ExFacebookMessenger

ExFacebookMessenger is a library that helps you create facebook messenger bots easily.

Installation

def deps do
  [{:facebook_messenger, "~> 0.3.0"}]
end

Usage

With plug

To create an echo back bot, do the following:

In your Plug.Router define a forward with a route to FacebookMessenger.Router

defmodule Sample.Router do
  use Plug.Router
  ...

  forward "/messenger/webhook",
    to: FacebookMessenger.Router,
    message_received: &Sample.Router.message/1

  def message(msg) do
    message = FacebookMessenger.Response.parse(msg)
      |> FacebookMessenger.Response.get_messaging

    case message.type do
      "postback" -> YourApplication.process_postback(message)
      "message" -> YourApplication.proccess_text_message(message)
      _ -> YourApplication.handle_default(message)
    end
  end
end

defmodule YourApplication do
  def process_postback(message) do
    sender = FacebookMessenger.Response.message_senders(message) |> hd

    case message.payload do
      "USER_CLICKED_BUTTON" -> FacebookMessenger.Sender.send(sender, "You have clicked the button")
      _ -> FacebookMessenger.Sender.send(sender, "I can't handle this message")
    end
  end


  def process_text_message(message) do
    text = FacebookMessenger.Response.message_texts(message) |> hd
    sender = FacebookMessenger.Response.message_senders(message) |> hd
    FacebookMessenger.Sender.send(sender, text)
  end
end

This defines a webhook endpoint at: http://your-app-url/messenger/webhook

Go to your config/config.exs and add the required configurations

config :facebook_messenger,
      facebook_page_token: "Your facebook page token",
      challenge_verification_token: "the challenge verify token"

To get the facebook_page_token and challenge_verification_token follow the instructions here

For the webhook endpoint use http://your-app-url/messenger/webhook

With Phoenix

If you use phoenix framework in your project, then you need the phoenix version of facebook_messenger this can be found at phoenix_facebook_messenger found here.

Sample

A sample facebook echo bot with plug can be found here. https://github.com/oarrabi/plug_facebook_echo_bot
For the phoenix echo bot, https://github.com/oarrabi/phoenix_facebook_echo_bot

Future Improvements

Handle other types of facebook messages
Support sending facebook structure messages
Handle facebook postback messages

Cheap and reliable Node.js hosting starts at $3/month, and $1/month static HTML hosting

nsomar / facebook_messenger