Example Ruby on Rails library for Google API, Google Analytics Network (GAN), events/list API, as well as others using Installed Applications approach

google_api.rb

module GoogleApi
#  Inspired by http://www.ericnagel.com/how-to-tips/google-affiliate-network-api.html
  require 'rest-client'
  require 'active_support'

  # Google Affiliate Network
  class GAN
    # These values obtained from https://code.google.com/apis/console, creating a client ID for Installed Applications
    CLIENT_ID = '<your-value>.apps.googleusercontent.com'
    CLIENT_SECRET = '<your-value>'
    REDIRECT_URI = '<your-value>'
    # URLs needed to get the authorization
    OAUTH_BASE_URL = 'https://accounts.google.com/o/oauth2'
    OAUTH_AUTH_URL = OAUTH_BASE_URL + '/auth'
    OAUTH_TOKEN_URL = OAUTH_BASE_URL + '/token'
    # Get this value by using the setup routine, after which the process can run without user interaction
    REFRESH_TOKEN = '<your-value>'  # see setup method below
    # URL for getting GAN events.  Other GAN APIs should follow a similar pattern
    API_SCOPE = 'https://www.googleapis.com/auth/gan.readonly'
    PUBLISHER_ID = '<your-value>'  # e.g. K123456
    GAN_EVENT_URL = "https://www.googleapis.com/gan/v1beta1/publishers/#{PUBLISHER_ID}/events"

    # calls the GAN API with a fresh access token to return event data from the given date range (ruby dates)
    def list_events(access_token, start_date, end_date)
      params = {
        :eventDateMin => date_to_format(start_date),
        :eventDateMax => date_to_format(end_date),
        }
      oauth_url = "#{GAN_EVENT_URL}?#{params.to_query}"
      puts "Listing events with URL: #{oauth_url}\n"
      response = RestClient.get(oauth_url, :authorization => "OAuth #{access_token}")
      if response.code != 200
        puts "ERROR: list_events GET failed with code #{response.code} and response\n#{response}\n"
        return
      end

      events = ActiveSupport::JSON.decode(response)
      parse_events(events)
    end

    # sample of how to parse the events response
    def parse_events(events)
      events['items'].each do |item|
        date_str = item['eventDate']
        order_total = item['commissionableSales']['amount']
        order_id = item['orderId']
        advertiser_name = item['advertiserName']
        user_id_proxy = item['memberId']
        commission = item['earnings']['amount']
        puts "#{date_from_format(date_str)}: order: #{order_id} total: $#{order_total} from: #{advertiser_name} by: #{user_id_proxy} commission: #{commission}"
      end
      nil
    end

    # for testing from rails console, for example
    def self.execute
      refresh_token = REFRESH_TOKEN
      gan = GoogleApi::GAN.new
      access_token = gan.access_token(refresh_token)
      start_date = Date.parse("2012-08-01")
      end_date = Date.today
      gan.list_events(access_token, start_date, end_date)
    end

    # two step process for getting a refresh token:
    # first run without arg -- prints URL to use to get an auth code
    # second, pass auth code to get a refresh token that is valid in some context for some lifetime.
    def self.setup(auth_code = nil)
      if auth_code.nil?
        self.application_auth_code_url
        # value returned in browser, e.g. '4/noBm-KAYLdGcES_8KYkbSZwMnGxx.8i1iPOKc-zYXaDn_6y0ZQNiUXSDvcgI'
      else
        self.refresh_token(auth_code)
      end
    end

    # Generates a URL to Google that we'll go to to get an auth code via browser (might be able to automate if needed)
    def self.application_auth_code_url
      params = {
          :response_type => 'code',
          :client_id => CLIENT_ID,
          :redirect_uri => REDIRECT_URI,
          :scope => API_SCOPE,
      }
      # build auth URL with params
      oauth_url = "#{OAUTH_AUTH_URL}?#{params.to_query}"
      puts "Go to #{oauth_url} and set the variable auth_code to the value provided"
      oauth_url
    end

    # Gets a refresh token given an authorization code.  This appears to last indefinitely.
    def self.refresh_token(auth_code)
      params = {
          :code => auth_code,
          :client_id => CLIENT_ID,
          :client_secret => CLIENT_SECRET,
          :redirect_uri => REDIRECT_URI,
          :grant_type => 'authorization_code'
      }
      oauth_url = OAUTH_TOKEN_URL
      puts "Posting to #{oauth_url} with params #{params}"
      response = RestClient.post(oauth_url, params)
      if response.code != 200
        puts "ERROR: refresh_token POST failed with code #{response.code} and response\n#{response}\n"
        return
      end

      data = ActiveSupport::JSON.decode(response)
      puts "Set refresh token from values:\n"
      puts data
    end

    # returns an access token given a refresh token, which at least says it is volatile -- lasting for an hour
    def access_token(refresh_token)
      oauth_url = OAUTH_TOKEN_URL
      params = {
          :client_secret => CLIENT_SECRET,
          :grant_type => 'refresh_token',
          :refresh_token => refresh_token,
          :client_id => CLIENT_ID,
      }
      puts "Posting to #{oauth_url} with params #{params}"
      response = RestClient.post(oauth_url, params)
      if response.code != 200
        puts "ERROR: access_token POST failed with code #{response.code} and response\n#{response}\n"
        return
      end

      data = ActiveSupport::JSON.decode(response)
      access_token = data["access_token"]
      access_token
    end

    private

    # Format of dates accepted as inputs is 2012-08-30T13:15:01.009Z
    def date_to_format(date)
      date.strftime("%FT%T.%LZ")
      end

    # Parses GAN's date format to a ruby datetime
    def date_from_format(date_str)
      DateTime.parse(date_str)
    end
  end
end