import { NextRequest, NextResponse } from 'next/server';
import { locales, defaultLocale } from './lib/i18n';

export function middleware(request: NextRequest) {
    // Check if there is any supported locale in the pathname
    const pathname = request.nextUrl.pathname;

    // Check if the pathname already includes a locale
    const pathnameIsMissingLocale = locales.every(
        (locale) => !pathname.startsWith(`/${locale}/`) && pathname !== `/${locale}`,
    );

    // Redirect if there is no locale
    if (pathnameIsMissingLocale) {
        // Try to get locale from Accept-Language header
        const locale = getLocale(request) || defaultLocale;

        return NextResponse.redirect(new URL(`/${locale}${pathname}`, request.url));
    }
}

function getLocale(request: NextRequest): string | undefined {
    // Get locale from Accept-Language header
    const acceptLanguage = request.headers.get('accept-language');

    if (!acceptLanguage) return undefined;

    // Parse Accept-Language header
    const languages = acceptLanguage.split(',').map((lang) => lang.split(';')[0].trim());

    // Find matching locale
    for (const lang of languages) {
        if (locales.includes(lang as any)) {
            return lang;
        }

        // Check for language without region (e.g., 'zh' matches 'zh-CN')
        const langWithoutRegion = lang.split('-')[0];
        const matchingLocale = locales.find((locale) => locale.startsWith(langWithoutRegion));

        if (matchingLocale) {
            return matchingLocale;
        }
    }

    return undefined;
}

export const config = {
    matcher: [
        // Skip all internal paths (_next)
        '/((?!_next|api|favicon.ico|.*\\..*).*)',
    ],
};