middleware.ts

import { match as matchLocale } from '@formatjs/intl-localematcher'
import Negotiator from 'negotiator'
import { NextResponse } from 'next/server'

import type { NextRequest } from 'next/server'

import { i18n } from '@/lib/config/i18n/config'

function getLocale(request: NextRequest): string | undefined {
  // Negotiator expects plain object so we need to transform headers
  const negotiatorHeaders: Record<string, string> = {}
  request.headers.forEach((value, key) => (negotiatorHeaders[key] = value))
  // @ts-ignore locales are readonly
  const locales: string[] = i18n.locales
  // Use negotiator and intl-localematcher to get best locale
  let languages = new Negotiator({ headers: negotiatorHeaders }).languages(
    locales,
  )
  const locale = matchLocale(languages, locales, i18n.defaultLocale)
  return locale
}

export function middleware(request: NextRequest) {
  const pathname = request.nextUrl.pathname
  // `/_next/` and `/api/` are ignored by the watcher, but we need to ignore files in `public` manually.
  // If you have one
  if (/\/(manifest\.json|sw\.js|workbox-(\d|\D)+\.js)/.test(pathname)) return
  // Check if there is any supported locale in the pathname
  const pathnameIsMissingLocale = i18n.locales.every(
    (locale) =>
      !pathname.startsWith(`/${locale}/`) && pathname !== `/${locale}`,
  )
  // Redirect if there is no locale
  if (pathnameIsMissingLocale) {
    const locale = getLocale(request)
    // e.g. incoming request is /products
    // The new URL is now /en-US/products
    return NextResponse.redirect(
      new URL(
        `/${locale}${pathname.startsWith('/') ? '' : '/'}${pathname}`,
        request.url,
      ),
    )
  }
  // Send URL value to server
  const requestHeaders = new Headers(request.headers)
  requestHeaders.set('x-url', request.url)
  return NextResponse.next({
    request: {
      headers: requestHeaders,
    },
  })
}

export const config = {
  // Matcher ignoring `/_next/` and `/api/`
  matcher: ['/((?!api|_next/static|_next/image|favicon.ico|assets).*)'],
}