// 获取长期用户访问令牌
async function getLongLivedUserToken(shortLivedToken, appId, appSecret) {
  const response = await fetch(
    `https://graph.facebook.com/v12.0/oauth/access_token?grant_type=fb_exchange_token&client_id=${appId}&client_secret=${appSecret}&fb_exchange_token=${shortLivedToken}`
  );
  const data = await response.json();
  return data.access_token; // 60天有效的令牌
}

// 获取页面访问令牌
async function getPageAccessToken(userToken, pageId) {
  const response = await fetch(
    `https://graph.facebook.com/v12.0/${pageId}?fields=access_token&access_token=${userToken}`
  );
  const data = await response.json();
  return data.access_token; // 无固定过期时间的页面令牌
}

// 使用页面令牌发布到Feed
async function postToPageFeed(pageToken, pageId, message) {
  const response = await fetch(
    `https://graph.facebook.com/v12.0/${pageId}/feed`,
    {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({
        message: message,
        access_token: pageToken,
      }),
    }
  );
  return response.json();
}