1 files changed, 140 insertions, 0 deletions
diff --git a/lib/banzai/filter/references/milestone_reference_filter.rb b/lib/banzai/filter/references/milestone_reference_filter.rb
new file mode 100644
index 00000000000..49110194ddc
--- /dev/null
+++ b/lib/banzai/filter/references/milestone_reference_filter.rb
@@ -0,0 +1,140 @@
+# frozen_string_literal: true
+
+module Banzai
+  module Filter
+    module References
+      # HTML filter that replaces milestone references with links.
+      class MilestoneReferenceFilter < AbstractReferenceFilter
+        include Gitlab::Utils::StrongMemoize
+
+        self.reference_type = :milestone
+
+        def self.object_class
+          Milestone
+        end
+
+        # Links to project milestones contain the IID, but when we're handling
+        # 'regular' references, we need to use the global ID to disambiguate
+        # between group and project milestones.
+        def find_object(parent, id)
+          return unless valid_context?(parent)
+
+          find_milestone_with_finder(parent, id: id)
+        end
+
+        def find_object_from_link(parent, iid)
+          return unless valid_context?(parent)
+
+          find_milestone_with_finder(parent, iid: iid)
+        end
+
+        def valid_context?(parent)
+          strong_memoize(:valid_context) do
+            group_context?(parent) || project_context?(parent)
+          end
+        end
+
+        def group_context?(parent)
+          strong_memoize(:group_context) do
+            parent.is_a?(Group)
+          end
+        end
+
+        def project_context?(parent)
+          strong_memoize(:project_context) do
+            parent.is_a?(Project)
+          end
+        end
+
+        def references_in(text, pattern = Milestone.reference_pattern)
+          # We'll handle here the references that follow the `reference_pattern`.
+          # Other patterns (for example, the link pattern) are handled by the
+          # default implementation.
+          return super(text, pattern) if pattern != Milestone.reference_pattern
+
+          milestones = {}
+          unescaped_html = unescape_html_entities(text).gsub(pattern) do |match|
+            milestone = find_milestone($~[:project], $~[:namespace], $~[:milestone_iid], $~[:milestone_name])
+
+            if milestone
+              milestones[milestone.id] = yield match, milestone.id, $~[:project], $~[:namespace], $~
+              "#{REFERENCE_PLACEHOLDER}#{milestone.id}"
+            else
+              match
+            end
+          end
+
+          return text if milestones.empty?
+
+          escape_with_placeholders(unescaped_html, milestones)
+        end
+
+        def find_milestone(project_ref, namespace_ref, milestone_id, milestone_name)
+          project_path = full_project_path(namespace_ref, project_ref)
+
+          # Returns group if project is not found by path
+          parent = parent_from_ref(project_path)
+
+          return unless parent
+
+          milestone_params = milestone_params(milestone_id, milestone_name)
+
+          find_milestone_with_finder(parent, milestone_params)
+        end
+
+        def milestone_params(iid, name)
+          if name
+            { name: name.tr('"', '') }
+          else
+            { iid: iid.to_i }
+          end
+        end
+
+        def find_milestone_with_finder(parent, params)
+          finder_params = milestone_finder_params(parent, params[:iid].present?)
+
+          MilestonesFinder.new(finder_params).find_by(params)
+        end
+
+        def milestone_finder_params(parent, find_by_iid)
+          { order: nil, state: 'all' }.tap do |params|
+            params[:project_ids] = parent.id if project_context?(parent)
+
+            # We don't support IID lookups because IIDs can clash between
+            # group/project milestones and group/subgroup milestones.
+            params[:group_ids] = self_and_ancestors_ids(parent) unless find_by_iid
+          end
+        end
+
+        def self_and_ancestors_ids(parent)
+          if group_context?(parent)
+            parent.self_and_ancestors.select(:id)
+          elsif project_context?(parent)
+            parent.group&.self_and_ancestors&.select(:id)
+          end
+        end
+
+        def url_for_object(milestone, project)
+          Gitlab::Routing
+            .url_helpers
+            .milestone_url(milestone, only_path: context[:only_path])
+        end
+
+        def object_link_text(object, matches)
+          milestone_link = escape_once(super)
+          reference = object.project&.to_reference_base(project)
+
+          if reference.present?
+            "#{milestone_link} <i>in #{reference}</i>".html_safe
+          else
+            milestone_link
+          end
+        end
+
+        def object_link_title(object, matches)
+          nil
+        end
+      end
+    end
+  end
+end