// 示例：Chrome扩展核心代码
function injectDownloadButton() {
  // 监听视频元素加载
  const observer = new MutationObserver(mutations => {
    mutations.forEach(mutation => {
      if (mutation.addedNodes.length) {
        // 查找视频元素
        const videoElements = document.querySelectorAll('video');
        videoElements.forEach(video => {
          if (!video.dataset.downloadAdded) {
            video.dataset.downloadAdded = true;
            
            // 创建下载按钮
            const downloadBtn = document.createElement('button');
            downloadBtn.textContent = '下载视频';
            downloadBtn.onclick = () => {
              const blobUrl = URL.createObjectURL(video.src);
              const a = document.createElement('a');
              a.href = blobUrl;
              a.download = `video_${Date.now()}.mp4`;
              document.body.appendChild(a);
              a.click();
              document.body.removeChild(a);
              URL.revokeObjectURL(blobUrl);
            };
            
            // 将按钮添加到视频附近
            video.parentNode.insertBefore(downloadBtn, video.nextSibling);
          }
        });
      }
    });
  });
  
  // 开始观察DOM变化
  observer.observe(document.body, {
    childList: true,
    subtree: true
  });
}

// 注入到视频号页面
injectDownloadButton();