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OAuth2 Facebook

A Facebook OAuth2 Provider for Elixir

OAuth2 Facebook is convenience library built on top of oauth2. It adds Facebook specific functions to interact with the Facebook Graph endpoints using OAuth2.

Installation

# mix.exs

def application do
  # Add the application to your list of applications.
  # This will ensure that it will be included in a release.
  [applications: [:logger, :oauth2_facebook]]
end

defp deps do
  # Add the dependency
  [{:oauth2_facebook, "~> 0.1"}]
end

Authenticating a User

For an easy-to-use, end-to-end solution enabling users to log in with Facebook see ueberauth/ueberauth_facebook

One common use-case is authenticating a user's identify. The get_user! function wraps two actions into one - exchanging the callback code for a short-lived access token and using the access token to return user data:

alias OAuth2.Provider.Facebook

Facebook.get_user!([code: "<callback-code>"], [redirect_uri: "..."])

When successful, it returns the user data:

{:ok, %{"email" => "user@gmail.com", "gender" => "male", "id" => "101", "link" => "https://www.facebook.com/app_scoped_user_id/101/", "locale" => "en_US", "name" => "user", "timezone" => -4, "updated_time" => "2015-06-05T14:59:20+0000", "verified" => true}}

Returning an Access Token

A valid access token can be used to make multiple requests to the Facebook Graph. The callback code can be exchanged for an access token using get_token!:

alias OAuth2.Provider.Facebook

client = Facebook.get_token!([code: "<callback-code>"], [redirect_uri: "..."])

When successful, it will return a valid OAuth2.Client:

%OAuth2.Client{authorize_url: "https://www.facebook.com/dialog/oauth", client_id: "<...>", client_secret: "<...>", headers: [], params: %{}, redirect_uri: "http://localhost:3000/login/facebook/callback", ref: nil, request_opts: [], site: "https://graph.facebook.com", strategy: OAuth2.Provider.Facebook, token: %OAuth2.AccessToken{access_token: "EAABw0PjpdjcBAMDUjWQtZApFV2nFJfhIUWaw3z8MSbi92fVooa2BNBdZBeRaxMcHO94zdmncoFuZBvQQdj0cmXosa8kAZCx7wtlSR5ByT2etOhURZCNjs9DDFfpU456Gk8f0tvzmtYsiMstSKkh69kIzSVOeQIx8TPQOLpXHnRCARNXCiiB1Y", expires_at: 1507926168, other_params: %{}, refresh_token: nil, token_type: "Bearer"}, token_method: :get, token_url: "/v2.8/oauth/access_token"}

Note: The access token is kept under the client's token key.

Using a Valid Client

A valid client with an access token can then be passed into endpoint specific functions. For example, to return user data using a client with a valid access token:

alias OAuth2.Provider.Facebook

{:ok, user} = Facebook.get_user(client)

When successful, it will return the same user information:

%{"email" => "user@gmail.com", "gender" => "male", "id" => "101", "link" => "https://www.facebook.com/app_scoped_user_id/101/", "locale" => "en_US", "name" => "user", "timezone" => -4, "updated_time" => "2015-06-05T14:59:20+0000", "verified" => true}

Filtering User fields

Both get_user! and get_user support passing custom query params. These can be used to filter the returned attributes:

alias OAuth2.Provider.Facebook

# Using `get_user!`
user = Facebook.get_user!([code: "<callback-code>"], [redirect_uri: "..."], [fields: "email,name"])

# Using `get_user`
client = Facebook.get_token!([code: "<callback-code>"], [redirect_uri: "..."])
{:ok, user} = Facebook.get_user(client, [fields: "email,name"])

When successful, will return a trimmed down user:

%{"email" => "user@gmail.com", "id" => "101", "name" => "user"}

Note: The id value is always returned.