Facebook OAuth2 strategy for Überauth.

1. Setup your application at Facebook Developers.

2. Add :ueberauth_facebook to your list of dependencies in mix.exs:

   def deps do
     [
       {:ueberauth_facebook, "~> 0.8"}
     ]
   end

3. Add the strategy to your applications:

   def application do
     [
       applications: [:ueberauth_facebook]
     ]
   end

4. Add Facebook to your Überauth configuration:

   config :ueberauth, Ueberauth,
     providers: [
       facebook: {Ueberauth.Strategy.Facebook, []}
     ]

5. Update your provider configuration:

   config :ueberauth, Ueberauth.Strategy.Facebook.OAuth,
     client_id: System.get_env("FACEBOOK_CLIENT_ID"),
     client_secret: System.get_env("FACEBOOK_CLIENT_SECRET")

6. Include the Überauth plug in your controller:

   defmodule MyApp.AuthController do
     use MyApp.Web, :controller
     plug Ueberauth
     ...
   end

7. Create the request and callback routes if you haven't already:

   scope "/auth", MyApp do
     pipe_through :browser
   
     get "/:provider", AuthController, :request
     get "/:provider/callback", AuthController, :callback
   end

8. Your controller needs to implement callbacks to deal with Ueberauth.Auth and Ueberauth.Failure responses.

For an example implementation see the Überauth Example application.

Depending on the configured URL you can initialize the request through:

/auth/facebook

Or with options (auth_type, scope, locale, display):

/auth/facebook?scope=email,public_profile

By default the requested scope is "public_profile". Scope can be configured either explicitly as a scope query value on the request path or in your configuration:

config :ueberauth, Ueberauth,
  providers: [
    facebook: {Ueberauth.Strategy.Facebook, [default_scope: "email,public_profile,user_friends"]}
  ]

Additionally you can now specify the display param to pass to Facebook:

config :ueberauth, Ueberauth,
  providers: [
    facebook: {Ueberauth.Strategy.Facebook, [
      default_scope: "email,public_profile,user_friends",
      display: "popup"
    ]}
  ]

display can be the following values: page (default), async, iframe, popup, touch, wap

Starting with Graph API version 2.4, Facebook has limited the default fields returned when fetching the user profile. Fields can be explicitly requested using the profile_fields option:

config :ueberauth, Ueberauth,
  providers: [
    facebook: {Ueberauth.Strategy.Facebook, [profile_fields: "name,email,first_name,last_name"]}
  ]

See Graph API Reference > User for full list of fields.

Copyright (c) 2015 Sean Callan

Released under the MIT License, which can be found in the repository in LICENSE.