Expose CA median and records via API

This MR exposes to the frontend the median and the related records
calculated for a given stage.

ee/app/controllers/analytics/cycle_analytics/stages_controller.rb

@@ -6,6 +6,7 @@ module Analytics
       check_feature_flag Gitlab::Analytics::CYCLE_ANALYTICS_FEATURE_FLAG
 
       before_action :load_group
+      before_action :validate_params, only: %i[median records]
 
       def index
         return render_403 unless can?(current_user, :read_group_cycle_analytics, @group)
@@ -37,8 +38,45 @@ module Analytics
         render_stage_service_result(delete_service.execute)
       end
 
+      def median
+        return render_403 unless can?(current_user, :read_group_stage, @group)
+
+        render json: { value: data_collector.median.seconds }
+      end
+
+      def records
+        return render_403 unless can?(current_user, :read_group_stage, @group)
+
+        render json: data_collector.serialized_records
+      end
+
       private
 
+      def validate_params
+        if request_params.invalid?
+          render(
+            json: { message: 'Invalid parameters', errors: request_params.errors },
+            status: :unprocessable_entity
+          )
+        end
+      end
+
+      def request_params
+        @request_params ||= Gitlab::Analytics::CycleAnalytics::RequestParams.new(params.permit(:created_before, :created_after))
+      end
+
+      def data_collector
+        @data_collector ||= Gitlab::Analytics::CycleAnalytics::DataCollector.new(stage: stage, params: {
+          current_user: current_user,
+          from: request_params.created_after,
+          to: request_params.created_before
+        })
+      end
+
+      def stage
+        @stage ||= Analytics::CycleAnalytics::StageFinder.new(parent: @group, stage_id: params[:id]).execute
+      end
+
       def cycle_analytics_configuration(stages)
         stage_presenters = stages.map { |s| StagePresenter.new(s) }
 

ee/config/routes/analytics.rb

@@ -8,7 +8,12 @@ namespace :analytics do
   constraints(::Constraints::FeatureConstrainer.new(Gitlab::Analytics::CYCLE_ANALYTICS_FEATURE_FLAG)) do
     resource :cycle_analytics, only: :show
     namespace :cycle_analytics do
-      resources :stages, only: [:index, :create, :update, :destroy]
+      resources :stages, only: [:index, :create, :update, :destroy] do
+        member do
+          get :median
+          get :records
+        end
+      end
     end
   end
 

ee/lib/gitlab/analytics/cycle_analytics/request_params.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Analytics
+    module CycleAnalytics
+      class RequestParams
+        include ActiveModel::Model
+        include ActiveModel::Validations
+        include ActiveModel::Attributes
+
+        attribute :created_after, :date
+        attribute :created_before, :date
+
+        validates :created_after, presence: true
+        validates :created_before, presence: true
+
+        validate :validate_created_before
+
+        private
+
+        def validate_created_before
+          return if created_after.nil? || created_before.nil?
+
+          errors.add(:created_before, :invalid) if created_after > created_before
+        end
+      end
+    end
+  end
+end

ee/spec/controllers/analytics/cycle_analytics/stages_controller_spec.rb

@@ -158,5 +158,53 @@ describe Analytics::CycleAnalytics::StagesController do
         expect(response).to have_gitlab_http_status(:forbidden)
       end
     end
+
+    describe 'GET `median`' do
+      subject { get :median, params: params }
+
+      before do
+        params[:created_after] = '2019-01-01'
+        params[:created_before] = '2020-01-01'
+      end
+
+      it 'succeeds' do
+        subject
+
+        expect(response).to be_successful
+        expect(response).to match_response_schema('analytics/cycle_analytics/median', dir: 'ee')
+      end
+
+      context 'when params are invalid' do
+        before do
+          params[:created_before] = '2018-01-01'
+        end
+
+        it 'renders `unprocessable_entity`' do
+          subject
+
+          expect(response).to have_gitlab_http_status(:unprocessable_entity)
+          expect(response).to match_response_schema('analytics/cycle_analytics/validation_error', dir: 'ee')
+        end
+      end
+
+      include_examples 'group permission check on the controller level'
+    end
+
+    describe 'GET `records`' do
+      subject { get :records, params: params }
+
+      before do
+        params[:created_after] = '2019-01-01'
+        params[:created_before] = '2020-01-01'
+      end
+
+      it 'succeeds' do
+        subject
+
+        expect(response).to be_successful
+      end
+
+      include_examples 'group permission check on the controller level'
+    end
   end
 end

ee/spec/fixtures/api/schemas/analytics/cycle_analytics/median.json

+{
+  "type": "object",
+  "properties": {
+    "value": {
+      "anyOf": [
+        { "type": "integer" },
+        { "type": "null" }
+      ]
+    }
+  },
+  "required": ["value"],
+  "additionalProperties": false
+}

ee/spec/lib/gitlab/analytics/cycle_analytics/data_collector_spec.rb

@@ -51,7 +51,7 @@ describe Gitlab::Analytics::CycleAnalytics::DataCollector do
     end
 
     it 'loads serialized records' do
-      items = data_collector.records_fetcher.serialized_records
+      items = data_collector.serialized_records
       expect(items.size).to eq(3)
     end
 

ee/spec/lib/gitlab/analytics/cycle_analytics/request_params_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::Analytics::CycleAnalytics::RequestParams do
+  let(:params) { { created_after: '2018-01-01', created_before: '2019-01-01' } }
+  subject { described_class.new(params) }
+
+  describe 'validations' do
+    it 'is valid' do
+      expect(subject).to be_valid
+    end
+
+    context 'when `created_before` is missing' do
+      before do
+        params[:created_before] = nil
+      end
+
+      it 'is invalid' do
+        expect(subject).not_to be_valid
+      end
+    end
+
+    context 'when `created_before` is earlier than `created_after`' do
+      before do
+        params[:created_before] = '2015-01-01'
+      end
+
+      it 'is invalid' do
+        expect(subject).not_to be_valid
+        expect(subject.errors.messages[:created_before]).not_to be_empty
+      end
+    end
+  end
+
+  it 'casts `created_after` to date' do
+    expect(subject.created_after).to be_a_kind_of(Date)
+  end
+
+  it 'casts `created_before` to date' do
+    expect(subject.created_before).to be_a_kind_of(Date)
+  end
+end

lib/gitlab/analytics/cycle_analytics/data_collector.rb

@@ -12,6 +12,8 @@ module Gitlab
       class DataCollector
         include Gitlab::Utils::StrongMemoize
 
+        delegate :serialized_records, to: :records_fetcher
+
         def initialize(stage:, params: {})
           @stage = stage
           @params = params