app.rb

require 'sinatra'
require 'oauth2'
require 'json'
enable :sessions

def client
  # OAuth2::Client.new("KEY", "SECRET", :site => "http://localhost:3000")
  OAuth2::Client.new("tV5Gks6HjhFskIL4j2I7NcPh85fCuplVjYQn6AEB", "R69Jcu2d8877YstLyd6DwvW7pxNSzlTLzyogZ7ux", :site => "http://localhost:3000")
end

get "/auth/test" do
  redirect client.auth_code.authorize_url(:redirect_uri => redirect_uri)
end

get '/auth/test/callback' do
  access_token = client.auth_code.get_token(params[:code], :redirect_uri => redirect_uri)
  session[:access_token] = access_token.token
  @message = "Successfully authenticated with the server"
  erb :success
end


get /\/test\/(.*)/ do |path|
  p path
  @message = get_response("#{path}.json")
  erb :another
end

get '/yet_another' do
  @message = get_response('data.json')
  erb :success
end

get '/another_page' do
  @message = get_response('contacts.json')
  erb :another
end

def get_response(url)
  access_token = OAuth2::AccessToken.new(client, session[:access_token])
  JSON.parse(access_token.get("/api/v1/#{url}").body)
end


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