import createMiddleware from "next-intl/middleware";
import { NextRequest, NextResponse } from "next/server";
import { routing } from "./i18n/routing";
import {
  acceptLanguageHasChinese,
  ZH_OK_COOKIE,
} from "./lib/chinese-locale";

const intlMiddleware = createMiddleware({
  ...routing,
  localeDetection: true,
});

function requestAllowsChinese(request: NextRequest): boolean {
  if (acceptLanguageHasChinese(request.headers.get("accept-language"))) {
    return true;
  }
  return request.cookies.get(ZH_OK_COOKIE)?.value === "1";
}

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

  // Shared /zh links: without Chinese signals → English only
  if (pathname === "/zh" || pathname.startsWith("/zh/")) {
    if (!requestAllowsChinese(request)) {
      const url = request.nextUrl.clone();
      url.pathname = pathname.replace(/^\/zh/, "/en") || "/en";
      return NextResponse.redirect(url);
    }
  }

  return intlMiddleware(request);
}

export const config = {
  matcher: ["/", "/(en|zh)/:path*", "/((?!api|_next|_vercel|.*\\..*).*)"],
};