How to adapt HTML5 games to be published on Telegram

The Announcement

On October 3rd, Telegram published its gaming platform. Now, the bots are able to launch HTML5 games inside Telegram and share your score with your friends. @gamebot and @gamee were the two first bots announced and Ludei is not going to be the last when it comes to HTML5.

The Rules

When creating a game with @BotFather, he will make you accept a series of rules:

You will not implement any ads or any external links on your custom URL pages.
You will not invite users to pay for any services provided on custom URL pages.
You will not use any data collected over the course of user interaction with your custom URLs for spamming Telegram users.
You will not transfer any Telegram data collected over the course of user interaction with your custom URLs to any third parties.
In order to protect the privacy of Telegram users, your custom URL pages must not set any cookies.

Now, those are some serious rules that made us change some things in our games.

Due to these rules we had to remove every way of promoting the rest of our games and every social media integration like Twitter or Facebook. Thankfully, we didn’t collect any information for third parties neither used cookies in our games -removing all that sounds like a headache.

Game rules by @BotFather

Sharing the games

The first thing you notice when reading the technical post is the script you have to include inside your games. It is a rather short script. This is because launching a game inside Telegram means opening a URL, provided by our bot, in the webview of Telegram. Our game should need hardly any changes.

<script src="https://telegram.org/js/games.js"></script>

This script provides us with the

TelegramGameProxy.shareScore()

method, which is used to share the game (but not a score, weird) with Telegram chats. It works like the usual share button in Telegram, there is no complexity with this part. We added a button with the

shareScore()

function at the result screen of each game in case you don’t know what to do with it.

Sending scores

The name “shareScore“ is quite confusing since you can’t even pass it a parameter to share. To actually send a score you should also read our post about a game bot creation. The game must send the score to the bot (with a HTTP POST, in our case) and the bot is responsible of notifying Telegram of our score. But how does the bot know who we are when it receives it? We solved this problem sending along the score a number of identifiers the bot previously added to the URL of the page. These identifiers are always userId (identifies the user) and either inlineId (if the bot was summoned with an inline call), or the pair chatId and messageId. The necessary ones are in the request Telegram sends to our bot when a user taps the play button.

@ludeiBot updates scores in Telegram

To sum it up: the user activates the play button, Telegram asks our bot for a URL to open and sends the identifications of the user, the bot returns a URL containing those identifiers in a query, and finally, our game can send the score and the identifiers of the user so the bot can update the rankings.

Detecting Telegram

At this point we have a game that can be published to Telegram, but why would we use two versions of the source code of our game? We still want to be able to promote our games if the user plays at ludei.net. If we can know when the game is executing as a Telegram game we can serve it from its original server to Telegram. Any special change we made for Telegram just has to follow a condition.

At first we tried checking

window.TelegramWebviewProxy !== undefined

(like Telegram does in its script), but somehow TelegramWebviewProxy is undefined even inside the Telegram webview, so in the end, we just check if the URL contains the identifiers of Telegram our bot adds. In our case the identifiers were query parameters because our games already had a method to parse them. Although they could have been hash parameter too; Telegram exposes an object containing them.

function getIsTelegram() {
  var qs = getQueryString();
  return !!qs.inlineId || !!qs.chatId || !!qs.messageId || !!qs.userId;
}

function getQueryString() {
  var query_string = {};
  var query = window.location.search.substring(1);
  var vars = query.split("&");
  for (var i = 0; i < vars.length; i++) {
    var pair = vars[i].split("=");
    // If first entry with this name
    if (typeof query_string[pair[0]] === "undefined") {
      query_string[pair[0]] = decodeURIComponent(pair[1]);
      // If second entry with this name
    } else if (typeof query_string[pair[0]] === "string") {
      var arr = [query_string[pair[0]], decodeURIComponent(pair[1])];
      query_string[pair[0]] = arr;
      // If third or later entry with this name
    } else {
      query_string[pair[0]].push(decodeURIComponent(pair[1]));
    }
  }
  return query_string;
}

function getIsTelegram() {
  var hs = window.TelegramGameProxy.initParams;
  return !!hs.inlineId || !!hs.chatId || !!hs.messageId || !!hs.userId;
}

Testing your game

The last thing to do is testing. Most of the testing can be done easily like with any web page development: set up a local server and open the URL in your devices. But we found some resolution problems when Telegram launched the games. Some elements appeared several times larger than when using a typical browser app. Therefore, one last advice from us is to create a minimal test bot, capable of just launching the games, enough to be able to fix any bug that might appear only in Telegram.