Adds an endpoint for downloading the usage CSV

Introduces a new controller, Admin::Licenses::UsageExportsController,
which defines a show action for downloading the usage export CSV.

Adds the `License.in_license_term` method for returning all
HistoricalData within the dates of a license.

ee/app/controllers/admin/concerns/license_request.rb

+# frozen_string_literal: true
+
+module Admin
+  module LicenseRequest
+    private
+
+    def license
+      @license ||= begin
+        License.reset_current
+        License.reset_future_dated
+        License.current
+      end
+    end
+
+    def require_license
+      return if license
+
+      flash.keep
+      redirect_to new_admin_license_path
+    end
+  end
+end

ee/app/controllers/admin/licenses/usage_exports_controller.rb

+# frozen_string_literal: true
+
+module Admin
+  module Licenses
+    class UsageExportsController < Admin::ApplicationController
+      include Admin::LicenseRequest
+
+      before_action :require_license, only: :show
+
+      def show
+        historical_data = HistoricalData.in_license_term(license)
+
+        respond_to do |format|
+          format.csv do
+            csv_data = HistoricalUserData::CsvService.new(historical_data).generate
+
+            send_data(csv_data, type: 'text/csv; charset=utf-8', filename: 'license_usage.csv')
+          end
+        end
+      end
+    end
+  end
+end

ee/app/controllers/admin/licenses_controller.rb

 # frozen_string_literal: true
 
 class Admin::LicensesController < Admin::ApplicationController
+  include Admin::LicenseRequest
+
   before_action :license, only: [:show, :download, :destroy]
   before_action :require_license, only: [:download, :destroy]
 
@@ -62,21 +64,6 @@ class Admin::LicensesController < Admin::ApplicationController
 
   private
 
-  def license
-    @license ||= begin
-      License.reset_current
-      License.reset_future_dated
-      License.current
-    end
-  end
-
-  def require_license
-    return if license
-
-    flash.keep
-    redirect_to new_admin_license_path
-  end
-
   def build_license
     @license ||= License.new(data: params[:trial_key])
   end

ee/app/models/historical_data.rb

@@ -29,5 +29,12 @@ class HistoricalData < ApplicationRecord
 
       HistoricalData.during(from..to).maximum(:active_user_count) || 0
     end
+
+    def in_license_term(license)
+      start_date = license.starts_at
+      expiration_date = license.expires_at || Date.current
+
+      HistoricalData.during(start_date..expiration_date)
+    end
   end
 end

ee/app/services/historical_user_data/csv_service.rb

@@ -35,8 +35,8 @@ module HistoricalUserData
       CSV.generate do |csv|
         csv << ['License Key', license.data]
         csv << ['Email', license.licensee['Email']]
-        csv << ['License Start Date', license.starts_at.to_s(:csv)]
-        csv << ['License End Date', license.expires_at.to_s(:csv)]
+        csv << ['License Start Date', license.starts_at&.to_s(:csv)]
+        csv << ['License End Date', license.expires_at&.to_s(:csv)]
         csv << ['Company', license.licensee['Company']]
         csv << ['Generated At', Time.current.to_s(:csv)]
         csv << ['']

ee/config/routes/admin.rb

@@ -29,6 +29,8 @@ namespace :admin do
 
   resource :license, only: [:show, :new, :create, :destroy] do
     get :download, on: :member
+
+    resource :usage_export, controller: 'licenses/usage_exports', only: [:show]
   end
 
   # using `only: []` to keep duplicate routes from being created

ee/spec/controllers/admin/licenses/usage_exports_controller_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Admin::Licenses::UsageExportsController do
+  let(:admin) { create(:admin) }
+
+  before do
+    sign_in(admin)
+  end
+
+  describe 'GET show' do
+    subject { get :show, format: :csv }
+
+    context 'with no current license' do
+      before do
+        allow(License).to receive(:current).and_return(nil)
+        allow(HistoricalUserData::CsvService).to receive(:new).and_call_original
+      end
+
+      it 'redirects the user' do
+        subject
+
+        expect(response).to have_gitlab_http_status(:redirect)
+      end
+
+      it 'does not attempt to create the CSV' do
+        subject
+
+        expect(HistoricalUserData::CsvService).not_to have_received(:new)
+      end
+    end
+
+    context 'with a current license' do
+      let(:csv_data) do
+        <<~CSV
+          Date,Active User Count
+          2020-08-26,1
+          2020-08-27,2
+        CSV
+      end
+
+      let(:csv_service) { instance_double(HistoricalUserData::CsvService, generate: csv_data) }
+      let(:historical_data_relation) { :historical_data_relation }
+
+      before do
+        allow(HistoricalData).to receive(:in_license_term).with(License.current).and_return(historical_data_relation)
+        allow(HistoricalUserData::CsvService).to receive(:new).with(historical_data_relation).and_return(csv_service)
+      end
+
+      it 'returns a csv file in response' do
+        subject
+
+        expect(response).to have_gitlab_http_status(:ok)
+        expect(response.headers['Content-Type']).to eq('text/csv; charset=utf-8')
+      end
+
+      it 'returns the expected response body' do
+        subject
+
+        expect(CSV.parse(response.body)).to eq([
+          ['Date', 'Active User Count'],
+          %w[2020-08-26 1],
+          %w[2020-08-27 2]
+        ])
+      end
+    end
+  end
+end

ee/spec/factories/licenses.rb

@@ -21,7 +21,7 @@ FactoryBot.define do
 
     starts_at { Date.new(1970, 1, 1) }
     expires_at { Date.current + 11.months }
-    block_changes_at { expires_at + 2.weeks }
+    block_changes_at { expires_at ? expires_at + 2.weeks : nil }
     notify_users_at  { expires_at }
     notify_admins_at { expires_at }
 

ee/spec/models/historical_data_spec.rb

@@ -136,4 +136,44 @@ RSpec.describe HistoricalData do
       end
     end
   end
+
+  describe '.in_license_term' do
+    let_it_be(:now) { DateTime.new(2014, 12, 15) }
+    let_it_be(:license) do
+      create_current_license(
+        starts_at: Date.new(2014, 7, 1),
+        expires_at: Date.new(2014, 12, 31)
+      )
+    end
+
+    before_all do
+      described_class.create!(date: license.starts_at - 1.day, active_user_count: 1)
+      described_class.create!(date: license.expires_at + 1.day, active_user_count: 2)
+      described_class.create!(date: now - 1.year - 1.day, active_user_count: 3)
+      described_class.create!(date: now + 1.day, active_user_count: 4)
+    end
+
+    around do |example|
+      travel_to(now) { example.run }
+    end
+
+    context 'with a license that has a start and end date' do
+      it 'returns correct number of records within the license range' do
+        expect(described_class.in_license_term(license).count).to eq(7)
+      end
+    end
+
+    context 'with a license that has no end date' do
+      let_it_be(:license) do
+        create_current_license(
+          starts_at: Date.new(2014, 7, 1),
+          expires_at: nil
+        )
+      end
+
+      it 'returns correct number of records within the past year' do
+        expect(described_class.in_license_term(license).count).to eq(6)
+      end
+    end
+  end
 end