Vzhuh Meme Generator for Telegram

TL;DR. This is a simplistic Telegram bot example. The demo is at http://telegram.me/vzh_bot. It takes the text sent to it, and sends back an image of a magic cat saying this text. To be hosted on Google App Engine.

What it actually does

• Sets up two urls to handle requests (both are set in main_vzhuh.py):
  • /vzhuh/img - takes the text passed as GET parameter, and returns an image. You can use it directly at, e.g. /vzhuh/img?t=and the bot is ready.
  • /vzhuh/webhook - parses POST requests from Telegram and forms a POST json response with an url to the image and some boilerplate info.
• Handles either direct messages, or chat messages starting with /vz.
  • Replies with text instructions through sendMessage method if the text after /vz is empty.
  • If the text is provided, the bot replies with an image url through sendPhoto method.
• The algorithm to fit the text into the rectangular area is in main_vzhuh.py/vzhuh_formatter.

Google App Engine (GAE)

The bot is hosted on GAE (a part of Google Cloud Platform). There are multiple advantages of GAE:

• Easy set-up. Or rather: a bit strange, but well-documented set-up.
• Free quotas. Generous enough for a small, non-viral bot.
• Free SSL/TLS encryption. For webhook bots, you need a server that can handle TLS1.0+ HTTPS-traffic signed with a trusted and verified certificate.

How to set it up

1. Register on Google Cloud Platform, create a new App Engine project with <app_engine_project_id>.
2. Test and deploy the application following these steps. gcloud app deploy app.yaml --project <app_engine_project_id>
3. Create a bot with the help of the BotFather, note down your <telegram_bot_authorization_token>.
4. Set up a webhook with the curl request:

curl -v -k -X POST -H "Content-Type: application/json" -H "Cache-Control: no-cache"  -d '{
"url":"https://<app_engine_project_id>.appspot.com/vzhuh/webhook",
}' "https://api.telegram.org/bot<telegram_bot_authorization_token>/setWebhook"

5. Send a message to your bot in Telegram, check that it replies. Add the bot to a chat with your friends. Have fun.

Debugging tips:

• You can always look up GAE logs, they are quite detailed by already, but they also show whatever you just print from your code.
• To test the server response for different messages, you can use requests sent with curl:

curl -v -k -X POST -H "Content-Type: application/json" -H "Cache-Control: no-cache"  -d '{
"update_id":10000,
"message":{
  "date":1441645532,
  "chat":{
     "last_name":"Test Lastname",
     "id":1111111,
     "type": "private",
     "first_name":"Test Firstname",
     "username":"Testusername"
  },
  "message_id":1365,
  "from":{
     "last_name":"Test Lastname",
     "id":1111111,
     "first_name":"Test Firstname",
     "username":"Testusername"
  },
  "text":"/vz and the bot is ready"
}
}' "http://localhost:8080/vzhuh/webhook"