Telegram Bot API official documentation: https://core.telegram.org/bots

The wrapper used here: https://github.com/atipugin/telegram-bot-ruby

This guide is mostly about the stuff you'll type in the editor building the logic of your bot. If you want to learn about Telegram, how its group chats work, how to edit the bot account or how to deploy it, use other sources.

Setup:

Create your bot account at @BotFather in Telegram. You'll receive an API token which you'll use to connect to your bot account from this program.
In main.rb:7, assign this value to the token variable as a String.
Run gem install telegram-bot-ruby or add gem 'telegram-bot-ruby' to your Gemfile.
Optional: do the same with the require_all gem; otherwise you'll have to require all the files by standard Ruby means.
Run your main.rb file, you should see Successfully started the program in regular mode in your console.
In Telegram, send /start to your bot. Then, reply (not forward!) to his message with /get_id command: he will send you the IDs of yours and of his account.
- For example, if your bot tries to send a message in a chat it's banned from, it will crash. For that reason, the methods described in message_senders.rb check if the bot can send messages before trying to do so; to check it, the bot needs to know the ID of its account, and I haven't found any way to access it without storing it in a file or getting from a message you know came from the bot account.

Other:

If your bot does crash, it is usually stuck trying to finish the task it cannot do (it will be happening on the Telegram side). For that reason, the clear.rb file exists, you'll need to run it instead of main.rb so that your bot will "forget" the previous task.
The context revolves around the message object. From it, bot understands in which chat he does the logic you write (further in this README, 'current chat' is message.chat), who the sender is, etc. Read more in the official documentation.
Look carefully at the list of arguments custom methods accept. Most of them will need bot, message or both objects to do anything. Keep this in mind when building your own methods.
Telegram doesn't allow more than one connection with the same API token.

Methods:

Telegram::Bot::Types::Message

Call these on the message object inside of the bot.listen do |message| block.

#command

Returns the first word in the message text (or the whole text if there's no whitespace). Use when getting the /command from a message.

#from_owner?

Returns true if the message is sent by the bot owner (configured at /tools/useful_ids.rb).

#from_privileged?

Returns true if the message is sent by anyone you meintioned in the PRIVILEGED_IDS array at /tools/useful_ids.rb.

#from_self?

Returns true if the message is sent by the bot (configured at /tools/useful_ids.rb).

#from_admin?(bot)

Returns true if the message sender is an admin or the creator in the current chat.

#from_creator?(bot)

Returns true if the message sender is the creator of the current chat.

Telegram::Bot::Client

Call these on the bot object. These are mostly shortcuts for everything you find in the API documentation (to call those, use #api.method_name on the bot). You'll often need to pass as an argument the message in the context of which your logic will be happening.

#complain_to_owner(text)

Sends a private message to the bot owner account.

#reply(message, text)

Replies to the sender of the current message in the current chat.

#reply_to_target(message, text)

Replies to the sender of the message current message replies to in the current chat.

#send_message(message, text, no_preview: false)

Sends a message in the current chat. Set no_preview: true to disable the web page preview in the resulting message.

Private: #get_member_info(message, id)

Fixes the #api.get_chat_member method, returns what that method is supposed to return.

#user_can_mute?(message, id)

Returns true if the user with id can restrict non-admin members in the current chat.

#user_admin?(message, id)

Returns true if the user is an admin or the creator in the current chat.

#user_creator?(message, id)

Returns true if the user is the creator in the current chat.

#user_can_delete_messages?(message, id)

Returns true if the user can delete messages in the current chat.

#self_can_delete_messages?(message)

Returns true if the bot can delete messages in the current chat.

#self_can_mute?(message)

Returns true if the bot can restrict non-admin members in the current chat.

#user_muted?(message, id)

Returns true if the user cannot send any messages in the current chat.

#self_can_send_text?(message)

Returns true if the bot can send text messages in the current chat. By Telegram group chat restrictions, if a user can send any messages at all, they can always send text messages.

#user_in_chat?(message, id)

Returns true if the user is in the current chat. Returns false if left, kicked or never been here at all.

#user_can_send_stickers?(message, id)

Returns true if the user can send stickers in the current chat.

#mute(message, user_to_mute_id, seconds)

If has the rights to do so, restricts the non-admin user with user_to_mute_id from sending messages in the current chat for seconds seconds. Else, replies to the message sender saying it can't.

#delete(message)

If has the rights to do so, deletes the message to which the current message is a reply. Else, replies to the command sender saying it can't.

Tools

Call these on the Tools module. Usually these encapsulate often used routine stuff.

::must_be_reply(bot, message, &block)

Executes the &block if the message is a reply to a valid message. Else, replies to the sender saying this command must be used in a reply.

::must_be_owner(bot, message, &block)

Executes the &block if the message comes from the owner of the bot. Else, replies to the sender saying this command can only be used by the owner.

::must_be_privileged(bot, message, &block)

Executes the &block if the message comes from a privileged account (configured manually at Tools::PRIVILEGED_IDS) or the owner. Else, replies to the sender blah-blah-blah you get it

::form_user_link(message, full_name: false)
::form_target_link(message, full_name: false)