module NewRelic
  module MetricParser
    class MetricParser

      SEPARATOR = '/' unless defined? SEPARATOR
      attr_reader :name

      # Load in the parsers classes in the plugin:
      Dir[File.join(File.dirname(__FILE__), "metric_parser", "*.rb")].each { | file | require file }

      # return a string that is parsable via the Metric parser APIs
      def self.for_metric_named(s)
        category = (s =~ /^([^\/]*)/) && $1
        parser_class = self
        if category
          if NewRelic::MetricParser.constants.map(&:to_s).include?(category)
            begin
              parser_class = NewRelic::MetricParser.const_get(category)
            rescue
              nil
            end
          end
        end
        parser_class.new s
      end

      def self.parse(s)
        for_metric_named(s)
      end

      def method_missing(method_name, *args)
        return false if method_name.to_s =~ /^is_.*\?/
        super
      end
      # The short name for the metric is defined as all of the segments
      # of the metric name except for its first (its domain).
      def short_name
        if segments.empty?
          ''
        elsif segments.length == 1
          segments[0]
        else
          segments[1..-1].join(SEPARATOR)
        end
      end

      def pie_chart_label
        developer_name
      end

      def developer_name
        short_name
      end

      def tooltip_name
        short_name
      end

      def apdex_metric_path
        %Q[Apdex/#{segments[1..-1].join('/')}]
      end

      # A short name for legends in the graphs
      def legend_name
        short_name
      end

      # Return the name of another metric if the current
      # metric is really add-on data for another metric.
      def base_metric_name
        nil
      end

      # Category is a UI description of the general
      # category of metrics for this metric.
      def category
        segments[0]
      end

      def segments
        return [] if !name
        @segments ||= name.split(SEPARATOR).freeze
      end

      # --
      # These accessors are used to allow chart to use a specific segment  in the metric
      # name for label construction as a zero-arg accessor
      # ++
      def segment_0; segments[0]; end
      def segment_1; segments[1]; end
      def segment_2; segments[2]; end
      def segment_3; segments[3]; end
      def segment_4; segments[4]; end
      def segment_5; segments[5]; end
      def last_segment; segments.last; end

      # This is the suffix used for call rate or throughput.  By default, it's cpm
      # but things like controller actions will override to use something like 'rpm'
      # for requests per minute
      def call_rate_suffix
        'cpm'
      end

      def url
        ''
      end
      # Return the list of dispatcher metrics that correspond to this metric.  That is,
      # the summary metrics which should also be recorded when this metric is recorded.
      def summary_metrics
        []
      end
      # returns a hash of params for url_for(), giving you a drilldown URL to an RPM page for this metric
      # define in subclasses - TB 2009-12-18
      # def drilldown_url(metric_id); end

      def initialize(name)
        @name = name
      end

      # These would be reflected properly by method missing; consider
      # this an optimization
      def is_controller?; false; end
      def is_transaction?; false; end

    end
  end
end