1 files changed, 63 insertions, 0 deletions
diff --git a/app/services/merge_requests/mergeability/detailed_merge_status_service.rb b/app/services/merge_requests/mergeability/detailed_merge_status_service.rb
new file mode 100644
index 00000000000..d25234183fd
--- /dev/null
+++ b/app/services/merge_requests/mergeability/detailed_merge_status_service.rb
@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+module MergeRequests
+  module Mergeability
+    class DetailedMergeStatusService
+      include ::Gitlab::Utils::StrongMemoize
+
+      def initialize(merge_request:)
+        @merge_request = merge_request
+      end
+
+      def execute
+        return :checking if checking?
+        return :unchecked if unchecked?
+
+        if check_results.success?
+
+          # If everything else is mergeable, but CI is not, the frontend expects two potential states to be returned
+          # See discussion: gitlab.com/gitlab-org/gitlab/-/merge_requests/96778#note_1093063523
+          if check_ci_results.success?
+            :mergeable
+          else
+            ci_check_failure_reason
+          end
+        else
+          check_results.failure_reason
+        end
+      end
+
+      private
+
+      attr_reader :merge_request, :checks, :ci_check
+
+      def checking?
+        merge_request.cannot_be_merged_rechecking? || merge_request.preparing? || merge_request.checking?
+      end
+
+      def unchecked?
+        merge_request.unchecked?
+      end
+
+      def check_results
+        strong_memoize(:check_results) do
+          merge_request.execute_merge_checks(params: { skip_ci_check: true })
+        end
+      end
+
+      def check_ci_results
+        strong_memoize(:check_ci_results) do
+          ::MergeRequests::Mergeability::CheckCiStatusService.new(merge_request: merge_request, params: {}).execute
+        end
+      end
+
+      def ci_check_failure_reason
+        if merge_request.actual_head_pipeline&.running?
+          :ci_still_running
+        else
+          check_ci_results.payload.fetch(:reason)
+        end
+      end
+    end
+  end
+end