import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';

const locales = ['zh-CN', 'zh-TW', 'en', 'ko', 'ja'];
const defaultLocale = 'zh-CN';

function getLocale(request: NextRequest): string {
    // Check if there is any supported locale in the pathname
    const pathname = request.nextUrl.pathname;
    const pathnameIsMissingLocale = locales.every(
        (locale) => !pathname.startsWith(`/${locale}/`) && pathname !== `/${locale}`,
    );

    // If there's no locale in the pathname, detect from headers
    if (pathnameIsMissingLocale) {
        const acceptLanguage = request.headers.get('accept-language');

        if (acceptLanguage) {
            // Parse accept-language header
            const languages = acceptLanguage.split(',').map((lang) => lang.split(';')[0].trim());

            // Find the first matching locale
            for (const lang of languages) {
                if (lang.startsWith('zh-TW') || lang.startsWith('zh-HK')) {
                    return 'zh-TW';
                } else if (lang.startsWith('zh')) {
                    return 'zh-CN';
                } else if (lang.startsWith('ko')) {
                    return 'ko';
                } else if (lang.startsWith('ja')) {
                    return 'ja';
                } else if (lang.startsWith('en')) {
                    return 'en';
                }
            }
        }

        return defaultLocale;
    }

    // Extract locale from pathname
    const locale = pathname.split('/')[1];
    return locales.includes(locale) ? locale : defaultLocale;
}

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

    // Skip middleware for sitemap.xml, robots.txt and other static files
    const staticFiles = ['/sitemap.xml', '/robots.txt', '/favicon.ico', '/manifest.json'];
    if (staticFiles.includes(pathname)) {
        return NextResponse.next();
    }

    // Check if there is any supported locale in the pathname
    const pathnameIsMissingLocale = locales.every(
        (locale) => !pathname.startsWith(`/${locale}/`) && pathname !== `/${locale}`,
    );

    // Redirect if there is no locale
    if (pathnameIsMissingLocale) {
        const locale = getLocale(request);
        return NextResponse.redirect(
            new URL(`/${locale}${pathname.startsWith('/') ? '' : '/'}${pathname}`, request.url),
        );
    }
}

export const config = {
    // Matcher ignoring static files, API routes, and special files
    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 (static files)
         */
        '/((?!api|_next/static|_next/image|favicon.ico|sitemap.xml|robots.txt|manifest.json).*)',
    ],
};