In the first part of the article, we took some time to configure the WhatsApp application to make requests and start sending messages.

In this article, we'll focus on deploying the application and configuring the flask application for webhook notifications.

Adding the webhook route

We need to add a route first to receive requests from Meta servers and validate the request.
In the app/main.py, add a new variable called VERIFY_TOKEN. This variable will be used to validate requests from Meta servers.
It's the authentication token for webhook.
And then add the route.

@app.route("/webhook/", methods=["POST", "GET"])
def webhook_whatsapp():
    """__summary__: Get message from the webhook"""

    if request.method == "GET":
        if request.args.get('hub.verify_token') == VERIFY_TOKEN:
            return request.args.get('hub.challenge')
        return "Authentication failed. Invalid Token."

    client = WhatsAppWrapper()

    response = client.process_webhook_notification(request.get_json())

    # Do anything with the response
    # Sending a message to a phone number to confirm the webhook is working

    return jsonify({"status": "success"}, 200)

The webhook route can accept GET and POST requests. The GET request is essential for the authentication challenge. After that, each POST request is treated as a notification.
We process it and can do anything with the result. Here's the code for the process_webhook_notification method.

...
    def process_webhook_notification(self, data):
        """_summary_: Process webhook notification
        For the moment, this will return the type of notification
        """

        response = []

        for entry in data["entry"]:

            for change in entry["changes"]:
                response.append(
                    {
                        "type": change["field"],
                        "from": change["value"]["metadata"]["display_phone_number"],
                    }
                )
        # Do whatever with the response
        return response

And this is it. You can learn more about the structure of the JSON object with the following documentation.
Let's configure the application for deployment on Heroku.

Deploying on Heroku

Create a file called Procfile at the beginning of the project.

web: gunicorn wsgi:app

Once it's added, create a file called runtime.txt that will contain the python version that Heroku will use.

python-3.10.4

To create the application on Heroku, I am using the command cli. Feel free to use the UI dashboard if you are more comfortable. Also, make sure to have created a git repository of the project.

First of all login.

heroku login

After that create an application.

heroku create whatsapp-api-app

Once the application is created, let's set the environment files before pushing. Use the heroku config:set VARIABLE_NAME=VARIABLE_VALUE command to add the environment variables.

After that, push the branch and deploy.

git push heroku main

The application is deployed and let's add configure the webhook URL for the WhatsApp application configuration.

Configuring Webhook on the WhatsApp application

To use Webhook, you need to configure the service into the application first. In the application dashboard, configure the Webhook feature.

Once it's chosen, configure the webhook URL with your Heroku project and finally add the token.

And once the configuration is validated, you will start receiving notifications on the application deployed on Heroku.

Next article, we'll dive deeper into sending different types of messages, images, or even stickers.

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