Sinatra code that gets your Google contacts through OAuth. Wrote this because OmniAuth was giving me trouble with the contacts data api scope for some reason, so I decided to go 'raw'.

sinatra_google_contacts_oauth.rb

require 'sinatra'
require 'net/http'
require 'json'

ENDPOINT = 'https://accounts.google.com/o/oauth2/auth'
TOKEN_ENDPOINT = 'https://accounts.google.com/o/oauth2/token'
CLIENT_ID = '<your app client id>'
CLIENT_SECRET = '<your app client secret>'
REDIRECT_URI = 'http://localhost:4567/auth/google_oauth2/callback'
SCOPE = 'https://www.google.com/m8/feeds/'
ACCESS_TYPE = 'offline'
#ACCESS_TYPE = 'online'
APPROVAL_PROMPT = 'auto'
#APPROVAL_PROMPT = 'force' # ensures we get a refresh token
STATE = 'contacts'
RESPONSE_TYPE = 'code'
GRANT_TYPE = 'authorization_code'
GRANT_TYPE_REFRESH = 'refresh_token'
ME = 'elad...@...'

def output_response(res)
  puts res.class
  puts res.message
  puts res.code
  res.each_header {|k, v| puts "#{k} = #{v}" }
  #puts res.body
end

def step1
  params = {
    :scope => SCOPE,
    :state => STATE,
    :redirect_uri => REDIRECT_URI,
    :response_type => RESPONSE_TYPE,
    :client_id => CLIENT_ID,
    :approval_prompt => APPROVAL_PROMPT,
    :access_type => ACCESS_TYPE,
  }
  uri = URI(ENDPOINT)
  res = Net::HTTP.start(uri.host, uri.port, :use_ssl => true) do |http|
    uri.query = URI.encode_www_form(params)
    req = Net::HTTP::Get.new uri.request_uri
    http.request(req)
  end
  output_response res
  res['location']
end

get '/' do
  <<-HTML
  <a href='/auth/google_oauth2'>Connect with Google</a>
  HTML
end

get '/auth/google_oauth2' do
  params = {
    :scope => SCOPE,
    :state => STATE,
    :redirect_uri => REDIRECT_URI,
    :response_type => RESPONSE_TYPE,
    :client_id => CLIENT_ID,
    :approval_prompt => APPROVAL_PROMPT,
    :access_type => ACCESS_TYPE,
  }
  query = URI.encode_www_form(params)
  puts "Query: #{query}"
  location = "#{ENDPOINT}?#{query}"
  puts "Redirecting to #{location}"
  redirect location
end

def form_html(code)
  <<-HTML
  <p>
  <form method='post' action='#{TOKEN_ENDPOINT}'>
  <input type='text' name='code' value='#{code}'/><br/>
  <input type='text' name='client_id' value='#{CLIENT_ID}'/><br/>
  <input type='text' name='client_secret' value='#{CLIENT_SECRET}'/><br/>
  <input type='text' name='redirect_uri' value='#{REDIRECT_URI}'/><br/>
  <input type='text' name='grant_type' value='#{GRANT_TYPE}'/>
  <input type='submit' value="Submit">
  </form>
  </p>
  HTML
end

def get_token_redirect(code)
  <<-HTML
  <p>
  <a href='/get_token?code=#{code}'>Get Token in Background</a>
  </p>
  HTML
end

get '/auth/google_oauth2/callback' do
  code = params[:code]
  puts "Code: #{code}"
  form_html(code) + get_token_redirect(code)
end

def data_html(data)
  contacts_link = "<p><a href='https://www.google.com/m8/feeds/contacts/#{ME}/full?access_token=#{data['access_token']}'>All my Google Contacts</a></p>"
  refresh_link = "<p><a href='/refresh_token?token=#{data['refresh_token']}'>Refresh</a></p>"
  data.to_a.map{|kv| kv.join(": ") }.join("<br/>") + refresh_link + contacts_link
end

def get_token(code)
  params = {
    :code => code,
    :client_id => CLIENT_ID,
    :client_secret => CLIENT_SECRET,
    :redirect_uri => REDIRECT_URI,
    :grant_type => GRANT_TYPE,
  }
  uri = URI(TOKEN_ENDPOINT)
  req = Net::HTTP::Post.new uri.path
  req.set_form_data params
  res = Net::HTTP.start(uri.host, uri.port, :use_ssl => true) do |http|
    http.request(req)
  end
  output_response res
  data = JSON.parse(res.body)
  data_html(data)
end

get '/get_token' do
  code = params[:code]
  puts "Code: #{code}"
  get_token(code)
end

def refresh_token(token)
  params = {
    :refresh_token => token,
    :client_id => CLIENT_ID,
    :client_secret => CLIENT_SECRET,
    :grant_type => GRANT_TYPE_REFRESH,
  }
  uri = URI(TOKEN_ENDPOINT)
  req = Net::HTTP::Post.new uri.path
  req.set_form_data params
  res = Net::HTTP.start(uri.host, uri.port, :use_ssl => true) do |http|
    http.request(req)
  end
  output_response res
  res.body
end

def refresh_token_form_html(token)
  <<-HTML
  <p>
  <form method='post' action='#{TOKEN_ENDPOINT}'>
  <input type='text' name='refresh_token' value='#{token}'/><br/>
  <input type='text' name='client_id' value='#{CLIENT_ID}'/><br/>
  <input type='text' name='client_secret' value='#{CLIENT_SECRET}'/><br/>
  <input type='text' name='grant_type' value='#{GRANT_TYPE_REFRESH}'/>
  <input type='submit' value="Submit">
  </form>
  </p>
  HTML
end

get '/refresh_token' do
  token = params[:token]
  refresh_token(token)
end