F[Tg] - Telegramium

F[Tg] is a pure functional Telegram Bot API for Scala.

This project is a try to provide a comprehensive, well documented and Scala-idiomatic client/server implementations to work with Telegram Bot API. Please refer to telegramium-examples module for usage examples. There is a support both for polling and webhooks. API core is generated from the official documentation, so it is believed to cover all the available methods, entities and to be up to date.

Currently the following backends are supported:

• http4s
• cats-effect
• circe

You may want to start with Methods.scala and EchoBot.scala.

How to use

Create the dependency by adding the following lines to your build.sbt:

libraryDependencies += "io.github.apimorphism" %% "telegramium-core" % "<version>"
libraryDependencies += "io.github.apimorphism" %% "telegramium-high" % "<version>"

Imports:

import telegramium.bots.high._
import telegramium.bots.high.implicits._

Use the Methods factory to create requests. You will need an instance of the BotApi class to execute them:

BlazeClientBuilder[F].resource.use { httpClient =>
  implicit val api: Api[F] = BotApi(httpClient, baseUrl = s"https://api.telegram.org/bot$token")
  val bot = new MyLongPollBot()
  bot.start()
}

Long polling

class MyLongPollBot[F[_]: Async: Parallel]()(implicit api: Api[F]) extends LongPollBot[F](api) {
  override def onMessage(msg: Message): F[Unit] =
    Methods.sendMessage(chatId = ChatIntId(msg.chat.id), text = "Hello, world!").exec.void
}

LongPollBot and WebhookBot extend the Methods trait so you can call sendMessage directly.

Webhooks

class MyWebhookBot[F[_]: Async](url: String, path: String)(
  implicit api: Api[F]
) extends WebhookBot[F](api, url, path) {
  override def onMessage(msg: Message): F[Unit] =
    sendMessage(chatId = ChatIntId(msg.chat.id), text = "Hello, world!").exec.void
}

You can also perform a request to the Bot API while sending an answer to the webhook:

override def onMessageReply(msg: Message): F[Option[Method[_]]] =
  Sync[F].pure(Some(sendMessage(chatId = ChatIntId(msg.chat.id), text = "Hello, world!")))

In addition, the library provides a way to compose multiple Webhook bots into a single Http4s Server that will handle the webhooks registration as well as the incoming requests of all the composed bots. You ultimately decide at which host:port the server will be binded to:

val api1: Api[IO] = BotApi(http, baseUrl = s"https://api.telegram.org/bot$bot_token1")
val api2: Api[IO] = BotApi(http, baseUrl = s"https://api.telegram.org/bot$bot_token1")
val bot1: MyWebhookbot = new MyWebhookbot[IO](api1, "ServerVisibleFromOutside", s"/$bot_token1")
val bot2: MyWebhookbot = new MyWebhookbot[IO](api2, "ServerVisibleFromOutside", s"/$bot_token2")

WebhookBot.compose[IO](
    List(bot1, bot2),
    8080,
    "127.0.0.1" //optional, localhost as default
  ).useForever.runSyncUnsafe()

For details, have a look at the Github Issue and the related Pull Request.

OpenEnum

The Telegram Bot API is not versioned, which means bots and libraries must try to be forward-compatible. Specifically for enumerations, this implies that bots should always anticipate new values being added. Handling these values depends on the bot's business logic. Some apps may simply ignore unknown values, while others might respond with "This message is not supported," save the message for manual processing later, or throw a request handling error.

Telegramium introduces OpenEnum, a wrapper for Telegram Bot API enumerations with two cases: Known and Unknown. This type allows unknown values to be explicitly handled (similar to Option or Either), enabling bots using Telegramium to be more robust, improve error handling, and degrade gracefully in light of frequent Telegram Bot API updates.

Keyboards

To use smart and safe constructors for keyboard markups, import telegramium.bots.high.keyboards._:

val button: KeyboardButton = KeyboardButtons.text("Hello, world!")
val keyboard: ReplyKeyboardMarkup = ReplyKeyboardMarkups.singleButton(button)

val inlineButton: InlineKeyboardButton =
  InlineKeyboardButtons.callbackData(text = "Press me", callbackData = "button_pressed")

val inlineKeyboard: InlineKeyboardMarkup =
  InlineKeyboardMarkups.singleButton(inlineButton)

Message entities

telegramium.bots.high.messageentities.MessageEntities is a utility class to work with styled messages using message entities. Compose your message's text using different formatting options like plain text, bold, italics, links, mentions, hashtags and more. This class automatically takes care of calculating text offsets and lengths required by the Telegram API.

import telegramium.bots.high.messageentities.*

val msgEntities = MessageEntities()
  .bold("Hello, ")
  .mention("@user")
  .plain("! Welcome to our ")
  .textLink("website", "https://example.com")
  .lineBreak()
  .plain("Enjoy your stay.")

Methods.sendMessage(
  chatId,
  // Hello, @user! Welcome to our website\nEnjoy your stay.
  text = msgEntities.toPlainText(),
  // List(BoldMessageEntity(0, 7), MentionMessageEntity(7, 5), TextLinkMessageEntity(29, 7, "https://example.com"))
  entities = msgEntities.toTelegramEntities()
)

Versioning

X.Y.Z where

• X major changes to telegramium high or internals of the core.
• Y denotes Telegram Bot API version which is supported by this X.Y.Z.
• Z bug fix changes.

Please, note, that this versioning scheme is started from version 1.48.0.

Contribution

I'd love to have more testing and more example bots. Ideas and PRs on telegramium-high - high level interface for the bot API are also highly encouraged.

If you want to change something in telegramium-core or found a bug in it, please create an issue. Do not create pull requests with changes on telegramium-core as we use semi-automatic way to work with it. Except that any PR-s are welcome.

Before you submit the PR, ensure that you've formatted your code by running the sbt fmtAll command.

Alternatives

You may also want to have a look at these projects:

• augustjune/canoe
• bot4s/telegram

Known usages

• johnspade/taskobot-scala: Taskobot is a task collaboration inline Telegram bot. Perhaps the most up-to-date bot from a Telegramium mantainer, built with ZIO.
• johnspade/s10ns_bot: Subscription Management Telegram Bot
• TurtleBots/playcs: create dedicated servers for CS 1.6 client
• TurtleBots/gdetram: public transport arrival tabloid with chat bot interface
• b1nd/stonks: Investment Portfolio Calculation Bot
• benkio/myTelegramBot
• TurtleBots/adjutant: adjutant provides shareplace for sc2 builds through the chatbot
• TurtleBots/bender: undefeatable tic-tac-toe player
• a-khakimov/undicator: simple bot for viewing unsplash user statistics