1 files changed, 87 insertions, 4 deletions

diff --git a/app/models/milestone.rb b/app/models/milestone.rb
index ff4fadb0f13..da07d8dd9fc 100644
--- a/app/models/milestone.rb
+++ b/app/models/milestone.rb
@@ -1,11 +1,13 @@
 # frozen_string_literal: true
 
 class Milestone < ApplicationRecord
+  include AtomicInternalId
   include Sortable
   include Timebox
   include Milestoneish
   include FromUnion
   include Importable
+  include IidRoutes
 
   prepend_mod_with('Milestone') # rubocop: disable Cop/InjectEnterpriseEditionModule
 
@@ -13,6 +15,9 @@ class Milestone < ApplicationRecord
     ALL = [::Timebox::None, ::Timebox::Any, ::Timebox::Started, ::Timebox::Upcoming].freeze
   end
 
+  belongs_to :project
+  belongs_to :group
+
   has_many :milestone_releases
   has_many :releases, through: :milestone_releases
 
@@ -30,13 +35,28 @@ class Milestone < ApplicationRecord
         .order(:project_id, :group_id, :due_date)
   end
 
+  scope :of_projects, ->(ids) { where(project_id: ids) }
+  scope :for_projects, -> { where(group: nil).includes(:project) }
+  scope :for_projects_and_groups, -> (projects, groups) do
+    projects = projects.compact if projects.is_a? Array
+    projects = [] if projects.nil?
+
+    groups = groups.compact if groups.is_a? Array
+    groups = [] if groups.nil?
+
+    from_union([where(project_id: projects), where(group_id: groups)], remove_duplicates: false)
+  end
+
   scope :order_by_name_asc, -> { order(Arel::Nodes::Ascending.new(arel_table[:title].lower)) }
   scope :reorder_by_due_date_asc, -> { reorder(arel_table[:due_date].asc.nulls_last) }
   scope :with_api_entity_associations, -> { preload(project: [:project_feature, :route, namespace: :route]) }
   scope :order_by_dates_and_title, -> { order(due_date: :asc, start_date: :asc, title: :asc) }
 
+  validates :group, presence: true, unless: :project
+  validates :project, presence: true, unless: :group
   validates :title, presence: true
   validates_associated :milestone_releases, message: -> (_, obj) { obj[:value].map(&:errors).map(&:full_messages).join(",") }
+  validate :parent_type_check
   validate :uniqueness_of_title, if: :title_changed?
 
   state_machine :state, initial: :active do
@@ -176,10 +196,18 @@ class Milestone < ApplicationRecord
   # TODO: remove after all code paths use `timebox_id`
   # https://gitlab.com/gitlab-org/gitlab/-/issues/215688
   alias_method :milestoneish_id, :timebox_id
-  # TODO: remove after all code paths use (group|project)_timebox?
-  # https://gitlab.com/gitlab-org/gitlab/-/issues/215690
-  alias_method :group_milestone?, :group_timebox?
-  alias_method :project_milestone?, :project_timebox?
+
+  def group_milestone?
+    group_id.present?
+  end
+
+  def project_milestone?
+    project_id.present?
+  end
+
+  def resource_parent
+    group || project
+  end
 
   def parent
     if group_milestone?
@@ -193,8 +221,63 @@ class Milestone < ApplicationRecord
     group_milestone? && parent.subgroup?
   end
 
+  def merge_requests_enabled?
+    if group_milestone?
+      # Assume that groups have at least one project with merge requests enabled.
+      # Otherwise, we would need to load all of the projects from the database.
+      true
+    elsif project_milestone?
+      project&.merge_requests_enabled?
+    end
+  end
+
+  ##
+  # Returns the String necessary to reference a milestone in Markdown. Group
+  # milestones only support name references, and do not support cross-project
+  # references.
+  #
+  # format - Symbol format to use (default: :iid, optional: :name)
+  #
+  # Examples:
+  #
+  #   Milestone.first.to_reference                           # => "%1"
+  #   Milestone.first.to_reference(cross_namespace_project)  # => "gitlab-org/gitlab-foss%1"
+  #
+  def to_reference(from = nil, format: :name, full: false)
+    format_reference = timebox_format_reference(format)
+    reference = "#{self.class.reference_prefix}#{format_reference}"
+
+    if project
+      "#{project.to_reference_base(from, full: full)}#{reference}"
+    else
+      reference
+    end
+  end
+
   private
 
+  def timebox_format_reference(format = :iid)
+    raise ArgumentError, _('Unknown format') unless [:iid, :name].include?(format)
+
+    if group_milestone? && format == :iid
+      raise ArgumentError, _('Cannot refer to a group milestone by an internal id!')
+    end
+
+    if format == :name && !name.include?('"')
+      %("#{name}")
+    else
+      iid
+    end
+  end
+
+  # Milestone should be either a project milestone or a group milestone
+  def parent_type_check
+    return unless group_id && project_id
+
+    field = project_id_changed? ? :project_id : :group_id
+    errors.add(field, _("milestone should belong either to a project or a group.") % { timebox_name: timebox_name })
+  end
+
   def issues_finder_params
     { project_id: project_id, group_id: group_id, include_subgroups: group_id.present? }.compact
   end