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

## Installation

```elixir
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`

```elixir
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

```elixir
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 ](https://developers.facebook.com/docs/messenger-platform/quickstart)

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](https://github.com/oarrabi/phoenix_facebook_messenger).

## 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
- [x] Handle facebook postback messages