proxy.ts

import { match } from "@formatjs/intl-localematcher";
import Negotiator from "negotiator";
import { NextResponse } from "next/server";
import {
  SUPPORTED_LOCALES,
  DEFAULT_LOCALE,
  LOCALE_COOKIE_NAME,
} from "@/constants/app";
import type { Locale } from "@/types";

const locales = [...SUPPORTED_LOCALES];
const defaultLocale = DEFAULT_LOCALE;

function getLocale(request: Request): string {
  // Check for saved locale preference in cookie
  const cookieHeader = request.headers.get("cookie") || "";
  const localeCookiePattern = new RegExp(`${LOCALE_COOKIE_NAME}=([^;]+)`);
  const localeCookieMatch = cookieHeader.match(localeCookiePattern);
  if (
    localeCookieMatch &&
    localeCookieMatch[1] &&
    (locales as readonly string[]).includes(localeCookieMatch[1])
  ) {
    return localeCookieMatch[1] as Locale;
  }

  // Fall back to browser language preferences
  const headers = new Headers(request.headers);
  const acceptLanguage = headers.get("accept-language") || "";
  const headersObject = { "accept-language": acceptLanguage };
  const languages = new Negotiator({ headers: headersObject }).languages();
  return match(languages, locales, defaultLocale);
}

export function proxy(request: Request) {
  const { pathname } = new URL(request.url);

  // Skip API routes and internal Next.js paths
  if (
    pathname.startsWith("/api/") ||
    pathname.startsWith("/_next/") ||
    pathname.startsWith("/favicon.ico")
  ) {
    return;
  }

  // Check if there is any supported locale in the pathname
  const pathnameHasLocale = locales.some(
    (locale) => pathname.startsWith(`/${locale}/`) || pathname === `/${locale}`
  );

  if (pathnameHasLocale) {
    return;
  }

  // Redirect if there is no locale
  const locale = getLocale(request);
  const newUrl = new URL(request.url);
  newUrl.pathname = `/${locale}${pathname}`;
  return NextResponse.redirect(newUrl);
}

export const config = {
  matcher: [
    // Skip all internal paths (_next)
    "/((?!_next|api|favicon.ico).*)",
  ],
};