1 files changed, 40 insertions, 0 deletions
diff --git a/lib/banzai/issuable_extractor.rb b/lib/banzai/issuable_extractor.rb
new file mode 100644
index 00000000000..cbabf9156de
--- /dev/null
+++ b/lib/banzai/issuable_extractor.rb
@@ -0,0 +1,40 @@
+module Banzai
+  # Extract references to issuables from multiple documents
+
+  # This populates RequestStore cache used in Banzai::ReferenceParser::IssueParser
+  # and Banzai::ReferenceParser::MergeRequestParser
+  # Populating the cache should happen before processing documents one-by-one
+  # so we can avoid N+1 queries problem
+
+  class IssuableExtractor
+    QUERY = %q(
+      descendant-or-self::a[contains(concat(" ", @class, " "), " gfm ")]
+      [@data-reference-type="issue" or @data-reference-type="merge_request"]
+    ).freeze
+
+    attr_reader :project, :user
+
+    def initialize(project, user)
+      @project = project
+      @user = user
+    end
+
+    # Returns Hash in the form { node => issuable_instance }
+    def extract(documents)
+      nodes = documents.flat_map do |document|
+        document.xpath(QUERY)
+      end
+
+      issue_parser = Banzai::ReferenceParser::IssueParser.new(project, user)
+      merge_request_parser = Banzai::ReferenceParser::MergeRequestParser.new(project, user)
+
+      issuables_for_nodes = issue_parser.issues_for_nodes(nodes).merge(
+        merge_request_parser.merge_requests_for_nodes(nodes)
+      )
+
+      # The project for the issue/MR might be pending for deletion!
+      # Filter them out because we don't care about them.
+      issuables_for_nodes.select { |node, issuable| issuable.project }
+    end
+  end
+end