1 files changed, 77 insertions, 0 deletions
diff --git a/lib/gitlab/ci/config/node/entry.rb b/lib/gitlab/ci/config/node/entry.rb
new file mode 100644
index 00000000000..52758a962f3
--- /dev/null
+++ b/lib/gitlab/ci/config/node/entry.rb
@@ -0,0 +1,77 @@
+module Gitlab
+  module Ci
+    class Config
+      module Node
+        ##
+        # Base abstract class for each configuration entry node.
+        #
+        class Entry
+          class InvalidError < StandardError; end
+
+          attr_accessor :description
+
+          def initialize(value)
+            @value = value
+            @nodes = {}
+            @errors = []
+
+            prevalidate!
+          end
+
+          def process!
+            return if leaf?
+            return unless valid?
+
+            compose!
+
+            nodes.each(&:process!)
+            nodes.each(&:validate!)
+          end
+
+          def nodes
+            @nodes.values
+          end
+
+          def valid?
+            errors.none?
+          end
+
+          def leaf?
+            allowed_nodes.none?
+          end
+
+          def errors
+            @errors + nodes.map(&:errors).flatten
+          end
+
+          def allowed_nodes
+            {}
+          end
+
+          def validate!
+            raise NotImplementedError
+          end
+
+          def value
+            raise NotImplementedError
+          end
+
+          private
+
+          def prevalidate!
+          end
+
+          def compose!
+            allowed_nodes.each do |key, essence|
+              @nodes[key] = create_node(key, essence)
+            end
+          end
+
+          def create_node(key, essence)
+            raise NotImplementedError
+          end
+        end
+      end
+    end
+  end
+end