场景教程：内容审核拦截

import { AdminClient } from '@ni-paas-im/server-sdk';

const admin = new AdminClient({ baseUrl: 'http://127.0.0.1:8080', adminSecret: process.env.IM_ADMIN_SECRET });

// 词表 + 处置动作；block=直接拒绝，replace=掩码放行并生成待审任务
await admin.request('POST', '/apps/demo/sensitive-words', {
  words: ['违规词A', '违规词B'],
  action: 'replace',
});

// App Server：接收发送前回调（Node / 原生 http 均可）
import { createServer } from 'node:http';
import { createHmac, timingSafeEqual } from 'node:crypto';

const SECRET = process.env.IM_CALLBACK_SECRET;

createServer(async (req, res) => {
  const chunks = [];
  for await (const chunk of req) chunks.push(chunk);
  const raw = Buffer.concat(chunks).toString('utf8');

  // 1) 验签：hex(hmac_sha256(secret, timestamp + '.' + nonce + '.' + rawBody))
  const ts = req.headers['x-im-timestamp'];
  const nonce = req.headers['x-im-nonce'];
  const sig = req.headers['x-im-signature'];
  const expected = createHmac('sha256', SECRET).update(`${ts}.${nonce}.${raw}`).digest('hex');
  if (!sig || sig.length !== expected.length || !timingSafeEqual(Buffer.from(sig), Buffer.from(expected))) {
    res.writeHead(401).end('bad signature');
    return;
  }

  const event = JSON.parse(raw);
  if (event.eventType !== 'message.publish.before') {
    res.writeHead(200, { 'content-type': 'application/json' }).end(JSON.stringify({ code: 0 }));
    return;
  }

  const text = event.data?.content?.text ?? '';
  let decision = { action: 'pass' };
  if (await hitRiskModel(event.data.senderId, text)) {
    decision = { action: 'block', reason: 'risk_model' };
  } else if (await needMask(text)) {
    // replace：返回完整 Content，客户端与历史都看到替换后的内容
    decision = { action: 'replace', content: { type: 'text', text: maskSensitive(text) } };
  }

  res.writeHead(200, { 'content-type': 'application/json' }).end(JSON.stringify({ code: 0, data: decision }));
}).listen(9090);

// 拉取待审任务（status: pending | approved | rejected | all；环形上限 2000）
const tasks = await admin.request('GET', '/apps/demo/moderation/tasks?status=pending&offset=0&limit=20');

// 裁决：reject 会标记消息并向发送者发送 message.blocked 系统通知
await admin.request('POST', `/apps/demo/moderation/tasks/${tasks.items[0].taskId}/decide`, {
  decision: 'reject',
  reason: 'policy_violation',
});

// 客户端：处理被拦截的系统通知（conversationType=4 / targetId="system"）
client.addEventListener(Events.MESSAGES, ({ messages }) => {
  for (const message of messages) {
    if (message.conversationType === ConversationType.SYSTEM) showSystemNotice(message.content);
  }
});

// 拉取系统通知历史
const { messages } = await client.getSystemMessages({ limit: 20 });