import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';
import { SUPPORTED_LOCALES, DEFAULT_LOCALE } from './lib/locales';

// Paths that should not be localized
const PUBLIC_FILE = /\.(.*)$/;
const SKIP_PATHS = ['/_next', '/api', '/favicon.ico', '/robots.txt', '/sitemap.xml', '/sitemap'];

export function proxy(request: NextRequest) {
  const { pathname } = request.nextUrl;

  // Skip Next.js internals, APIs, and public files
  if (
    SKIP_PATHS.some((p) => pathname.startsWith(p)) ||
    PUBLIC_FILE.test(pathname)
  ) {
    return NextResponse.next();
  }

  // Check if the pathname already has a locale
  const matchedLocale = SUPPORTED_LOCALES.find(
    (locale) => pathname.startsWith(`/${locale}/`) || pathname === `/${locale}`
  );

  if (matchedLocale) {
    const requestHeaders = new Headers(request.headers);
    requestHeaders.set('x-homaroma-locale', matchedLocale);

    return NextResponse.next({
      request: {
        headers: requestHeaders,
      },
    });
  }

  // Determine the preferred locale
  // 1. Check cookie
  const cookieLocale = request.cookies.get('app_lang')?.value;
  let targetLocale = DEFAULT_LOCALE;

  if (cookieLocale && (SUPPORTED_LOCALES as readonly string[]).includes(cookieLocale)) {
    targetLocale = cookieLocale as typeof SUPPORTED_LOCALES[number];
  } else {
    // 2. Check Accept-Language header
    const acceptLang = request.headers.get('accept-language');
    if (acceptLang) {
      const preferred = acceptLang.split(',')[0].split('-')[0].toLowerCase();
      if ((SUPPORTED_LOCALES as readonly string[]).includes(preferred)) {
        targetLocale = preferred as typeof SUPPORTED_LOCALES[number];
      }
    }
  }

  // Redirect to the localized path
  const newUrl = request.nextUrl.clone();
  newUrl.pathname = `/${targetLocale}${pathname === '/' ? '' : pathname}`;
  
  return NextResponse.redirect(newUrl);
}

// Next.js 16 Proxy configuration
export const config = {
  matcher: [
    /*
     * Match all request paths except for the ones starting with:
     * - api (API routes)
     * - _next/static (static files)
     * - _next/image (image optimization files)
     * - favicon.ico, sitemap.xml, robots.txt (metadata files)
     */
    '/((?!api|_next/static|_next/image|favicon.ico|sitemap.xml|robots.txt).*)',
  ],
};