Burndown Chart backend implementation

app/controllers/projects/milestones_controller.rb

@@ -39,6 +39,7 @@ class Projects::MilestonesController < Projects::ApplicationController
   end
 
   def show
+    @burndown = Burndown.new(@milestone)
   end
 
   def create

app/models/burndown.rb

+class Burndown
+  attr_accessor :start_date, :end_date, :open_issues_count, :open_issues_weight
+
+  def initialize(milestone)
+    @milestone          = milestone
+    @start_date         = @milestone.start_date
+    @end_date           = @milestone.due_date
+
+    open_issues         = @milestone.issues.opened
+
+    @open_issues_count  = open_issues.count
+    @open_issues_weight = open_issues.sum(:weight)
+  end
+
+  def closed_issues
+    return {} unless @start_date && @end_date
+
+    Hash[
+      get_count.map do |row|
+        [row.date.strftime('%d %b'), [row.count, row.weight]]
+      end
+    ]
+  end
+
+  private
+
+  def get_count
+    start_date = @start_date.to_time.beginning_of_day
+    end_date = @end_date.to_time.end_of_day
+
+    @milestone.issues.
+      select("DATE_TRUNC('day', closed_at) AS date, COUNT(*) AS count, SUM(weight) as weight").
+      where('closed_at BETWEEN (?) AND (?) AND state = ?', start_date, end_date, 'closed').
+      group(1).reorder(1)
+  end
+end

changelogs/unreleased-ee/issue_91.yml

+---
+title: Add burndown chart to milestones
+merge_request:
+author:

db/fixtures/development/20_burndown.rb

+require './spec/support/sidekiq'
+require './spec/support/test_env'
+
+class Gitlab::Seeder::Burndown
+  def initialize(project, perf: false)
+    @project = project
+  end
+
+  def seed!
+    Sidekiq::Testing.inline! do
+      create_milestone
+      puts '.'
+
+      create_issues
+      puts '.'
+
+      close_issues
+      puts '.'
+    end
+
+    print '.'
+  end
+
+  private
+
+  def create_milestone
+    milestone_params = {
+      title: "Sprint - #{FFaker::Lorem.sentence}",
+      description: FFaker::Lorem.sentence,
+      state: 'active',
+      start_date: Date.today,
+      due_date: rand(15..30).days.from_now
+    }
+
+    @milestone = Milestones::CreateService.new(@project, @project.team.users.sample, milestone_params).execute
+  end
+
+  def create_issues
+    40.times do
+      issue_params = {
+        title: FFaker::Lorem.sentence(6),
+        description: FFaker::Lorem.sentence,
+        state: 'opened',
+        milestone: @milestone,
+        assignee: @project.team.users.sample
+      }
+
+      Issues::CreateService.new(@project, @project.team.users.sample, issue_params).execute
+    end
+  end
+
+  def close_issues
+    @milestone.start_date.upto(@milestone.due_date) do |date|
+      Timecop.travel(date)
+
+      close_number = rand(1..3)
+      open_issues = @milestone.issues.where(state: "opened")
+      open_issues = open_issues.slice(0..close_number)
+
+      open_issues.each do |issue|
+        Issues::CloseService.new(@project, @project.team.users.sample, {}).execute(issue)
+      end
+    end
+
+    Timecop.return
+  end
+end
+
+Gitlab::Seeder.quiet do
+  if project_id = ENV['PROJECT_ID']
+    project = Project.find(project_id)
+    seeder = Gitlab::Seeder::Burndown.new(project)
+    seeder.seed!
+  else
+    Project.all.each do |project|
+      seeder = Gitlab::Seeder::Burndown.new(project)
+      seeder.seed!
+    end
+  end
+end

spec/models/burndown_spec.rb

+require 'spec_helper'
+
+describe Burndown, models: true do
+  let(:range) { 10 }
+  let(:milestone) { create(:milestone, start_date: range.days.ago, due_date: Date.today) }
+  let(:project) { milestone.project }
+  let(:user) { create(:user) }
+
+  before do
+    project.add_master(user)
+    @closed_by_date = {}
+
+    range.times do |i|
+      date = i.days.ago
+      @closed_by_date[date] ||= []
+
+      issue_params = {
+        title: FFaker::Lorem.sentence(6),
+        description: FFaker::Lorem.sentence,
+        state: 'closed',
+        milestone: milestone,
+        closed_at: date,
+        weight: rand(9)
+      }
+
+      rand(1..4).times do |i|
+        @closed_by_date[date] << Issues::CreateService.new(project, user, issue_params).execute
+      end
+    end
+  end
+
+  subject { described_class.new(milestone).closed_issues }
+
+  it "groups count and weight by closed_at" do
+    sample =
+      Hash[
+        @closed_by_date.sort.map do |k, v|
+          [k.strftime('%d %b'), [v.count, v.map { |issues| issues.weight }.sum]]
+        end
+      ]
+
+    expect(sample).to eq(subject)
+  end
+end