oauth2_example.rb

# see http://github.com/intridea/oauth2
require 'rubygems'
require 'sinatra'
require 'oauth2'
require 'json'

class ConnectionLogger < Faraday::Middleware
  def call(env)
    env[:response].on_complete do |env|
      puts "RESULT: #{env[:status]}\n#{env[:body]}"
    end

    process_body_for_request(env)
    puts "#{env[:method].inspect} #{env[:url].to_s}"
    puts env[:request_headers].inspect if !env[:request_headers].empty?
    puts env[:body] if env[:body]
    @app.call env
  end
end

$client = OAuth2::Client.new('120094574673767', 'b54dc82476af2814e620b86776c42c0e', :site => 'https://graph.facebook.com', :adapter => :test)
$client.connection.build do |b|
  b.use ConnectionLogger
  b.adapter :net_http
end

get '/auth/facebook' do
  url = $client.web_server.authorize_url(
    :redirect_uri => redirect_uri,
    :scope => 'email,offline_access'
  )
  puts "Redirecting to URL: #{url.inspect}"
  redirect url
end

get '/auth/facebook/callback' do
  access_token = $client.web_server.access_token(params[:code], :redirect_uri => redirect_uri)
  user = JSON.parse(access_token.get('/me'))

  user.inspect
end

def redirect_uri
  uri = URI.parse(request.url)
  uri.path = '/auth/facebook/callback'
  uri.query = nil
  uri.to_s
end