Implementing Server-Side Authentication Middleware in Vue.js with TypeScript

This challenge focuses on building robust authentication for your Vue.js applications by implementing server-side middleware. You will create middleware that intercepts incoming requests to your Vue application's server-side rendering (SSR) process, checks for valid authentication tokens, and either allows access or redirects unauthenticated users. This is crucial for protecting sensitive routes and ensuring a secure user experience.

Problem Description

Your task is to implement a server-side middleware function in a Vue.js application that utilizes Nuxt.js (or a similar SSR framework) for server rendering. This middleware will be responsible for checking if a user is authenticated before allowing them to access certain protected routes.

Key Requirements:

Middleware Function: Create a TypeScript middleware function that can be registered with your SSR framework.
Token Verification: The middleware should check for an authentication token (e.g., a JWT) in the request headers or cookies.
Conditional Access:
- If a valid token is found, the request should proceed to render the requested page.
- If no valid token is found, the user should be redirected to a specified login page.
Protected Routes: The middleware should be configurable to apply to specific routes or a group of routes.
TypeScript Integration: Ensure all code is written in TypeScript, leveraging type safety for request/response objects and middleware context.

Expected Behavior:

When a user navigates to a route protected by this middleware without a valid authentication token, they should be immediately redirected to /login.
When a user navigates to a protected route with a valid token, the page should render as expected.
The middleware should be able to handle different types of token storage (e.g., Authorization header or cookies).

Edge Cases to Consider:

Requests for non-protected routes should bypass the middleware entirely.
Handling expired or invalid tokens gracefully.
Ensuring the redirection logic works correctly in both client-side and server-side navigation.

Examples

Example 1: User attempts to access a protected route without a token.

Scenario: A user navigates to /dashboard. The request hits the SSR server. No valid Authorization header or cookie containing an authentication token is present.

Expected Output: The server redirects the user's browser to /login. The /dashboard page is not rendered.

Example 2: User attempts to access a protected route with a valid token.

Scenario: A user navigates to /profile. The request hits the SSR server. A valid JWT is present in the Authorization: Bearer <token> header.

Expected Output: The server renders the /profile page.

Example 3: User attempts to access a non-protected route.

Scenario: A user navigates to /about. This route is not configured to use the authentication middleware.

Expected Output: The server renders the /about page without any authentication checks.

Constraints

The solution should be implemented using TypeScript.
Assume a basic project structure with a Nuxt.js application or a similar SSR setup.
The authentication token can be stored either in an Authorization header (e.g., Bearer <token>) or in a cookie named auth_token.
The login page is assumed to be at the route /login.
The middleware should be designed to be reusable.
Performance is important; middleware should execute efficiently.

Notes

You will likely need to interact with the context object provided by your SSR framework (e.g., Nuxt's Context). This object typically contains request and response objects, route information, and methods for redirection.
Consider how you will simulate or handle the actual token verification logic. For this challenge, you can assume a simple check (e.g., token exists and is not an empty string) or a mock verification function.
Think about how to configure which routes are protected by this middleware. This might involve route meta fields or a separate configuration array.
The goal is to demonstrate the implementation of the middleware itself, not a full-blown authentication system with user registration and login forms.

Implementing Server-Side Authentication Middleware in Vue.js with TypeScript

Problem Description

Key Requirements:

Middleware Function: Create a TypeScript middleware function that can be registered with your SSR framework.
Token Verification: The middleware should check for an authentication token (e.g., a JWT) in the request headers or cookies.
Conditional Access:
- If a valid token is found, the request should proceed to render the requested page.
- If no valid token is found, the user should be redirected to a specified login page.
Protected Routes: The middleware should be configurable to apply to specific routes or a group of routes.
TypeScript Integration: Ensure all code is written in TypeScript, leveraging type safety for request/response objects and middleware context.

Expected Behavior:

When a user navigates to a route protected by this middleware without a valid authentication token, they should be immediately redirected to /login.
When a user navigates to a protected route with a valid token, the page should render as expected.
The middleware should be able to handle different types of token storage (e.g., Authorization header or cookies).

Edge Cases to Consider:

Requests for non-protected routes should bypass the middleware entirely.
Handling expired or invalid tokens gracefully.
Ensuring the redirection logic works correctly in both client-side and server-side navigation.