google_analytics.rb

require 'googleauth'
require 'google/apis/analytics_v3'

# /via https://github.com/google/google-api-ruby-client/issues/291
class GoogleAnalytics
  def self.client
    service = new
    service.analytics_service
  end

  def google_api_key
    # We /should/ be able to set the GOOGLE_APPLICATION_CREDENTIALS and forget it
    # but this doesn't seem to work. So, we pass it in manually.
    File.open(ENV['GOOGLE_APPLICATION_CREDENTIALS'], "r")
  end

  def authorization(scope)
    Google::Auth::ServiceAccountCredentials.new(json_key_io: google_api_key, scope: scope)
  end

  def analytics_service
    scope = [
      'https://www.googleapis.com/auth/analytics.readonly'
    ]
    client = Google::Apis::AnalyticsV3::AnalyticsService.new
    client.authorization = authorization(scope)
    client.authorization.fetch_access_token!
    client
  end
end