oauth2 sample

app.rb

require 'rubygems'
require 'sinatra'              
require 'oauth2'               
require 'json'

configure :production do       
  @@client = OAuth2::Client.new(  
    'xxxxxxxxxxxxx',         
    'xxxxxxxxxxxxxxxxxxxxxxxx',
    :site => 'https://graph.facebook.com' 
  )
end

configure :development, :test do
  @@client = OAuth2::Client.new(  
    'xxxxxxxxxxxxx',
    'xxxxxxxxxxxxxxxxxxxxxxxx',
    :site => 'https://graph.facebook.com' 
  )
end

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

get '/' do
  '<a href="/auth/facebook">login</a>'
end

post '/' do
  '<a href="/auth/facebook">login</a>'
end

get '/auth/facebook' do
  redirect @@client.web_server.authorize_url(
    :redirect_uri => redirect_uri,  
    :scope => 'email,offline_access'
  )
end

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