Telegram Bot with Cloudflare Workers

index.js

/**
 * After Save & Deploy, invoke `/register`
 * Open Telegram, go to your bot, write something: you should receive it back.
 */
export default {
  async fetch(request, env, context) {
    const { headers } = request
    const { hostname, pathname } = new URL(request.url)
    const telegram = 'https://api.telegram.org/bot' + env.TOKEN

    const sendText = async (chatId, text) => {
      const params = new URLSearchParams({ chat_id: chatId, text })
      const r = await fetch(telegram + '/sendMessage?' + params)
      return await r.json()
    }

    const setWebhook = async (url) => {
      const r = await fetch(url)
      const j = await r.json()
      return new Response('ok' in j && j.ok ? 'Ok' : JSON.stringify(j, null, 2))
    }

    if (pathname === '/update') {
      if (env.SECRET_TOKEN !== headers.get('X-Telegram-Bot-Api-Secret-Token')) {
        return new Response('Unauthorized', { status: 403 })
      }
      const requestData = await request.json()
      if ('message' in requestData) {
        const chatId = requestData.message.chat.id
        const text = 'Echo:\n' + requestData.message.text
        // Non-blocking; might end after we return the Response
        context.waitUntil(sendText(chatId, text))
        return new Response('Ok')
      } else {
        return new Response('Bad Request', { status: 400 })
      }
    } else if (pathname === '/register') {
      const updateUrl = `https://${hostname}/update`
      const setWebhookParams = new URLSearchParams({ url: updateUrl, secret_token: env.SECRET_TOKEN })
      const setWebhookUrl = telegram + '/setWebhook?' + setWebhookParams
      return await setWebhook(setWebhookUrl)
    } else if (pathname === '/deregister') {
      const unsetWebhookUrl = telegram + '/setWebhook?url='
      return await setWebhook(unsetWebhookUrl)
    } else {
      return new Response('Not Found', { status: 404 })
    }
  },
}