1 files changed, 69 insertions, 0 deletions
diff --git a/app/finders/resource_milestone_event_finder.rb b/app/finders/resource_milestone_event_finder.rb
new file mode 100644
index 00000000000..7af34f0a4bc
--- /dev/null
+++ b/app/finders/resource_milestone_event_finder.rb
@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+class ResourceMilestoneEventFinder
+  include FinderMethods
+
+  MAX_PER_PAGE = 100
+
+  attr_reader :params, :current_user, :eventable
+
+  def initialize(current_user, eventable, params = {})
+    @current_user = current_user
+    @eventable = eventable
+    @params = params
+  end
+
+  def execute
+    Kaminari.paginate_array(visible_events)
+  end
+
+  private
+
+  def visible_events
+    @visible_events ||= visible_to_user(events)
+  end
+
+  def events
+    @events ||= eventable.resource_milestone_events.include_relations.page(page).per(per_page)
+  end
+
+  def visible_to_user(events)
+    events.select { |event| visible_for_user?(event) }
+  end
+
+  def visible_for_user?(event)
+    milestone = event_milestones[event.milestone_id]
+    return if milestone.blank?
+
+    parent = milestone.parent
+    parent_availabilities[key_for_parent(parent)]
+  end
+
+  def parent_availabilities
+    @parent_availabilities ||= relevant_parents.to_h do |parent|
+      [key_for_parent(parent), Ability.allowed?(current_user, :read_milestone, parent)]
+    end
+  end
+
+  def key_for_parent(parent)
+    "#{parent.class.name}_#{parent.id}"
+  end
+
+  def event_milestones
+    @milestones ||= events.map(&:milestone).uniq.to_h do |milestone|
+      [milestone.id, milestone]
+    end
+  end
+
+  def relevant_parents
+    @relevant_parents ||= event_milestones.map { |_id, milestone| milestone.parent }
+  end
+
+  def per_page
+    [params[:per_page], MAX_PER_PAGE].compact.min
+  end
+
+  def page
+    params[:page] || 1
+  end
+end