index.js

// Import required libraries
const express = require('express');
const { v4: uuidv4 } = require('uuid'); // Used to generate unique IDs

// Create an Express app
const app = express();

// app.use here means that we are using middleware to parse JSON bodies. Middleware is a function that runs before the request reaches the route handler.
app.use(express.json());

// In-memory task storage (data is lost when server restarts)
let tasks = [];


// Create a new task (POST /tasks)
app.post('/tasks', (req, res) => {
  const { title, description, status } = req.body;

  // Validation: title must exist
  if (!title) {
    return res.status(400).send('Title is required');
  }

  // Validation: status must be either 'pending' or 'completed'
  if (status && status !== 'pending' && status !== 'completed') {
    return res.status(400).send('Status must be "pending" or "completed"');
  }

  // Create the task object
  const newTask = {
    id: uuidv4(),
    title,
    description: description || '',
    status: status || 'pending',
    createdAt: new Date().toISOString()
  };

  // Save to memory
  tasks.push(newTask);

  // Return the newly created task
  res.status(201).send(newTask);
});


// Get all tasks (GET /tasks)
app.get('/tasks', (req, res) => {
  res.send(tasks);
});


// Get a single task by ID (GET /tasks/:id)
app.get('/tasks/:id', (req, res) => {
  const task = tasks.find(t => t.id === req.params.id);

  if (!task) {
    return res.status(404).send('Task not found');
  }

  res.send(task);
});


// Update a task by ID (PUT /tasks/:id)
app.put('/tasks/:id', (req, res) => {
  const task = tasks.find(t => t.id === req.params.id);

  if (!task) {
    return res.status(404).send('Task not found');
  }

  const { title, description, status } = req.body;

  // Optional updates if values are sent
  if (title !== undefined) task.title = title;
  if (description !== undefined) task.description = description;
  if (status !== undefined) {
    if (status !== 'pending' && status !== 'completed') {
      return res.status(400).send('Status must be "pending" or "completed"');
    }
    task.status = status;
  }

  res.send(task);
});


// Delete a task by ID (DELETE /tasks/:id)
app.delete('/tasks/:id', (req, res) => {
  const index = tasks.findIndex(t => t.id === req.params.id);

  if (index === -1) {
    return res.status(404).send('Task not found'); // just in case agar task mojod na ho. not neccesarry wesy hi add kiya
  }

  tasks.splice(index, 1); // Remove task from array
  res.send('Task deleted');
});


// Start the server on port 3000
app.listen(3000, () => {
  console.log('Server running at http://localhost:3000');
});