Create framework for build prerequisites

Introduces the concept of Prerequisites for a CI build.
If a build has unmet prerequisites it will go through the
:preparing state before being made available to a runner.

There are no actual prerequisites yet, so current
behaviour is unchanged.

1 files changed, 25 insertions, 0 deletions

diff --git a/app/services/ci/prepare_build_service.rb b/app/services/ci/prepare_build_service.rb
new file mode 100644
index 00000000000..32f11438b79
--- /dev/null
+++ b/app/services/ci/prepare_build_service.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module Ci
+  class PrepareBuildService
+    attr_reader :build
+
+    def initialize(build)
+      @build = build
+    end
+
+    def execute
+      prerequisites.each(&:complete!)
+
+      unless build.enqueue
+        build.drop!(:unmet_prerequisites)
+      end
+    end
+
+    private
+
+    def prerequisites
+      build.prerequisites
+    end
+  end
+end