在网站上播放R2存储桶音乐并避免CORS错误并启用206 Partial Content

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export default {
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  async fetch(request, env) {
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    try {
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      // 1. === 防盗链 / Allowed Domains ===
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      const ALLOWED_DOMAINS = (env.ALLOWED_DOMAINS_STR || "")
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        .split(',')
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        .map(d => d.trim())
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        .filter(d => d);
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      const origin = request.headers.get("Origin") || "";
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      const referer = request.headers.get("Referer") || "";
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      if (ALLOWED_DOMAINS.length > 0) {
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        const isAllowed = ALLOWED_DOMAINS.some(d =>
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          origin.startsWith(d) || referer.startsWith(d)
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        );
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        if (!isAllowed) {
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          return new Response("Forbidden: 防盗链已启用", {
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            status: 403,
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            headers: { "Access-Control-Allow-Origin": "*" }
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          });
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        }
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      }
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      // 2. === 请求方法检查 ===
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      if (!["GET", "HEAD"].includes(request.method)) {
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        return new Response("Method Not Allowed", { status: 405 });
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      }
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      const url = new URL(request.url);
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      const objectKey = decodeURIComponent(url.pathname.slice(1));
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      // 3. === 准备基础响应头 (CORS 等) ===
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      const baseHeaders = new Headers();
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      baseHeaders.set("Access-Control-Allow-Origin", origin || ALLOWED_DOMAINS[0] || "*");
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      baseHeaders.set("Access-Control-Allow-Headers", "Range");
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      baseHeaders.set("Access-Control-Expose-Headers", "Content-Length, Content-Range, ETag");
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      baseHeaders.set("Accept-Ranges", "bytes");
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      baseHeaders.set("Cache-Control", "public, max-age=259200, immutable");
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      const rangeHeader = request.headers.get("Range");
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      // ==========================================
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      // 场景 A: 带有 Range 头的请求 (视频播放/拖动)
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      // ==========================================
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      if (rangeHeader) {
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        // 先获取文件元数据（不读取内容），拿到文件总大小
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        const objectHead = await env.R2_BUCKET.head(objectKey);
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        if (!objectHead) {
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          return new Response("Not Found", { status: 404 });
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        }
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        const total = objectHead.size;
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        const match = /^bytes=(\d*)-(\d*)$/.exec(rangeHeader);
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        if (!match) {
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          return new Response("Range Not Satisfiable", { status: 416 });
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        }
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        const start = match[1] ? parseInt(match[1]) : 0;
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        const end = match[2] ? parseInt(match[2]) : total - 1;
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        // 简单的越界检查
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        if (start >= total || end >= total || start > end) {
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           baseHeaders.set("Content-Range", `bytes */${total}`);
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           return new Response("Range Not Satisfiable", { status: 416, headers: baseHeaders });
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        }
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        // 【关键修复】：告诉 R2 只去取这一段数据，不要把整个文件读入内存
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        const object = await env.R2_BUCKET.get(objectKey, {
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          range: { offset: start, length: end - start + 1 },
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          onlyIf: request.headers // 支持 ETag 验证
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        });
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        if (!object) {
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          return new Response("Not Found", { status: 404 });
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        }
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        // 设置 206 专用头
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        object.writeHttpMetadata(baseHeaders);
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        baseHeaders.set("etag", object.httpEtag);
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        baseHeaders.set("Content-Range", `bytes ${start}-${end}/${total}`);
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        baseHeaders.set("Content-Length", (end - start + 1).toString());
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        return new Response(object.body, {
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          status: 206,
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          headers: baseHeaders
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        });
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      }
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      // ==========================================
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      // 场景 B: 普通请求 (下载完整文件)
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      // ==========================================
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      const object = await env.R2_BUCKET.get(objectKey, {
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        onlyIf: request.headers
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      });
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      if (!object) {
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        return new Response("Not Found", { status: 404 });
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      }
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      object.writeHttpMetadata(baseHeaders);
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      baseHeaders.set("etag", object.httpEtag);
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      return new Response(object.body, {
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        headers: baseHeaders
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      });
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    } catch (err) {
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      console.error("Worker Error:", err);
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      return new Response("Internal Server Error\n" + err.message, { status: 500 });
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    }
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  }
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};