Fill out response from CoverageReportsController

A Groups::Analytics controller based on
Ci::DailyBuildGroupReportResultsController that uses the new
DailyBuildGroupReportResultByGroupFinder to return results for projects
across an entire group

changelogs/unreleased/group-coverage-reporting-csv.yml

+---
+title: Add CoverageReportsController#index CSV response
+merge_request: 38520
+author:
+type: added

ee/app/controllers/groups/analytics/coverage_reports_controller.rb

@@ -3,12 +3,70 @@
 class Groups::Analytics::CoverageReportsController < Groups::Analytics::ApplicationController
   check_feature_flag Gitlab::Analytics::CYCLE_ANALYTICS_FEATURE_FLAG
 
+  REPORT_WINDOW = 90.days.freeze
+
   before_action :load_group
   before_action -> { check_feature_availability!(:group_coverage_reports) }
+  before_action :validate_param_type!
 
   def index
     respond_to do |format|
-      format.csv { send_data([].to_csv, type: 'text/csv; charset=utf-8') }
+      format.csv { send_data(render_csv(report_results), type: 'text/csv; charset=utf-8') }
     end
   end
+
+  private
+
+  def validate_param_type!
+    respond_422 unless allowed_param_types.include?(param_type)
+  end
+
+  def render_csv(collection)
+    CsvBuilders::SingleBatch.new(
+      collection,
+      {
+        date: 'date',
+        group_name: 'group_name',
+        project_name: -> (record) { record.project.name },
+        param_type => -> (record) { record.data[param_type] }
+      }
+    ).render
+  end
+
+  def report_results
+    Ci::DailyBuildGroupReportResultsByGroupFinder.new(finder_params).execute
+  end
+
+  def finder_params
+    {
+      current_user: current_user,
+      group: @group,
+      ref_path: params.require(:ref_path),
+      start_date: start_date,
+      end_date: end_date
+    }
+  end
+
+  def start_date
+    strong_memoize(:start_date) do
+      start_date = Date.parse(params.require(:start_date))
+
+      # The start_date cannot be older than `end_date - 90 days`
+      [start_date, end_date - REPORT_WINDOW].max
+    end
+  end
+
+  def end_date
+    strong_memoize(:end_date) do
+      Date.parse(params.require(:end_date))
+    end
+  end
+
+  def allowed_param_types
+    Ci::DailyBuildGroupReportResult::PARAM_TYPES
+  end
+
+  def param_type
+    params.require(:param_type)
+  end
 end

ee/spec/controllers/groups/analytics/coverage_reports_controller_spec.rb

@@ -5,6 +5,22 @@ require 'spec_helper'
 RSpec.describe Groups::Analytics::CoverageReportsController do
   let(:user)  { create(:user) }
   let(:group) { create(:group) }
+  let(:project) { create(:project, namespace: group) }
+  let(:ref_path) { 'refs/heads/master' }
+
+  let!(:first_coverage) { create_daily_coverage('rspec', 79.0, '2020-03-09') }
+  let!(:last_coverage)  { create_daily_coverage('karma', 95.0, '2020-03-10') }
+
+  let(:index_request) do
+    get :index, params: {
+      group_id: group.name,
+      param_type: 'coverage',
+      start_date: '2020-03-01',
+      end_date: '2020-03-31',
+      ref_path: ref_path,
+      format: :csv
+    }
+  end
 
   context 'without permissions' do
     before do
@@ -13,7 +29,7 @@ RSpec.describe Groups::Analytics::CoverageReportsController do
 
     describe 'GET index' do
       it 'responds 403' do
-        get :index, params: { group_id: group.name, format: :csv }
+        index_request
 
         expect(response).to have_gitlab_http_status(:forbidden)
       end
@@ -33,7 +49,7 @@ RSpec.describe Groups::Analytics::CoverageReportsController do
 
       describe 'GET index' do
         it 'responds 403 because the feature is not licensed' do
-          get :index, params: { group_id: group.name, format: :csv }
+          index_request
 
           expect(response).to have_gitlab_http_status(:forbidden)
         end
@@ -48,7 +64,7 @@ RSpec.describe Groups::Analytics::CoverageReportsController do
 
       describe 'GET index' do
         it 'responds 403 because the feature is not licensed' do
-          get :index, params: { group_id: group.name, format: :csv }
+          index_request
 
           expect(response).to have_gitlab_http_status(:forbidden)
         end
@@ -60,11 +76,29 @@ RSpec.describe Groups::Analytics::CoverageReportsController do
         stub_licensed_features(group_coverage_reports: true)
       end
 
-      it 'responds 200 OK' do
-        get :index, params: { group_id: group.name, format: :csv }
+      it 'responds 200 with CSV coverage data' do
+        index_request
 
         expect(response).to have_gitlab_http_status(:ok)
+        expect(csv_response).to eq([
+          %w[date group_name project_name coverage],
+          [last_coverage.date.to_s, last_coverage.group_name, project.name, last_coverage.data['coverage'].to_s],
+          [first_coverage.date.to_s, first_coverage.group_name, project.name, first_coverage.data['coverage'].to_s]
+        ])
       end
     end
   end
+
+  private
+
+  def create_daily_coverage(group_name, coverage, date)
+    create(
+      :ci_daily_build_group_report_result,
+      project: project,
+      ref_path: ref_path,
+      group_name: group_name,
+      data: { 'coverage' => coverage },
+      date: date
+    )
+  end
 end