Cloudflare Worker URL掩码与高效内容转发指南

export default {
  async fetch(request) {
    const someHost = "https://storage.googleapis.com";
    const imageUrl = someHost + "/mybucket/image1.png"; // 示例上游图片URL

    // 此函数尝试根据Content-Type处理响应体
    async function gatherResponse(response) {
      const { headers } = response;
      const contentType = headers.get("content-type") || "";

      if (contentType.includes("application/json")) {
        return JSON.stringify(await response.json());
      } else if (contentType.includes("text/plain") || contentType.includes("text/html")) {
        return response.text();
      } else if (contentType.includes("image/png") || contentType.includes("image/jpeg")) {
        // 对于二进制数据，正确的获取方式是使用arrayBuffer()
        return response.arrayBuffer(); 
      } else {
        // 默认处理为文本或直接返回原始body
        return response.text();
      }
    }

    const upstreamResponse = await fetch(imageUrl);
    const results = await gatherResponse(upstreamResponse);

    // 注意：这里的init对象应包含正确的Content-Type，否则客户端可能无法正确解析
    const responseInit = {
      headers: {
        "content-type": upstreamResponse.headers.get("content-type") || "application/octet-stream",
      },
    };
    return new Response(results, responseInit);
  },
};

export default {
  async fetch(request) {
    // 动态构建上游URL，例如从请求路径中提取
    const url = new URL(request.url);
    const upstreamHost = "https://storage.googleapis.com"; // 您的内容源
    const upstreamPath = url.pathname; // 假设路径直接映射
    const upstreamUrl = upstreamHost + upstreamPath; 

    try {
      // 1. 发起对上游资源的请求
      // 转发原始请求的方法、头部等，确保请求与客户端请求一致
      const upstreamResponse = await fetch(upstreamUrl, {
        method: request.method,
        headers: request.headers, // 复制客户端请求的所有头部
        redirect: 'follow',      // 遵循上游重定向
      });

      // 2. 构建响应：直接使用上游响应的body，并复制所有原始头部
      // 这是实现流式传输的关键，避免了在Worker中缓冲整个响应
      const response = new Response(upstreamResponse.body, {
        status: upstreamResponse.status,
        statusText: upstreamResponse.statusText,
        headers: upstreamResponse.headers, // 复制所有上游响应头部
      });

      // 可选：根据需要修改或添加响应头部，例如CORS头部
      // response.headers.set('Access-Control-Allow-Origin', '*');
      // response.headers.set('Cache-Control', 'public, max-age=3600'); 

      return response;

    } catch (error) {
      // 捕获fetch操作可能出现的网络错误或上游服务器问题
      console.error("Cloudflare Worker fetch error:", error);
      return new Response("Internal Server Error: Could not fetch upstream resource.", { status: 500 });
    }
  },
};