post(`${AI_API_URL}/description`, { task });
  return response.data.description;
};

/**
 * @desc Generate a task schedule based on available time
 * @param tasks - Array of tasks
 * @param totalTime - Total time (in hours) available to complete tasks
 * @returns Generated schedule from the backend
 */
export const generateTaskSchedule = async (tasks: string[], totalTime: number) => {
  const response = await axios.post(`${AI_API_URL}/schedule`, { tasks, totalTime });
  return response.data.schedule;
};

/**
 * @desc Generate subtasks for a given main task using OpenAI
 * @param task - The main task
 * @returns Array of subtasks generated from the backend
 */
export const generateSubtasks = async (task: string) => {
  const response = await axios.post(`${AI_API_URL}/subtasks`, { task });
  return response.data.subtasks;
};

Explanation:

  1. API_BASE_URL:

    • The base URL for the backend API, loaded from the .env file: 

      REACT_APP_BACKEND_URL=http://localhost:5000

  2. Todo API:

    • fetchTodos: Sends a GET request to fetch all Todo items.
    • createTodo: Sends a POST request to create a new Todo with the provided title.
    • deleteTodo: Sends a DELETE request to remove a Todo by its ID.

  3. AI API:

    • generateTaskDescription: Sends a POST request to generate a detailed description for a given task.
    • generateTaskSchedule: Sends a POST request with tasks and time to get a schedule.
    • generateSubtasks: Sends a POST request with a task to get a list of subtasks.

  4. Usage:

    • Each function sends HTTP requests using Axios.
    • They return the relevant data field from the backend response.

Example Usage in Components:

  1. Fetching Todos:

    import { fetchTodos } from '../api/todoApi';

const todos = await fetchTodos();
console.log(todos);

  2. Creating a Todo:

    import { createTodo } from '../api/todoApi';

const newTodo = await createTodo('Write a blog post');
console.log(newTodo);

  3. Generating Task Description:

    import { generateTaskDescription } from '../api/todoApi';

const description = await generateTaskDescription('Clean the kitchen');
console.log(description);

Dependencies:

  1. Axios: Installed via: 

    npm install axios

  2. Environment Variable:
    Ensure the following is set in your .env file:

    REACT_APP_BACKEND_URL=http://localhost:5000

This file serves as the single source of truth for all API interactions, keeping the frontend clean and organized.

1. File: src/components/AddTodo.tsx

Purpose: A form component for adding new todos to the list.

import React, { useState } from 'react';
import { useMutation, useQueryClient } from '@tanstack/react-query';
import { createTodo } from '../api/todoApi';

const AddTodo: React.FC = () => {
  const [title, setTitle] = useState('');
  const queryClient = useQueryClient();

  // Mutation for adding a new todo
  const mutation = useMutation(createTodo, {
    onSuccess: () => {
      queryClient.invalidateQueries(['todos']); // Refetch the todos list
      setTitle(''); // Clear the input field
    },
  });

  const handleSubmit = (e: React.FormEvent) => {
    e.preventDefault();
    if (title.trim()) {
      mutation.mutate(title); // Trigger the API call
    }
  };

  return (
    <form onSubmit={handleSubmit} style={{ marginBottom: '1rem' }}>
      <input
        type="text"
        placeholder="Add a new task..."
        value={title}
        onChange={(e) => setTitle(e.target.value)}
        style={{ padding: '0.5rem', marginRight: '0.5rem', width: '250px' }}
      />
      <button
        type="submit"
        disabled={mutation.isLoading}
        style={{ padding: '0.5rem' }}
      >
        {mutation.isLoading ? 'Adding...' : 'Add Todo'}
      </button>
    </form>
  );
};

export default AddTodo;

Explanation:

  1. State Management:

    • title tracks the value of the input field.
    • Cleared after successfully adding a Todo.

  2. React Query:

    • useMutation: Handles the creation of a new Todo using the createTodo API call.
    • onSuccess: Invalidates the todos query to refetch the updated list.

  3. Form Submission:

    • Prevents default behavior and triggers the mutation if input is not empty.

2. File: src/components/TodoItem.tsx

Purpose: Renders a single todo item with a delete button and a checkbox for marking completion.

import React from 'react';
import * as Checkbox from '@radix-ui/react-checkbox';
import { Check, Trash } from 'phosphor-react';

interface TodoItemProps {
  id: string;
  title: string;
  completed: boolean;
  onDelete: () => void;
  onToggle: () => void;
}

const TodoItem: React.FC<TodoItemProps> = ({
  id,
  title,
  completed,
  onDelete,
  onToggle,
}) => {
  return (
    <div
      style={{
        display: 'flex',
        justifyContent: 'space-between',
        alignItems: 'center',
        padding: '0.5rem 1rem',
        border: '1px solid #ddd',
        borderRadius: '5px',
        marginBottom: '0.5rem',
        backgroundColor: completed ? '#f0f0f0' : '#fff',
      }}
    >
      <div style={{ display: 'flex', alignItems: 'center', gap: '0.5rem' }}>
        <Checkbox.Root checked={completed} onCheckedChange={onToggle}>
          <Checkbox.Indicator>
            <Check size={18} />
          </Checkbox.Indicator>
        </Checkbox.Root>
        <span style={{ textDecoration: completed ? 'line-through' : 'none' }}>
          {title}
        </span>
      </div>
      <button
        onClick={onDelete}
        style={{
          background: 'none',
          border: 'none',
          cursor: 'pointer',
          color: 'red',
        }}
      >
        <Trash size={20} />
      </button>
    </div>
  );
};

export default TodoItem;

Explanation:

  1. Props:

    • id, title, completed: Data for the todo item.
    • onDelete, onToggle: Event handlers for deleting or toggling completion.

  2. Radix UI Checkbox:

    • Used for marking a task as completed.
    • Checkbox.Indicator: Displays a check icon when the box is checked.

  3. Phosphor Icons:

    • Check: For the checkbox.
    • Trash: For the delete button.

  4. Styling:

    • Highlights completed tasks with a grey background and strikethrough text.

3. File: src/components/TodoList.tsx

Purpose: Fetches and displays the list of todos using React Query.

import React from 'react';
import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
import { fetchTodos, deleteTodo, createTodo } from '../api/todoApi';
import TodoItem from './TodoItem';

const TodoList: React.FC = () => {
  const queryClient = useQueryClient();

  // Fetch Todos
  const { data: todos = [], isLoading, error } = useQuery(['todos'], fetchTodos);

  // Mutation for deleting a Todo
  const deleteMutation = useMutation(deleteTodo, {
    onSuccess: () => queryClient.invalidateQueries(['todos']),
  });

  // Mutation for toggling a Todo's completion status
  const toggleMutation = useMutation(
    async (todo: any) => {
      return createTodo({ ...todo, completed: !todo.completed });
    },
    {
      onSuccess: () => queryClient.invalidateQueries(['todos']),
    }
  );

  if (isLoading) return <p>Loading todos...</p>;
  if (error) return <p>Failed to load todos.</p>;

  return (
    <div>
      {todos.map((todo: any) => (
        <TodoItem
          key={todo._id}
          id={todo._id}
          title={todo.title}
          completed={todo.completed}
          onDelete={() => deleteMutation.mutate(todo._id)}
          onToggle={() => toggleMutation.mutate(todo)}
        />
      ))}
    </div>
  );
};

export default TodoList;

Explanation:

  1. React Query:

    • useQuery: Fetches the list of Todos from the backend using fetchTodos.
    • useMutation:
    • Handles deletion with deleteTodo.
    • Toggles the completion status by re-creating a Todo with modified completed status.

  2. Loading and Error States:

    • Shows a loading message while fetching data.
    • Displays an error message if fetching fails.

  3. Mapping Todos:

    • Each todo is rendered using the TodoItem component.
    • Handlers for deleting and toggling are passed as props.

How It All Connects:

  • AddTodo: Allows users to add new todos.
  • TodoList: Fetches and displays the list of todos.
  • TodoItem: Handles individual todo actions like delete and toggle.

1. File: src/components/__tests__/AddTodo.test.tsx

Purpose: Tests the AddTodo component to ensure it works as expected when adding new todos.

import React from 'react';
import { render, screen, fireEvent } from '@testing-library/react';
import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
import AddTodo from '../AddTodo';
import { createTodo } from '../../api/todoApi';

jest.mock('../../api/todoApi'); // Mock the API calls

const queryClient = new QueryClient();

describe('AddTodo Component', () => {
  it('renders input and button', () => {
    render(
      <QueryClientProvider client={queryClient}>
        <AddTodo />
      </QueryClientProvider>
    );

    expect(screen.getByPlaceholderText(/add a new task/i)).toBeInTheDocument();
    expect(screen.getByRole('button', { name: /add todo/i })).toBeInTheDocument();
  });

  it('calls createTodo API and clears input on submission', async () => {
    const mockedCreateTodo = createTodo as jest.Mock;
    mockedCreateTodo.mockResolvedValue({ title: 'Test Todo', completed: false });

    render(
      <QueryClientProvider client={queryClient}>
        <AddTodo />
      </QueryClientProvider>
    );

    const input = screen.getByPlaceholderText(/add a new task/i);
    const button = screen.getByRole('button', { name: /add todo/i });

    fireEvent.change(input, { target: { value: 'Test Todo' } });
    fireEvent.click(button);

    expect(mockedCreateTodo).toHaveBeenCalledWith('Test Todo');
    expect(input).toHaveValue('');
  });
});

Explanation:

  1. Mocking:

    • The createTodo function is mocked to avoid real API calls.

  2. Test Cases:

    • Render Test: Verifies the input and button render correctly.
    • Submission Test: Ensures the API is called with correct data and the input clears after submission.

2. File: src/components/__tests__/TodoItem.test.tsx

Purpose: Tests the TodoItem component for toggling completion and deleting a todo.

import React from 'react';
import { render, screen, fireEvent } from '@testing-library/react';
import TodoItem from '../TodoItem';

describe('TodoItem Component', () => {
  const mockOnDelete = jest.fn();
  const mockOnToggle = jest.fn();

  const todoProps = {
    id: '1',
    title: 'Test Todo',
    completed: false,
    onDelete: mockOnDelete,
    onToggle: mockOnToggle,
  };

  it('renders the todo item with title and delete button', () => {
    render(<TodoItem {...todoProps} />);

    expect(screen.getByText('Test Todo')).toBeInTheDocument();
    expect(screen.getByRole('button')).toBeInTheDocument();
  });

  it('calls onDelete when delete button is clicked', () => {
    render(<TodoItem {...todoProps} />);

    fireEvent.click(screen.getByRole('button'));
    expect(mockOnDelete).toHaveBeenCalled();
  });

  it('calls onToggle when checkbox is clicked', () => {
    render(<TodoItem {...todoProps} />);

    const checkbox = screen.getByRole('checkbox');
    fireEvent.click(checkbox);
    expect(mockOnToggle).toHaveBeenCalled();
  });
});

Explanation:

  1. Mock Functions:

    • mockOnDelete and mockOnToggle simulate the handlers passed as props.

  2. Test Cases:

    • Render Test: Ensures the title and delete button render correctly.
    • Event Tests:
    • Verifies the delete handler triggers when the button is clicked.
    • Ensures the toggle handler triggers when the checkbox is clicked.

3. File: src/components/__tests__/TodoList.test.tsx

Purpose: Tests the TodoList component to verify data fetching and rendering behavior.

import React from 'react';
import { render, screen, waitFor } from '@testing-library/react';
import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
import TodoList from '../TodoList';
import { fetchTodos } from '../../api/todoApi';

jest.mock('../../api/todoApi'); // Mock the API calls

const queryClient = new QueryClient();

describe('TodoList Component', () => {
  const mockTodos = [
    { _id: '1', title: 'Todo 1', completed: false },
    { _id: '2', title: 'Todo 2', completed: true },
  ];

  it('renders loading state initially', () => {
    (fetchTodos as jest.Mock).mockReturnValue(new Promise(() => {})); // Simulate pending promise

    render(
      <QueryClientProvider client={queryClient}>
        <TodoList />
      </QueryClientProvider>
    );

    expect(screen.getByText(/loading todos/i)).toBeInTheDocument();
  });

  it('renders todos after fetching data', async () => {
    (fetchTodos as jest.Mock).mockResolvedValue(mockTodos);

    render(
      <QueryClientProvider client={queryClient}>
        <TodoList />
      </QueryClientProvider>
    );

    await waitFor(() => {
      expect(screen.getByText('Todo 1')).toBeInTheDocument();
      expect(screen.getByText('Todo 2')).toBeInTheDocument();
    });
  });

  it('handles error state', async () => {
    (fetchTodos as jest.Mock).mockRejectedValue(new Error('Failed to fetch'));

    render(
      <QueryClientProvider client={queryClient}>
        <TodoList />
      </QueryClientProvider>
    );

    await waitFor(() => {
      expect(screen.getByText(/failed to load todos/i)).toBeInTheDocument();
    });
  });
});

Explanation:

  1. Mocking:

    • fetchTodos is mocked to simulate data fetching.

  2. Test Cases:

    • Loading State: Ensures "Loading todos..." is shown when data is still loading.
    • Success State: Verifies that the list of todos renders correctly after fetching.
    • Error State: Tests that an error message is displayed when fetching fails.

How to Run These Tests:

  1. Ensure Jest and React Testing Library are installed.

  2. Run the tests with the following command: 

    npm test

Summary:

  • AddTodo.test.tsx: Tests form behavior and API interaction.
  • TodoItem.test.tsx: Tests UI rendering and event handling for a single todo item.
  • TodoList.test.tsx: Tests data fetching, loading, success, and error states for the todo list.

1. File: src/pages/TodoPage.tsx

Purpose: This is the main page for managing todos. It integrates the AddTodo form and the TodoList components.

import React from 'react';
import AddTodo from '../components/AddTodo';
import TodoList from '../components/TodoList';

const TodoPage: React.FC = () => {
  return (
    <div style={{ padding: '2rem', maxWidth: '600px', margin: '0 auto' }}>
      <h1 style={{ textAlign: 'center', marginBottom: '1.5rem' }}>Todo List</h1>
      <AddTodo /> {/* Component for adding new todos */}
      <TodoList /> {/* Component for displaying the todo list */}
    </div>
  );
};

export default TodoPage;

Explanation:

  1. Integration: Combines two key components:

    • AddTodo: Handles adding new todo items.
    • TodoList: Fetches and displays the list of todos.

  2. Styling:

    • Basic inline styles to center content and add spacing.
    • Title "Todo List" is centered with some margin.
  3. Purpose: Serves as the primary page where users manage their tasks.

2. File: src/pages/AiToolsPage.tsx

Purpose: This page allows users to use AI-powered tools for generating task descriptions, schedules, and subtasks.

import React, { useState } from 'react';
import { generateTaskDescription, generateTaskSchedule, generateSubtasks } from '../api/todoApi';

const AiToolsPage: React.FC = () => {
  const [task, setTask] = useState('');
  const [description, setDescription] = useState('');
  const [subtasks, setSubtasks] = useState<string[]>([]);
  const [tasks, setTasks] = useState<string[]>([]);
  const [totalTime, setTotalTime] = useState<number>(0);
  const [schedule, setSchedule] = useState('');

  const handleGenerateDescription = async () => {
    if (task.trim()) {
      const result = await generateTaskDescription(task);
      setDescription(result);
    }
  };

  const handleGenerateSubtasks = async () => {
    if (task.trim()) {
      const result = await generateSubtasks(task);
      setSubtasks(result);
    }
  };

  const handleGenerateSchedule = async () => {
    if (tasks.length > 0 && totalTime > 0) {
      const result = await generateTaskSchedule(tasks, totalTime);
      setSchedule(result);
    }
  };

  return (
    <div style={{ padding: '2rem', maxWidth: '800px', margin: '0 auto' }}>
      <h1 style={{ textAlign: 'center', marginBottom: '1.5rem' }}>AI Tools</h1>

      {/* Task Description Section */}
      <div style={{ marginBottom: '2rem' }}>
        <h2>Generate Task Description</h2>
        <input
          type="text"
          placeholder="Enter a task..."
          value={task}
          onChange={(e) => setTask(e.target.value)}
          style={{ padding: '0.5rem', width: '80%' }}
        />
        <button
          onClick={handleGenerateDescription}
          style={{ marginLeft: '0.5rem', padding: '0.5rem' }}
        >
          Generate
        </button>
        {description && <p style={{ marginTop: '1rem' }}>Description: {description}</p>}
      </div>

      {/* Subtasks Section */}
      <div style={{ marginBottom: '2rem' }}>
        <h2>Generate Subtasks</h2>
        <button onClick={handleGenerateSubtasks} style={{ padding: '0.5rem' }}>
          Generate Subtasks
        </button>
        {subtasks.length > 0 && (
          <ul style={{ marginTop: '1rem' }}>
            {subtasks.map((subtask, index) => (
              <li key={index}>{subtask}</li>
            ))}
          </ul>
        )}
      </div>

      {/* Schedule Section */}
      <div style={{ marginBottom: '2rem' }}>
        <h2>Generate Task Schedule</h2>
        <textarea
          placeholder="Enter tasks separated by commas..."
          onChange={(e) => setTasks(e.target.value.split(',').map((t) => t.trim()))}
          style={{ padding: '0.5rem', width: '80%', height: '80px' }}
        />
        <input
          type="number"
          placeholder="Enter total time (hours)..."
          onChange={(e) => setTotalTime(Number(e.target.value))}
          style={{ padding: '0.5rem', marginLeft: '0.5rem', width: '20%' }}
        />
        <button onClick={handleGenerateSchedule} style={{ marginTop: '1rem', padding: '0.5rem' }}>
          Generate Schedule
        </button>
        {schedule && <p style={{ marginTop: '1rem' }}>Schedule: {schedule}</p>}
      </div>
    </div>
  );
};

export default AiToolsPage;

Explanation:

  1. State Management:

    • Tracks inputs and results for each AI tool:
    • task → User input for descriptions or subtasks.
    • description → Result from the AI-generated task description.
    • subtasks → List of subtasks generated.
    • tasks and totalTime → Inputs for generating a task schedule.
    • schedule → Generated task schedule output.

  2. API Calls:

    • Uses the generateTaskDescription, generateSubtasks, and generateTaskSchedule functions from todoApi.ts.

  3. Input Fields:

    • Text inputs and a textarea allow users to provide tasks, subtasks, or schedules.

  4. Output:

    • Displays the generated description, subtasks, or schedule dynamically.

  5. Styling:

    • Inline styles are used for simple layout and spacing.

Summary:

  • TodoPage.tsx: Main page for managing todos. Combines AddTodo and TodoList components.
  • AiToolsPage.tsx: Provides AI tools for task descriptions, subtasks, and schedules. Integrates with OpenAI endpoints via todoApi.ts.

1. File: src/routes.tsx

Purpose: Defines the application's routes using TanStack/React Router.

import { createBrowserRouter, RouterProvider, Outlet } from '@tanstack/react-router';
import TodoPage from './pages/TodoPage';
import AiToolsPage from './pages/AiToolsPage';
import App from './App';

// Define the main routes
const router = createBrowserRouter([
  {
    path: '/',
    element: <App />,
    children: [
      { path: '/', element: <TodoPage /> },
      { path: '/ai-tools', element: <AiToolsPage /> },
    ],
  },
]);

export default function Routes() {
  return <RouterProvider router={router} />;
}

Explanation:

  1. createBrowserRouter: Configures the React Router with routes for TodoPage and AiToolsPage.
  2. Parent Route (App): The layout for shared elements like navigation.

  3. Child Routes:

    • / → TodoPage (main Todo List).
    • /ai-tools → AiToolsPage (AI-powered tools).
  4. RouterProvider: Makes the router available throughout the app.

2. File: src/queryClient.ts

Purpose: Configures React Query for managing server state.

import { QueryClient } from '@tanstack/react-query';

const queryClient = new QueryClient();

export default queryClient;

Explanation:

  1. QueryClient: Initializes a React Query client instance.
  2. Usage: The queryClient will be provided to the app via QueryClientProvider in index.tsx.

3. File: src/App.tsx

Purpose: Serves as the root layout for the app, including navigation and routing.

import React from 'react';
import { Link, Outlet } from '@tanstack/react-router';

const App: React.FC = () => {
  return (
    <div style={{ fontFamily: 'Arial, sans-serif' }}>
      <nav
        style={{
          display: 'flex',
          justifyContent: 'space-around',
          padding: '1rem',
          borderBottom: '1px solid #ddd',
        }}
      >
        <Link to="/" style={{ textDecoration: 'none', fontWeight: 'bold' }}>
          Todo List
        </Link>
        <Link to="/ai-tools" style={{ textDecoration: 'none', fontWeight: 'bold' }}>
          AI Tools
        </Link>
      </nav>
      <main style={{ padding: '2rem' }}>
        <Outlet /> {/* Renders child components */}
      </main>
    </div>
  );
};

export default App;

Explanation:

  1. Navigation: Provides links to / (Todo List) and /ai-tools (AI Tools).
  2. Outlet: Acts as a placeholder for child routes.
  3. Styling: Simple inline styles for layout and navigation bar.

4. File: src/index.tsx

Purpose: Entry point for the React application.

import React from 'react';
import ReactDOM from 'react-dom/client';
import { QueryClientProvider } from '@tanstack/react-query';
import Routes from './routes';
import queryClient from './queryClient';

const root = ReactDOM.createRoot(document.getElementById('root') as HTMLElement);

root.render(
  <React.StrictMode>
    <QueryClientProvider client={queryClient}>
      <Routes /> {/* Provides the app's routing */}
    </QueryClientProvider>
  </React.StrictMode>
);

Explanation:

  1. ReactDOM: Mounts the app onto the DOM node with the ID root.
  2. QueryClientProvider: Makes React Query's queryClient available throughout the app.
  3. Routes: Wraps the app with routing configuration.

5. File: src/setupTests.ts

Purpose: Configures Jest for React Testing Library.

import '@testing-library/jest-dom';

Explanation:

  1. @testing-library/jest-dom: Provides additional Jest matchers (e.g., toBeInTheDocument()).

Summary:

  • routes.tsx: Manages application routing using TanStack/React Router.
  • queryClient.ts: Configures React Query's client for managing server state.
  • App.tsx: Root layout with navigation and Outlet for routing child components.
  • index.tsx: Entry point for the React application, integrating React Query and routing.
  • setupTests.ts: Configures Jest with React Testing Library.

1. File: tsconfig.json

Purpose: Configures TypeScript compiler settings for the frontend.

{
  "compilerOptions": {
    "target": "es6",                        // Target ECMAScript version
    "lib": ["dom", "dom.iterable", "esnext"], // Libraries to include
    "allowJs": true,                        // Allow JavaScript files
    "skipLibCheck": true,                   // Skip checking type declarations
    "esModuleInterop": true,                // Enable ES module compatibility
    "strict": true,                         // Enable strict type-checking options
    "forceConsistentCasingInFileNames": true, // Enforce consistent file casing
    "module": "esnext",                     // Use ES module syntax
    "moduleResolution": "node",             // Node.js-style module resolution
    "resolveJsonModule": true,              // Allow importing JSON files
    "isolatedModules": true,                // Emit files independently
    "jsx": "react-jsx",                     // Use React JSX syntax
    "baseUrl": "./",                        // Base directory for module resolution
    "paths": {
      "@/*": ["src/*"]                      // Alias for imports
    },
    "outDir": "./dist"                      // Output directory for compiled files
  },
  "include": ["src"],
  "exclude": ["node_modules", "dist"]
}

Explanation:

  1. target: Sets the JavaScript version for compiled code to es6.
  2. lib: Includes DOM libraries for browser compatibility.
  3. strict: Enforces strict type-checking rules for safer code.
  4. module and moduleResolution: Configures ES module usage and Node-style resolution.
  5. jsx: Enables React JSX support.
  6. paths: Allows the use of @/ as an alias for src/ to simplify imports.
  7. include/exclude: Specifies which files TypeScript should include or ignore.

2. File: package.json

Purpose: Manages the frontend's dependencies, scripts, and metadata.

{
  "name": "todolist-frontend",
  "version": "1.0.0",
  "description": "A frontend React application for a TodoList integrated with AI tools.",
  "scripts": {
    "start": "react-scripts start",       // Starts the development server
    "build": "react-scripts build",       // Builds the app for production
    "test": "react-scripts test",         // Runs tests
    "eject": "react-scripts eject"        // Ejects the app configuration
  },
  "dependencies": {
    "@radix-ui/react-checkbox": "^1.0.0", // UI component for checkboxes
    "@tanstack/react-query": "^4.0.0",    // React Query for state management
    "@tanstack/react-router": "^1.0.0",   // TanStack React Router
    "axios": "^1.0.0",                    // HTTP client for API calls
    "phosphor-react": "^1.4.1",           // Icon library for React
    "react": "^18.2.0",                   // React library
    "react-dom": "^18.2.0",               // React DOM for rendering
    "react-scripts": "5.0.1"              // React scripts for CRA
  },
  "devDependencies": {
    "@testing-library/jest-dom": "^5.16.5",
    "@testing-library/react": "^13.3.0",
    "@testing-library/user-event": "^14.4.3",
    "@types/jest": "^29.0.3",
    "@types/node": "^18.0.0",
    "@types/react": "^18.0.15",
    "@types/react-dom": "^18.0.6",
    "typescript": "^5.0.0"
  },
  "browserslist": {
    "production": [">0.2%", "not dead", "not op_mini all"],
    "development": ["last 1 chrome version", "last 1 firefox version", "last 1 safari version"]
  },
  "keywords": ["todo", "react", "ai", "typescript", "todolist"],
  "author": "Your Name",
  "license": "MIT"
}

Explanation:

  1. Scripts:

    • start: Starts the development server (localhost:3000).
    • build: Builds the project for production.
    • test: Runs unit tests using Jest.
    • eject: Ejects the configuration (advanced usage).

  2. Dependencies:

    • Core Libraries:
    • react and react-dom → React framework.
    • react-scripts → Tooling provided by Create React App.
    • State Management:
    • @tanstack/react-query → Fetch and manage server state.
    • Routing:
    • @tanstack/react-router → For handling routes.
    • API Calls:
    • axios → Simplifies HTTP requests.
    • UI & Icons:
    • @radix-ui/react-checkbox → Checkbox components.
    • phosphor-react → Icons for buttons and visuals.

  3. Dev Dependencies:

    • Testing Libraries:
    • @testing-library/react → Unit testing for React components.
    • @testing-library/jest-dom → Extra Jest matchers.
    • TypeScript:
    • typescript → TypeScript compiler.
    • @types/* → Type definitions for dependencies.

  4. browserslist:

    • Specifies which browsers to support in production and development.

How to Install and Run:

  1. Install dependencies:

    npm install

  2. Start the development server:

    npm start

  3. Build for production:

    npm run build

  4. Run tests:

    npm test

Summary:

  • tsconfig.json: Configures TypeScript to support React and ESNext features.
  • package.json: Manages scripts, dependencies, and metadata for the React frontend.

Overview of Major Topics and Key Concepts

This section explains the major concepts covered in building the TodoList with AI Tools project and how these concepts can be generalized to build other applications using the modern stack of React, TypeScript, React Query, React Router, Express, MongoDB, and OpenAI API.

1. React and TypeScript Fundamentals

What You Learned:

  • React Components: You used React functional components (AddTodo, TodoItem, TodoList) to structure the UI.

  • Props and State:

    • Props allow data to flow from parent to child components.
    • State is managed with React hooks like useState to handle input fields and UI states.

  • TypeScript Integration:

    • TypeScript ensures type safety, reducing runtime errors.
    • Interface declarations like interface TodoItemProps help define expected component props.

    • Example:

      interface TodoItemProps {
id: string;
title: string;
completed: boolean;
onDelete: () => void;
}

Why It’s Important:

Understanding React with TypeScript helps you build scalable and maintainable frontends. You can extend this knowledge to build other apps like a notes app, bookmarks app, or a task tracker.

2. React Query for State Management

What You Learned:

  • Fetching Data: You used useQuery to fetch todos from the backend:

    const { data: todos } = useQuery(['todos'], fetchTodos);

  • Mutating Data: You used useMutation to add, delete, or update data:

    const mutation = useMutation(createTodo, {
 onSuccess: () => queryClient.invalidateQueries(['todos']);
});
  • Cache Invalidation: When the data changes (e.g., adding a todo), you invalidated the query to trigger a refetch and sync the UI.

Why It’s Important:

React Query simplifies data fetching and state management by caching data, reducing the need for manual state handling. Use it to fetch data from REST APIs, GraphQL, or any server-side endpoint for apps like blogs, chat systems, or e-commerce stores.

3. React Router for Navigation

What You Learned:

  • Routes Setup: You created routes for different pages using createBrowserRouter:

    const router = createBrowserRouter([
 { path: '/', element: <TodoPage /> },
 { path: '/ai-tools', element: <AiToolsPage /> },
]);
  • Outlet: Used <Outlet /> in the root layout to render nested routes dynamically.

Why It’s Important:

React Router allows you to navigate between different pages in your app. You can use this for multi-page applications like blogs, admin dashboards, or e-commerce sites.

4. Building a Backend with Express and MongoDB

What You Learned:

  • Express Server: You created a REST API with endpoints to handle CRUD operations.

  • MongoDB Integration: You used Mongoose to define schemas and interact with the MongoDB database:

    const TodoSchema = new Schema({
 title: { type: String, required: true },
 completed: { type: Boolean, default: false },
});

  • Routes and Controllers:

    • Routes define API endpoints: /api/todos.
    • Controllers handle the logic: fetching, creating, and deleting todos.

Why It’s Important:

Express and MongoDB allow you to create a scalable and flexible backend. You can reuse this knowledge to build APIs for apps like user authentication, content management systems, or inventory trackers.

5. OpenAI API Integration

What You Learned:

  • Interacting with OpenAI: You used the OpenAI API to generate task descriptions, schedules, and subtasks:

    const response = await openai.createCompletion({
 model: 'text-davinci-003',
 prompt: `Describe the task: ${task}`,
 max_tokens: 50,
});
  • AI Tools: You leveraged AI to enhance the app’s functionality by automating repetitive tasks.

Why It’s Important:

Integrating third-party APIs like OpenAI opens doors for intelligent features such as:

  • Chatbots (e.g., FAQ bots).
  • Content Generation (e.g., blog posts).
  • Task Automation (e.g., AI scheduling and subtasks).

This approach can be extended to integrate other APIs like Stripe (payments), Twilio (SMS), or Google Maps.

6. Testing with Jest and React Testing Library

What You Learned:

  • Component Tests: You tested components like AddTodo, TodoItem, and TodoList using Jest and Testing Library.
  • Mocking: You mocked API calls using Jest to simulate backend interactions.

Why It’s Important:

Testing ensures your application works as expected. By writing unit and integration tests, you can confidently make changes without breaking existing functionality.

7. Frontend-Backend Communication

What You Learned:

  • API Calls:

    • You used Axios to communicate between the frontend and backend.

    • Example:

      const response = await axios.post(`${API_URL}/api/todos`, { title });
  • Error Handling: You added error handling for failed requests and displayed messages accordingly.

Why It’s Important:

Understanding how to integrate the frontend with a backend API is crucial. This can be extended to work with other backends like Firebase, Supabase, or GraphQL servers.

Key Concepts to Relate to Other Applications

Here’s how you can generalize the concepts learned:

Concept What You Can Build
React + TypeScript Forms, CRUD-based dashboards, user interfaces.
React Query Apps requiring data fetching (blogs, task apps).
React Router Multi-page apps like blogs, portfolios, or stores.
Express + MongoDB REST APIs for CRUD apps, auth systems, and more.
Third-Party APIs AI tools, payment systems, email/SMS notifications.
Testing (Jest) Ensure reliability in production-ready apps.

Frequently Asked Questions (FAQs)

1. How do I extend this stack to add user authentication?

  • Backend: Add a user model with bcrypt for password hashing and jsonwebtoken for token-based authentication.
  • Frontend: Use React’s useContext or React Query to manage the authentication state.

2. How do I add more AI features using OpenAI?

  • Explore OpenAI’s documentation to implement chatbots, content summaries, or language translations.
  • Example: Use a chatbot API to interact with a user’s queries.

3. How do I deploy this app?

  • Backend: Deploy to Heroku, Render, or Vercel.
  • Frontend: Deploy to Netlify, Vercel, or AWS S3.
  • Use a CI/CD pipeline with GitHub Actions for automation.

4. How do I add real-time features?

  • Use Socket.IO in your Express backend for real-time communication.
  • Example: Real-time task updates for multiple users.

5. Can I replace MongoDB with another database?

  • Yes! You can use PostgreSQL, Firebase, or Supabase as alternatives. Replace Mongoose with an ORM like Prisma or Sequelize.

Conclusion

By completing this project, you’ve learned how to:

  1. Structure a modern full-stack application.
  2. Integrate state management (React Query) and navigation (React Router).
  3. Create a RESTful API with Express and MongoDB.
  4. Add intelligent features using OpenAI API.
  5. Write unit tests for components and APIs.

Next Steps:

  • Build a similar app like a Bookmarks Manager or Blog Platform.
  • Explore deployment to make your app live.
  • Add features like user authentication or real-time updates.

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