Server
Middlewares

Middlewares

You can also use middlewares to handle requests. Middlewares are functions that are called before the request is handled by the router. You can use them to handle authentication, logging, etc.

If a handler function doesn't return a Response object, the request will be passed to the next handler.

import { createRouter, Response } from 'fets'
 
const router = createRouter()
  // Logging some headers before the response
  .route({
    path: '*',
    handler: request => {
      // Log some headers
      console.log(`User Agent: ${request.headers.get('user-agent')}`)
    }
  })
  // or stop the request earlier
  .route({
    path: '*',
    handler: request => {
      if (!request.headers.get('authorization')) {
        return new Response(null, {
          status: 401
        })
      }
    }
  })
  .route({
    path: '/users',
    method: 'GET',
    schemas: {
      /** .. */
    },
    handler: request => {
      // It doesn't reach here if the request doesn't have an `Authorization` header.
    }
  })

Chaining handlers

You can also chain multiple handlers to a single route. In the following example, we are checking if the request has an Authorization header and if the user is an admin.

import { createRouter, Response, RouteHandler } from 'fets'
 
const withAuth: RouteHandler = request => {
  if (!request.headers.get('Authorization')) {
    return new Response(null, {
      status: 401
    })
  }
}
 
const router = createRouter().route({
  path: '/users',
  method: 'GET',
  schemas: {
    /** .. */
  },
  handler: [
    withAuth,
    request => {
      // It doesn't reach here if the request doesn't have an `Authorization` header.
    }
  ]
})

Using schemas instead of middlewares

Instead of middlewares, you can use the schemas directly to validate Authorization header.

import { createRouter, Response } from 'fets'
 
const router = createRouter().route({
  path: '/me',
  method: 'GET',
  schemas: {
    request: {
      headers: {
        authorization: {
          type: 'string',
          // We can use a regex to validate the `Authorization` header.
          pattern: /^Bearer .+$/
        },
        required: ['authorization']
      }
    },
    response: {
      /** .. */
    },
    handler: request => {
      // It doesn't reach here if the request doesn't have a valid Bearer token in the `Authorization` header.
    }
  } as const
})
Type-Safety & ValidationError Handling