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

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

// 获取首选语言
function getLocale(request: NextRequest): string {
    // 1. 检查URL路径中是否已包含语言代码
    const pathname = request.nextUrl.pathname;
    const pathnameIsMissingLocale = locales.every(
        (locale) => !pathname.startsWith(`/${locale}/`) && pathname !== `/${locale}`
    );

    if (!pathnameIsMissingLocale) {
        return locales.find(locale => pathname.startsWith(`/${locale}`)) || defaultLocale;
    }

    // 2. 检查Accept-Language头
    const acceptLanguage = request.headers.get('accept-language');
    if (acceptLanguage) {
        const preferredLocale = locales.find(locale => 
            acceptLanguage.toLowerCase().includes(locale.toLowerCase())
        );
        if (preferredLocale) {
            return preferredLocale;
        }
    }

    return defaultLocale;
}

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

    // 检查路径是否已经包含语言代码
    const pathnameIsMissingLocale = locales.every(
        (locale) => !pathname.startsWith(`/${locale}/`) && pathname !== `/${locale}`
    );

    // 如果路径缺少语言代码，则重定向
    if (pathnameIsMissingLocale) {
        const locale = getLocale(request);
        return NextResponse.redirect(
            new URL(`/${locale}${pathname.startsWith('/') ? '' : '/'}${pathname}`, request.url)
        );
    }
}

export const config = {
    // 匹配所有路径，除了api、_next/static、_next/image、favicon.ico等
    matcher: [
        /*
         * 匹配所有请求路径，除了以下开头的：
         * - api (API routes)
         * - _next/static (静态文件) 
         * - _next/image (图片优化文件)
         * - favicon.ico (网站图标)
         * - locales (翻译文件)
         * - docs (文档文件)
         * - 各种静态资源文件
         */
        '/((?!api|_next/static|_next/image|favicon.ico|locales|docs|.*\\.png$|.*\\.jpg$|.*\\.jpeg$|.*\\.gif$|.*\\.svg$|.*\\.ico$|.*\\.css$|.*\\.js$|.*\\.json$|.*\\.md$).*)',
    ],
};