SinatraとOAuthとTwitter

twitter_oauth.rb

require 'rubygems'
require 'sinatra'
require 'oauth'
require 'twitter'

configure do
  CONSUMER_KEY = "twitter_consumer_key"
  CONSUMER_SECRET = "twitter_consumer_secret"
  set :sessions, true
  enable :sessions
end

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

def oauth_consumer
  consumer = OAuth::Consumer.new(CONSUMER_KEY, CONSUMER_SECRET, :site => "http://twitter.com")
end

before do
  if session[:access_token]
    Twitter.configure do |config|
      config.consumer_key = CONSUMER_KEY
      config.consumer_secret = CONSUMER_SECRET
      config.oauth_token = session[:access_token]
      config.oauth_token_secret = session[:access_token_secret]
    end
    @twitter = Twitter
  else
    @twitter = nil
  end
end

get '/' do
  if @twitter
    erb %{
      <p><%= @twitter.user.screen_name %></p>
      <img src="<%= @twitter.profile_image() %>" alt="profile image">
    }
  else
    erb %{ <a href="/request_token">OAuth Login</a> }
  end
end

get '/request_token' do
  callback_url = "#{base_url}/access_token"
  request_token = oauth_consumer.get_request_token(:oauth_callback => callback_url)
  session[:request_token] = request_token.token
  session[:request_token_secret] = request_token.secret
  redirect request_token.authorize_url
end

get '/access_token' do
  request_token = OAuth::RequestToken.new(oauth_consumer, session[:request_token], session[:request_token])
  begin
    @access_token = request_token.get_access_token({}, :oauth_token => params[:oauth_token], :oauth_verifier => params[:oauth_verifier])
  rescue OAuth::Unauthorized => @exception
    return erb %{ oauth failed: <%=h @exception.message %> }
  end
  session[:access_token] = @access_token.token
  session[:access_token_secret] = @access_token.secret
  redirect '/'
end