The Messenger Exchange Rate Bot on Hasura

This tutorial helps you in setting up the messenger exchange rate bot which offers functionalities to retrieve currency exchange rates by the bot.

For the chat bot to function we'll need a server that will receive the messages sent by the Facebook users, process this message and respond back to the user. To send messages back to the server we will use the graph API provided by Facebook. For the Facebook servers to talk to our server, the endpoint URL of our server should be accessible to the Facebook server and should use a secure HTTPS URL. For this reason, running our server locally will not work and instead we need to host our server online. In this tutorial, we are going to deploy our server on Hasura which automatically provides SSL-enabled domains.

Contents

• Pre-requisites
• Getting the bot running
• Bot Functionalities

Pre-requisites

• NodeJS

• hasura CLI

Getting the bot running

Create a facebook application

• Navigate to https://developers.facebook.com/apps/
• Click on '+ Create a new app’.

• Give a display name for your app and a contact email.

• In the select a product screen, hover over Messenger and click on Set Up

• To start using the bot, we need a facebook page to host our bot.
  • Scroll over to the Token Generation section
  • Choose a page from the dropdown (Incase you do not have a page, create one)
  • Once you have selected a page, a Page Access Token will be generated for you.
  • Save this token somewhere.

• Now, we need to trigger the facebook app to start sending us messages
  • Switch back to the terminal
  • Paste the following command:

# Replace <PAGE_ACCESS_TOKEN> with the page access token you just generated.
$ curl -X POST "https://graph.facebook.com/v2.6/me/subscribed_apps?access_token=<PAGE_ACCESS_TOKEN>"

Getting the Hasura project

$ hasura quickstart akashiiitv/fb-exchange-rate-bot
$ cd fb-exchange-rate-bot
# Add FACEBOOK_VERIFY_TOKEN to secrets. This is any pass phrase that you decide on, keep a note on what you are choosing as your verify token, we will be using it later while setting things up for your bot on the facebook developer page.
$ hasura secrets update bot.fb_verify_token.key <YOUR-VERIFY-TOKEN>
# Add FACEBOOK_PAGE_ACCESS_TOKEN to secrets
$ hasura secrets update bot.fb_page_token.key <YOUR-FB-PAGE-ACCESS-TOKEN>
# Deploy
$ git add . && git commit -m "Deployment commit"
$ git push hasura master

After the git push completes:

$ hasura microservice list

You will get an output like so:

INFO Getting microservices...                     
INFO Custom microservices:                        
NAME   STATUS    INTERNAL-URL(tcp,http)   EXTERNAL-URL
bot    Running   bot.default              https://bot.furnished70.hasura-app.io

INFO Hasura microservices:                        
NAME            STATUS    INTERNAL-URL(tcp,http)   EXTERNAL-URL
auth            Running   auth.hasura              https://auth.furnished70.hasura-app.io
data            Running   data.hasura              https://data.furnished70.hasura-app.io
filestore       Running   filestore.hasura         https://filestore.furnished70.hasura-app.io
gateway         Running   gateway.hasura           
le-agent        Running   le-agent.hasura          
notify          Running   notify.hasura            https://notify.furnished70.hasura-app.io
platform-sync   Running   platform-sync.hasura     
postgres        Running   postgres.hasura          
session-redis   Running   session-redis.hasura     
sshd            Running   sshd.hasura              
vahana          Running   vahana.hasura

Find the EXTERNAL-URL for the service named bot(in this case -> https://bot.furnished70.hasura-app.io).

Enabling webhooks

In your fb app page, scroll down until you find a card name Webhooks. Click on the setup webhooks button.

• The callback URL is the URL that the facebook servers will hit to verify as well as forward the messages sent to our bot. The nodejs app in this project uses the /webhook path as the callback URL. Making the callback URL https://bot.YOUR-CLUSTER-NAME.hasura-app.io/webhook (in this case -> https://bot.furnished70.hasura-app.io/webhook/)
• The verify tokenis the verify token that you set in your secrets above (in the command $ hasura secrets update bot.fb_verify_token.key )
• After selecting all the Subsciption Fields. Submit and save.
• You will also see another section under Webhooks that says Select a page to subscribe your webhook to the page events, ensure that you select the respective facebook page here.

Next, open up your facebook page.

• Hover over the Send Message button and click on Test Button.

• Instead, if your button says + Add Button, click on it.

• Next, click on Use our messenger bot. Then, Get Started and finally Add Button.
• You will now see that the + Add button has now changed to Get Started. Hovering over this will show you a list with an item named Test this button. Click on it to start chatting with your bot.
• Send a message to your bot.

Bot Functionalities

This bot offers five different functionalities, three of them are for getting the exchange rates for cryptocurrencies and fiat currencies, while the other two are for retrieving the currency symbols. Also note that all the commands are case-insensitive(The capital/small letters or their combination does not affect the command functionality).

Getting Exchange Rate of a Cryptocurrency with another Fiat/Crypto Currency

This feature can be accessed by the command c2o. Eg:

c2o btc usd 0.1

or

c2o BCH INR

Note:

• The API used for this functionality is: CryptoCompare.
• The value part is optional after the two symbols. The default conversion value taken is 1.

Getting Exchange Rate of a Fiat Currency with another Cryptocurrency

This feature can be accessed by the command f2c. Eg:

f2c inr btc 103250

or

f2c pen bcd

Note:

• The API used for this functionality is: CryptoCompare.
• The value part is optional after the two symbols. The default conversion value taken is 1.

Getting Fiat exchange rates

This feature can be accessed by the command curr. Eg:

curr inr usd 500

Note:

• The API used for this functionality is: The Free Currency Converter API.
• The value part is optional after the two symbols. The default conversion value taken is 1.
• There is a limit of 100 requests/hour by the API. So, you may sometimes have to try later depending on the request traffic.

Getting Fiat Currency Symbol

This feature can be accessed by the command ctrcode. Eg:

ctrcode India

Note: The API used for this functionality is: Rest Countries.

Getting Cryptocurrency Symbol

This feature can be accessed by the command ctrcode. Eg:

crycode Bitcoin Cash

Note: The Hasura Database is queried to retrieve the symbol for this functionality.

Commands List

The command list can be accessed via the command help.