code sample added: Hono authentication example

snippets/top.md

@@ -1,3 +1,70 @@
 # Snippets
 
 A collection of code samples.
+
+### Hono Authentication Example
+This code sample demonstrates a basic authentication system using Hono [JWT](https://hono.dev/helpers/jwt) and [Cookie](https://hono.dev/helpers/cookie).
+
+```javascript
+import { Hono } from 'hono'
+import { getCookie, setCookie, deleteCookie } from 'hono/cookie'
+import { decode, sign, verify } from 'hono/jwt'
+
+const app = new Hono()
+
+app.post('/login', async (c) => {
+  const { user, password } = await c.req.parseBody();
+  if (user == "admin") {
+    if (password == "admin") {
+      const payload = {
+        sub: user,
+        role: 'admin',
+        exp: Math.floor(Date.now() / 1000) + 60 * 5, // Token expires in 5 minutes
+      }
+      const secret = 'hono-is-cool'
+      const token = await sign(payload, secret)
+      setCookie(c, 'jwt-token', token)
+      return c.text(`logged in`)
+    }
+    else {
+      return c.text(`Wrong Password`)
+    }
+  }
+  else {
+    return c.text('Invalid!', 401)
+  }
+})
+
+app.get('/dashboard', async (c) => {
+  const cookie_with_jwt = getCookie(c, 'jwt-token')
+  const tokenToVerify = cookie_with_jwt as string
+  const secretKey = 'hono-is-cool'
+  try {
+    await verify(tokenToVerify, secretKey)
+    const { header, payload } = decode(tokenToVerify)
+    console.log('JWT Header:', header)
+    console.log('JWT Payload:', payload)
+    //It is a good practice to track all previous tokens, you can use a fast db like Redis for this
+    return c.text(`You are valid user, use dashboard!\n Header algorithm: ${header.alg} \n Sub: ${payload.sub}`)
+  } catch (error) {
+    console.error('JWT verification failed:', error)
+    return c.json({ "message": "You have to login!" }, 404)
+  }
+})
+
+app.get('/logout', (c) => {
+  deleteCookie(c, 'jwt-token')
+  return c.text('Logout Done!')
+})
+
+export default app
+```
+**Endpoints:**
+
+- POST /login: Endpoint for user login. Requires user and password parameters in the request body. If successful, returns a JWT token.
+- GET /dashboard: Protected endpoint for accessing the dashboard. Requires a valid JWT token in the request cookie. Returns user information from the JWT token payload.
+- GET /logout: Endpoint for user logout. Deletes the JWT token from the request cookie.
+
+Store sensitive information securely ([env()](https://hono.dev/helpers/adapter#env)), such as the JWT secret, and avoid hardcoding it directly in the code.
+
+Code sample added by: [Sakib Mahmud](https://github.com/Sigmakib2)