proxy.ts

import { NextRequest, NextResponse } from "next/server"
import acceptLanguage from "accept-language"
import { fallbackLng, languages, cookieName, headerName } from "@/app/i18n/settings"

acceptLanguage.languages(languages)

export const config = {
  // Avoid matching for static files, API routes, etc.
  matcher: ["/((?!api|_next/static|_next/image|assets|favicon.ico|sw.js|site.webmanifest).*)"],
}

export function proxy(req: NextRequest) {
  // Ignore paths with "icon" or "chrome"
  if (req.nextUrl.pathname.indexOf("icon") > -1 || req.nextUrl.pathname.indexOf("chrome") > -1)
    return NextResponse.next()

  let lng
  // Try to get language from cookie
  if (req.cookies.has(cookieName)) lng = acceptLanguage.get(req.cookies.get(cookieName)?.value)
  // If no cookie, check the Accept-Language header
  if (!lng) lng = acceptLanguage.get(req.headers.get("Accept-Language"))
  // Default to fallback language if still undefined
  if (!lng) lng = fallbackLng

  // Check if the language is already in the path
  const lngInPath = languages.find((loc) => req.nextUrl.pathname.startsWith(`/${loc}`))
  const headers = new Headers(req.headers)
  headers.set(headerName, lngInPath || lng)

  // If the language is not in the path, redirect to include it
  if (!lngInPath && !req.nextUrl.pathname.startsWith("/_next")) {
    return NextResponse.redirect(new URL(`/${lng}${req.nextUrl.pathname}${req.nextUrl.search}`, req.url))
  }

  // If a referer exists, try to detect the language from there and set the cookie accordingly
  if (req.headers.has("referer")) {
    const refererUrl = new URL(req.headers.get("referer") || "", req.url)
    const lngInReferer = languages.find((l) => refererUrl.pathname.startsWith(`/${l}`))
    const response = NextResponse.next({ headers })
    if (lngInReferer) response.cookies.set(cookieName, lngInReferer)
    return response
  }

  return NextResponse.next({ headers })
}