pmontrasio/wifi-presence-bot

Telegram bot to report presence data collected by wifi-receiver. Demo at Codemotion Milano 2016.

Setup

Copy the .env file from the receiver directory to here

serverless create --template aws-nodejs --name presence-bot

...

Input

Telegram gets commands from the users from the webhook.

Possible entry points:

• update_id, integer
• message, https://core.telegram.org/bots/api#message ** message.user.id is the unique identifier of the user
• edited_message, https://core.telegram.org/bots/api#message ** edited_message.user.id is the unique identifier of the user
• inline_query, https://core.telegram.org/bots/api#inlinequery ** inline_query.from.id is the unique identifier of the user
• chosen_inline_result, https://core.telegram.org/bots/api#choseninlineresult ** chosen_inline_result.from.id is the unique identifier of the user
• callback_query, https://core.telegram.org/bots/api#callbackquery ** callback_query.from.id is the unique identifier of the user

DynamoDB sends new presence data to the bot by using triggers on a stream.

Serverless doesn't create the stream for us.

Go to the AWS Console: DynamoDB, Table, select the Presences table, click the Overview tab, click on Manage Stream in Stream details. Accept the default and click Enable. Copy the Latest stream ARN to serverless.yml to the stream declaration at the end of the functions section:

According to the documentation It creates the trigger, by hooking up the stream with our lambda function. So it's not fully automatic this time. Big disappointment. Actually I had to create the trigger myself.

Go to the AWS Console: DynamoDB, Table, select the Presences table, click the Triggers tab, click on Create Trigger, Existing Lambda function. Select presence-bot-dev-presenceNotifier. Click Create.

functions:
  presenceAlertWebhook:
    ...
  presenceNotifier:
    handler: handler.presenceNotifier
    events:
    - stream: arn:aws:dynamodb:eu-west-1:XXXXXXXX:table/Presences/stream/yyyy-mm-ddTHH:MM:SS.sss

Run serverless deploy and notice that the presenceNotifier function doesn't have a HTTP endpoint.

Output

The bot sends messages back to users using the sendMessage API method documented at https://core.telegram.org/bots/api#sendmessage

It calls the API at the end of the presenceAlertWebhook

Deployment

serverless deploy

Note the URL returned by the deploy command. You have to use it to register the webhook at Telegram.

curl -X POST https://api.telegram.org/bot<access token>/setWebhook -d url=<lambda-url>

Bot UI

The bot responds to two commands

• /start to add the user to the notification list
• /stop to remove the user from the list

Any other message will return the help text.

When the countersReceiver function writes a value of presences larger than the alarm threshold (it's 10, check handler.js), the users on the notification list get a message with the alarm. Example: "There are 39 presences on 2016/10/08 15:07"