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

/**
 * Next.js 16 代理层
 *
 * 1. API 请求速率限制
 * 2. 页面身份验证
 */

/* ==================== 速率限制 ==================== */

interface RateLimitEntry {
  count: number;
  windowStart: number;
}

const rateLimitStore = new Map<string, RateLimitEntry>();

/** 不需要速率限制的路径 */
const EXCLUDED_PREFIXES = ['/api/v1/config', '/epay/', '/lpay/'];

/** 速率限制规则: [最大请求数, 窗口时长(ms)] */
const RATE_LIMITS: Record<string, [number, number]> = {
  '/api/v1/oauth/login': [1, 5000],
  '/api/v1/oauth/callback': [1, 5000],
};

/** 默认限制: 60次/60秒 */
const DEFAULT_RATE_LIMIT: [number, number] = [60, 60000];

function getRateLimit(pathname: string): [number, number] {
  if (RATE_LIMITS[pathname]) return RATE_LIMITS[pathname];

  const match = Object.keys(RATE_LIMITS)
    .filter((prefix) => pathname.startsWith(prefix))
    .sort((a, b) => b.length - a.length)[0];

  return match ? RATE_LIMITS[match] : DEFAULT_RATE_LIMIT;
}

function shouldRateLimit(pathname: string): boolean {
  return !EXCLUDED_PREFIXES.some((prefix) => pathname.startsWith(prefix));
}

function checkRateLimit(
  identifier: string,
  pathname: string,
): [boolean, number] {
  const [maxRequests, windowMs] = getRateLimit(pathname);
  const key = `${identifier}:${pathname}`;
  const now = Date.now();
  const entry = rateLimitStore.get(key);

  if (!entry || now - entry.windowStart >= windowMs) {
    rateLimitStore.set(key, { count: 1, windowStart: now });
    return [true, 0];
  }

  entry.count++;
  if (entry.count > maxRequests) {
    return [false, Math.ceil((windowMs - (now - entry.windowStart)) / 1000)];
  }
  return [true, 0];
}

if (typeof setInterval !== 'undefined') {
  setInterval(() => {
    const now = Date.now();
    for (const [key, entry] of rateLimitStore.entries()) {
      if (now - entry.windowStart > 120000) rateLimitStore.delete(key);
    }
  }, 60000);
}

/* ==================== 代理主函数 ==================== */

export function proxy(request: NextRequest) {
  const { pathname, search } = request.nextUrl;
  const sessionCookieName =
    process.env.WAVELET_SESSION_COOKIE_NAME || 'openflare_session_id';
  const sessionCookie = request.cookies.get(sessionCookieName);

  /* API 请求：速率限制后放行 */
  if (pathname.startsWith('/api/')) {
    const rateLimitEnabled = process.env.WAVELET_RATE_LIMIT_ENABLED === 'true';

    if (rateLimitEnabled && shouldRateLimit(pathname)) {
      const identifier =
        sessionCookie?.value ||
        request.headers.get('x-forwarded-for')?.split(',')[0].trim() ||
        request.headers.get('x-real-ip') ||
        'anonymous';

      const [allowed, waitTime] = checkRateLimit(identifier, pathname);
      if (!allowed) {
        return NextResponse.json(
          {
            error_code: 'RATE_LIMITED',
            error_msg: `请求过于频繁，请 ${waitTime} 秒后重试`,
          },
          { status: 429, headers: { 'Retry-After': String(waitTime) } },
        );
      }
    }
    return NextResponse.next();
  }

  /* 页面请求：默认私域，仅登录流程入口无需 session */
  const authEntryRoutes = ['/login', '/register', '/callback'];

  if (!authEntryRoutes.includes(pathname) && !sessionCookie) {
    const loginUrl = new URL('/login', request.url);
    loginUrl.searchParams.set('callbackUrl', pathname + search);
    return NextResponse.redirect(loginUrl);
  }

  return NextResponse.next();
}

export const config = {
  matcher: [
    '/api/:path*',
    '/((?!_next|favicon.ico|robots.txt|sitemap.xml|.*\\.(?:jpg|jpeg|gif|png|svg|ico|webp)).*)',
  ],
};