function doGet(e) {
  const primaryBase = "https://siawaseok.duckdns.org";
  const fallbackBase = "https://siatube.wjg.jp";
  const routes = {
    video:    id => `/api/video2/${encodeURIComponent(id)}`,
    stream:   id => `/api/stream/${encodeURIComponent(id)}`,
    stream2:  id => `/api/stream/${encodeURIComponent(id)}/type2`,
    channel:  id => `/api/channel/${encodeURIComponent(id)}`,
    q:        q  => `/api/search2?q=${encodeURIComponent(q)}`,
    comments: id => `/api/comments/${encodeURIComponent(id)}`,
    trend:    () => `/api/trend`,
    playlist: id => `/api/playlist/${encodeURIComponent(id)}`
  };

  let targetPath = null;
  for (let key in routes) {
    if (e.parameter[key] !== undefined) {
      targetPath = routes[key](e.parameter[key]);
      break;
    }
  }

  if (!targetPath) {
    return createResponse({ error: "No valid parameter provided" }, e.parameter.callback);
  }

  const maxRetries = 3;
  for (let attempt = 1; attempt <= maxRetries; attempt++) {
    try {
      const primaryUrl = primaryBase + targetPath;
      let response = UrlFetchApp.fetch(primaryUrl, {
        method: "get",
        muteHttpExceptions: true,
        timeoutSeconds: 40
      });
      if (response.getResponseCode() === 200) {
        return createResponse(response.getContentText(), e.parameter.callback);
      }

      const fallbackUrl = fallbackBase + targetPath;
      response = UrlFetchApp.fetch(fallbackUrl, {
        method: "get",
        muteHttpExceptions: true,
        timeoutSeconds: 30
      });
      if (response.getResponseCode() === 200) {
        return createResponse(response.getContentText(), e.parameter.callback);
      }

    } catch (err) {}
  }

  return createResponse({ error: "失敗しました" }, e.parameter.callback);
}

/**
 * JSONP対応レスポンス生成
 * - callback が指定されていれば JSONP
 * - 指定されていなければ通常の JSON
 */
function createResponse(content, callback) {
  let text;
  try {
    const obj = typeof content === "string" ? JSON.parse(content) : content;
    if (callback) {
      text = `${callback}(${JSON.stringify(obj)})`;
      return ContentService.createTextOutput(text).setMimeType(ContentService.MimeType.JAVASCRIPT);
    } else {
      text = JSON.stringify(obj);
      return ContentService.createTextOutput(text).setMimeType(ContentService.MimeType.JSON);
    }
  } catch (e) {
    if (callback) {
      text = `${callback}(${JSON.stringify({ raw: content })})`;
      return ContentService.createTextOutput(text).setMimeType(ContentService.MimeType.JAVASCRIPT);
    } else {
      return ContentService.createTextOutput(content).setMimeType(ContentService.MimeType.JSON);
    }
  }
}

<script defer data-domain="html.cafe" src="https://milkymouse.com/js/script.js"></script>