middleware.ts

import { parse } from 'cookie'

let locales = ['en-US', 'de', 'fr', 'it', 'jp']

export function middleware(request) {
  let { pathname } = request.nextUrl

  // Only proceed if the request method is GET
  if (request.method !== 'GET') {
    return
  }

  // Parse the cookies from the request
  const cookies = parse(request.headers.get('Cookie') || '')
  const cookieLocale = cookies.lang || 'en-US'

  const requestLocale = locales.find((reqLocale) => pathname.startsWith(`/${reqLocale}/`) || pathname === `/${reqLocale}`)
  
  // Ignore image and video files
  const isMediaFile = /\.(jpe?g|png|gif|svg|mp4|ico|json)$/i.test(pathname)
  
  if (isMediaFile) return

  if (requestLocale && requestLocale !== cookieLocale) {
    request.nextUrl.pathname = pathname.replace(`/${requestLocale}`, `/${cookieLocale}`)
    return Response.redirect(request.nextUrl)
  }

  if (!requestLocale) {
    request.nextUrl.pathname = `/${cookieLocale}${pathname}`
    return Response.redirect(request.nextUrl)
  }
}
 
export const config = {
  matcher: ['/((?!_next).*)']
}