1 files changed, 86 insertions, 0 deletions
diff --git a/lib/gitlab/usage/metric_definition.rb b/lib/gitlab/usage/metric_definition.rb
new file mode 100644
index 00000000000..96e572bb3db
--- /dev/null
+++ b/lib/gitlab/usage/metric_definition.rb
@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Usage
+    class MetricDefinition
+      METRIC_SCHEMA_PATH = Rails.root.join('config', 'metrics', 'schema.json')
+
+      attr_reader :path
+      attr_reader :attributes
+
+      def initialize(path, opts = {})
+        @path = path
+        @attributes = opts
+      end
+
+      # The key is defined by default_generation and full_path
+      def key
+        full_path[default_generation.to_sym]
+      end
+
+      def to_h
+        attributes
+      end
+
+      def validate!
+        self.class.schemer.validate(attributes.stringify_keys).map do |error|
+          Gitlab::ErrorTracking.track_and_raise_for_dev_exception(Metric::InvalidMetricError.new("#{error["details"] || error['data_pointer']} for `#{path}`"))
+        end
+      end
+
+      alias_method :to_dictionary, :to_h
+
+      class << self
+        def paths
+          @paths ||= [Rails.root.join('config', 'metrics', '**', '*.yml')]
+        end
+
+        def definitions
+          @definitions ||= load_all!
+        end
+
+        def schemer
+          @schemer ||= ::JSONSchemer.schema(Pathname.new(METRIC_SCHEMA_PATH))
+        end
+
+        private
+
+        def load_all!
+          paths.each_with_object({}) do |glob_path, definitions|
+            load_all_from_path!(definitions, glob_path)
+          end
+        end
+
+        def load_from_file(path)
+          definition = File.read(path)
+          definition = YAML.safe_load(definition)
+          definition.deep_symbolize_keys!
+
+          self.new(path, definition).tap(&:validate!)
+        rescue => e
+          Gitlab::ErrorTracking.track_and_raise_for_dev_exception(Metric::InvalidMetricError.new(e.message))
+        end
+
+        def load_all_from_path!(definitions, glob_path)
+          Dir.glob(glob_path).each do |path|
+            definition = load_from_file(path)
+
+            if previous = definitions[definition.key]
+              Gitlab::ErrorTracking.track_and_raise_for_dev_exception(Metric::InvalidMetricError.new("Metric '#{definition.key}' is already defined in '#{previous.path}'"))
+            end
+
+            definitions[definition.key] = definition
+          end
+        end
+      end
+
+      private
+
+      def method_missing(method, *args)
+        attributes[method] || super
+      end
+    end
+  end
+end
+
+Gitlab::Usage::MetricDefinition.prepend_if_ee('EE::Gitlab::Usage::MetricDefinition')