SinatraとOAuthとFacebook

facebook_oauth.rb

#!/usr/bin/env ruby

require 'rubygems'
require 'sinatra'
require 'koala'

configure do
  APPLICATION_ID = "facebook_application_id"
  APPLICATION_SECRET = "facebook_application_secret"
  set :sessions, true
  enable :sessions
end

def base_url
  "#{request.scheme}://#{request.host}:#{request.port.to_s}"
end

before do
  if session[:facebook_access_token]
    @graph = Koala::Facebook::API.new(session[:facebook_access_token])
  else
    @graph = nil
  end
end

def oauth_consumer
  Koala::Facebook::OAuth.new(APPLICATION_ID, APPLICATION_SECRET)
end

get '/' do
  if @graph
    @me = @graph.get_object('me')
    erb %{
      <p><%= @me['name'] %></p>
      <img src="<%= @graph.get_picture('me') %>" alt="profile image">
    }
  else
    erb %{ <a href="/request_token">OAuth Login</a> }
  end
end

get '/request_token' do
  callback_url = "#{base_url}/access_token"
  Koala::Facebook::OAuth.new(APPLICATION_ID, APPLICATION_SECRET, callback_url)
  redirect oauth_consumer.url_for_oauth_code(:callback => callback_url)
end

get '/access_token' do
  if params[:code]
    callback_url = "#{base_url}/access_token"
    session[:facebook_access_token] = oauth_consumer.get_access_token(params[:code], :redirect_uri => callback_url)
    redirect '/'
  end
end