Bot Appunti (Notes Bot)

A serverless Telegram bot for selling university notes.

This bot is based on:

• Telegraf as its main framework.
• Stripe for handling payments.
• AWS DynamoDB for storing notes' information.
• AWS Lambda for handling events sent by Telegram through webhooks.

A working example can be found in this Telegram channel and at this user.

Most strings and attributes are written in Italian 🇮🇹.

Features

• Process payments directly from Telegram using their Payments 2.0 API and Stripe. When a payment is successful, the user immediately receives the notes' file as a private message.
• Upload and update notes' files, which are stored in Telegram's servers.
• Send announcements to every user who has already bought notes of certain (or all) courses. Useful to notify updates to your notes.
• Send user satisfaction polls to quantify how users liked your notes.
• Automatic forwarding to the bot's creator of all private messages sent by any user.
• Separate behaviour for dev and production stages.

Commands

The following commands can only be executed by the creator of the bot:

Command	Description
/addpurchase <tg_userid> <course>	Manually adds a purchase to your DynamoDB database. This may be the case when the customer uses a payment method which can't be saved automatically by Stripe.
/announce <course> <date> <message>	Announces a message to users who have bought notes of a given course after date. course may also be All to send the announcement to every customer. date may be specified in any format supported by Javascript's Date object. To include the user's first name inside the message, use the variable %name%.
/askfeedback <from> <to>	Sends a satisfaction poll to all users who have bought notes of any course between from and to timestamps/dates. The poll is also sent to the creator, so they can view the results.
/deletemessage <url>	Deletes a message given its URL. The bot must have permissions to delete the message.

To update a file, the creator can privately send a document to the bot with the name of the course as the caption.

The bot also supports inline mode to send invoice messages related to notes and bundles. This can be done by any user.

Environment variables

Environment variables' values change depending on the current stage and are stored in the following files:

• .env.prod for production stage
• .env.dev for development stage
• .env.test is used by the testing library. Should contain dummy values.

These files must contain the following environment variables:

Variable	Notes
STAGE	Can be dev, prod or test. The bot behaves differently depending on the current working stage.
TELEGRAM_TOKEN	Sent to you by BotFather after creating the new bot.
PAYMENT_TOKEN	Sent to you by BotFather after linking Stripe to your bot.
CREATOR_USERID
SHOP_CHANNEL	Name or ID of the channel that you intend to use as showcase for your notes. This channel can serve as an example.
SHOP_CHANNEL_LINK
STRIPE_API_KEY	Obtained from your Stripe dashboard.

Database

This project uses a DynamoDB database to store notes' and additional purchases' information. The following tables need to be created:

• appunti (Notes):

  Attribute	Type	Description
  materia (course)	String (partition key)	Name of the course the notes belong to.
  descrizione (description)	String	Brief description of the notes.
  prezzo (price)	Number	Price of the notes specified as the number of cents (must be an integer).
  fileId_full	String	ID of the notes' file stores in Telegram's servers.
  fileId_full_DEV	String	Same as fileId_full, but this attribute is used only in development stage.
  url_anteprima (url_preview)	String	URL of the message containing a preview of the notes (provided by Telegram).
  ordine (order)	Number	Specifies in which order the notes should be listed.
  url_foto (url_image)	String	URL containing the image to be displayed inside the invoice messsage.

• appunti-bundle (note-bundles):

  Attribute	Type	Description
  nome (name)	String (partition key)	Name of the bundle.
  descrizione (description)	String	Brief description of the bundle
  materie_prezzi (course_prices)	Map<String, Number>	Object that maps each course contained in the bundle and its contribute to the total price: { course: price }. course refers to the name of the course, as specified in the appunti (notes) table.
  ordine (order)	Number	Specifies in which order the bundles should be listed. (Should be relative to only bundles, bundles are always displayed after notes.)
  url_foto (url_image)	String	URL containing the image to be displayed inside the invoice messsage.

• acquisti-appunti (notes-purchases):

  Attribute	Type	Description
  materia (course)	String (partition key)	Name of the course, as specified in the appunti (notes) table.
  timestamp	Number (sort key)	Time of purchase.
  tguser	Number	Telegram ID of the customer.

Setup

1. Create a new database and populate it as specified here.

2. Create a new Telegram bot.

3. Link the new bot to your Stripe account and generate a token.

4. Create the files .env.dev and .env.prod inside the root folder and setup the environment variables as specified here.

5. Deploy the project to AWS:

   serverless deploy -s <stage>
   

6. Setup a webhook on Telegram's end with the following URL:

   https://api.telegram.org/bot<token>/setWebhook?url=<api_endpoint>
   

   The API endpoint is provided by the output of the serverless command executed previously.