Building a Telegram bot: Detail tutorial write up | Ecency

In this telegram video tutorial, I will be sharing on the guide on creating a telegram bot on top of steem blockchain. This bot will broadcast out in the Telegram Channel, whenever someone posted on steem with the tag #teammalaysia and #contest.

This bot allow users/subscribers to know the contest at the moment of posting, and participate it immediately.

What Will I Learn?

Create a bot on Telegram
Code the bot on top of steem blockchain, watch for a certain tags (In this case it is #teammalaysia and #contest)

Requirements

Telegram account
Node.js Installed

Difficulty

Intermediate

Description

This video tutorial is separated into 2 parts, where the first part is to get the necessary keys to start the project and the second part is to code the bot.

Part 1: Setting up the bot

There are 2 keys that we need to extract out before we start coding, which is the telegram bot API key and Channel ID.

Getting telegram bot API key

To get the Bot API key, you just need to message BotFather on telegram, starting with the command /newbot. Follow the instruction given by BotFather and eventually he will give out a message and give you the key.

Screen Shot 2018-03-24 at 5.07.49 PM.png

Getting the channel ID key

For this part, it requires you to use the telegram web interface. After you create a new Channel, add in the bot you created previously and made it an admin. To get the channel ID, just get the URL of the telegram channel, and extract out the first combination of numbers. Then, add -100 as a prefix in front of the numbers.

Screen Shot 2018-03-24 at 5.14.26 PM.png

You can read through the guide on stack overflow

Part 2: Coding the bot

Save both of the key you generated in Part 1 into `.env` file

In the .env file, it looks like this:

CHANNEL_ID=-100<CHANNEL_ID>
BOT_KEY=<API_KEY>

Initialize the project

Start the project with npm init or yarn init.

Install necessary dependencies.

In this tutorial, I will make use of 3 library:

node-telegram-bot-api - an API layer for us to deal with telegram using Node.js
steem - Official Steem API, using it to watch all steem new posts.
dotenv - a library to use .env file.

To install, just run npm install --save node-telegram-bot-api steem dotenv or yarn add node-telegram-bot-api steem dotenv.

Start Coding

After installing the dependencies, we can just create variables out from the library.

const telegram = require('node-telegram-bot-api');
const steem = require('steem');
const dotenv = require('dotenv');

We import all the .env file with the function:

dotenv.config();

Then, create a new telegram variable by passing in the private API key in the .env file and connect to the telegram bot with the method of long polling.

const bot = new telegram(process.env.BOT_KEY, {
  polling: true
});

Next, we need to watch the Steem transaction. So, whenever there is a transaction (new post) on steem, it will watch for that. It is just like on Web interface, we use JS to watch when a user pressed a button.

steem.api.streamTransactions('head', function(err, result) {
  if (err) {
    return;
  }
  // Insert Code Here
})

From the result of the transaction, we look for 2 data that we need.

  let txType = result.operations[0][0];
  let txData = result.operations[0][1];

Then, we make sure that the post is a post (not a comment), and it is not a resteem

  if (txType === 'comment' && txData.parent_author === '') {
      // Insert Code Here
  } else {
    return;
  }

Next, we try and see wether the post contain tags or not. If it doesn't, just return.

    let tags;

    try {
      tags = JSON.parse(txData.json_metadata).tags;
    } catch (e) {
      return;
    }

Next, we check wether the tags has #teammalaysia and #contest. If it doesn't, just return it.

 if (
      tags.includes('contest') &&
      tags.includes('teammalaysia')
    ) {
    // Insert Code Here
} else {
  return:
}

Then, just extract out the author and permlink , and make it into steemit link.

let link = `@${txData.author}/${txData.permlink}`; // @superoo7/something

Then, we just need to telegram bot to send the message in the channel, by passing in the channel ID from .env and the steemit link.

bot.sendMessage(
        process.env.CHANNEL_ID,
        `https://steemit.com/${link}`
      );

The full source code

const telegram = require('node-telegram-bot-api');
const steem = require('steem');
const dotenv = require('dotenv');

dotenv.config();

const bot = new telegram(process.env.BOT_KEY, {
  polling: true
});

steem.api.streamTransactions('head', function(err, result) {
  if (err) {
    return;
  }

  let txType = result.operations[0][0];
  let txData = result.operations[0][1];

  // Check a post and it is not being resteem
  if (txType === 'comment' && txData.parent_author === '') {
    let tags;

    try {
      tags = JSON.parse(txData.json_metadata).tags;
    } catch (e) {
      return;
    }

    if (
      tags.includes('contest') &&
      tags.includes('teammalaysia')
    ) {
      let link = `@${txData.author}/${txData.permlink}`;

      bot.sendMessage(
        process.env.CHANNEL_ID,
        `https://steemit.com/${link}`
      );
    }
  }
});