module Prometheus
  module Client
    module Helper
      module MetricsProcessing
        def self.merge_metrics(metrics)
          metrics
        end

        def self.min(a, b)
          if a < b
            a
          else
            b
          end
        end

        def self.max(a, b)
          if a > b
            a
          else
            b
          end
        end

        def self.merge_samples(raw_samples, metric_type, multiprocess_mode)
          samples = {}
          raw_samples.each do |name, labels, value|
            key = { name: name, labels: labels }
            # without_pid = labels.delete(:pid)

            case metric_type
              when :gauge
                case multiprocess_mode
                  when 'min'
                    labels.delete(:pid)
                    s = samples.fetch(key, value)
                    samples[key] = min(s, value)
                  when 'max'
                    labels.delete(:pid)
                    s = samples.fetch(key, value)
                    samples[key] = max(s, value)
                  when 'livesum'
                    labels.delete(:pid)
                    s = samples.fetch(key, 0.0)
                    samples[key] = s + value
                  else # all/liveall
                    samples[key] = value
                end
              else
                labels.delete(:pid)
                # Counter, Histogram and Summary.
                s = samples.fetch(key, 0.0)
                samples[key] = s + value
            end
          end

          samples
        end
      end
    end
  end
end