export default {
  async fetch(request, env) {
    const url = new URL(request.url);

    // 只处理 /proxy 路径
    if (url.pathname !== "/proxy") {
      return new Response("Not Found", { status: 404 });
    }

    // 可选认证：如果传递了凭据则验证，但不强制要求也不阻止请求
    const auth = request.headers.get("Authorization");
    if (auth && auth.startsWith("Basic ")) {
      const expected = btoa(`${env.PROXY_USER}:${env.PROXY_PASS}`);
      if (auth.slice(6) !== expected) {
        console.log(`[Auth] Invalid credentials provided`);
      }
    }

    // 获取目标 URL
    const target = url.searchParams.get("target_url");
    if (!target) {
      return new Response("Missing target_url parameter", { status: 400 });
    }

    try {
      // 构建转发头，过滤 host（Worker网关的host，不是目标的）
      const headers = new Headers();
      for (const [key, value] of request.headers) {
        const lower = key.toLowerCase();
        if (lower !== "host") {
          headers.set(key, value);
        }
      }

      // 转发请求，不跟随重定向（与原版行为一致）
      const body = ["GET", "HEAD"].includes(request.method) ? null : request.body;
      const resp = await fetch(target, {
        method: request.method,
        headers: headers,
        body: body,
        redirect: "manual",
      });

      // 构建响应头，去掉 hop-by-hop 头
      const respHeaders = new Headers();
      for (const [key, value] of resp.headers) {
        const lower = key.toLowerCase();
        if (lower !== "transfer-encoding" && lower !== "connection") {
          respHeaders.set(key, value);
        }
      }

      // 流式返回响应体
      return new Response(resp.body, {
        status: resp.status,
        headers: respHeaders,
      });
    } catch (e) {
      return new Response(`Proxy Error: ${e.message}`, { status: 500 });
    }
  },
};