import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';
import { match } from '@formatjs/intl-localematcher';
import Negotiator from 'negotiator';

import { i18n } from '@/i18n-config';
import { getPathnameLocale } from '@/src/utils/getLocale';

/** Pick the best locale from the Accept-Language header */
function getLocale(request: NextRequest): string {
  // Negotiator wants a plain JS object, not a Headers instance
  const negotiatorHeaders: Record<string, string> = {};
  request.headers.forEach((value, key) => {
    negotiatorHeaders[key] = value;
  });

  try {
    const languages = new Negotiator({ headers: negotiatorHeaders }).languages();
    // Filter out invalid locale values that would cause Intl.getCanonicalLocales to fail
    const validLanguages = languages.filter((lang) => {
      try {
        Intl.getCanonicalLocales(lang);
        return true;
      } catch {
        return false;
      }
    });

    if (validLanguages.length === 0) {
      return i18n.defaultLocale;
    }

    return match(validLanguages, i18n.locales, i18n.defaultLocale);
  } catch (error) {
    // Fallback to default locale if locale negotiation fails
    console.error('Locale negotiation error:', error);
    return i18n.defaultLocale;
  }
}

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

  /* ------------------------------------------------------------------ */
  /* Locale handling: redirect /dashboard → /en-US/dashboard           */
  /* ------------------------------------------------------------------ */
  const hasLocale = Boolean(getPathnameLocale(pathname));

  if (!hasLocale) {
    const locale = getLocale(request);
    const url = request.nextUrl.clone();
    url.pathname = `/${locale}${pathname}`;
    return NextResponse.redirect(url);
  }

  // Auth is handled client-side by swissoid-front
  return NextResponse.next();
}

/**
 * Run the middleware on every request except:
 *   • /_next/static & /_next/image
 *   • any file that looks like a static asset (has a file extension)
 *   • images folder
 */
export const config = {
  matcher: [
    '/((?!_next/static|_next/image|images/.*|favicon.ico|robots.txt|sitemap.xml|.*\\.(?:jpg|jpeg|gif|png|svg|ico|webp|avif)).*)',
  ],
};