Rails service + OAuth

I'm having trouble structuring the logic of OAuth integration into my web app. In the app, a user creates a Report that consists of data from their Google Analytics account.

User steps:

• User clicks 'New Report'

• Google presents the 'Allow Access' page for OAuth access

• User is presented with a list of their GA web properties and selects one

• A report is created using data from the selected web property

My issue is in structuring the code below.

When the user clicks "New Report", they are actually redirected to google_analytics#ga_session to begin the authorization process. The code to retrieve the user's web properties succeeds, but the code at the bottom needs to be refactored so it is reusable when retrieving web property data. The main two issues I can't figure out is how to make the Google Analytics instance reusable and how to structure the OAuth redirects.

Retrieve web properties:

GoogleAnalyticsController

def ga_session
    client = OAuth2::Client.new(ENV['GA_CLIENT_ID'], ENV['GA_SECRET_KEY'], {
        :authorize_url => 'https://accounts.google.com/o/oauth2/auth',
        :token_url => 'https://accounts.google.com/o/oauth2/token'
    })
    redirect_to client.auth_code.authorize_url({
         :scope => 'https://www.googleapis.com/auth/analytics.readonly',
         :redirect_uri => ENV['GA_OAUTH_REDIRECT_URL'],
         :access_type => 'offline'
     })
  end

  def oauth_callback
    session[:oauth_code] = params[:code]
    redirect_to new_report_path
  end

ReportsController

def new
     @report = Report.new
     ga_obj = GoogleAnalytics.new
     ga_obj.initialize_ga_session(session[:oauth_code])
     @ga_web_properties = ga_obj.fetch_web_properties
end

GoogleAnalytics model

```
def initialize_ga_session(oauth_code)
client = OAuth2::Client.new(ENV['GA_CLIENT_ID'], ENV['GA_SECRET_KEY'], {
:authorize_url => 'https://accounts.google.com/o/oauth2/auth',
:token_url => 'https://accounts.google.com/o/oau

The first step would be to refactor out the instanciation of the Oauth2 client:

# lib/analytics_oauth2_client
class AnalyticsOAuth2Client > OAuth2::Client
  def initialize(client_id, client_secret, options = {}, &block)
    client_id || = ENV['GA_CLIENT_ID']
    client_secret || = ENV['GA_SECRET_KEY']
    options.merge!(
        authorize_url: 'https://accounts.google.com/o/oauth2/auth',
          token_url: 'https://accounts.google.com/o/oauth2/token'
    )   
    super(client_id, client_secret, options, &block)
  end 
end

And then maybe we should devise a strategy to save those pesky oauth tokens:

class AccessToken  ENV['GA_OAUTH_REDIRECT_URL'])
    @saved_token = AccessToken.create!(token.to_hash)
    session[:oauth_token] = @saved_token.id
    redirect_to new_report_path
  end
end

And we need a controller method to get the access token from the session:

def authorize!
  # ... @todo redirect to back to authentication if no `session[:oauth_token]`
  stored_token = Token.find!(session[:oauth_token])
  @token = OAuth2::AccessToken(AnalyticsOAuth2Client.new, stored_token.attributes)
  @client = GoogleAnalytics.new(token: @token)
end

And we need to shove the token into GoogleAnalytics:

class GoogleAnalytics
  include ActiveModel::Model

  attr_writer :token
  attr_accessor :user

  def initialize(attrs: {})
    super
    @user ||= Legato::User.new(@token) if @token
  end
end

Then we consider the separation of concerns - models should not deal with authentication - thats a controller concern. You should pass whatever authorized object the models needs
from the controller. Dependency injection is commonly used for this:

class Report
  attr_writer :client

  def get_keywords(oauth_code)
    self.url = @client.fetch_url(self.web_property_id)
    self.keywords = # Get keywords for self.url from another service
    keyword_revenue_data(oauth_code)
  end
end

class ReportsController
  # ...

  def create
    @report = Report.new(client: @client, params[:report])
    @report.get_top_traffic_keywords
    create!
  end

  # ...
end

StackExchange Code Review Q#27144, answer score: 2