1 files changed, 54 insertions, 0 deletions
diff --git a/lib/gitlab/pagination/gitaly_keyset_pager.rb b/lib/gitlab/pagination/gitaly_keyset_pager.rb
new file mode 100644
index 00000000000..651e3d5a807
--- /dev/null
+++ b/lib/gitlab/pagination/gitaly_keyset_pager.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Pagination
+    class GitalyKeysetPager
+      attr_reader :request_context, :project
+      delegate :params, to: :request_context
+
+      def initialize(request_context, project)
+        @request_context = request_context
+        @project = project
+      end
+
+      # It is expected that the given finder will respond to `execute` method with `gitaly_pagination: true` option
+      # and supports pagination via gitaly.
+      def paginate(finder)
+        return paginate_via_gitaly(finder) if keyset_pagination_enabled?
+
+        branches = ::Kaminari.paginate_array(finder.execute)
+        Gitlab::Pagination::OffsetPagination
+          .new(request_context)
+          .paginate(branches)
+      end
+
+      private
+
+      def keyset_pagination_enabled?
+        Feature.enabled?(:branch_list_keyset_pagination, project) && params[:pagination] == 'keyset'
+      end
+
+      def paginate_via_gitaly(finder)
+        finder.execute(gitaly_pagination: true).tap do |records|
+          apply_headers(records)
+        end
+      end
+
+      def apply_headers(records)
+        if records.count == params[:per_page]
+          Gitlab::Pagination::Keyset::HeaderBuilder
+            .new(request_context)
+            .add_next_page_header(
+              query_params_for(records.last)
+            )
+        end
+      end
+
+      def query_params_for(record)
+        # NOTE: page_token is name for now, but it could be dynamic if we have other gitaly finders
+        # that is based on something other than name
+        { page_token: record.name }
+      end
+    end
+  end
+end