Load initial analytics report configuration

- Replace dummy chart configuration API with real implementation.
- Introduce ConfigLoader to load the default report configuration YAML
file.
- Add JSON schema test for the chart configuration API endpoint.

ee/fixtures/report_pages/default.yml

+recent_merge_requests_by_group:
+  title: Recent Issues (90 days)
+  chart:
+    type: bar
+    series:
+      open_merge_requests:
+        title: Merge Requests
+        data_retrieval: Metrics::InsightsQuery
+        data_retrieval_options:
+          issuable_type: merge_request
+          issuable_state: opened
+          group_by: week
+          period_limit: 12

ee/lib/api/analytics/reports.rb

@@ -12,6 +12,19 @@ module API
           # This will be scoped to a project or a group
           Feature.enabled?(:report_pages) && ::License.feature_available?(:group_activity_analytics)
         end
+
+        def load_report
+          loader_class = Gitlab::Analytics::Reports::ConfigLoader
+          report_id = params[:report_id]
+
+          loader_class.new.find_report_by_id!(report_id)
+        rescue loader_class::MissingReportError
+          not_found!("Report(#{report_id})")
+        end
+
+        def report
+          @report ||= load_report
+        end
       end
 
       params do
@@ -25,20 +38,7 @@ module API
               get do
                 not_found! unless api_endpoints_available?
 
-                # Dummy response
-                {
-                  id: params[:report_id],
-                  title: 'Recent Issues (90 days)',
-                  chart: {
-                    type: 'bar',
-                    series: [
-                      {
-                        id: 'open_merge_requests',
-                        title: 'Merge requests'
-                      }
-                    ]
-                  }
-                }
+                present report, with: EE::API::Entities::Analytics::Reports::Chart
               end
             end
           end

ee/lib/ee/api/entities/analytics/reports/chart.rb

+# frozen_string_literal: true
+
+module EE
+  module API
+    module Entities
+      module Analytics
+        module Reports
+          class Chart < Grape::Entity
+            class ChartSeriesConfig < Grape::Entity
+              expose :id
+              expose :title
+            end
+
+            class ChartConfig < Grape::Entity
+              expose :type
+              expose :series, using: ChartSeriesConfig
+            end
+
+            expose :id
+            expose :title
+            expose :chart, using: ChartConfig
+          end
+        end
+      end
+    end
+  end
+end

ee/lib/gitlab/analytics/reports/chart.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Analytics
+    module Reports
+      class Chart
+        attr_reader :type, :series
+
+        def initialize(type:, series:)
+          @type = type
+          @series = series
+        end
+      end
+    end
+  end
+end

ee/lib/gitlab/analytics/reports/config_loader.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Analytics
+    module Reports
+      class ConfigLoader
+        include ::Gitlab::Utils::StrongMemoize
+
+        MissingReportError = Class.new(StandardError)
+        MissingSeriesError = Class.new(StandardError)
+
+        DEFAULT_CONFIG = File.join('ee', 'fixtures', 'report_pages', 'default.yml').freeze
+
+        def find_report_by_id!(report_id)
+          raw_report = default_config[report_id.to_s.to_sym]
+
+          raise(MissingReportError.new) if raw_report.nil?
+
+          ReportBuilder.build(raw_report.merge(id: report_id))
+        end
+
+        def find_series_by_id!(report_id, series_id)
+          report = find_report_by_id!(report_id)
+
+          series = report.find_series_by_id(series_id)
+
+          raise(MissingSeriesError.new) if series.nil?
+
+          series
+        end
+
+        private
+
+        def default_config
+          strong_memoize(:default_config) do
+            yaml = File.read(Rails.root.join(DEFAULT_CONFIG).to_s)
+            ::Gitlab::Config::Loader::Yaml.new(yaml).load!
+          rescue Gitlab::Config::Loader::FormatError
+            {}
+          end
+        end
+      end
+    end
+  end
+end

ee/lib/gitlab/analytics/reports/report.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Analytics
+    module Reports
+      class Report
+        attr_reader :id, :title, :chart
+
+        def initialize(id:, title:, chart:)
+          @id = id
+          @title = title
+          @chart = chart
+        end
+
+        def find_series_by_id(series_id)
+          chart.series.find { |series| series.id.to_s.eql?(series_id.to_s) }
+        end
+      end
+    end
+  end
+end

ee/lib/gitlab/analytics/reports/report_builder.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Analytics
+    module Reports
+      class ReportBuilder
+        def self.build(raw_report)
+          series = raw_report[:chart][:series].map { |id, series| build_series(series.merge(id: id)) }
+
+          chart = Chart.new(type: raw_report[:chart][:type], series: series)
+
+          Report.new(
+            id: raw_report[:id],
+            title: raw_report[:title],
+            chart: chart
+          )
+        end
+
+        def self.build_series(raw_series)
+          Series.new(
+            id: raw_series[:id],
+            title: raw_series[:title],
+            data_retrieval_options: {
+              data_retrieval: raw_series[:data_retrieval]
+            }.merge(raw_series[:data_retrieval_options])
+          )
+        end
+
+        private_class_method :build_series
+      end
+    end
+  end
+end

ee/lib/gitlab/analytics/reports/series.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Analytics
+    module Reports
+      class Series
+        attr_reader :id, :title, :data_retrieval_options
+
+        def initialize(id:, title:, data_retrieval_options:)
+          @id = id
+          @title = title
+          @data_retrieval_options = data_retrieval_options
+        end
+      end
+    end
+  end
+end

ee/spec/fixtures/api/schemas/analytics/reports/chart.json

+{
+  "type": "object",
+  "properties": {
+    "id": { "type": "string" },
+    "title": { "type": "string" },
+    "chart": {
+      "type": "object", 
+      "properties": {
+        "type": { "type": "string" },
+        "series": {
+          "type": "array",
+          "items": [
+            {
+              "type": "object",
+              "properties": {
+                "id": { "type": "string" },
+                "title": { "type": "string" }
+              },
+              "additionalProperties": false
+            }
+          ]
+        }
+      },
+      "additionalProperties": false
+    }
+  },
+  "additionalProperties": false
+}

ee/spec/lib/gitlab/analytics/reports/config_loader_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Analytics::Reports::ConfigLoader do
+  let(:report_id) { 'recent_merge_requests_by_group' }
+
+  shared_examples 'missing report_id' do
+    it 'raises ReportNotFoundError' do
+      expect { subject }.to raise_error(described_class::MissingReportError)
+    end
+  end
+
+  shared_examples 'missing series_id' do
+    it 'raises ReportNotFoundError' do
+      expect { subject }.to raise_error(described_class::MissingSeriesError)
+    end
+  end
+
+  describe '#find_report_by_id' do
+    subject { described_class.new.find_report_by_id!(report_id) }
+
+    context 'when unknown report_id is given' do
+      let(:report_id) { 'unknown_report_id' }
+
+      include_examples 'missing report_id'
+    end
+
+    context 'when nil report_id is given' do
+      let(:report_id) { nil }
+
+      include_examples 'missing report_id'
+    end
+
+    it 'loads the report configuration' do
+      expect(subject.title).to eq('Recent Issues (90 days)')
+    end
+  end
+
+  describe '#find_series_by_id' do
+    let(:series_id) { 'open_merge_requests' }
+
+    subject { described_class.new.find_series_by_id!(report_id, series_id) }
+
+    context 'when unknown report_id is given' do
+      let(:report_id) { 'unknown_report_id' }
+
+      include_examples 'missing report_id'
+    end
+
+    context 'when unknown series_id is given' do
+      let(:series_id) { 'unknown_series_id' }
+
+      include_examples 'missing series_id'
+    end
+
+    context 'when nil series_id is given' do
+      let(:series_id) { nil }
+
+      include_examples 'missing series_id'
+    end
+
+    it 'loads the report configuration' do
+      expect(subject.title).to eq('Merge Requests')
+    end
+  end
+end

ee/spec/lib/gitlab/analytics/reports/report_builder_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Analytics::Reports::ReportBuilder do
+  describe '#build' do
+    let(:config_path) { Rails.root.join(Gitlab::Analytics::Reports::ConfigLoader::DEFAULT_CONFIG).to_s }
+    let(:report_file) { Gitlab::Config::Loader::Yaml.new(File.read(config_path)).load! }
+
+    subject { described_class.build(report_file[:recent_merge_requests_by_group]) }
+
+    it 'builds the report object' do
+      expect(subject).to be_a_kind_of(Gitlab::Analytics::Reports::Report)
+      expect(subject.chart).to be_a_kind_of(Gitlab::Analytics::Reports::Chart)
+      expect(subject.chart.series.first).to be_a_kind_of(Gitlab::Analytics::Reports::Series)
+    end
+  end
+end

ee/spec/lib/gitlab/analytics/reports/report_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Analytics::Reports::Report do
+  describe '#find_series_by_id' do
+    let(:series) { Gitlab::Analytics::Reports::Series.new(id: 'series_1', title: 'series title', data_retrieval_options: nil) }
+    let(:chart) { Gitlab::Analytics::Reports::Chart.new(type: 'bar', series: [series]) }
+
+    subject { described_class.new(id: 'id', title: 'title', chart: chart) }
+
+    it 'returns the series object' do
+      expect(subject.find_series_by_id('series_1')).to eq(series)
+    end
+
+    it 'returns nil when series cannot be found' do
+      expect(subject.find_series_by_id('unknown')).to be_nil
+    end
+  end
+end

ee/spec/requests/api/analytics/reports_spec.rb

@@ -4,7 +4,7 @@ require 'spec_helper'
 
 RSpec.describe API::Analytics::Reports do
   let_it_be(:user) { create(:user) }
-  let_it_be(:report_id) { 'some_report_id' }
+  let_it_be(:report_id) { 'recent_merge_requests_by_group' }
 
   shared_examples 'error response examples' do
     context 'when `report_pages` feature flag is off' do
@@ -46,7 +46,19 @@ RSpec.describe API::Analytics::Reports do
       api_call
 
       expect(response).to have_gitlab_http_status(:ok)
-      expect(response.parsed_body["id"]).to eq(report_id)
+      expect(response.parsed_body['id']).to eq(report_id)
+      expect(response.parsed_body).to match_schema('analytics/reports/chart', dir: 'ee')
+    end
+
+    context 'when unknown report_id is given' do
+      let(:report_id) { 'unknown_report_id' }
+
+      it 'renders 404, not found' do
+        api_call
+
+        expect(response).to have_gitlab_http_status(:not_found)
+        expect(response.parsed_body['message']).to eq('404 Report(unknown_report_id) Not Found')
+      end
     end
 
     include_examples 'error response examples'
@@ -63,7 +75,7 @@ RSpec.describe API::Analytics::Reports do
       api_call
 
       expect(response).to have_gitlab_http_status(:ok)
-      expect(response.parsed_body["datasets"].size).to eq(1)
+      expect(response.parsed_body['datasets'].size).to eq(1)
     end
 
     include_examples 'error response examples'