Felix Förtsch
123 lines
5.8 KiB
Markdown
123 lines
5.8 KiB
Markdown
---
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layout: post
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title: "Create a Telegram Bot"
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categories:
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- Code
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tags:
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- English
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- software
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last_modified_at:
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excerpt_separator: <!-- more -->
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---
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I like [Telegram](https://telegram.org). Even though it **absolutely _cannot_ be recommended** if you need security and privacy---I can't stress this enough: Telegram **is not secure**---, it offers very nice, fast and convenient features. One feature I particularly like are stickers. They basically are over sized emoji that give artists a lot of freedom to express emotion. These stickers are collected in sets that can be added to your client. Look at this cool Dino:
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<video controls>
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<source src="/img/20200827-dino.mp4" type="video/mp4">
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</video>
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They have one problem: Many times a sticker set has only a few really good stickers.
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To get around this problem Telegram offers a system to collect favorite stickers. This is a very good idea. But only in theory. The clients implement a very confusing design decision (or is it a bug?). The list of favorites is only 5 stickers wide; and the moment you add another sticker, the oldest one gets pushed into nothingness. 5 favorites are not enough.
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There are two solutions to this problem: 1) Contribute to the source code of Telegram and try to fix this bug, 2) Create a Telegram bot, that can curate a personal sticker collection.
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Since I participated in the GitHub repository of Telegram in the past and it wasn't a good experience, I decided to try myself on a Telegram Bot. This way, I am not reliant on anybody and I can learn something in the meanwhile.
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## The Goal
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Creating a bot. Send a sticker to the bot and it puts it in a curated set; curated by the user. Ultimately this makes it possible to only be subscribed to a personal sticker set that contains all favorite stickers of the user.
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## Preparation
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### First Decisions
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The first step for any project is reading available documentation to better understand the problem space. Luckily, the [Telegram Bots API](https://core.telegram.org/bots/api) is very well documented. It also contains a [comprehensive list of Bot API implementations](https://core.telegram.org/bots/samples).
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I decided to use the programming language Java for the bot implementation, since I am most comfortable with it. I will use [rubenlagus's TelegramBots](https://github.com/rubenlagus/TelegramBots) API implementation. The *test* bot will be hosted on my Raspberry Pi, the *production* bot on my [Uberspace](https://uberspace.de).
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### Telegram API Overview
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To identify and understand how to use the API, my first step is looking through the [available types](https://core.telegram.org/bots/api#available-types). The types and attributes of interest are:
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- User:
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- id (necessary to attribute the sticker set)
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- username (to construct the sticker set name)
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- Chat:
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- id (to respond to the correct chat, post status messages, etc.)
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- Message:
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- message_id
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- from -> Returns the User (see above)
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- chat -> Returns the Chat (see above)
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- reply_to_message (reply to the posted sticker), text (a field where we can receive text and communicate with the user)
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- sticker -> Returns a/the Sticker (see below)
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- BotCommand:
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- command
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- description
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- Sticker:
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- file_id
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- is_animated -> Important, since regular and animated stickers can't be in the same set
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It seems to be possible to extract the required information from the Message object. However, there are limits to the sticker sets: 50 in animated sticker sets and 120 in unanimated sets. Once we reach the limit, we need to create a new set. This means we need to somehow keep state or have the user keep track of it.
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### Understanding the Connection to the Java Implementation
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After adding all required dependencies, the entry point of the Java API looks like this:
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```java
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public class Main {
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public static void main(String[] args) {
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ApiContextInitializer.init();
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TelegramBotsApi telegramBotsApi = new TelegramBotsApi();
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try {
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telegramBotsApi.registerBot(new FavoriteStickersBot());
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} catch (TelegramApiException e) {
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e.printStackTrace();
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}
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}
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}
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```
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We initialize the API implementation and then we register our custom `FavoriteStickersBot` class with it. There are different ways to implement a bot, but we will go with the *Getting Started* way and extend `TelegramLongPollingBot`. [Long polling](https://en.wikipedia.org/wiki/Push_technology#Long_polling) is a method that enables the system to use push behavior without actually having push capabilities.
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```java
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public class FavoriteStickersBot extends TelegramLongPollingBot {
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public String getBotUsername() {
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return BotConfig.BOT_USERNAME;
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}
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public String getBotToken() {
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return BotConfig.BOT_TOKEN;
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}
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public void onUpdateReceived(Update update) {}
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```
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When running the program, the bot will execute and
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The Java implementation basically uses a 1:1 mapping of the API to Java. To instantiate a Telegram User object you can either use `User user = new User()` and then use the setters
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Methods are implemented the similarly. To create a new sticker set we do the following:
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```java
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CreateNewStickerSet createNewStickerSet = new CreateNewStickerSet()`. We then
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```
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## Implementation
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### Project setup
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Following the [Getting Started Guide](https://github.com/rubenlagus/TelegramBots/wiki/Getting-Started) from TelegramBots, the first step is registering your new and shiny bot with the Telegram [@BotFather](https://telegram.me/BotFather). During this process you will receive the required API token to enable communication between the bot and the Telegram service.
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## Potential Pitfalls
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I am using the file_id instead of creating the stickers from scratch
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## Next Steps
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Currently, the bot is single-user only. It should be reasonably easy to add multi-user support by creating a group, adding the bot to it and then having a shared best sticker set.
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