# encoding: UTF-8

require 'prometheus/client/metric'

module Prometheus
  module Client
    # Summary is an accumulator for samples. It captures Numeric data and
    # provides the total count and sum of observations.
    class Summary < Metric
      def type
        :summary
      end

      # Records a given value. The recorded value is usually positive
      # or zero. A negative value is accepted but prevents current
      # versions of Prometheus from properly detecting counter resets
      # in the sum of observations. See
      # https://prometheus.io/docs/practices/histograms/#count-and-sum-of-observations
      # for details.
      def observe(value, labels: {})
        base_label_set = label_set_for(labels)

        @store.synchronize do
          @store.increment(labels: base_label_set.merge(quantile: "count"), by: 1)
          @store.increment(labels: base_label_set.merge(quantile: "sum"), by: value)
        end
      end

      # Returns a hash with "sum" and "count" as keys
      def get(labels: {})
        base_label_set = label_set_for(labels)

        internal_counters = ["count", "sum"]

        @store.synchronize do
          internal_counters.each_with_object({}) do |counter, acc|
            acc[counter] = @store.get(labels: base_label_set.merge(quantile: counter))
          end
        end
      end

      # Returns all label sets with their values expressed as hashes with their sum/count
      def values
        values = @store.all_values

        values.each_with_object({}) do |(label_set, v), acc|
          actual_label_set = label_set.reject{|l| l == :quantile }
          acc[actual_label_set] ||= { "count" => 0.0, "sum" => 0.0 }
          acc[actual_label_set][label_set[:quantile]] = v
        end
      end

      def init_label_set(labels)
        base_label_set = label_set_for(labels)

        @store.synchronize do
          @store.set(labels: base_label_set.merge(quantile: "count"), val: 0)
          @store.set(labels: base_label_set.merge(quantile: "sum"), val: 0)
        end
      end

      private

      def reserved_labels
        [:quantile]
      end
    end
  end
end