Facebook Mobile Hack Demo

client-side-authentication.rb

# Login endpoint for client side flow
# Takes a token paremeter and creates a user if necessary
post "/auth" do
  client = Facebook.exchange_token(params[:token])
  user = User.from_facebook(client)
  session[:user] = user.uid
  redirect '/'
end

class Facebook
  # Refresh short-lived token with a long-lived one
  def self.exchange_token(token)
    res = access_token(:grant_type => "fb_exchange_token", :fb_exchange_token => token)
    new(parse_token(res.body))
  end
end

fetching-actions.rb

# Shows a list of recent plays on SoundCloud
get "/" do
  begin
    if user
      # Logged in users have a Facebook connection
      @actions = user.facebook.get('/me/soundcloud:listen')['data']
    end

    # rendering html template
    erb :index

  # Access Token is expired, so we reauth the user on Facebook
  rescue Facebook::OAuthException
    redirect auth_url
  end
end

javascript-auth.js

$(function() {
  FB.init({
    appId   : App.appId,
    cookie  : true,
    oauth   : true
  });

  // If user is not logged in, we try to authenticate from Facebook.
  if (!App.userId) {
    
    // Query Facebook API for authentication data
    FB.getLoginStatus(function(response) {
      
      // The user already connected to the app, so we just need to 
      // send the access token to login the user.
      if (response.status === 'connected') {
        $('#access-token').val(response.authResponse.accessToken);
        $('#auth-form').submit();
      }
      else {
        // The user hasn't connected yet, so we redirect to the 
        // Facebook Authentication Dialog.
        window.location = App.authUrl;
        // https://www.facebook.com/dialog/oauth?scope=user_actions:soundcloud&redirect_uri=https://mobile-hack.herokuapp.com/auth
      }
    });
  }
});

server-side-authentication.rb

# Callback endpoint for server side flow
# Takes a OAuth code parameter and creates a user if necessary
get "/auth" do
  client = Facebook.exchange_code(params[:code], url('/auth'))
  user = User.from_facebook(client)
  session[:user] = user.uid
  redirect '/'
end

class Facebook
  # Request access token for given authorization code
  def self.exchange_code(code, redirect_uri)
    res = access_token(:code => code, :redirect_uri => redirect_uri)
    new(parse_token(res.body))
  end
end

soundcloud.rb

class Soundcloud
  APP_ID = 'YOUR_CLIENT_ID'

  def self.http(domain = "api.soundcloud.com")
    Net::HTTP.new(domain, 80)
  end

  def self.get(path, params={})
    JSON.parse(http.get(path + '.json?' + urlencode_hash({ :client_id => APP_ID }.merge(params))).body)
  end

  # Returns an embeddable player
  def self.oembed(url)
    JSON.parse(http('soundcloud.com').get('/oembed?' + urlencode_hash(:format => 'json', :url => url)).body)
  rescue JSON::ParserError
  end
end