1 files changed, 83 insertions, 0 deletions
diff --git a/lib/gitlab/ci/config/entry/node.rb b/lib/gitlab/ci/config/entry/node.rb
new file mode 100644
index 00000000000..5eef2868cd6
--- /dev/null
+++ b/lib/gitlab/ci/config/entry/node.rb
@@ -0,0 +1,83 @@
+module Gitlab
+  module Ci
+    class Config
+      module Entry
+        ##
+        # Base abstract class for each configuration entry node.
+        #
+        class Node
+          class InvalidError < StandardError; end
+
+          attr_reader :config, :metadata
+          attr_accessor :key, :parent, :description
+
+          def initialize(config, **metadata)
+            @config = config
+            @metadata = metadata
+            @entries = {}
+
+            @validator = self.class.validator.new(self)
+            @validator.validate(:new)
+          end
+
+          def [](key)
+            @entries[key] || Entry::Undefined.new
+          end
+
+          def compose!(deps = nil)
+            return unless valid?
+
+            yield if block_given?
+          end
+
+          def leaf?
+            @entries.none?
+          end
+
+          def descendants
+            @entries.values
+          end
+
+          def ancestors
+            @parent ? @parent.ancestors + [@parent] : []
+          end
+
+          def valid?
+            errors.none?
+          end
+
+          def errors
+            @validator.messages + descendants.flat_map(&:errors)
+          end
+
+          def value
+            if leaf?
+              @config
+            else
+              meaningful = @entries.select do |_key, value|
+                value.specified? && value.relevant?
+              end
+
+              Hash[meaningful.map { |key, entry| [key, entry.value] }]
+            end
+          end
+
+          def specified?
+            true
+          end
+
+          def relevant?
+            true
+          end
+
+          def self.default
+          end
+
+          def self.validator
+            Validator
+          end
+        end
+      end
+    end
+  end
+end