An example of how to authorize your app with Punchtab's OAuth2 API

config.ru

begin
  # Require preresolved locked gems
  require ::File.expand_path('.bundle/environment', __FILE__)
rescue LoadError
  # Fallback on resolving at runtime
  require 'rubygems'
  require 'bundler'
  Bundler.setup
end

require 'sinatra/base'
require 'oauth2'
require 'json'

class App < Sinatra::Base

  set :sessions, true

  get '/' do
    if session[:access_token]
      redirect '/auth/punchtab/test'
    else
      "Why not authenticate with <a href=\'/auth/punchtab\'>Punchtab</a>?"
    end
  end

  get '/auth/punchtab' do
    auth_url = client.auth_code.authorize_url(:redirect_uri => redirect_uri)
    ### Do this as Punchtab needs response_type=token
    auth_url.gsub!("?response_type=code&", "?response_type=token&")
    redirect(auth_url)
  end

  get '/auth/punchtab/callback' do
    if (params = {} || params[:access_token] == "")
      "PunchTab only supports authentication via Javascript client-side applications."
    else
      begin
        session[:access_token] = client.auth_code.get_token(params[:access_token], :redirect_uri => redirect_uri)
      rescue OAuth2::Error => err
        return "OAuth2 Error: #{err.backtrace}"
      end

      if session[:access_token]
        redirect '/auth/punchtab/test'
      else
        "Error retrieving access token."
      end
    end
  end

  get '/auth/punchtab/test' do
    if session[:access_token]
      connection = OAuth2::AccessToken.new(client, session[:access_token])
      headers = {'Accept' => 'application/json'}
      connection.get('/v1/leaderboard', {}, headers).inspect
    else
      redirect '/auth/punchtab'
    end
  end

  protected

  def client
    api_key = ENV['API_KEY']
    api_secret = ENV['API_SECRET']
    options = {
      :site => ENV['SITE'] || 'https://www.punchtab.com',
      :authorize_url => ENV['AUTHORIZE_URL'] || '/oauth/authorize'
    }
    OAuth2::Client.new(api_key, api_secret, options)
  end

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

end

run App

Gemfile

source :rubygems

gem 'sinatra', '1.0'
gem 'oauth2'
gem 'json'

group :development do
  gem 'shotgun'
end