implement todo API

backend/todo-api/server.js

@@ -0,0 +1,95 @@
+const express = require('express');
+const app = express();
+const PORT = 3000;
+
+// Middleware for parsing JSON
+app.use(express.json());
+
+// In-memory storage
+let todos = [];
+let nextId = 1;
+
+// GET /api/todos - list all todos
+app.get('/api/todos', (req, res) => {
+  res.json(todos);
+});
+
+// GET /api/todos/:id - get single todo
+app.get('/api/todos/:id', (req, res) => {
+  const id = parseInt(req.params.id);
+  const todo = todos.find(t => t.id === id);
+
+  if (!todo) {
+    return res.status(404).json({ error: 'Todo not found' });
+  }
+
+  res.json(todo);
+});
+
+// POST /api/todos - create new todo
+app.post('/api/todos', (req, res) => {
+  const { title, completed } = req.body;
+
+  // Validation
+  if (!title || typeof title !== 'string' || !title.trim()) {
+    return res.status(400).json({ error: 'Title is required and must be a non-empty string' });
+  }
+
+  const newTodo = {
+    id: nextId++,
+    title: title.trim(),
+    completed: completed === true, // default false unless explicitly true
+    createdAt: new Date().toISOString(),
+  };
+
+  todos.push(newTodo);
+  res.status(201).json(newTodo);
+});
+
+// PUT /api/todos/:id - update todo
+app.put('/api/todos/:id', (req, res) => {
+  const id = parseInt(req.params.id);
+  const { title, completed } = req.body;
+  const todo = todos.find(t => t.id === id);
+
+  if (!todo) {
+    return res.status(404).json({ error: 'Todo not found' });
+  }
+
+  // Validation
+  if (title !== undefined && (typeof title !== 'string' || !title.trim())) {
+    return res.status(400).json({ error: 'Title must be a non-empty string if provided' });
+  }
+  if (completed !== undefined && typeof completed !== 'boolean') {
+    return res.status(400).json({ error: 'Completed must be a boolean value' });
+  }
+
+  if (title !== undefined) todo.title = title.trim();
+  if (completed !== undefined) todo.completed = completed;
+
+  res.json(todo);
+});
+
+// DELETE /api/todos/:id - delete todo
+app.delete('/api/todos/:id', (req, res) => {
+  const id = parseInt(req.params.id);
+  const index = todos.findIndex(t => t.id === id);
+
+  if (index === -1) {
+    return res.status(404).json({ error: 'Todo not found' });
+  }
+
+  todos.splice(index, 1);
+  res.status(204).send(); // No content
+});
+
+// Generic error handler
+app.use((err, req, res, next) => {
+  console.error('Unexpected error:', err);
+  res.status(500).json({ error: 'Internal server error' });
+});
+
+// Start server
+app.listen(PORT, () => {
+  console.log(`🚀 Server running at http://localhost:${PORT}`);
+});