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

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

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
    text = FacebookMessenger.Response.message_texts(msg) |> hd
    sender = FacebookMessenger.Response.message_senders(msg) |> hd
    FacebookMessenger.Sender.send(sender, text)
  end
enda

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

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.

• 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

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