Google API OAuth 2.0 refresh token (Ruby on Rails)

token.rb

# The OAuth access token provided by the Google API expires in 60 minutes. After expiration,
# you must exchange a refresh token for a new access token. Unfortunately, the the Google API 
# ruby gem does not include a method for refreshing access tokens. 

# You can read up on how to refresh an access token here: 
# https://developers.google.com/accounts/docs/OAuth2WebServer#refresh

# This Token model implements that process. It's based off of a Token model that can be created 
# by running: 
# rails g model Token token:text refresh_token:string expires_at:datetime

# This code assumes you Google API CLIENT_ID and CLIENT_SECRET are set as environment variables. 

# Google only sends the refresh token the first time you authorize your account. 
# If you didn't save it, go to your Gmail Account Permissions and revoke permissions to your app

class Token < ActiveRecord::Base

  def to_params
    { 'refresh_token' => refresh_token,
      'client_id'     => ENV['CLIENT_ID'],
      'client_secret' => ENV['CLIENT_SECRET'],
      'grant_type'    => 'refresh_token'}
  end

  def request_token_from_google
    url = URI("https://accounts.google.com/o/oauth2/token")
    Net::HTTP.post_form(url, self.to_params)
  end

  def refresh!
    data = JSON.parse(request_token_from_google.body)
    update_attributes(
      token: data['access_token'],
      expires_at: Time.now + data['expires_in'].to_i.seconds
    )
  end
  
  def self.access_token
    #convenience method to retrieve the latest token and refresh if necessary
    t = Token.last
    t.refresh! if t.expires_at < Time.now
    t.token
  end

end

Net::HTTP does not raise exceptions on HTTP failures (it just returns one of like 40 different error classes).

So when Google returns an error, which it occasionally does, response.body will be something like "{\n \"error\": \"\",\n \"error_description\": \"\"\n}".

This is valid JSON, so it will parse and evaluate to update_attributes(access_token: nil, expires_at: Time.now). Even if your refresh token is valid.

This is probably not what you want, so use a sane library, like RestClient, which will raise an exception instead:

  def request_token_from_google
    RestClient.post("https://accounts.google.com/o/oauth2/token", self.to_params)
  end