Slack用Google翻訳Bot on Firebase Functions

translate_slack_bot.js

const functions = require('firebase-functions');
const request = require('request');
const { Translate } = require('@google-cloud/translate');
/*
Firebase Functionsの環境変数
slack.bot_user_tokenとgoogle.project_idを適当に設定してください
*/


async function postMessage(payload) {
  return await request.post('https://slack.com/api/chat.postMessage', {
      headers: { 'Authorization': `Bearer ${functions.config().slack.bot_user_token}` },
      json: payload,
  });
}
const projectId = functions.config().google.project_id;

exports.bot = functions.https.onRequest(async (req, res) => {
  const payload = req.body;

  if (payload.type === 'url_verification') {
    return res.status(200).json({ 'challenge': payload.challenge });
  }
  else if (payload.event && payload.event.type === 'app_mention') {
    console.log("payload:",JSON.stringify(payload) );
    var originalText = payload.event.text;
    payload.authed_users.forEach(user => (originalText = originalText.split(`<@${user}>`).join("")));

    const translate = new Translate({ projectId });
    const langulagesResult = await translate.detect(originalText);
    
    let translateTo = ['en', 'ja'];
    if(langulagesResult[0].language == 'en') {
      translateTo = ['ja'];
    }
    else if(langulagesResult[0].language == 'ja') {
      translateTo = ['en'];
    }

    let translatedText = [];
    for (var lang of translateTo) {
      const translatedResult = await translate.translate(originalText, lang);
      translatedText.push(translatedResult[0].replace(/<@\s+/g, '<@'));
    };
  
    const slackRes = await postMessage({
      text: translatedText.join("\n\n"),
      channel: payload.event.channel,
      thread_ts: payload.event.ts
    });
  }

  res.status(200).send('OK');
});