use oauth 2.0 to get google contact list (use httparty gem)

google_contact.rb

# access_token = "abcdefg123456hijklmn"
# curl -H "Authorization: OAuth abcdefg123456hijklmn" "https://www.google.com/m8/feeds/contacts/default/full?alt=json&v=3.0"
# https://developers.google.com/google-apps/contacts/v3/
# https://developers.google.com/google-apps/contacts/v3/reference
# OAuth 2.0 Playground: https://developers.google.com/oauthplayground/
# Get a contact photo: http://stackoverflow.com/questions/5983484/google-api-getting-a-contacts-photo
def contact_list
  url = "https://www.google.com/m8/feeds/contacts/default/full"
  response = HTTParty.get(url, 
      :query => {:alt => "json", :"max-results" => "100000000"}, 
      :headers => {"Authorization" => "OAuth #{access_token}", "GData-Version" => "3.0"}
  )

  return {:error => "#{response.code}: authorization error"} if response.code == 401

  entries = response["feed"]["entry"]

  list = entries.collect do |e|
    next if e["gd$name"].blank? || e["gd$email"].blank?
    
    {
      :name  => e["gd$name"]["gd$fullName"]["$t"], 
      :email => e["gd$email"].first["address"], 
      :photo => e["link"].select{ |l| l["rel"] == "http://schemas.google.com/contacts/2008/rel#photo" }.first["href"]
    }
  end

  return list.compact!
end